CA1180258A - Method for shaping and finishing a workpiece - Google Patents
Method for shaping and finishing a workpieceInfo
- Publication number
- CA1180258A CA1180258A CA000400524A CA400524A CA1180258A CA 1180258 A CA1180258 A CA 1180258A CA 000400524 A CA000400524 A CA 000400524A CA 400524 A CA400524 A CA 400524A CA 1180258 A CA1180258 A CA 1180258A
- Authority
- CA
- Canada
- Prior art keywords
- workpiece
- template
- masking material
- set forth
- workpiece surface
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- ing And Chemical Polishing (AREA)
- Moulds For Moulding Plastics Or The Like (AREA)
Abstract
METHOD FOR SHAPING AND
FINISHING A WORKPIECE
ABSTRACT OF THE DISCLOSURE
The invention includes the process of shaping a workpiece and for producing a surface contour complementary to the surface contour of a model The process comprises the steps of applying a masking material to at least a portion of the surface of the workpiece to be shaped, the masking material being adapted to protect the surface from the effects of etchant. A template is then pressed against the surface, the template having a surface contour comprising a negative image of the surface contour to be formed in the workpiece, the template surface being comprised of material adapted to remove the masking material when the template is pressed against the surface and removed from the surface. The template is then withdrawn from the surface to remove masking material from those portions of the surface contacted by the template surface. Etchant is then applied to the surface not covered by the masking material. The steps of pressing the template against the surface to remove masking material and etching the surface of the workpiece are repeated until the surface contour of the workpiece conforms to the surface contour of the model.
FINISHING A WORKPIECE
ABSTRACT OF THE DISCLOSURE
The invention includes the process of shaping a workpiece and for producing a surface contour complementary to the surface contour of a model The process comprises the steps of applying a masking material to at least a portion of the surface of the workpiece to be shaped, the masking material being adapted to protect the surface from the effects of etchant. A template is then pressed against the surface, the template having a surface contour comprising a negative image of the surface contour to be formed in the workpiece, the template surface being comprised of material adapted to remove the masking material when the template is pressed against the surface and removed from the surface. The template is then withdrawn from the surface to remove masking material from those portions of the surface contacted by the template surface. Etchant is then applied to the surface not covered by the masking material. The steps of pressing the template against the surface to remove masking material and etching the surface of the workpiece are repeated until the surface contour of the workpiece conforms to the surface contour of the model.
Description
2~
METHOD FOE~ SHAPING AND
FINISHING A WORKPIECE
FIELD F THE INVENTION
The present invention relates to a method for shaping and finishing a workpiece, such that the workpiece will have a contour or surface configuration complementary or identical to a model.
BACKGROU~D PRIOR ART
In the manufacture of molds and other similar products~ or o~ machined and ~ini$hed metal parts, wherein it i5 necessary to form an intricate configura~ion, maintain close tolerances, or produce highly polished configurations or finished surfaces, the workpiece is commonly machined to produce a rough configuration similar to that requi.red and then hand finished and polished to produce a finished article. For example/ in the production of molds of the type for use in-injection molding r,lachines or in die casting, whecein it is frequently necessary to forrn intricate des;gns or very precise detail in metal and to maintain fine tolerances, manufacture of such products requires machining of the metal to roughly orm the mold cavity and then extensive hand polishingO Furthermore, creation o~ intricate designs ;n metal is both time consuming and requires an artisan of substantial skill. Since such intricate and extensive manual labor is required or the production of such products, it is generally recognized that the product;on of molds or othér machined finished metal parts is very expensive. Additionallyg the requirement of manual creation of intricate designs in metal by hand labor prevents the production of truly identical parts.
SUMMARY ~F THE INVENTlON
. .
The present invention provides a new process for fînishing a workpiece without polishing or other machining and for producing a surface coniguratiQn in the workpiece duplicating the surace confi~uration o the model used to produce the finished metal part.
~lore particularly, the present invention încludes the process of shaping a workpiece and for producing a surace contour complementary to the surEace contour of a model. The process co~prises the steps of (~a~ providing a non-planar template which is a negative image of -the workpiece surface contour to be reproduced; ~b) applying a coating of an etchant resistant masking material to at least a portion of the surface of the workpiece, with the masking material being adapted to protect the workpiece surface from the effects of etchant; (c) pressing the template against the workpiece surface; ld) withdrawing the template from the workpiece surface to selectively adhere the masking material to the template and correspondingly selectively remove masking material from those portions of the workpiece surface contacted by the non-planar template surface; (e) applying etchant to the workpiece surface to etch portions of the worXpiece surface not covered by the masking material, and (f~ xepeating steps (b) through (e) until the surface contour of the workpiece conorms to the non-planax surface contour of the model.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view of a molded street light lens comprising a model for use in construction of a mold for making similar products.
Fig. 2 i5 an enlarged partial view of a portion of the street light lens shown in Fig. 1.
802~
Fig. 3 is a par~ial cross section elevation vie~ of a template made from the model shown in Fig. 1, the template being pressed into a cavity in a work--piece, the work surface of the workpiece being covered with a masking material.
Fig. 4 is a view similar to Fig. 3 but show-ing the template being withdrawn from the workpiece and removing selected portions of the masking material.
Fig. 5 is a view similar to Fig. 3 but show-ing the work surface aftex being subjected to anetchant and recoated with masking material.
Fig. 6 ;s a view similar to Fig. 3 but show-ing the template pressed against the coating of masking material.
Fig. 7 is a view similar to Fig. ~ but show-ing the workpiece after repetitive etching s~eps.
Fig~ B is a perspectiYe view of an embodi-ment for maintaining alignment between the template and workpiece.
Fig. 9 is a perspective view o~ another embodiment for maintaininy alignmen-t between the template and w~rkpiece, Fi~. 10 i~ a perspectiv~ view o~ an em~odi-ment of the invention shown with a cylindrical tem-plate and an assembly for maintaining alignment be-tween the workpiece and template.
Before describing at least one embodiment of the invention in detail, it is to be unaerstood 1 18~
that the invention is not limited in its application to the details of the process set forth in the follow-ing description, The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood -that the phraseology and -terminology employed herein are for the purpose of description and should not be regarded as limiting.
DESCP<IPTION OF A PREFERRE.D E~lBODI~SENT
10 The present invention provides a process for producing finished metal parts and including metal parts of the type having finely polished surfaces, fine tolerances and intricate detail. For example, the p~ro-cess of the present invention can be employed to form and finish mold parts including mold members and mold cores of the type employed in die casting or injection molding wherein the mold cavities may have intricate detail and require finèly polished surfaces. While the process of the invention will be recited in con-~0 nection with production of finished metal parts suchas mold members, it should be understood that the in-vention can also be employed in the production of any other part having a highly de~ined surEace configura-tion or a highly polished sur~ace~ Additionally, the ~5 process of the invention should be understood to be applicable ~o any material s~ch as metals, plast;c, ceramic or glas$ which can be shaped by an etchant or other solvent.
The process of the invention will first be described in connection with the shaping and finishing of a mold cavity of a metal mold of the type for use in the production o die cast or injection molded parts.
The model for the mold cavity can comprise either 2~
another mold member which is to be duplicated by pxac-ticing the process of the invention, or an item to be produced in such a mold me~,~er. The process of the invention will first be described in connection with the production of a mold memher having a mold cavity therein and wherein an identical original mold member to be duplicated is used as a moael. The mold cavity of the model mold member is cleaned with mineral spirits and then alcohol to remove any foreign matter, oil, or grease. The mold cavity is then coaked with a suitable release agent such as vaseline, silicone, oil or the like. Air is then blown into the mold cavity of the model to remove any excess release agent and to provide for an evenly distributed thin coating of release agent on the surface of the mold cavity. A
cast template or a cast negative image is then made Erom the clean mold cavity of the model by pouring a castable hardenable material into the mold cavity.
