CA2051565A1 - Maintaining press platens in parallel relationship - Google Patents
Maintaining press platens in parallel relationshipInfo
- Publication number
- CA2051565A1 CA2051565A1 CA 2051565 CA2051565A CA2051565A1 CA 2051565 A1 CA2051565 A1 CA 2051565A1 CA 2051565 CA2051565 CA 2051565 CA 2051565 A CA2051565 A CA 2051565A CA 2051565 A1 CA2051565 A1 CA 2051565A1
- Authority
- CA
- Canada
- Prior art keywords
- platens
- platen
- leveling
- leveling cylinders
- spacing
- 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.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B30—PRESSES
- B30B—PRESSES IN GENERAL
- B30B15/00—Details of, or accessories for, presses; Auxiliary measures in connection with pressing
- B30B15/007—Means for maintaining the press table, the press platen or the press ram against tilting or deflection
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B30—PRESSES
- B30B—PRESSES IN GENERAL
- B30B15/00—Details of, or accessories for, presses; Auxiliary measures in connection with pressing
- B30B15/16—Control arrangements for fluid-driven presses
- B30B15/24—Control arrangements for fluid-driven presses controlling the movement of a plurality of actuating members to maintain parallel movement of the platen or press beam
- B30B15/245—Control arrangements for fluid-driven presses controlling the movement of a plurality of actuating members to maintain parallel movement of the platen or press beam using auxiliary cylinder and piston means as actuating members
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Casting Or Compression Moulding Of Plastics Or The Like (AREA)
- Moulds For Moulding Plastics Or The Like (AREA)
- Control Of Presses (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Press platens are maintained parallel in critical central regions proximate to a mold between the platens. Leveling cylinders acting between the platens to resist downward action of a central ram on a movable platen. Data identifying expected local platen deflection in response to various operating pressures of the leveling cylinders are recorded. For each leveling cylinder, the current operating pressure is determined and the relative spacing of the platens proximate to the leveling cylinder is sensed. The operating pressures of the cylinders are controlled in response to the sensed relative spacing of the platens and in response to the expected local platen deflection for each leveling cylinder at its current operating pressure to maintain a substantially parallel relationship between the platens proximate to the mold. The platen deflection data required for each leveling cylinder are obtained in a preliminary process involving operation of the platens to compress the mold, operating the leveling cylinders at their various operating pressures, and sensing and recording local platen deflection that results.
Press platens are maintained parallel in critical central regions proximate to a mold between the platens. Leveling cylinders acting between the platens to resist downward action of a central ram on a movable platen. Data identifying expected local platen deflection in response to various operating pressures of the leveling cylinders are recorded. For each leveling cylinder, the current operating pressure is determined and the relative spacing of the platens proximate to the leveling cylinder is sensed. The operating pressures of the cylinders are controlled in response to the sensed relative spacing of the platens and in response to the expected local platen deflection for each leveling cylinder at its current operating pressure to maintain a substantially parallel relationship between the platens proximate to the mold. The platen deflection data required for each leveling cylinder are obtained in a preliminary process involving operation of the platens to compress the mold, operating the leveling cylinders at their various operating pressures, and sensing and recording local platen deflection that results.
Description
2~
MAIN-rAINING PRESS PLATENS IN PARALLEL RELATIONSHrP
FIELD OF THE INVENl'ION
The invention relates generally to presses, and more particularly, to maintaining press platens in parallel relationship during compression of a 5 workp;ece.
BACKGR(:)IJN~ OF ~IE INVENIION
Hydraulic presses are now used extensively for compression rnolding of large and comparatively thin plastic products. Mold halves are fixedto upper and lower platens. The upper platen may typically be displaced under 10 very substantial driving forces to compress a molding charge. Very strict control of platen parallelism is required to produce a satisfactory product. Theplanar platen surfaces that actually engage the molds may be required to deviatefrom a parallel relationship by no more than .001-.005 inches per foot. A basic understanding of press parallelism control rnay be obtained by reference to U.S.l~ patent No. 4,076,780 which issued on February 28, 1978 to Ditto.
Many old hydraulic presses have a stationary lower platen and a movable upper platen that is displaced by a large overhead hydraulic ram. The guiding structures used to direct movement of the upper platen are generally inadequate to maintain the strict platen parallelism required for contemporary ~0 compression molding. To adapt such presses for such strict parallelism control, hydraulic leveling cylinders may typically be mounted at each corner on the lower platen. These act against the upper platen and apply forces countervailingthe action to the central rarn. Alternatively, the leveling cylinders may be ~Ixed to the upper platen and engageable with the lower platen. Each leveling cylindermay be associated with a platen spacing sensor that indicates the relative spacing of the platens proximate to the leveling cylinder. Such sensors may comprise, for example, a magnetic track that displaces with the upper platen and a ~ 3 ~ 3' ~
complementaTy sensor head that is fixed to the stationary lower platen. In an aIrangement described in U.S. patent No. 4,828,474 to Ballantyne, the platen spacing sensors are actually built into the leveling cylinders. A microprocessorwill typically control the leveling cylinders in response to the spacing signals to maintain a common spacing between the platens adjacent to each cylinder and, assuming limited overall deformation of the platens, a parallel relationship. The common spacing value is changed as the press proceeds through preliminary compression and curing phases of operation.
A very significant problern in such prior presses appears to have 10 gone unnoticed. The inventor has initiated finite element analysis to assess overall platen deformation in typical platens during c.ompression phases of operation. Such analysis has revealed very significant local relative de-flection of the platens in response to operation of the leveling cylinders themselves. The amount of such deflection can approach the alignment tolerances that must be 1~ maintained in parallelism control and varies with the force exerted by each cylinder. Since the spacing sensors identify such local relative deflection as part of the spacing between the platens, the spacing signals produced by the sensors do not reflect the actual alignment of the platens in the critical regions proxima~e to the mold. Instead of maintaining parallelism in such critical regions, the ~0 control system may actually induce a significantly non-parallel relationship at the mold itself. Such a problem may arise in more contemporary presses, depending on their exact configuration. The present invention addresses this problem.
BRI~F SUMMARY OP THE INVENT10~
2~ In one aspect, the invention provides a method of maintairling platen parallelism while a molding charge is being compressed. The method is applicable to a press comprising a pair of platens, a mold located substantiallycentrally between the platens, means for applying a driving force to one of the ,2 ~ 3 platens ~o displace it towards the other platen thereby to compress a molding charge within the mold, and a plurality of leveling cylinders spaced from ~e mold and acting between the platens to apply forces that vary with the operatingpressures of the cylinders to countervail the driving force. The method involves5 providing data identifying for each leveling cylinder the local relative deflection of the platens expected in response to operation of the leveling cylinder at various operating pressures (while the molding charge is being compressed).
