FR2635026A1 - Method for the manufacture of tools based on polymer (resin) concrete for forming, especially drawing (stamping), cutting-out and other processes, of workpieces (components) made of metal sheet - Google Patents

Abstract

Method for the manufacture of forming tools, characterised in that at least one resin and its curing agent (hardener) are mixed, in that to this mixture is added a siliceous powdery filler, the ratio by weight of the resin and its curing agent (hardener) to the filler being determined so that, during a mixing operation whose duration is a function of the temperature, the resin is free of macromolecules, but it wets the filler particles and fills the interstices separating the said particles without creating matted material (mats) sagging between them.

Description

 The present invention relates to the manufacture of forming tools, in particular stamping and the like intended to be mounted on presses for shaping metal sheets, for trimming workpieces, as well as for other operations to be Pressed.

 The invention essentially relates to the manufacture of concrete for all-concrete forming tools and also of composite tools, that is to say tools which include working parts made of metal or other suitable materials and resistant to wear, these working parts being supported and anchored in a resinous mass.

 Tools of this type can be used essentially for the production of a few prototypes and by using them on hydraulic presses to prevent them from being subjected to impacts which may cause the resinous mass to rupture.

 The invention creates a new process for manufacturing concrete and tools which makes it possible to produce composite tools which can be used on mechanical presses with a high working rate, for example 18 # 20 cycles per minute, instead of 2 ss 3 for a hydraulic press. The tools according to the invention also allow manufacturing of the order of 100,000 pieces, so that they can be used for productions in small and medium series. The method of the invention makes it possible to obtain tools which can undergo operations of rectification by mechanical machining, as well as repairs by refills, which authorizes the carrying out of substantial modifications.

 Another advantage of the invention lies in the fact that some of the working parts of the tool can be made of resins, the qualities of which are then put to use to allow the sliding of certain parts of a metal blank to be shaped without that it results from excessive tearing or thinning of the stretched parts.

 The invention also makes possible the production of complex tools making it possible to ensure the falling of the edges of stamped parts and the drilling thereof.

 In accordance with the invention, the process for the production of resin concrete intended for the production of tools for forming, stamping, trimming and other treatments of sheet metal parts is characterized in that at least one resin and its hardener, in that a siliceous pulverulent filler is added to this mixture, the weight ratio between the resin and its hardener, on the one hand, and the filler, on the other hand, being determined so that during kneading, the duration of which is determined as a function of the working temperature, said resin is still at least partly free of macromolecules, but that it wets the grains of the filler and fills the interstices separating said grains without creating bending mattresses between them and in that the concrete is poured into a formwork containing working parts or molding elements.

 Various other characteristics of the invention will also emerge from the detailed description which follows.

 Embodiments of the object of the invention are shown, by way of nonlimiting examples, in the accompanying drawings.

 Fig. 1 is a schematic elevation cut of a stamping tool produced in accordance with the invention.

 Fig. 2 is a schematic sectional elevation similar to FIG. 1 of a stamping tool complementary to that of FIG. 1.

 In the following, to illustrate the object of the invention, there is shown in FIG. 1 a stamping die and S fig. 2 a stamping punch intended to cooperate with the matrix of FIG. 1.

 The manufacturing operations are described successively in the following for both tools, in order to show the identity of their manufacture.

 In fig. 1, 1 designates a marble on which a reference model 2 is placed, made for example of wood, in particular of alder wood, covered with a sheet 3.

The reference model 2 is fixed on the marble 1, for example by means of adhesive elements not shown but allowing its removal after the production of the tool.

The cover sheet 3 is chosen with a thickness corresponding to that to be worked by the tool.

Then, on the reference model 2, metal inserts 4 previously provided with sealing tabs 5 are added.

 When making the inserts, care should be taken that all the edges directed towards the inside of the tool and which must be sealed in the plastic concrete described below, are cut down and rounded, so that the forces transmitted to the metal inserts during subsequent tool work are distributed over as large an area as possible and that there are no sharp edges between the inserts and the resin concrete.

 Similarly, the future working parts are placed on the reference model, one of which, designated by the reference 6, is constituted by a medallion which can be produced in approximate cast iron or in another suitable material. As with the inserts, sealing tabs Sa protrude from the working parts 6 which must be in contact with the resin concrete.

 A retaining rod 7, for example a rod, is arranged around the reference model 2 for the subsequent delimitation of a retaining groove of a sheet metal blank to be worked. The retaining flange 7 is placed directly on the base plate 1 in the same way as a peripheral key 8 intended to delimit a recess in the tool produced. Next, a formwork 9 may be made of wood and intended to delimit the external wall of the tool. The formwork 9 is optionally provided on its internal wall with various accessories, for example a belt or studs 10, intended to delimit a groove or niches for clamping the Tool on the press in front of the action = Br. The formwork 9 is made very rigidly so as not to undergo deformation during the pouring of the plastic concrete.

 In addition to the above, holes, such as that designated by 11, are provided at least in the sheet of the reference model 2 and tubes 12 are engaged in these holes to extend substantially to the top of the formwork 9. The holes 11 and the tubes 12 are intended to allow the evacuation of the air trapped between the cooperating working tools during the execution of the stamping cycles.

 When the various parts described above, as well as all other necessary accessories, are put in place, the visible walls of both the parts and accessories and the internal walls of the formwork 9 are coated with a mold release product, for example a wax.