While other materials can be employed to form the cast negative image of the mold cavity contour, a room temperature curing urethane has been found to be a suitable material. In preferred forms of the inven-tion, the template can he produced from a room tem-perature curiny urethane such as Flexane*94, produced by ~evcon Corporation of Danvers, Massachus~t-ts, or similarly by the use of HR~9 Seal-Peal*~rand coating material, produced ~y Seal-Peal, Inc., Troy, Michigan~
Other materials, such as room temperature vulcani~ing rub~er, could alsQ be used. If room temperature curin~ urethane i~ used to produce the cast -template, it is p~ured into the mold cavity, allowed to cure, and then removed. While the cast template can be cast entirely of urethane, in other forms of the in-vention wherein the cast template will be relatively large, the mold cavity of -the sample mold can first *trade mark 2 ~ ~
be coated with a layer of urethane this coating layer allo~ed to cure, and then the remainder of the mold cavity can be filled with plaster of paris or the like. After the plaster has cured, it can be removed from the urethane layer and a glue or other bonding agent applied to the surfac2 o~ the urethane. The plaster body can then be reinserted so as to be bonded to the urethane layer. The plaster and urethane template is then removed from the mold cavity of che mold model.
If the process of the invention is emplo~ed to produce a mold cavity in a mold member and a model of tlle product to be molded in such a mold [nerllber is e~ployed to provide a form for making a template havin~ a cast negative ima~e of the slJrface configuration to be formed, the model is cleaned and placed in a suitable confinement or cavity. A room te~lperature curing urethane, or any oth~r SL)i table rnaterial which can be poured around thc material and which will h2rden to form a mold, is then poured around the model and allol~ed to cure~ In one preferred form of the invention, a suitable material for use in forming the mold around the model is Flexane*30, also produced by Devcon Corporation of Danvers, Massachusetts.
After the room temperatured cur;ng ùrethane has cured, the model of the product to be produced is removed from the urethane mold so formed. The rold cav;ty of this mold is then coated with a relea,e agent as described above and then che Flexane*94 or Seal-Peal*material can be poured into the Flexane 30 mold to thereby produce the cast template hav;ng *trade mark fi~
a ne~ative image of the surface contour to be formed in th-e ~orkpiece.
The template so formed is then employed as a form for use in shaping and forming the ~o~kpiece by means of a repetitive selective etching process.
In a preferred form of the invention, when the process oE the invention is to be used to shape and finish a metal block workpiece requiring removal of substantial quantities of metal, ~or example, in the production of mo~ds having relatively deep mold cavities, it is desirable that the mold block irs~
be machined to pre-form a mold cavity therein, ae least roughly, whereby less metal will have to be re~oved by the repetitive etching process.
The pre-formed mold block is first cleaned with a suitable cleaning age~t such as mineral spirits and then alcohol. Those portions oE the mold block which are not to be etched, thae îs, which are intended to be protected from contact with acid, are covered with vinyl tape and/or dyed shellacO The ~hellac is normally applied to the ed~es o~ the tape to pre~ent acid ~rom ~etting under the vinyl tc~pe and is al~so applied to poctions o~ the block ~h;ch cannot be conveniently taped.
The portion o~ the workpîece surface, or ~he pre-formed cavity, which is ~o be shaped and f;nished by the application of the repetitîve etching process is then coated with a coating or mas~ing material oE ~ type for resisting contac~ o the etching acid with the metal. ~hile other `~3~
2~
.9 masking materials can be used, the rnasking ~atecial may comprise re-etchin~ ;nk, asphaltum va~nisn, a combination o~ re-etching ink and asphaltum varnish, or a co~bination of tar, mineral spirits and lard.
S Generallv, the ~asking material is brushed or spcayed unto the desired surface of the mold. A
suitable re-etching inK is Type l-B re-etching ink, produced by Sigma Photo Chemical Laboratories of Newton, New Jersey. A suitable asphaltum varnish masking material is produced by ~arold M. Pitman Company, Chicago, Illinois. When asphaltum varnish is employed, a suitable viscosity ;s achieved for application with a paint brush or with a spray;ng device if 20 parts asphaltum varnish are mixed with 5 parts benzene.
After the surfaces of the workpiece have been coated with the re-etching ink or asphaltum varnish masking material, the cast template is pressed against the coated surEace of the workpiece under a sli~ht hand pressure and the pulled away from the coated surface. The surface properties of the urethane template cause that portion of the masking material contacted by the surface oÇ the template to be pulled away from the mold surface~ It ~rill be appceciated by those skilled in the art that h~hen the surEace of the te~plate is placed a~ainst the mold sucface, the template sucface will engase only poctions oc hinh spots o the surface of the mold and, conse-quently, t~ill pick up only a portion of the cemov-able mold coatin~ material. In o~der to efEectively remove all of the mold coatin~ material From those `; ~
\ ~"
.
1~8~2~
hi~h spots of the work piece, it is desirable to repetitively press the template against the work-p;ece to repeatedly pick up the mold masking material from the contacted portions of the surface oE the workpiece. In the preferred form of the process, after each pick-up step, the surface of the te~plate is cleaned by wiping the surface with alcohol or benzene. It is preferred that the workpiece and template be supported by a suitable align~ent jig assembly so that they will be main-tained in alignment with each other during the repeated pick-up steps.
I~hi:Le the cast template has been described as beinO comprised of Flexane*or Seal-Peal*
it should be understood that other materials which can be cast to form a self supporting body and which have surface properties which will permit the mold masking material to be suitably pulled away from the mold surface in the mannler described, can be used. Similarly, while examplles of suitable mold coatin~ materials have been described, it should be understood that materials which are effe~ctive to coat the surface oE ~he workpiece to protect it from attack by etching acids, yet which can be selectively re~oved from the wor~piece surface by contact of the template with the coating material, could also be e~ployed.
After a portion of the workpiece maskin~
material has been removed, a suitable etching acid is applied to the wock surface. ln a pre~erred form of the inventiOn, the work-piece is dipped in an acid bath. Since the entire workpiece, ~ut for the surt`ace portions contacted by the templ3te, are * t ra~e ma f k ~ ~8~2~
protected against contact with the acid by vinyl tape, shellac, and the masking materia~, the acid will remove metal from only those selected portions of the workpiece wherein the coatir~g material was removed by the pick-up process us~ing the template.
While the workpiece may be dipped in various suitable acid baths such as those co~monly employed in etching processes, an example of a suitable acid bath is comprised of four parts water mixed wi~h one part 42-BE Nitric Acid produced by ~cKesson Chemical Company, West Allis, Wîsconsin.
Another suitable acid bath comprises one gallon of nitric acid mixed with eight ounces of Delboy Sulfuric Acid 66, produced by McKesson Chemical Co., West Allis, Wisconsin, and four gallons of water~ An additional suitable acid bath comprises one gallon of nitric acid, e;ght ounces of sulfuric acid, one ounce of Mc~esson Chemical Gompany Hydrochloric Acid 20 BE and four gallons of water.
Another suita~le etchant comprises an etchant produced by The Cronite Co., Inc. of North Becgen, New Jersey1 and sold under the name "New Impcoved Steel Acid".
~he len~th of time a wockpiece is sub-jected to the acid bath is dependent on the amountof material to be remoYed from the workp;ece and the caustic stcength of the acid bath.