The current operating pressure of each leveling cylinder is deterrnined. For each leveling cylinder, the relative spacing of the platens proximate to the 10 leveling cylinder is sensed. The operating pressures of the leveling cylinders ar~ controlled in response to the relative spacing of the platens as indicated for each leveling cylinder and in response to the data identifying the expected local relative platen deflection for each leveling cylinder at its current operating pressure, to maintain a substantially parallel relationship between the platens 15 proximate to the mold. For purposes of this specification, "local relative deflection of the platens" for a leveling cylinder should be understood as the relative deflection of the platens away from one another proximate to the leveling cylinder. Such deflec~ion affects readings of the sensors proximate to the leveling cylinders, whether physically separate from or incorporated into the 20 leveling cylinders.
The data indicating expected relative deflection can be estimated for a particular platen with a typical mold or equivalent workpiece. Such estimates can be obtained by finite element analysis, but this is comparatively costly. Ille data may be stored on disk or other non-volatile memory, or an electronic means may be provided to generate the data. The data are preferably obtained through a preliminary process (prior to actual production runs) which involves positioning a workpiece centrally between the molds, and applying the driving force compress the worlq)iece between the platens. While the `
workpiece is being compressed, each leveling cylinder is operated at various operating pressures, the local relative deflection of the platens proximate to the leveling cylinder is sensed, and the sensed local relative deflection at the various operating pressures is recorded. This process may be used each time a mold is 5 changed, using the new mold, preferably but not essentially with a sacrificialmolding charge, as the worlcpiece, to condition press controls for subsequent molding operations. This process can also be repeated after each shut down of the press to recalibrate deflection data.
The invention also provides a press appropriately adapted to 10 implement the above method of platen parallelism control and apparatus for retrofitting a pre-existing press for stricter platen parallelism con~rol. Various aspects of the invention will be apparent from a description below of a preferred embodiment and will be more specifically defined in the appended claims.
DESCRlPTION ~)~ THE DR~WINGS
The invention will be better understood with reference to drawings in which:
fig. 1 is a fragment elevational view of a press embodying control features of the invention;
fig. 2 diagrammatically illustrates local platen deflection ~0 proximate to two leveling cylinders of the press; and fig. 3 diagrammatically illustrates a control system adapted to accomlrlodate such local platen deflection; and, flg. 4 diagrammatically illustrates stored data identifying expected local relative platen deflection for a particular leveling cylinder as a 25 function of the operating pressure of the cylinder.
DE3~RlErrl0N OF PREFERRED EMBQDIMENT
Fig. 1 illustrates a press 10 adapted for compression molding.
'J 3J ~
The press 10 includes upper and lower platens 12, 14 respectively carrying upper and lower bolster plates 16, 18. Upper and lower halves 20, 22 of a mold 24 are fixed in a conventional manner to the platens 12) 14. A molding charge 26 has been diagramrnatically indicated in phantom outlin~ within the 5 lower mold half 22. A large central ram 28 suspended from a cross-head permits substantial driving forces (typically up to 2000 tons) to be applied to the upper platen 12 to displace it towards the lower platen 14 to compress the molding charge 26.
Four leveling cylinders are fixed to the lower platen 14 in a conventional rectangular spacing arrangement with one at each corner of the lower platen 14. Only two forward leveling cylinders 32, 34 are illustrated, and these are identified herein as the "left" and "right" l~veling cylinders, respectively. The leveling cylinders are spaced outwardly from the mold ~4 and the central regions of the platens 12, 14 to facilitate access to the mold 24. The leveling cylinders act between the platens 12, 14 and apply upward forces to theupper movable platen to countenail the driving force of the central ram 28.
Each leveling cylinder has an internal spacing sensor, such as the spacing sensor 36 associated with the left leveling cylinder 32, which detects relative spacing of the platens 12, 14 proximate to the cylinder. Details of constructionof such spacing sensors will be apparent from U.S. patent No. 4,828,474 to Ballantyne, whose teachings are incorporated herein by reference. Details of the general construction and overall operation of such a press 10 will be apparent to those skilled in the art.
The problem associated with the prior art will be described with ~5 reference to fig. 2. Fig. 2 shows the local relative deflection of the upper and lower platens 12, 14 proximate to the two leveling cylinders, grossly exaggerated. It should be understood that such deflection is expected to be in the order of several thousands of an inch, which is nevertheless critical to parallelism control. It is assumed that the relative spacing proximate to the molds is actually at a value S wbich is substantially uniform about the mold 24 tallowing for acceptable tolerances). It is also assumed that the relative platen spacing proximate to the left cylinder 32 has a value L that is significantly greater than the value S (owing to a local relative deflection of the upper and lower platens 12, 14) and that the relative platen spac;ng proxirnate to ~he right leveling cylinder 34 is at a slightly smaller value R, still in excess of the value S. In the control system of the present invention, such a spacing arrangement would be maintained (as explained more fully below), which is desirable since 10 the platens 12, 14 are in fact substantially parallel in their critical central regions, proximate to the mold 24.
In tlle prior art, however, the controls would identify that the two corners of the platen are not spaced appropriately for a parallel relationship.
The controls would actuate the leveling cylinders to attempt to produce common 15 spacing at the corners. If, for example, the right leveling cylinder 34 were treated as a master reference cylinder, as in one prior art fonn of leveling control, then the operating pressure of the left cylinder 32 rnight be reduced with the object of reducing the relative platen spacing L to the value R. If theaverage platen spacing as sensed proximate to the four leveling cylinders serves20 as a reference value, as in another prior art form o~ leveling control, then the operating pressure of both cylinders might be adjusted, to equalize the spac;ng values L and R at some intermediate value (assuming that the other pair of cylind~rs are associated w;th comparable spacing values). In either case, the substantially parallel relationship of the platens 12, 14 proximate to the mold 24 is disturbed.
Fig. 3 diagrammatically illustrates the control system that regulates the leveling cylinders. Only components necessary for regula~on of the left leveling cylinder 32 have been shown. The other leveling cylinders are ~ 3 ~
regulated in a similar manner.
A controller 38 processes spacing and pressure signals and regulates operation of the leveling cylind~r 32. The operating pressure of the leveling cylinder 32 is ~mmediately controlled by a servovalve 40. A pressure 5 sensor 42 produces a signal indicating the current operating pressure of the leveling cylinder 32. The spacing sensor 3~ contained within the leveling cylinder 32 produces a signal indicating the relative platen spacing proximate to the cylinder 3? (the value L indicated in fig. 2). Both sensor signals are received by an adjustment block 44 of the controller 38.