A~ter the first dipping step~ the workpiece is removed Erom the acid bath, rinsed with water and th~n cleaned with minecal spir;ts. If metal deposits have accumulated on the sucface oE that portion of the ~o~kpiece surEace being etched, the surface is brushed with a brass brush or otherwise suitably cleaned. The cleaning process is also effective to remove the remaining re-etching ink or asphaltum varnish masking material on the surface o~ the workpiece. Follo~ing the cleaning process, the mold is air dried~
The work surface of the workpiece is then recoated with the re-etching ink, or asphal~um varnish9 and the cast negative i~age is again pressed against the work surface of the workpiece, to pick up selected portions of the masking material Erom the work surface. Again, only portions o the negative image surface of the template will contact the work sur~ace and, accordingly, only portions of the masking material will be removed from the work surface. While the surface contour of the template and the contour of the work sur~ace will still not meet perEectly, since metal was removed rom the workpîece surEace dur;ng the first acid dipping step, during the second step of picking up coatin~
material from the wock surface, the template will tend to fit the contour of the work sur~ace more closely. Accordingly, the surEace of ~he cast negative image will pick up a greatec quant;ty or peccentage oE the coatin~ material. As durin~ the ~irst pick-up step, it is desirable to repeat the applieation of the template to the work surface during the ~econd pick-up step to remove as much of the coating material from the wock sur~ace as possible
METHOD FOE~ SHAPING AND
FINISHING A WORKPIECE
FIELD F THE INVENTION
The present invention relates to a method for shaping and finishing a workpiece, such that the workpiece will have a contour or surface configuration complementary or identical to a model.
BACKGROU~D PRIOR ART
In the manufacture of molds and other similar products~ or o~ machined and ~ini$hed metal parts, wherein it i5 necessary to form an intricate configura~ion, maintain close tolerances, or produce highly polished configurations or finished surfaces, the workpiece is commonly machined to produce a rough configuration similar to that requi.red and then hand finished and polished to produce a finished article. For example/ in the production of molds of the type for use in-injection molding r,lachines or in die casting, whecein it is frequently necessary to forrn intricate des;gns or very precise detail in metal and to maintain fine tolerances, manufacture of such products requires machining of the metal to roughly orm the mold cavity and then extensive hand polishingO Furthermore, creation o~ intricate designs ;n metal is both time consuming and requires an artisan of substantial skill. Since such intricate and extensive manual labor is required or the production of such products, it is generally recognized that the product;on of molds or othér machined finished metal parts is very expensive. Additionallyg the requirement of manual creation of intricate designs in metal by hand labor prevents the production of truly identical parts.
SUMMARY ~F THE INVENTlON
. .
The present invention provides a new process for fînishing a workpiece without polishing or other machining and for producing a surface coniguratiQn in the workpiece duplicating the surace confi~uration o the model used to produce the finished metal part.
~lore particularly, the present invention încludes the process of shaping a workpiece and for producing a surace contour complementary to the surEace contour of a model. The process co~prises the steps of (~a~ providing a non-planar template which is a negative image of -the workpiece surface contour to be reproduced; ~b) applying a coating of an etchant resistant masking material to at least a portion of the surface of the workpiece, with the masking material being adapted to protect the workpiece surface from the effects of etchant; (c) pressing the template against the workpiece surface; ld) withdrawing the template from the workpiece surface to selectively adhere the masking material to the template and correspondingly selectively remove masking material from those portions of the workpiece surface contacted by the non-planar template surface; (e) applying etchant to the workpiece surface to etch portions of the worXpiece surface not covered by the masking material, and (f~ xepeating steps (b) through (e) until the surface contour of the workpiece conorms to the non-planax surface contour of the model.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view of a molded street light lens comprising a model for use in construction of a mold for making similar products.
Fig. 2 i5 an enlarged partial view of a portion of the street light lens shown in Fig. 1.
802~
Fig. 3 is a par~ial cross section elevation vie~ of a template made from the model shown in Fig. 1, the template being pressed into a cavity in a work--piece, the work surface of the workpiece being covered with a masking material.
Fig. 4 is a view similar to Fig. 3 but show-ing the template being withdrawn from the workpiece and removing selected portions of the masking material.
Fig. 5 is a view similar to Fig. 3 but show-ing the work surface aftex being subjected to anetchant and recoated with masking material.
Fig. 6 ;s a view similar to Fig. 3 but show-ing the template pressed against the coating of masking material.
Fig. 7 is a view similar to Fig. ~ but show-ing the workpiece after repetitive etching s~eps.
Fig~ B is a perspectiYe view of an embodi-ment for maintaining alignment between the template and workpiece.
Fig. 9 is a perspective view o~ another embodiment for maintaininy alignmen-t between the template and w~rkpiece, Fi~. 10 i~ a perspectiv~ view o~ an em~odi-ment of the invention shown with a cylindrical tem-plate and an assembly for maintaining alignment be-tween the workpiece and template.
Before describing at least one embodiment of the invention in detail, it is to be unaerstood 1 18~
that the invention is not limited in its application to the details of the process set forth in the follow-ing description, The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood -that the phraseology and -terminology employed herein are for the purpose of description and should not be regarded as limiting.
DESCP<IPTION OF A PREFERRE.D E~lBODI~SENT
10 The present invention provides a process for producing finished metal parts and including metal parts of the type having finely polished surfaces, fine tolerances and intricate detail. For example, the p~ro-cess of the present invention can be employed to form and finish mold parts including mold members and mold cores of the type employed in die casting or injection molding wherein the mold cavities may have intricate detail and require finèly polished surfaces. While the process of the invention will be recited in con-~0 nection with production of finished metal parts suchas mold members, it should be understood that the in-vention can also be employed in the production of any other part having a highly de~ined surEace configura-tion or a highly polished sur~ace~ Additionally, the ~5 process of the invention should be understood to be applicable ~o any material s~ch as metals, plast;c, ceramic or glas$ which can be shaped by an etchant or other solvent.
The process of the invention will first be described in connection with the shaping and finishing of a mold cavity of a metal mold of the type for use in the production o die cast or injection molded parts.
The model for the mold cavity can comprise either 2~
another mold member which is to be duplicated by pxac-ticing the process of the invention, or an item to be produced in such a mold me~,~er. The process of the invention will first be described in connection with the production of a mold memher having a mold cavity therein and wherein an identical original mold member to be duplicated is used as a moael. The mold cavity of the model mold member is cleaned with mineral spirits and then alcohol to remove any foreign matter, oil, or grease. The mold cavity is then coaked with a suitable release agent such as vaseline, silicone, oil or the like. Air is then blown into the mold cavity of the model to remove any excess release agent and to provide for an evenly distributed thin coating of release agent on the surface of the mold cavity. A
cast template or a cast negative image is then made Erom the clean mold cavity of the model by pouring a castable hardenable material into the mold cavity.
While other materials can be employed to form the cast negative image of the mold cavity contour, a room temperature curing urethane has been found to be a suitable material. In preferred forms of the inven-tion, the template can he produced from a room tem-perature curiny urethane such as Flexane*94, produced by ~evcon Corporation of Danvers, Massachus~t-ts, or similarly by the use of HR~9 Seal-Peal*~rand coating material, produced ~y Seal-Peal, Inc., Troy, Michigan~
Other materials, such as room temperature vulcani~ing rub~er, could alsQ be used. If room temperature curin~ urethane i~ used to produce the cast -template, it is p~ured into the mold cavity, allowed to cure, and then removed. While the cast template can be cast entirely of urethane, in other forms of the in-vention wherein the cast template will be relatively large, the mold cavity of -the sample mold can first *trade mark 2 ~ ~
be coated with a layer of urethane this coating layer allo~ed to cure, and then the remainder of the mold cavity can be filled with plaster of paris or the like. After the plaster has cured, it can be removed from the urethane layer and a glue or other bonding agent applied to the surfac2 o~ the urethane. The plaster body can then be reinserted so as to be bonded to the urethane layer. The plaster and urethane template is then removed from the mold cavity of che mold model.
If the process of the invention is emplo~ed to produce a mold cavity in a mold member and a model of tlle product to be molded in such a mold [nerllber is e~ployed to provide a form for making a template havin~ a cast negative ima~e of the slJrface configuration to be formed, the model is cleaned and placed in a suitable confinement or cavity. A room te~lperature curing urethane, or any oth~r SL)i table rnaterial which can be poured around thc material and which will h2rden to form a mold, is then poured around the model and allol~ed to cure~ In one preferred form of the invention, a suitable material for use in forming the mold around the model is Flexane*30, also produced by Devcon Corporation of Danvers, Massachusetts.