The adjustment block 44 retrieves from a storage block 46 the data identifying the expected local relative platen deflection for the leveling cylinder 32 at its current operating pressure and for the particular operating conditions of the press lO (primary the particular mold 24 and to a lesser extent the driving force). This data has been graphically represented in ~lg. 4 as a lS curve indicating the relationship expected between such deflection D (indicated on a vertical axis) as a function of var~ous operating pressures P (indicated on a horizontal axis). In this embodiment of the invention, the adjustment block 44 reduces the sensed spacer value L for the left cylinder 32 in accordance with the retrieved data identifying the expected local deflection, essentially sub~acting20 the value of the expected deflection from the sensed spacing value S. The resulting adjusted spacing value confolms more closely to the actual platen spacing D proximate to the mold 24 (once again allowing for tolerable measure of platen deflection in the order of .001-.002 inches per foot). In a similar mansler, the adjusting block adjusts the sensed spacing value R associated with 25 the right leveling cylinder 34 to conform more closely to the actual spacing bet veen the molds and adjust those of the other leveling cylinders.
A cylinder control block 48 then actuates the servovalve 40 2 {3 ~ ~ 3 ~ ~
associaeed with the left cylinder 32 (and similar valves associated with the other leveling cylinders) ~o maintain all adjusted spacing signals at a common value.
This causes the platen to remain substantially parallel in the vicini~ of the mold 24, essentially preserving the spacing D observed in ~ig. ~, for example. This arrangement effectively ignores peripheral deformation of the platens 12, 14, which is inconsequential to proper molding of the charge 26. It will be understood of course that the controller 38 oth~rwise implements, in a conventional manner, required velocity and pressure profiles appropriate for initial compression and ultimat~ curing of the charge 26. Such additional 10 matters are well known, and will not be described.
Although the controller 38 is illustrated as distinct blocks and might be constructed of elec~onic components, the prefel~ed implementat;on involves a microprocessor. The adjustment and control ~unctions may be implemented as appropriate algorithms, stored on disk or otherwise, and 1~ executed by the microprocessor. The storage block 46 may be a conventional disk drive from which the expected relative deflection values for each leveling cylinder at its various operating pressures may be retrieved, ~or appropriate reduction of sensed spacing values. Alternatively, the stored data may be in theform of scaling factors (gain/attenuation) which are used to scale the sensed ~0 spacing value proximate to each leveling cylinder prior to regulation of the operating pressure of the cylinder. In either case, the data may be stored effectively as parameters of an equation specifying either the spacing reduc~ionor scaling factors, rather than discrete items of deflection and pressure data.
Rather than adjusting the sensed spacing value, the data indicating expected '~ local relative platen deflection can be used to adjust reference signals (~orexample, a required spacing value for each leveling cylinder derived from a master leveling cylinder or an average spacing value calculated for all levelingcylinders) to achieve the same result. It will be appreciated that platen r parallelism proximate to the mold ~4 may be regulated in a variety o~ ways relying on the current operating pressure of a leveling cylinder, sensed platen spacing, and data indicating expected local platen deflection.
The deflec~on data required for each cylinder can be obtained in :~ several ways. Finite element analysis or other estimating techniques can be used to model the platen and its expected response to operation of the leveling cylinders under various operating pressures. The same data may be used for all leveling cylinders, if appropriate syrnmetry can b assumed. It should be noted that the benefits of the invention can be obtained even if no exact compensationlO occurs.
A preferred method of generating the required data involves deriving it from actual operation of the press 10 on an exemplary workpiece in advance of actual production molding~ The workpiece is preferably the particular mold 24 to be used and preferably containing a sacrificial molding 15 charge~ The workpiece may be positioned cen~ally between the upper and lower platens 12, 14. The ram 28 is then used to apply the driving force to the upper platen 12 to compress the workpiece~ While the workpiece is being compressed, each leveling cylinder may be operated (separately or simultaneously) at various operating pressures~ The sensors associated with the 2n leveling c.ylinders are used to sense the local relative deflection of the platens 12, 14 proximate to each leveling cylinder, essentially as changes from a particular platen spacing value that serves as a datum~ These sets of values arerecorded in the storage block 46 as they are generated~ For each leveling cylinder, the datum may be the platen spac;ng at any appropriate operating pressllre, for example, a minimal pressure necessary to maintain contact with the upper platen, a pressure midway in the cylinder's operating range or the cylinder's maximum operating pressure. If the datum is the spacing for a non-zero operating p~essure, the differential changes in spacing values recorded for J ;~_ a full range of operating pressures can be related to actual expected deflections at the various operating pressures by simply adding a common increment to each recorded differential spacing value. l hat increment is essentially the value required to reduce to zero the sensed differential change in spacing at a zero or 5 near-zero operating pressure. It is preferred that this initial data-producingprocess be followed each time a new mold 24 is to be introduced between the platens 12, 14, using the particular mold 24. This provides more exact estimates of expected platen deflection for purposes of subsequent product production.
A preliminary calibration process is normal in the operation of such presses. Mold stops or a molding charge will be placed in the mold fixed to the p~ess platens, and the rarn operated to compress the mold. The spacing sensors are then effectively calibrated, establishing reference values for subsequent platen parallelism control. This is done whenever the press is 15 shut-down and re-started. Such matters are well known to those skilled in the art and will not be described in detail.
The preliminary data-producing process associated with the present invention is preferably fully automated and incorporated into the preliminary calibration process otherwise reguired for operation of the press.
20 The control system is of course coupled to the leveling cylinders through thesenovalves to control their operation, to the pressure sensors to receive operating pressures of the cylinders, to the spacing sensors to receive local platen spacing proximate to each leveling cylinder, and to the storage means both to read and write data. The controller 38 may additionally be coupled to 25 the ram 28 to actuate compression of the workpiece. In a data-recording mode of operation, the controller 38 operates the rarn 28 to compress the mold 24, steps each of the leveling cylinders through its various operating pressures by
MAIN-rAINING PRESS PLATENS IN PARALLEL RELATIONSHrP
FIELD OF THE INVENl'ION
The invention relates generally to presses, and more particularly, to maintaining press platens in parallel relationship during compression of a 5 workp;ece.