After the room temperatured cur;ng ùrethane has cured, the model of the product to be produced is removed from the urethane mold so formed. The rold cav;ty of this mold is then coated with a relea,e agent as described above and then che Flexane*94 or Seal-Peal*material can be poured into the Flexane 30 mold to thereby produce the cast template hav;ng *trade mark fi~
a ne~ative image of the surface contour to be formed in th-e ~orkpiece.
The template so formed is then employed as a form for use in shaping and forming the ~o~kpiece by means of a repetitive selective etching process.
In a preferred form of the invention, when the process oE the invention is to be used to shape and finish a metal block workpiece requiring removal of substantial quantities of metal, ~or example, in the production of mo~ds having relatively deep mold cavities, it is desirable that the mold block irs~
be machined to pre-form a mold cavity therein, ae least roughly, whereby less metal will have to be re~oved by the repetitive etching process.
The pre-formed mold block is first cleaned with a suitable cleaning age~t such as mineral spirits and then alcohol. Those portions oE the mold block which are not to be etched, thae îs, which are intended to be protected from contact with acid, are covered with vinyl tape and/or dyed shellacO The ~hellac is normally applied to the ed~es o~ the tape to pre~ent acid ~rom ~etting under the vinyl tc~pe and is al~so applied to poctions o~ the block ~h;ch cannot be conveniently taped.
The portion o~ the workpîece surface, or ~he pre-formed cavity, which is ~o be shaped and f;nished by the application of the repetitîve etching process is then coated with a coating or mas~ing material oE ~ type for resisting contac~ o the etching acid with the metal. ~hile other `~3~
2~
.9 masking materials can be used, the rnasking ~atecial may comprise re-etchin~ ;nk, asphaltum va~nisn, a combination o~ re-etching ink and asphaltum varnish, or a co~bination of tar, mineral spirits and lard.
S Generallv, the ~asking material is brushed or spcayed unto the desired surface of the mold. A
suitable re-etching inK is Type l-B re-etching ink, produced by Sigma Photo Chemical Laboratories of Newton, New Jersey. A suitable asphaltum varnish masking material is produced by ~arold M. Pitman Company, Chicago, Illinois. When asphaltum varnish is employed, a suitable viscosity ;s achieved for application with a paint brush or with a spray;ng device if 20 parts asphaltum varnish are mixed with 5 parts benzene.
After the surfaces of the workpiece have been coated with the re-etching ink or asphaltum varnish masking material, the cast template is pressed against the coated surEace of the workpiece under a sli~ht hand pressure and the pulled away from the coated surface. The surface properties of the urethane template cause that portion of the masking material contacted by the surface oÇ the template to be pulled away from the mold surface~ It ~rill be appceciated by those skilled in the art that h~hen the surEace of the te~plate is placed a~ainst the mold sucface, the template sucface will engase only poctions oc hinh spots o the surface of the mold and, conse-quently, t~ill pick up only a portion of the cemov-able mold coatin~ material. In o~der to efEectively remove all of the mold coatin~ material From those `; ~
\ ~"
.
1~8~2~
hi~h spots of the work piece, it is desirable to repetitively press the template against the work-p;ece to repeatedly pick up the mold masking material from the contacted portions of the surface oE the workpiece. In the preferred form of the process, after each pick-up step, the surface of the te~plate is cleaned by wiping the surface with alcohol or benzene. It is preferred that the workpiece and template be supported by a suitable align~ent jig assembly so that they will be main-tained in alignment with each other during the repeated pick-up steps.
I~hi:Le the cast template has been described as beinO comprised of Flexane*or Seal-Peal*
it should be understood that other materials which can be cast to form a self supporting body and which have surface properties which will permit the mold masking material to be suitably pulled away from the mold surface in the mannler described, can be used. Similarly, while examplles of suitable mold coatin~ materials have been described, it should be understood that materials which are effe~ctive to coat the surface oE ~he workpiece to protect it from attack by etching acids, yet which can be selectively re~oved from the wor~piece surface by contact of the template with the coating material, could also be e~ployed.
After a portion of the workpiece maskin~
material has been removed, a suitable etching acid is applied to the wock surface. ln a pre~erred form of the inventiOn, the work-piece is dipped in an acid bath. Since the entire workpiece, ~ut for the surt`ace portions contacted by the templ3te, are * t ra~e ma f k ~ ~8~2~
protected against contact with the acid by vinyl tape, shellac, and the masking materia~, the acid will remove metal from only those selected portions of the workpiece wherein the coatir~g material was removed by the pick-up process us~ing the template.
While the workpiece may be dipped in various suitable acid baths such as those co~monly employed in etching processes, an example of a suitable acid bath is comprised of four parts water mixed wi~h one part 42-BE Nitric Acid produced by ~cKesson Chemical Company, West Allis, Wîsconsin.
Another suitable acid bath comprises one gallon of nitric acid mixed with eight ounces of Delboy Sulfuric Acid 66, produced by McKesson Chemical Co., West Allis, Wisconsin, and four gallons of water~ An additional suitable acid bath comprises one gallon of nitric acid, e;ght ounces of sulfuric acid, one ounce of Mc~esson Chemical Gompany Hydrochloric Acid 20 BE and four gallons of water.
Another suita~le etchant comprises an etchant produced by The Cronite Co., Inc. of North Becgen, New Jersey1 and sold under the name "New Impcoved Steel Acid".
~he len~th of time a wockpiece is sub-jected to the acid bath is dependent on the amountof material to be remoYed from the workp;ece and the caustic stcength of the acid bath.
A~ter the first dipping step~ the workpiece is removed Erom the acid bath, rinsed with water and th~n cleaned with minecal spir;ts. If metal deposits have accumulated on the sucface oE that portion of the ~o~kpiece surEace being etched, the surface is brushed with a brass brush or otherwise suitably cleaned. The cleaning process is also effective to remove the remaining re-etching ink or asphaltum varnish masking material on the surface o~ the workpiece. Follo~ing the cleaning process, the mold is air dried~
The work surface of the workpiece is then recoated with the re-etching ink, or asphal~um varnish9 and the cast negative i~age is again pressed against the work surface of the workpiece, to pick up selected portions of the masking material Erom the work surface. Again, only portions o the negative image surface of the template will contact the work sur~ace and, accordingly, only portions of the masking material will be removed from the work surface. While the surface contour of the template and the contour of the work sur~ace will still not meet perEectly, since metal was removed rom the workpîece surEace dur;ng the first acid dipping step, during the second step of picking up coatin~
material from the wock surface, the template will tend to fit the contour of the work sur~ace more closely. Accordingly, the surEace of ~he cast negative image will pick up a greatec quant;ty or peccentage oE the coatin~ material. As durin~ the ~irst pick-up step, it is desirable to repeat the applieation of the template to the work surface during the ~econd pick-up step to remove as much of the coating material from the wock sur~ace as possible
3~25~
The workpiece is then dipped again in the acid bath to remove or etch away additional portions of the ~orkpiece material. The workpiece is then again rinsed and cleaned of metal residue and the S coating material. As in the previous steps, the work surface is again coated with a coating material after which some of the coating material is removed by repeated applications of the template against the work surface. Since even more of the high spots of the workpiece have been removed, the template will mate more completely with the wor~
surEace and will contact an even greater portion of the ~ork surface, thereby removing even more coating material. The remaining coating material is then sub~ected to a drying step and the etching step is then repeated.
The steps described above are repeated continually until the contour or surface configura-tion o the workpiece confcrms exactly to the ~0 surface coniguration of the template. This can be determined when the template is completely covered with masking material when pressed against ~he surface of the workpiece.
In one embodiment o~ the method of the invention, durin~ the ;nitial step of the processl the wor~piece ;s dipped ~or relatively long periods o~ time, ~oc examplet one-half to three hours~ in acid solutions having a relatively high ac;d concentration. The work surÇace~ after being subjected to a strong acid concentration for these ex~ended periods of time, will have a relatively ~ .
'~' ~ ~8~2~
rough surface texture. Accordingly, as the shapin~
and finishi~g of the work surface nears co~pletion, the workpiece is dipped in a ~ore dilute acid solution and/or for decreasing time periods to thereby produce an i~proved definition in the work product and a highly polished or finished surface texture.
EXAMPLE
As an example of the use oE the process of the ;nvention, the process may be used to produce a mold cavity in a mold member Erom a sample article of the type to be molded therein such as the street light lens 10 illustrated in Figs. 1 and 2, the street light lens 10 having a generally concave lower surface crosshatched with projecting ribs 11.
The workpiece 18 (Fig. 3) Eor use in ~orming the mold member is first machined to rough out a cavity 20 in the workpiece approximating the shape of the finished cavity. The peripheral portions o the workpiece and those portions which are to be protected from e~chin~, are covered with vinyl ta~e and shellac~ The mac'nined surace 20 o the wo~kpiece is covered with a masking ~aterial coating 22 comprising 5 parts benzene per 20 parts asphaltual varnish, the maskin~ materlal bein~
applied with a paint bru~h to orm a thîn, continu-ous coating on the wor~ sur~ace.
A cast template 14 having a surface 16 wi~h a contour which is a negative ima~e of the surface 2~
conf;guration to be p~oduced in the workpiece 18 is produced from the sample article 10 by f;rst makin~
a a)old of the sample article by casting Flexane*30 around the model article and then pe~itting it to S cuce. The model 10 is then removed fro~ the Flexane*30 mold, and after being coated by a release a~ent, the mold is filled with Flexane*94 to form a cast template 14. After the Flexane*94 cures, the template 14 is removed from the ~lexane*
30 mold. This template 14 is then cleaned and pressed against the coated surace 20 of the workp;ece 1~ such that projecting portions 12 of the workpiece will pick up selected portions o~ the asphaltum varnish ~ask;ng material 22 applied to the work surface 20 as shown in Figs. 3 and 4.
The template 14 is then cleaned and again pressed against the work surface 20 to remove additional masking material 22. After a second cleaning and a subsequ~nt pickup step, the coating material is subjected to a drying step. The workpiece 18 is then ready to be dipped in the etching acid.
During the first etching step the workpiece 18 is dipped or 1.5 hours in an aqueous solution of nitric acid as described a~ove and comprised oE ~
2S parts water to 1 par~ 42-BE nitr;c acid manufactured by the ~c~esson Che~lical Company. The workp;ece 1 is then removed from the acid bath and rinsed with water and then air dried. A~ter this etching step, additional asphaltum varnish is painted over the original ~asking material layer 22 as shown in Fig.
S. The template 14 îs again repeatedly applied against the work surface ~0 of the workpiece 18 to remove selected portions of the masking material 20 *trade mark ~;~
2~
as shown in Fig. 6. The masking mate~ial 22 is then dried and the workpiece 18 is again soaked in the etchant for 1.5 hours and then removed and rinsed with ~ater. The masking material 22 is then removed from the ~ork surface ~0 with mineral spirits and, after drying, another layer of masking material 22 is applied to the work surface 20. The template 14 is again pressed against the work surface to remove additional portions o~ the masking material ~2 and, after the maskin~ material 22 has been dried, the workpiece 18 is placed in the acid bath for 1 hour. After this dipping cycle, the workpiece 18 is rinsed and the maskin~
material 22 is removed with mineral spirits. The work surface 20 is then brushed with a brass brush to remove any loose residual me~al. After drying, the ~ork surface 20 is recoated with the asphaltum varnish masking material 22 and, after application o~ he template 14 to the work surface 20 and ~0 drying, the workpiece is etched for 1/2 hour.
These steps are repeated and the workpiece is etched ~or another 1/2 hour. The workpiece is again cleaned, recoated with the asphaltum varnish~
the template reapplied to remove portions of ~h~
asphaltum varnish. ~he masking material 22 is dried and the workpiece is etched ~or 15 minutes.
This process is repeated twice. Followin~ these etching cycl~s, the w~rkpîece is again cleaned to remove the asphaltu~l varnish coatîng material and, aE~e~ drying, is recoated wi~h the re-etching ink, Type l-B, produced by Sigma Photv-chemical Labora-tories, New Jersey. The template is once again pressed against the work surface to pick up the re-etching ink material contacted by the template and, aEt~r drying the re-etching ink, is then etched for 8 minutes. This process is then repeated with the etching time being reduced during succes-si~e etchin~ cycles, ~rom 8 minutes to 4 minutes to2 minutes, and finally, to a 1 minute etching cycle to produce a finished mold cavity, having a sur~ace configuration confor~ing exactly to that of the model and to the surface contour o~ the template as shown in Fig. 7.
While the process of the invention has been described in connection with shaping and finishing a cavity in a workpiece, it will be appreciateu by those skilled in the art that the process c--n also be employed to shape and finish the positive contour of products such as mold cores or any other work product colnmonly produced by machining.
To produce a mold core, wherein a sa~ple of the mold core is to be used as a model, a cast template havin~ a sur~ace contour which is a ne~ative image oE th`e surface conf;~uration of the sa~ple mold core may be made by casting a room temperature curing urethane against the sample mold core. The resultant casting will have a cavity therein with a 2S sur~ace contour which is a negat;ve i~age o~ the surface contour to be ~ormed in the workp;ece.
AEter curing, the cast negative image ;s separated ~rom the sample core~ The workpiece may then be mach;ned to give it a contour roughly approximatin~
that o~ the sample core. As in the process described above, the surface of the workpiece is then cleaned and co~ered with a suitable coating mateciai such '~
~ ~8~2$~
as asphalt~ Yarnish or re-etching ink. The template can then be forced against the workpiece to remove portions of -the n~asking ~aterial from the workpiece~
those portions being the surface portions of the work~
piece which contact the surface of the template. The workpiece can then be dipped in a suitable etching acid as described above, whereby portions of the metal of the workpiece which are no longer co~ered by coating material will be re~o~ed by the etching acid. This process is then repeated until the workpiece has a surface configuration identical to the complementary surface configuration of the template.
Turning now to Fig. 8, a means for maintaining alignment between a template 14a and a workpiece 18a is shown generally as a mechanized alignment jig 26. The template 14a is appxopriately secured to a platen 28 affixed to a column 30 which mo~es reciprocally as designed by arrow 32. The jig 26 includes a table 34 haYing a positi~e stop member or brackets 36 to securely fasten and align the workpiece 18a on the table 34 rela-ti~e to the platen 28 and template 14a~ The workpiece 18a is easily removed from the ~rackets 36 ~or the etching processes and is subsequently replaced in the same location and orientation on the table 34. Accord-ingly, the jig 26 insures that the sur~ace o~ thetemplata 14a will repea~edl~ CQ ntaCt the same correspon-ding surface o~ the workpiece 18a~
~ s generally shownl a track member 38 aligns the column 30 or reciprocally moving the -template 14a in a reproducable linear motion to repeatedly contact the workpiece 18a in the same location throughout the steps o~ remoYing maskant from the workpiece 18a. The jig 26 is proYided with a suitable limit swith ~not shown) to terminate the linear travel at the point of i~`
25~
desired contact and pressure between the template 14a and the workpiece 18a. From the description of the process steps earlier described in detail, the templa~e will be progressively mo~ed in accordance with the degree of etching or reproduction of the surface contours of ~he template into the workpiece surface.