BACKGR(:)IJN~ OF ~IE INVENIION
Hydraulic presses are now used extensively for compression rnolding of large and comparatively thin plastic products. Mold halves are fixedto upper and lower platens. The upper platen may typically be displaced under 10 very substantial driving forces to compress a molding charge. Very strict control of platen parallelism is required to produce a satisfactory product. Theplanar platen surfaces that actually engage the molds may be required to deviatefrom a parallel relationship by no more than .001-.005 inches per foot. A basic understanding of press parallelism control rnay be obtained by reference to U.S.l~ patent No. 4,076,780 which issued on February 28, 1978 to Ditto.
Many old hydraulic presses have a stationary lower platen and a movable upper platen that is displaced by a large overhead hydraulic ram. The guiding structures used to direct movement of the upper platen are generally inadequate to maintain the strict platen parallelism required for contemporary ~0 compression molding. To adapt such presses for such strict parallelism control, hydraulic leveling cylinders may typically be mounted at each corner on the lower platen. These act against the upper platen and apply forces countervailingthe action to the central rarn. Alternatively, the leveling cylinders may be ~Ixed to the upper platen and engageable with the lower platen. Each leveling cylindermay be associated with a platen spacing sensor that indicates the relative spacing of the platens proximate to the leveling cylinder. Such sensors may comprise, for example, a magnetic track that displaces with the upper platen and a ~ 3 ~ 3' ~
complementaTy sensor head that is fixed to the stationary lower platen. In an aIrangement described in U.S. patent No. 4,828,474 to Ballantyne, the platen spacing sensors are actually built into the leveling cylinders. A microprocessorwill typically control the leveling cylinders in response to the spacing signals to maintain a common spacing between the platens adjacent to each cylinder and, assuming limited overall deformation of the platens, a parallel relationship. The common spacing value is changed as the press proceeds through preliminary compression and curing phases of operation.
A very significant problern in such prior presses appears to have 10 gone unnoticed. The inventor has initiated finite element analysis to assess overall platen deformation in typical platens during c.ompression phases of operation. Such analysis has revealed very significant local relative de-flection of the platens in response to operation of the leveling cylinders themselves. The amount of such deflection can approach the alignment tolerances that must be 1~ maintained in parallelism control and varies with the force exerted by each cylinder. Since the spacing sensors identify such local relative deflection as part of the spacing between the platens, the spacing signals produced by the sensors do not reflect the actual alignment of the platens in the critical regions proxima~e to the mold. Instead of maintaining parallelism in such critical regions, the ~0 control system may actually induce a significantly non-parallel relationship at the mold itself. Such a problem may arise in more contemporary presses, depending on their exact configuration. The present invention addresses this problem.
BRI~F SUMMARY OP THE INVENT10~
2~ In one aspect, the invention provides a method of maintairling platen parallelism while a molding charge is being compressed. The method is applicable to a press comprising a pair of platens, a mold located substantiallycentrally between the platens, means for applying a driving force to one of the ,2 ~ 3 platens ~o displace it towards the other platen thereby to compress a molding charge within the mold, and a plurality of leveling cylinders spaced from ~e mold and acting between the platens to apply forces that vary with the operatingpressures of the cylinders to countervail the driving force. The method involves5 providing data identifying for each leveling cylinder the local relative deflection of the platens expected in response to operation of the leveling cylinder at various operating pressures (while the molding charge is being compressed).
The current operating pressure of each leveling cylinder is deterrnined. For each leveling cylinder, the relative spacing of the platens proximate to the 10 leveling cylinder is sensed. The operating pressures of the leveling cylinders ar~ controlled in response to the relative spacing of the platens as indicated for each leveling cylinder and in response to the data identifying the expected local relative platen deflection for each leveling cylinder at its current operating pressure, to maintain a substantially parallel relationship between the platens 15 proximate to the mold. For purposes of this specification, "local relative deflection of the platens" for a leveling cylinder should be understood as the relative deflection of the platens away from one another proximate to the leveling cylinder. Such deflec~ion affects readings of the sensors proximate to the leveling cylinders, whether physically separate from or incorporated into the 20 leveling cylinders.
The data indicating expected relative deflection can be estimated for a particular platen with a typical mold or equivalent workpiece. Such estimates can be obtained by finite element analysis, but this is comparatively costly. Ille data may be stored on disk or other non-volatile memory, or an electronic means may be provided to generate the data. The data are preferably obtained through a preliminary process (prior to actual production runs) which involves positioning a workpiece centrally between the molds, and applying the driving force compress the worlq)iece between the platens. While the `
workpiece is being compressed, each leveling cylinder is operated at various operating pressures, the local relative deflection of the platens proximate to the leveling cylinder is sensed, and the sensed local relative deflection at the various operating pressures is recorded. This process may be used each time a mold is 5 changed, using the new mold, preferably but not essentially with a sacrificialmolding charge, as the worlcpiece, to condition press controls for subsequent molding operations. This process can also be repeated after each shut down of the press to recalibrate deflection data.
The invention also provides a press appropriately adapted to 10 implement the above method of platen parallelism control and apparatus for retrofitting a pre-existing press for stricter platen parallelism con~rol. Various aspects of the invention will be apparent from a description below of a preferred embodiment and will be more specifically defined in the appended claims.
DESCRlPTION ~)~ THE DR~WINGS
The invention will be better understood with reference to drawings in which:
fig. 1 is a fragment elevational view of a press embodying control features of the invention;
fig. 2 diagrammatically illustrates local platen deflection ~0 proximate to two leveling cylinders of the press; and fig. 3 diagrammatically illustrates a control system adapted to accomlrlodate such local platen deflection; and, flg. 4 diagrammatically illustrates stored data identifying expected local relative platen deflection for a particular leveling cylinder as a 25 function of the operating pressure of the cylinder.
DE3~RlErrl0N OF PREFERRED EMBQDIMENT
Fig. 1 illustrates a press 10 adapted for compression molding.
'J 3J ~
The press 10 includes upper and lower platens 12, 14 respectively carrying upper and lower bolster plates 16, 18. Upper and lower halves 20, 22 of a mold 24 are fixed in a conventional manner to the platens 12) 14. A molding charge 26 has been diagramrnatically indicated in phantom outlin~ within the 5 lower mold half 22. A large central ram 28 suspended from a cross-head permits substantial driving forces (typically up to 2000 tons) to be applied to the upper platen 12 to displace it towards the lower platen 14 to compress the molding charge 26.
Four leveling cylinders are fixed to the lower platen 14 in a conventional rectangular spacing arrangement with one at each corner of the lower platen 14. Only two forward leveling cylinders 32, 34 are illustrated, and these are identified herein as the "left" and "right" l~veling cylinders, respectively. The leveling cylinders are spaced outwardly from the mold ~4 and the central regions of the platens 12, 14 to facilitate access to the mold 24. The leveling cylinders act between the platens 12, 14 and apply upward forces to theupper movable platen to countenail the driving force of the central ram 28.
Each leveling cylinder has an internal spacing sensor, such as the spacing sensor 36 associated with the left leveling cylinder 32, which detects relative spacing of the platens 12, 14 proximate to the cylinder. Details of constructionof such spacing sensors will be apparent from U.S. patent No. 4,828,474 to Ballantyne, whose teachings are incorporated herein by reference. Details of the general construction and overall operation of such a press 10 will be apparent to those skilled in the art.
The problem associated with the prior art will be described with ~5 reference to fig. 2. Fig. 2 shows the local relative deflection of the upper and lower platens 12, 14 proximate to the two leveling cylinders, grossly exaggerated. It should be understood that such deflection is expected to be in the order of several thousands of an inch, which is nevertheless critical to parallelism control. It is assumed that the relative spacing proximate to the molds is actually at a value S wbich is substantially uniform about the mold 24 tallowing for acceptable tolerances). It is also assumed that the relative platen spacing proximate to the left cylinder 32 has a value L that is significantly greater than the value S (owing to a local relative deflection of the upper and lower platens 12, 14) and that the relative platen spac;ng proxirnate to ~he right leveling cylinder 34 is at a slightly smaller value R, still in excess of the value S. In the control system of the present invention, such a spacing arrangement would be maintained (as explained more fully below), which is desirable since 10 the platens 12, 14 are in fact substantially parallel in their critical central regions, proximate to the mold 24.
In tlle prior art, however, the controls would identify that the two corners of the platen are not spaced appropriately for a parallel relationship.
The controls would actuate the leveling cylinders to attempt to produce common 15 spacing at the corners. If, for example, the right leveling cylinder 34 were treated as a master reference cylinder, as in one prior art fonn of leveling control, then the operating pressure of the left cylinder 32 rnight be reduced with the object of reducing the relative platen spacing L to the value R. If theaverage platen spacing as sensed proximate to the four leveling cylinders serves20 as a reference value, as in another prior art form o~ leveling control, then the operating pressure of both cylinders might be adjusted, to equalize the spac;ng values L and R at some intermediate value (assuming that the other pair of cylind~rs are associated w;th comparable spacing values). In either case, the substantially parallel relationship of the platens 12, 14 proximate to the mold 24 is disturbed.
Fig. 3 diagrammatically illustrates the control system that regulates the leveling cylinders. Only components necessary for regula~on of the left leveling cylinder 32 have been shown. The other leveling cylinders are ~ 3 ~
regulated in a similar manner.
A controller 38 processes spacing and pressure signals and regulates operation of the leveling cylind~r 32. The operating pressure of the leveling cylinder 32 is ~mmediately controlled by a servovalve 40. A pressure 5 sensor 42 produces a signal indicating the current operating pressure of the leveling cylinder 32. The spacing sensor 3~ contained within the leveling cylinder 32 produces a signal indicating the relative platen spacing proximate to the cylinder 3? (the value L indicated in fig. 2). Both sensor signals are received by an adjustment block 44 of the controller 38.
The adjustment block 44 retrieves from a storage block 46 the data identifying the expected local relative platen deflection for the leveling cylinder 32 at its current operating pressure and for the particular operating conditions of the press lO (primary the particular mold 24 and to a lesser extent the driving force). This data has been graphically represented in ~lg. 4 as a lS curve indicating the relationship expected between such deflection D (indicated on a vertical axis) as a function of var~ous operating pressures P (indicated on a horizontal axis). In this embodiment of the invention, the adjustment block 44 reduces the sensed spacer value L for the left cylinder 32 in accordance with the retrieved data identifying the expected local deflection, essentially sub~acting20 the value of the expected deflection from the sensed spacing value S. The resulting adjusted spacing value confolms more closely to the actual platen spacing D proximate to the mold 24 (once again allowing for tolerable measure of platen deflection in the order of .001-.002 inches per foot). In a similar mansler, the adjusting block adjusts the sensed spacing value R associated with 25 the right leveling cylinder 34 to conform more closely to the actual spacing bet veen the molds and adjust those of the other leveling cylinders.
A cylinder control block 48 then actuates the servovalve 40 2 {3 ~ ~ 3 ~ ~
associaeed with the left cylinder 32 (and similar valves associated with the other leveling cylinders) ~o maintain all adjusted spacing signals at a common value.
This causes the platen to remain substantially parallel in the vicini~ of the mold 24, essentially preserving the spacing D observed in ~ig. ~, for example. This arrangement effectively ignores peripheral deformation of the platens 12, 14, which is inconsequential to proper molding of the charge 26. It will be understood of course that the controller 38 oth~rwise implements, in a conventional manner, required velocity and pressure profiles appropriate for initial compression and ultimat~ curing of the charge 26. Such additional 10 matters are well known, and will not be described.
Although the controller 38 is illustrated as distinct blocks and might be constructed of elec~onic components, the prefel~ed implementat;on involves a microprocessor. The adjustment and control ~unctions may be implemented as appropriate algorithms, stored on disk or otherwise, and 1~ executed by the microprocessor. The storage block 46 may be a conventional disk drive from which the expected relative deflection values for each leveling cylinder at its various operating pressures may be retrieved, ~or appropriate reduction of sensed spacing values. Alternatively, the stored data may be in theform of scaling factors (gain/attenuation) which are used to scale the sensed ~0 spacing value proximate to each leveling cylinder prior to regulation of the operating pressure of the cylinder. In either case, the data may be stored effectively as parameters of an equation specifying either the spacing reduc~ionor scaling factors, rather than discrete items of deflection and pressure data.
Rather than adjusting the sensed spacing value, the data indicating expected '~ local relative platen deflection can be used to adjust reference signals (~orexample, a required spacing value for each leveling cylinder derived from a master leveling cylinder or an average spacing value calculated for all levelingcylinders) to achieve the same result. It will be appreciated that platen r parallelism proximate to the mold ~4 may be regulated in a variety o~ ways relying on the current operating pressure of a leveling cylinder, sensed platen spacing, and data indicating expected local platen deflection.
The deflec~on data required for each cylinder can be obtained in :~ several ways. Finite element analysis or other estimating techniques can be used to model the platen and its expected response to operation of the leveling cylinders under various operating pressures. The same data may be used for all leveling cylinders, if appropriate syrnmetry can b assumed. It should be noted that the benefits of the invention can be obtained even if no exact compensationlO occurs.