Fig. 9 illustrates another e~bodiment,such a~
die set 40,for maintaining align~ent between template 14b and workpiece 18b. The die set 40 includes platens 42 and 44 ha~ing cooperating apera~ures 46 and shafts 48. Although not shown, it will be understood that die set 40 may be hand operated in a suitable alignment jig or any suitable linear press which will reproducably maintain the alignment between the template and workpiece throughout steps o~ pressing the template against the workpiece to selectively adhere and remove masking material from the workpiece, Oftentimes it will be pre-~erable to orient the die set 40 for horizontal linear movement to facilitate the cleaning of and the inspection of the template by the operator during the steps o selectively adhering maskant to the template.
~ he present invention is employed to reproduce the contours or surface textures of numero-ls mcdels haYing ~ery shallow or very pronounced heights and depths.
From the description s~t forth abo~e, models having a texturized or shallow s~rface contour, such as wood-grainl leakher, or okher similar sur~aces, are reprodllced by castin~ a template ha~ing the negative image; non-planar surface con~our of the model to be ~crmed in -the workpiece in the same manner as set ~orth above. The cast rub~er or xu~ber~like ~emplate will reproduce the tex-turize~ ox non planar image re~ardless of the height and depth of the mode~ contour~
Fig. 10 sho~s another e~bodiment of the inYen-tion and includes a template 50 which has been wrapped P~
~ ~8~
~ 20 -and secured around a cylinder 52. As shown generally, the template 50 assumes the configuration of the cylinder and is pro~ided with an alignment means 54 to maintain the orientation of the template 50 relative to a work-piece 56. The alignment means 54 includes an adjustabletable 58 and brackets 60 to secure the workpiece 56 in a fixed position. The table 58 is supported by and recip-rocally movable within a frame 61 by an appropriate means 62 for movement illustrated by arrow 64. A bracket member 66 supports the ~~oller 52 within adjustable track member 68 enabling adjustment of the rollex 52 towards and away from the workpiece 56~ Appropriate adjustable, positive stop me~bers 70 are provided on both sides of the track 68 to reproducably control the distance between the cylindrlcal template 50 and the workpiece 56. The tem-plate 50 i5 positioned to contact the workpiece 56, coated with the masXant material~ with the table 58 in a starting position. The starting position is set by a micro-ad3ustable stop m~mber 72. From the starting position~ the table is moved in a linear stroke causing the surface o the template 50 to xoll o~er the sur~ace o the workpiece 56. At the end of each stroke, the cylinder may be raised and the table returned and if desired, the surface of the template 50 may be cleaned.
The table 58 and workpiece 56 are returned to the position determined by ~stop 7~ and the cylinder 52 is lowered~ The template 50 is xeproducably rolled over the workpiece 56 fQr as many times as desired to re-move maskant as more ~ully described above~ The woxk-3Q piece 5~ is readily remoYed fxom the table 58 ~or etchingand retuxned to the same location within the bracket~s.
Other arrang~ments of the cylindrical template and means for reproducably maintaining align~ent between the template and workpiece ~ay be employed. One such embodiment~ not shown, would ~e to maintain the workpiece 1 ~025~
in a stationary position, for example on a magnetic table, and moYe the roller across the st~t.ionary surface of the workpiece~ To maintain reproducability of the path of contact between the sur~aces of the template and workpiece, it is critical that the starting point of contact between the template and the workpiece be accur-a~ely duplicated~ Accordingly, the surface of the template repetiti~ely contacts the surface of the work-piece at the same relative locations during the repetiti~e remo~al of maskant steps.
A cylindrical.template may be preferred for those applications xequiring the reproduction of non-planar~ shallow surface texturizing into à large ~ork-piece surface. The cylindrical template eliminates some of the difficulties of supporting and inspecting a linear template having a large suxface area.
~ arious eatures of the invention are set forth in the follo~in~ claims.
The workpiece is then dipped again in the acid bath to remove or etch away additional portions of the ~orkpiece material. The workpiece is then again rinsed and cleaned of metal residue and the S coating material. As in the previous steps, the work surface is again coated with a coating material after which some of the coating material is removed by repeated applications of the template against the work surface. Since even more of the high spots of the workpiece have been removed, the template will mate more completely with the wor~
surEace and will contact an even greater portion of the ~ork surface, thereby removing even more coating material. The remaining coating material is then sub~ected to a drying step and the etching step is then repeated.
The steps described above are repeated continually until the contour or surface configura-tion o the workpiece confcrms exactly to the ~0 surface coniguration of the template. This can be determined when the template is completely covered with masking material when pressed against ~he surface of the workpiece.
In one embodiment o~ the method of the invention, durin~ the ;nitial step of the processl the wor~piece ;s dipped ~or relatively long periods o~ time, ~oc examplet one-half to three hours~ in acid solutions having a relatively high ac;d concentration. The work surÇace~ after being subjected to a strong acid concentration for these ex~ended periods of time, will have a relatively ~ .
'~' ~ ~8~2~
rough surface texture. Accordingly, as the shapin~
and finishi~g of the work surface nears co~pletion, the workpiece is dipped in a ~ore dilute acid solution and/or for decreasing time periods to thereby produce an i~proved definition in the work product and a highly polished or finished surface texture.
EXAMPLE
As an example of the use oE the process of the ;nvention, the process may be used to produce a mold cavity in a mold member Erom a sample article of the type to be molded therein such as the street light lens 10 illustrated in Figs. 1 and 2, the street light lens 10 having a generally concave lower surface crosshatched with projecting ribs 11.
The workpiece 18 (Fig. 3) Eor use in ~orming the mold member is first machined to rough out a cavity 20 in the workpiece approximating the shape of the finished cavity. The peripheral portions o the workpiece and those portions which are to be protected from e~chin~, are covered with vinyl ta~e and shellac~ The mac'nined surace 20 o the wo~kpiece is covered with a masking ~aterial coating 22 comprising 5 parts benzene per 20 parts asphaltual varnish, the maskin~ materlal bein~
applied with a paint bru~h to orm a thîn, continu-ous coating on the wor~ sur~ace.
A cast template 14 having a surface 16 wi~h a contour which is a negative ima~e of the surface 2~
conf;guration to be p~oduced in the workpiece 18 is produced from the sample article 10 by f;rst makin~
a a)old of the sample article by casting Flexane*30 around the model article and then pe~itting it to S cuce. The model 10 is then removed fro~ the Flexane*30 mold, and after being coated by a release a~ent, the mold is filled with Flexane*94 to form a cast template 14. After the Flexane*94 cures, the template 14 is removed from the ~lexane*
30 mold. This template 14 is then cleaned and pressed against the coated surace 20 of the workp;ece 1~ such that projecting portions 12 of the workpiece will pick up selected portions o~ the asphaltum varnish ~ask;ng material 22 applied to the work surface 20 as shown in Figs. 3 and 4.
The template 14 is then cleaned and again pressed against the work surface 20 to remove additional masking material 22. After a second cleaning and a subsequ~nt pickup step, the coating material is subjected to a drying step. The workpiece 18 is then ready to be dipped in the etching acid.
During the first etching step the workpiece 18 is dipped or 1.5 hours in an aqueous solution of nitric acid as described a~ove and comprised oE ~
2S parts water to 1 par~ 42-BE nitr;c acid manufactured by the ~c~esson Che~lical Company. The workp;ece 1 is then removed from the acid bath and rinsed with water and then air dried. A~ter this etching step, additional asphaltum varnish is painted over the original ~asking material layer 22 as shown in Fig.
S. The template 14 îs again repeatedly applied against the work surface ~0 of the workpiece 18 to remove selected portions of the masking material 20 *trade mark ~;~
2~
as shown in Fig. 6. The masking mate~ial 22 is then dried and the workpiece 18 is again soaked in the etchant for 1.5 hours and then removed and rinsed with ~ater. The masking material 22 is then removed from the ~ork surface ~0 with mineral spirits and, after drying, another layer of masking material 22 is applied to the work surface 20. The template 14 is again pressed against the work surface to remove additional portions o~ the masking material ~2 and, after the maskin~ material 22 has been dried, the workpiece 18 is placed in the acid bath for 1 hour. After this dipping cycle, the workpiece 18 is rinsed and the maskin~
material 22 is removed with mineral spirits. The work surface 20 is then brushed with a brass brush to remove any loose residual me~al. After drying, the ~ork surface 20 is recoated with the asphaltum varnish masking material 22 and, after application o~ he template 14 to the work surface 20 and ~0 drying, the workpiece is etched for 1/2 hour.
These steps are repeated and the workpiece is etched ~or another 1/2 hour. The workpiece is again cleaned, recoated with the asphaltum varnish~
the template reapplied to remove portions of ~h~
asphaltum varnish. ~he masking material 22 is dried and the workpiece is etched ~or 15 minutes.
This process is repeated twice. Followin~ these etching cycl~s, the w~rkpîece is again cleaned to remove the asphaltu~l varnish coatîng material and, aE~e~ drying, is recoated wi~h the re-etching ink, Type l-B, produced by Sigma Photv-chemical Labora-tories, New Jersey. The template is once again pressed against the work surface to pick up the re-etching ink material contacted by the template and, aEt~r drying the re-etching ink, is then etched for 8 minutes. This process is then repeated with the etching time being reduced during succes-si~e etchin~ cycles, ~rom 8 minutes to 4 minutes to2 minutes, and finally, to a 1 minute etching cycle to produce a finished mold cavity, having a sur~ace configuration confor~ing exactly to that of the model and to the surface contour o~ the template as shown in Fig. 7.
While the process of the invention has been described in connection with shaping and finishing a cavity in a workpiece, it will be appreciateu by those skilled in the art that the process c--n also be employed to shape and finish the positive contour of products such as mold cores or any other work product colnmonly produced by machining.
To produce a mold core, wherein a sa~ple of the mold core is to be used as a model, a cast template havin~ a sur~ace contour which is a ne~ative image oE th`e surface conf;~uration of the sa~ple mold core may be made by casting a room temperature curing urethane against the sample mold core. The resultant casting will have a cavity therein with a 2S sur~ace contour which is a negat;ve i~age o~ the surface contour to be ~ormed in the workp;ece.
AEter curing, the cast negative image ;s separated ~rom the sample core~ The workpiece may then be mach;ned to give it a contour roughly approximatin~
that o~ the sample core. As in the process described above, the surface of the workpiece is then cleaned and co~ered with a suitable coating mateciai such '~
~ ~8~2$~
as asphalt~ Yarnish or re-etching ink. The template can then be forced against the workpiece to remove portions of -the n~asking ~aterial from the workpiece~
those portions being the surface portions of the work~
piece which contact the surface of the template. The workpiece can then be dipped in a suitable etching acid as described above, whereby portions of the metal of the workpiece which are no longer co~ered by coating material will be re~o~ed by the etching acid. This process is then repeated until the workpiece has a surface configuration identical to the complementary surface configuration of the template.
Turning now to Fig. 8, a means for maintaining alignment between a template 14a and a workpiece 18a is shown generally as a mechanized alignment jig 26. The template 14a is appxopriately secured to a platen 28 affixed to a column 30 which mo~es reciprocally as designed by arrow 32. The jig 26 includes a table 34 haYing a positi~e stop member or brackets 36 to securely fasten and align the workpiece 18a on the table 34 rela-ti~e to the platen 28 and template 14a~ The workpiece 18a is easily removed from the ~rackets 36 ~or the etching processes and is subsequently replaced in the same location and orientation on the table 34. Accord-ingly, the jig 26 insures that the sur~ace o~ thetemplata 14a will repea~edl~ CQ ntaCt the same correspon-ding surface o~ the workpiece 18a~
~ s generally shownl a track member 38 aligns the column 30 or reciprocally moving the -template 14a in a reproducable linear motion to repeatedly contact the workpiece 18a in the same location throughout the steps o~ remoYing maskant from the workpiece 18a. The jig 26 is proYided with a suitable limit swith ~not shown) to terminate the linear travel at the point of i~`
25~
desired contact and pressure between the template 14a and the workpiece 18a. From the description of the process steps earlier described in detail, the templa~e will be progressively mo~ed in accordance with the degree of etching or reproduction of the surface contours of ~he template into the workpiece surface.
Fig. 9 illustrates another e~bodiment,such a~
die set 40,for maintaining align~ent between template 14b and workpiece 18b. The die set 40 includes platens 42 and 44 ha~ing cooperating apera~ures 46 and shafts 48. Although not shown, it will be understood that die set 40 may be hand operated in a suitable alignment jig or any suitable linear press which will reproducably maintain the alignment between the template and workpiece throughout steps o~ pressing the template against the workpiece to selectively adhere and remove masking material from the workpiece, Oftentimes it will be pre-~erable to orient the die set 40 for horizontal linear movement to facilitate the cleaning of and the inspection of the template by the operator during the steps o selectively adhering maskant to the template.
~ he present invention is employed to reproduce the contours or surface textures of numero-ls mcdels haYing ~ery shallow or very pronounced heights and depths.
From the description s~t forth abo~e, models having a texturized or shallow s~rface contour, such as wood-grainl leakher, or okher similar sur~aces, are reprodllced by castin~ a template ha~ing the negative image; non-planar surface con~our of the model to be ~crmed in -the workpiece in the same manner as set ~orth above. The cast rub~er or xu~ber~like ~emplate will reproduce the tex-turize~ ox non planar image re~ardless of the height and depth of the mode~ contour~
Fig. 10 sho~s another e~bodiment of the inYen-tion and includes a template 50 which has been wrapped P~
~ ~8~
~ 20 -and secured around a cylinder 52. As shown generally, the template 50 assumes the configuration of the cylinder and is pro~ided with an alignment means 54 to maintain the orientation of the template 50 relative to a work-piece 56. The alignment means 54 includes an adjustabletable 58 and brackets 60 to secure the workpiece 56 in a fixed position. The table 58 is supported by and recip-rocally movable within a frame 61 by an appropriate means 62 for movement illustrated by arrow 64. A bracket member 66 supports the ~~oller 52 within adjustable track member 68 enabling adjustment of the rollex 52 towards and away from the workpiece 56~ Appropriate adjustable, positive stop me~bers 70 are provided on both sides of the track 68 to reproducably control the distance between the cylindrlcal template 50 and the workpiece 56. The tem-plate 50 i5 positioned to contact the workpiece 56, coated with the masXant material~ with the table 58 in a starting position. The starting position is set by a micro-ad3ustable stop m~mber 72. From the starting position~ the table is moved in a linear stroke causing the surface o the template 50 to xoll o~er the sur~ace o the workpiece 56. At the end of each stroke, the cylinder may be raised and the table returned and if desired, the surface of the template 50 may be cleaned.
The table 58 and workpiece 56 are returned to the position determined by ~stop 7~ and the cylinder 52 is lowered~ The template 50 is xeproducably rolled over the workpiece 56 fQr as many times as desired to re-move maskant as more ~ully described above~ The woxk-3Q piece 5~ is readily remoYed fxom the table 58 ~or etchingand retuxned to the same location within the bracket~s.
Other arrang~ments of the cylindrical template and means for reproducably maintaining align~ent between the template and workpiece ~ay be employed. One such embodiment~ not shown, would ~e to maintain the workpiece 1 ~025~
in a stationary position, for example on a magnetic table, and moYe the roller across the st~t.ionary surface of the workpiece~ To maintain reproducability of the path of contact between the sur~aces of the template and workpiece, it is critical that the starting point of contact between the template and the workpiece be accur-a~ely duplicated~ Accordingly, the surface of the template repetiti~ely contacts the surface of the work-piece at the same relative locations during the repetiti~e remo~al of maskant steps.
A cylindrical.template may be preferred for those applications xequiring the reproduction of non-planar~ shallow surface texturizing into à large ~ork-piece surface. The cylindrical template eliminates some of the difficulties of supporting and inspecting a linear template having a large suxface area.