A preferred method of generating the required data involves deriving it from actual operation of the press 10 on an exemplary workpiece in advance of actual production molding~ The workpiece is preferably the particular mold 24 to be used and preferably containing a sacrificial molding 15 charge~ The workpiece may be positioned cen~ally between the upper and lower platens 12, 14. The ram 28 is then used to apply the driving force to the upper platen 12 to compress the workpiece~ While the workpiece is being compressed, each leveling cylinder may be operated (separately or simultaneously) at various operating pressures~ The sensors associated with the 2n leveling c.ylinders are used to sense the local relative deflection of the platens 12, 14 proximate to each leveling cylinder, essentially as changes from a particular platen spacing value that serves as a datum~ These sets of values arerecorded in the storage block 46 as they are generated~ For each leveling cylinder, the datum may be the platen spac;ng at any appropriate operating pressllre, for example, a minimal pressure necessary to maintain contact with the upper platen, a pressure midway in the cylinder's operating range or the cylinder's maximum operating pressure. If the datum is the spacing for a non-zero operating p~essure, the differential changes in spacing values recorded for J ;~_ a full range of operating pressures can be related to actual expected deflections at the various operating pressures by simply adding a common increment to each recorded differential spacing value. l hat increment is essentially the value required to reduce to zero the sensed differential change in spacing at a zero or 5 near-zero operating pressure. It is preferred that this initial data-producingprocess be followed each time a new mold 24 is to be introduced between the platens 12, 14, using the particular mold 24. This provides more exact estimates of expected platen deflection for purposes of subsequent product production.
A preliminary calibration process is normal in the operation of such presses. Mold stops or a molding charge will be placed in the mold fixed to the p~ess platens, and the rarn operated to compress the mold. The spacing sensors are then effectively calibrated, establishing reference values for subsequent platen parallelism control. This is done whenever the press is 15 shut-down and re-started. Such matters are well known to those skilled in the art and will not be described in detail.
The preliminary data-producing process associated with the present invention is preferably fully automated and incorporated into the preliminary calibration process otherwise reguired for operation of the press.
20 The control system is of course coupled to the leveling cylinders through thesenovalves to control their operation, to the pressure sensors to receive operating pressures of the cylinders, to the spacing sensors to receive local platen spacing proximate to each leveling cylinder, and to the storage means both to read and write data. The controller 38 may additionally be coupled to 25 the ram 28 to actuate compression of the workpiece. In a data-recording mode of operation, the controller 38 operates the rarn 28 to compress the mold 24, steps each of the leveling cylinders through its various operating pressures by
3 ~ e~
appropriate control of the servovalves, and automatically records platen deflection in the storage block 46, the deflection values being sensed by the spacing sensors as differential spacing changes from a preselected datum, in themanner described above.
Control systems for regulating leveling cylinders are now largely microprocessor-based and operated by software algonthms. The necessary programming of a microprocessor-based controller 38 to add the additional control features o~ the present invention will be readily apparent to those skilled in the art, as will the necessary programming to implement the data-recording mode of operation as described above.
It will be appreciated that a particular embodiment of the invention has been described and that modifications may be made therein without departing from the spirit of the invention or necessarily departing ~romthe scope of the appended claims.
appropriate control of the servovalves, and automatically records platen deflection in the storage block 46, the deflection values being sensed by the spacing sensors as differential spacing changes from a preselected datum, in themanner described above.
Control systems for regulating leveling cylinders are now largely microprocessor-based and operated by software algonthms. The necessary programming of a microprocessor-based controller 38 to add the additional control features o~ the present invention will be readily apparent to those skilled in the art, as will the necessary programming to implement the data-recording mode of operation as described above.
It will be appreciated that a particular embodiment of the invention has been described and that modifications may be made therein without departing from the spirit of the invention or necessarily departing ~romthe scope of the appended claims.
Claims (13)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a press comprising a pair of platens, a mold located between the platens substantially centrally relative to the platens, means for applying a driving force to one of the platens to displace the one platen towards the other platen thereby to compress a molding charge within the mold, and a plurality of leveling cylinders spaced from the mold and acting between the platens to apply forces varying with operating pressures of the leveling cylinders to the one platen to countervail the driving force, a method of controlling the leveling cylinders to maintain platen parallelism while the molding charge is being compressed, comprising:
providing data identifying for each of the leveling cylinders the local relative deflection of the platens expected in response to operation of the leveling cylinder at various operating pressures while the molding charge is being compressed;
sensing the current operating pressure of each of the leveling cylinders;
sensing for each of the leveling cylinders the relative spacing of the platens proximate to the leveling cylinders; and, controlling the operating pressures of the leveling cylinders in response to the relative spacing of the platens sensed for each of the leveling cylinders and in response to the data identifying the expected local relative platen deflection for each of the leveling cylinders at its current operating pressure thereby to maintain a substantially parallel relationship between the platens proximate to the mold.
providing data identifying for each of the leveling cylinders the local relative deflection of the platens expected in response to operation of the leveling cylinder at various operating pressures while the molding charge is being compressed;
sensing the current operating pressure of each of the leveling cylinders;
sensing for each of the leveling cylinders the relative spacing of the platens proximate to the leveling cylinders; and, controlling the operating pressures of the leveling cylinders in response to the relative spacing of the platens sensed for each of the leveling cylinders and in response to the data identifying the expected local relative platen deflection for each of the leveling cylinders at its current operating pressure thereby to maintain a substantially parallel relationship between the platens proximate to the mold.
2. The method of claim 1 in which the step of controlling the operating pressures of the leveling cylinders, comprises:
adjusting the relative platen spacing as sensed for each of the leveling cylinders according to the expected local relative deflection of the platens for the leveling cylinder at its sensed operating pressure such that the adjusted relative platen spacing for each of the leveling cylinders conforms more closely to the relative spacing of the platens proximate to the mold; and, adjusting the operating pressures of the leveling cylinders to maintain the adjusted relative platen spacing for each of the leveling cylinders at substantially a common value.
adjusting the relative platen spacing as sensed for each of the leveling cylinders according to the expected local relative deflection of the platens for the leveling cylinder at its sensed operating pressure such that the adjusted relative platen spacing for each of the leveling cylinders conforms more closely to the relative spacing of the platens proximate to the mold; and, adjusting the operating pressures of the leveling cylinders to maintain the adjusted relative platen spacing for each of the leveling cylinders at substantially a common value.
3. The method of claim 1 in which the step of providing the data comprises estimating the expected local relative deflection of the platens for each of the leveling cylinders at the various operating pressures.
4. The method of claim 1 in which the step of providing the data includes a preliminary process, prior to compressing the molding charge, comprising:
positioning a workpiece centrally between the platens;
applying the driving force to the one platen to advance the one platen toward the other platen and compressing the workpiece; and, while the workpiece is being compressed and for each of the leveling cylinders:
(a) operating the leveling cylinder at the various operating pressures, (b) sensing the local relative deflection of the platens proximate to the leveling cylinder, and (c) recording the sensed local relative deflection of the platens at the various operating pressures of the leveling cylinder.
positioning a workpiece centrally between the platens;
applying the driving force to the one platen to advance the one platen toward the other platen and compressing the workpiece; and, while the workpiece is being compressed and for each of the leveling cylinders:
(a) operating the leveling cylinder at the various operating pressures, (b) sensing the local relative deflection of the platens proximate to the leveling cylinder, and (c) recording the sensed local relative deflection of the platens at the various operating pressures of the leveling cylinder.
The method of claim 4 in which the workpiece comprises the mold.
6. A press for compressing a molding charge within a mold, comprising:
a pair of platens;
platen displacing means for applying a driving force to one of the platens to displace the one platen towards the other platen thereby to compress the molding charge within the mold;
a plurality of leveling cylinders in a spacing arrangement permitting the mold to be positioned centrally between the pair of platens inset from the leveling cylinders, the leveling cylinders acting between the platens to apply forces to the one platen varying with operating pressures of the leveling cylinders to countervail the driving force;
means for providing data identifying for each of the leveling cylinders the local relative deflection of the platens expected in response to operation of the leveling cylinder at various operating pressures while the molding charge is being compressed;
pressure sensing means for sensing the current operating pressure of each of the leveling cylinders;
spacing sensing means for sensing for each of the leveling cylinders the relative spacing of the platens proximate to the leveling cylinders;
and, control means for controlling the operating pressures of the leveling cylinders in response to the relative spacing of the platens sensed for each of the leveling cylinders and in response to the data identifying the expected local relative platen deflection for each of the leveling cylinders at its current operating pressure thereby to maintain a substantially parallel relationship between the platens proximate to the mold.
a pair of platens;
platen displacing means for applying a driving force to one of the platens to displace the one platen towards the other platen thereby to compress the molding charge within the mold;
a plurality of leveling cylinders in a spacing arrangement permitting the mold to be positioned centrally between the pair of platens inset from the leveling cylinders, the leveling cylinders acting between the platens to apply forces to the one platen varying with operating pressures of the leveling cylinders to countervail the driving force;
means for providing data identifying for each of the leveling cylinders the local relative deflection of the platens expected in response to operation of the leveling cylinder at various operating pressures while the molding charge is being compressed;
pressure sensing means for sensing the current operating pressure of each of the leveling cylinders;
spacing sensing means for sensing for each of the leveling cylinders the relative spacing of the platens proximate to the leveling cylinders;
and, control means for controlling the operating pressures of the leveling cylinders in response to the relative spacing of the platens sensed for each of the leveling cylinders and in response to the data identifying the expected local relative platen deflection for each of the leveling cylinders at its current operating pressure thereby to maintain a substantially parallel relationship between the platens proximate to the mold.
7. The press of claim 6 in which the control means comprise:
means for adjusting the relative platen spacing as sensed for each of the leveling cylinders according to the expected local relative deflection of the platens for the leveling cylinder at its current operating pressure such that the adjusted relative platen spacing for each of the leveling cylinders conforms more closely to the relative spacing of the platens proximate to the mold; and, means for adjusting the operating pressures of the leveling cylinders to maintain the adjusted relative platen spacing for each of the leveling cylinders at substantially a common value.
means for adjusting the relative platen spacing as sensed for each of the leveling cylinders according to the expected local relative deflection of the platens for the leveling cylinder at its current operating pressure such that the adjusted relative platen spacing for each of the leveling cylinders conforms more closely to the relative spacing of the platens proximate to the mold; and, means for adjusting the operating pressures of the leveling cylinders to maintain the adjusted relative platen spacing for each of the leveling cylinders at substantially a common value.
8. The press of claim 6 in which the data-providing means comprise means for storing the expected local relative deflection of the platens for each of the leveling cylinders at the various operating pressures.
9. The press of claim 8 in which the control means comprise a data-recording mode of operation and in which the control means are coupled to the platen displacing means, the leveling cylinders, and the storing means such that, in the data-recording mode, the control means:
actuate the platen displacing means to apply the driving force to the one platen thereby to advance the one platen toward the other platen to compress a workpiece located centrally between the platens;
operate each of the leveling cylinders at the various operating pressures while the workpiece is being compressed; and, cause the storing means to store the local relative deflection of the platens sensed by the spacing sensing means for each of the leveling cylinders during operation of the leveling cylinder at the various operating pressures.
actuate the platen displacing means to apply the driving force to the one platen thereby to advance the one platen toward the other platen to compress a workpiece located centrally between the platens;
operate each of the leveling cylinders at the various operating pressures while the workpiece is being compressed; and, cause the storing means to store the local relative deflection of the platens sensed by the spacing sensing means for each of the leveling cylinders during operation of the leveling cylinder at the various operating pressures.
10. Apparatus for adapting a pressing comprising a pair of platens, and platen displacing means for applying a driving force to one of the platens to displace the one platen towards the other platen thereby to compress a molding charge within a mold positioned centrally between the platens to maintain platen parallelism while the molding charge is being compressed, comprising:
a plurality of leveling cylinders adapted to be located between the platens in a spacing arrangement permitting the mold to be positioned centrally between the pair of platens inset from the leveling cylinders and to act between the platens to apply forces to the one platen varying with operating pressures of the leveling cylinders thereby to countervail the driving force;
means for providing data identifying for each of the leveling cylinders the local relative deflection of the platens expected in response to operation of the leveling cylinder at various operating pressures while the molding charge is being compressed;
pressure sensing means for sensing the current operating pressure of each of the leveling cylinders;
spacing sensing means for sensing for each of the leveling cylinders the relative spacing of the platens proximate to the leveling cylinders;
and, control means for controlling the operating pressures of the leveling cylinders in response to the relative spacing of the platens sensed for each of the leveling cylinders and in response to the data identifying the expected local relative platen deflection for each of the leveling cylinders at its current operating pressure thereby to maintain a substantially parallel relationship between the platens proximate to the mold.
a plurality of leveling cylinders adapted to be located between the platens in a spacing arrangement permitting the mold to be positioned centrally between the pair of platens inset from the leveling cylinders and to act between the platens to apply forces to the one platen varying with operating pressures of the leveling cylinders thereby to countervail the driving force;
means for providing data identifying for each of the leveling cylinders the local relative deflection of the platens expected in response to operation of the leveling cylinder at various operating pressures while the molding charge is being compressed;
pressure sensing means for sensing the current operating pressure of each of the leveling cylinders;
spacing sensing means for sensing for each of the leveling cylinders the relative spacing of the platens proximate to the leveling cylinders;
and, control means for controlling the operating pressures of the leveling cylinders in response to the relative spacing of the platens sensed for each of the leveling cylinders and in response to the data identifying the expected local relative platen deflection for each of the leveling cylinders at its current operating pressure thereby to maintain a substantially parallel relationship between the platens proximate to the mold.