~ arious eatures of the invention are set forth in the follo~in~ claims.
Claims (34)
1. A process for shaping a workpiece and for producing a workpiece surface contour complementary to the surface contour of a model desired to be reproduced, the process comprising the steps of:
a) providing a non-planar template which is a negative image of the workpiece surface contour to be reproduced;
b) applying a coating of an etchant re-sistant masking material to at least a portion of the surface of said workpiece, said masking material being adapted to protect said workpiece surface from the effects of etchant, c) pressing said template against said workpiece surface;
d) withdrawing said template from said work-piece surface to selectively adhere the masking material to the template and correspondingly selectively remove masking material from those portions of said workpiece surface contacted by said non-planar template surface;
e) applying etchant to said workpiece sur-face to etch portions of said workpiece surface not covered by said masking material; and f) repeating steps b) through e) until the surface contour of the workpiece conforms to the non-planar surface contour of the model.
a) providing a non-planar template which is a negative image of the workpiece surface contour to be reproduced;
b) applying a coating of an etchant re-sistant masking material to at least a portion of the surface of said workpiece, said masking material being adapted to protect said workpiece surface from the effects of etchant, c) pressing said template against said workpiece surface;
d) withdrawing said template from said work-piece surface to selectively adhere the masking material to the template and correspondingly selectively remove masking material from those portions of said workpiece surface contacted by said non-planar template surface;
e) applying etchant to said workpiece sur-face to etch portions of said workpiece surface not covered by said masking material; and f) repeating steps b) through e) until the surface contour of the workpiece conforms to the non-planar surface contour of the model.
2. A process as set forth in Claim 1 wherein following the step of withdrawing said template, the process further includes the steps of cleaning said template of said masking material, and repeat-ing said steps of pressing said template against said workpiece surface, withdrawing said template and cleaning said template of masking material until said template ceases to remove appreciable quantities of said masking material from said workpiece surface.
3. A process as set forth in Claim 2 wherein following said steps of applying etchant, said process further includes the steps of cleaning said workpiece surface to thereby remove said masking material and recoating said workpiece surface with said masking material.
4. A process as set forth in Claim 1 wherein said template is comprised of cast room temperature curing urethane.
5. A process as set forth in Claim 1 wherein said step of applying a masking material to said metal workpiece includes the application of a coating of re-etching ink to said workpiece surface.
6. A process as set forth in Claim 1 wherein said step of applying a masking material to said workpiece surface includes the application of asphaltum varnish to said workpiece surface.
7. A process as set forth in Claim 1 wherein said workpiece includes a preformed cavity therein, said cavity having an internal surface, and wherein said coating material is applied to said preformed cavity surface.
8. A process as set forth in Claim 1 and further including the step of covering portions of said workpiece to be protected from attack by acid with a protective covering of shellac.
9. A process as set forth in Claim 1 wherein said step of applying etchant to said workpiece surface includes dipping said workpiece in an aqueous acid solution.
10. A process as set forth in Claim 1 wherein after withdrawing of said template from said workpiece surface and before said step of applying acid to said workpiece surface, the process further includes the step of cleaning said template to remove coating material therefrom and placing said template against said workpiece surface to remove additional amounts of said coating material from said workpiece surface.
11. A process as set forth in Claim 1 wherein, following said steps or applying etchant, said process further includes the steps of cleaning said workpiece surface to thereby remove masking material and recoating said surface with masking material.
12. A process as set forth in Claim 1 wherein said model has a surface contour which is a positive image of the surface contour to be produced in said workpiece and further including the step of casting a hardenable material against the surface of said model to form said template.
13. A process as set forth in Claim 1 wherein following the step of withdrawing said template, the process further includes the steps of cleaning said template of said masking material, and repeat-ing said steps of pressing said template against said workpiece surface, withdrawing said template and cleaning said template of masking material until said template ceases to remove appreciable quantities of said masking material from said workpiece surface.
14. A process as set forth in Claim 13 wherein, following said steps of applying etchant, said process further includes the steps of cleaning said surface to thereby remove said masking material and recoating said surface with said masking material.
15. A process as set forth in Claim 12 wherein said template is comprised of cast room temperature curing urethane.
16. A process as set forth in Claim 12 wherein said step of applying a masking material to said workpiece includes the application of a coating of re etching ink to said workpiece surface.
17. A process as set forth in Claim 12 wherein said step of applying a masking material to said workpiece surface includes the application of asphaltum varnish to said workpiece surface.
18. A process as set forth in Claim 12 wherein said workpiece includes a preformed cavity therein, said cavity having an internal surface, and wherein said coating material is applied to said preformed cavity surface.
19. A process as set forth in Claim 12 and further including the step of covering portions of said workpiece to be protected from attack by acid with a protective covering of shellac.
20. A process as set forth in Claim 12 wherein said step of applying etchant to said workpiece surface includes dipping said workpiece in an aqueous acid solution.
21. A process as set forth in Claim 12 wherein, following said steps of applying etchant, said process further includes the steps of cleaning said workpiece surface to thereby remove masking material and recoating said workpiece surface with masking material.
22. A process as set forth in Claim 1 wherein said model has a surface contour which is a negative image of the surface contour to be produced in said workpiece and further including the steps of casting a hardenable material against the surface contour of said model to form a mold, casting a hardenable material in said mold to form said template, and separating said template from said mold.
23. A process as set forth in Claim 22 wherein following the step of withdrawing said template, the process further includes the steps of cleaning said template of said masking material, and repeat-ing said steps of pressing said template against said workpiece surface, withdrawing said template and cleaning said template of masking material until said template ceases to remove appreciable quantities of said masking material from said workpiece surface.
24. A process as set forth in Claim 22 wherein, following said steps of applying etchant, said process further includes the steps of cleaning said workpiece surface to thereby remove said masking material and recoating said workpiece surface with said masking material.
25. A process as set forth in Claim 22 wherein said templates is comprised of cast room temperature curing urethane.
26. A process as set forth in Claim 22 wherein said step of applying a masking material to said metal workpiece includes the application of a coating of re-etching ink to said workpiece surface.
27. A process as set forth in Claim 22 wherein said step of applying a masking material to said workpiece surface includes the application of asphaltum varnish to said workpiece surface.
28. A process as set forth in Claim 22 wherein said workpiece includes a preformed cavity therein, said cavity having an internal surface, and wherein said coating material is applied to said preformed cavity surface.
29. A process as set forth in Claim 22 and further including the step of covering portions of said workpiece to be protected from attack by acid with a protective covering of shellac.
30. A process as set forth in Claim 22 wherein said step of applying etchant to said workpiece surface includes dipping said workpiece in an aqueous acid solution.
31. A process as set forth in Claim 22 wherein, following said steps of applying etchant, said process further includes the steps of cleaning said workpiece surface to thereby remove masking material and re-coating said workpiece surface with masking material.
32. A process as set forth in Claim 1 further including the step of maintaining the template in alignment with the workpiece.
33. A process as set forth in Claim 32 wherein said step of maintaining alignment includes orienting the template to the workpiece to thereby linearly and repeatedly contact the same portions of the template and the workpiece surface during the pressing and with-drawing steps.
34. A process as set forth in Claim 32 wherein said pressing and withdrawing steps include rolling the template across the workpiece surface.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000400524A CA1180258A (en) | 1982-04-06 | 1982-04-06 | Method for shaping and finishing a workpiece |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000400524A CA1180258A (en) | 1982-04-06 | 1982-04-06 | Method for shaping and finishing a workpiece |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1180258A true CA1180258A (en) | 1985-01-02 |
Family
ID=4122520
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000400524A Expired CA1180258A (en) | 1982-04-06 | 1982-04-06 | Method for shaping and finishing a workpiece |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1180258A (en) |
-
1982
- 1982-04-06 CA CA000400524A patent/CA1180258A/en not_active Expired
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