11. The apparatus of claim 10 in which the control means comprise:
means for adjusting the relative platen spacing as sensed for each of the leveling cylinders according to the expected local relative deflection of the platens for the leveling cylinder at its current operating pressure such that the adjusted relative platen spacing for each of the leveling cylinders conforms more closely to the relative spacing of the platens proximate to the mold; and, means for adjusting the operating pressures of the leveling cylinders to maintain the adjusted relative platen spacing for each of the leveling cylinders at substantially a common value.
means for adjusting the relative platen spacing as sensed for each of the leveling cylinders according to the expected local relative deflection of the platens for the leveling cylinder at its current operating pressure such that the adjusted relative platen spacing for each of the leveling cylinders conforms more closely to the relative spacing of the platens proximate to the mold; and, means for adjusting the operating pressures of the leveling cylinders to maintain the adjusted relative platen spacing for each of the leveling cylinders at substantially a common value.
12. The apparatus of claim 11 in which the data-providing means comprise means for storing the expected local relative deflection of the platens for each of the leveling cylinders at the various operating pressures.
13. The apparatus of claim 12 in which the control means comprise a data-recording mode of operation in which the control means:
actuate the platen displacing means to apply the driving force to the one platen thereby to advance the one platen toward the other platen to compress a workpiece located centrally between the platens;
operate each of the leveling cylinders at the various operating pressures while the workpiece is being compressed; and, cause the storing means to store the local relative deflection of the platens sensed by the spacing sensing means for each of the leveling cylinders during operation of the leveling cylinder at the various operating pressures.
actuate the platen displacing means to apply the driving force to the one platen thereby to advance the one platen toward the other platen to compress a workpiece located centrally between the platens;
operate each of the leveling cylinders at the various operating pressures while the workpiece is being compressed; and, cause the storing means to store the local relative deflection of the platens sensed by the spacing sensing means for each of the leveling cylinders during operation of the leveling cylinder at the various operating pressures.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2051565 CA2051565A1 (en) | 1991-09-17 | 1991-09-17 | Maintaining press platens in parallel relationship |
| PCT/CA1992/000398 WO1993005954A1 (en) | 1991-09-17 | 1992-09-17 | Maintaining press platens in parallel relationship |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2051565 CA2051565A1 (en) | 1991-09-17 | 1991-09-17 | Maintaining press platens in parallel relationship |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2051565A1 true CA2051565A1 (en) | 1993-03-18 |
Family
ID=4148386
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2051565 Abandoned CA2051565A1 (en) | 1991-09-17 | 1991-09-17 | Maintaining press platens in parallel relationship |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA2051565A1 (en) |
| WO (1) | WO1993005954A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114160729A (en) * | 2021-11-30 | 2022-03-11 | 南京麦克菲自动控制有限公司 | Servo pump control hydraulic machine with high-precision positioning |
| CN114893484A (en) * | 2022-05-20 | 2022-08-12 | 立讯智造(浙江)有限公司 | Pressure maintaining mechanism |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| DE4337825A1 (en) * | 1993-11-05 | 1995-05-11 | Erfurt Umformtechnik Gmbh | Process for simulating the load-dependent ram tilting of mechanical presses on a hydraulic incorporation press |
| JP3689010B2 (en) * | 2001-03-15 | 2005-08-31 | 株式会社放電精密加工研究所 | Press machine |
| JP4402863B2 (en) * | 2002-02-14 | 2010-01-20 | 株式会社放電精密加工研究所 | Press machine |
| DE10233679B4 (en) * | 2002-07-24 | 2006-09-14 | Franz Josef Summerer | Device for compensating tilting forces occurring during injection-compression molding and method for producing plastic molded parts |
| ITMI20111918A1 (en) * | 2011-10-24 | 2013-04-25 | Persico Spa | VERTICAL HYDRAULIC PRESS SUITABLE FOR MOLDING OF THERMOPLASTIC OR THERMO-HARDENING COMPOSITE MATERIAL. |
| US20180264765A1 (en) | 2015-01-08 | 2018-09-20 | Persico S.P.A. | Press and method for molding an ingot made of thermoplastic or thermosetting material |
| CN108044981A (en) * | 2017-12-31 | 2018-05-18 | 佛山市南海区心海悠金属制品有限公司 | A kind of hydraulic pressure backwashes device |
| CN108819308A (en) * | 2018-08-30 | 2018-11-16 | 苏州宏奇锐自动化有限公司 | A kind of online hot press |
| CN109986828B (en) * | 2019-05-13 | 2021-03-30 | 福州大学 | Composite press four-corner leveling system for realizing total tonnage control |
| CN117269197B (en) * | 2023-11-21 | 2024-02-02 | 昆明理工大学 | Method and device for detecting surface quality of polycrystalline silicon raw material |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1051137A (en) * | 1900-01-01 | |||
| US4076780A (en) * | 1977-01-27 | 1978-02-28 | General Motors Corporation | Programmable velocity and force control method for compression molding |
| US4784058A (en) * | 1986-08-13 | 1988-11-15 | Kabushiki Kaisha Kobe Seiko Sho | Press control for maintaining a level position and a uniform pressure on a workpiece |
| CA1275892C (en) * | 1986-10-10 | 1990-11-06 | Ronald Ballantyne | Hydraulic cylinder device for platen spacing indication and control |
-
1991
- 1991-09-17 CA CA 2051565 patent/CA2051565A1/en not_active Abandoned
-
1992
- 1992-09-17 WO PCT/CA1992/000398 patent/WO1993005954A1/en active Application Filing
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114160729A (en) * | 2021-11-30 | 2022-03-11 | 南京麦克菲自动控制有限公司 | Servo pump control hydraulic machine with high-precision positioning |
| CN114160729B (en) * | 2021-11-30 | 2023-10-20 | 南京麦克菲自动控制有限公司 | Servo pump control hydraulic machine with high-precision positioning function |
| CN114893484A (en) * | 2022-05-20 | 2022-08-12 | 立讯智造(浙江)有限公司 | Pressure maintaining mechanism |
Also Published As
| Publication number | Publication date |
|---|---|
| WO1993005954A1 (en) | 1993-04-01 |
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