 A following manufacturing operation consists in applying, to the internal walls of the formwork and to the parts and accessories it contains, a surface layer 13 or "gel-coat" advantageously made of ethoxyline resin preferably that known under the brand Araldite mixed with a compatible hardener.

Particularly satisfactory results have been obtained by producing the surface layer 13 by applying two successive layers of a mixture of Araldite of type SW 419 and of a hardener of type HV 419 both manufactured by the company CIBA-GEIGY. The proportion of hardener was 13 + 0.5 parts by weight per 100 parts by weight of Araldite. The application of the second surface layers was carried out as soon as the first layer reached a polymerization stage corresponding to a tacky state.

 A next operation consists in coating the surface layer produced, the thickness of which is preferably between 0.5 and 2.5 mm, with a bonding layer which is also applied as soon as the surface layer reaches a tacky state.

Particularly satisfactory results were obtained by making the bonding layer so that it contains 100 parts by weight of Araldite of the type
SW 419, 15 + 0.5 parts by weight of the hardener of HM type and 25 + 10 parts by weight of slate powder with a particle size between 0.4 and 3 mm, a particle size close to 0.5 mm being favorite.

 To fill the remaining free volume t inside the formwork, a resin composite concrete is used, hereinafter called filling concrete.

A concrete filling having given particular deny satisfaction was constituted in the following way:
Araldite CY 219 = 100 parts by weight
hardener HM 50 + 1 part by weight
sand reference G2 650 + 50 parts by weight
sand reference F35 650 + 50 parts by weight
Araldite CY 219 as well as hardener EN are products marketed by the company
CIBA-GEIGY, while the reference sand G2 is quartz silica sand containing grains distributed as follows
5% grain from 1.25 to 1.60 mm
25% -id- 1 to 1.25 mm
45% -id- 0.8 to 1 mm
15% -id- 0.63 to 0.8 mm
10% -id- 0.5 to 0.63 mm
A particularly satisfactory sand is marketed by the company SILICE ET KAOLIN and has the following physical and chemical properties
Physical properties
Actual density 2.65 to 2.7
Bulk bulk density. 1.3 to 1.5
Melting point approx. 7500C
Mohs hardness .......................... about 7
Humidity recovery to 98% relative humidity ............................ below 0.03 pH 8
Milky color to pinkish beige
Chemical properties
Chemical analysis in% SiO2 ....................... 98.5 to 99 A1203 0.3 to 0.5
Loss on ignition A 800 .................. 0.1 A 0.2
Fe203 0.2
CaO + MgO ............................ 0.15 K2O NaȎ .............. ................ 0.20
The constituents of the filling concrete are poured into the formwork 9 after kneading for a period allowing the resin to wet and completely fill the interstices of the sand grains, but the kneading is interrupted before the initiation of a polymerization liable to result in the physical rupture of the macromolecules created.

 It appeared that the kneading of the resin-sand composite should not exceed a duration of 15 min. At a working temperature of 160C, the kneading time being reduced to a shorter duration, of the order of 10 min for a temperature of 19 to 200C.

 The prepared filling concrete is poured, either continuously or in successive fractions and as the formwork is filled 9. Reinforcement elements 14, for example concrete irons, are placed in said formwork to constitute reinforcements similar to the reinforcement of a concrete construction having to work essentially with compression.

 After filling the formwork 9, the assembly of the tool produced is kept stable on the marble 1 for a sufficient time for the polymerization of the resin to give it adequate strength. At the temperature of 160C and under the conditions set out in the above, a rest time of 24 hours appeared to be sufficient. At the end of this resting time, the formwork 9 can be removed if it is to be reused, but the polymerization of the resin concrete should preferably be continued without moving said tool for at least a new period. 24 hours. If desired, polymerization can be accelerated by subjecting the tool to steaming at a temperature corresponding to that generally used for the treatment of Araldite resins.

 The hardening for obtaining a complete polymerization when the tool is kept at the temperature of 160C is approximately 7 days.

 Fig. 2 schematically illustrates the production of a punch from the matrix obtained as described in the foregoing. The matrix already polymerized at least partially, that is to say after a period of at least about 24 hours, is machined on its top to present a flat top, or locating shims 15 (fig. 1) are formed before the matrix is raised from the marble 1 to delimit a reference plane whose geometric position is perfectly known. Planing by adding a surface resin can also be carried out. After turning, the matrix is placed on a marble la (fig. 2) which can be the one on which it was made. The turning is carried out using handling legs 16 (fig. 1) placed in the concrete filling in recesses 17 provided for this purpose by sockets previously arranged in the formwork 9 or by any other means known in the art.

 In the same way as with regard to the die, to make the punch, inserts 4a and working parts 6a and possibly bars 18 are put in place when necessary, as in the example illustrated by the fig. 1 and 2, that the tool performs not only the stamping of a part but also the falling of edges and their joggling. Other accessories can, as before, be put in place in particular covers 19 intended to leave free spaces of determined ranges between the punch and the die.

 In the same way as described in the foregoing, the surface of the punch is produced by a "gel-coat" consisting of Araldite and its hardener placed in one or more layers, then as previously a bonding layer consisting by resin added with mineral powder, preferably a slate powder, constitutes an intermediate layer before the placement of the filling concrete in a formwork 9a disposed on the formwork 9 turned over as explained in the foregoing.

 Reinforcement elements 14a, for example concrete irons, are put in place as the filling concrete is poured.

 To illustrate the invention, an example of the preparation of the various resins and concrete concretes used is given below.

EXAMPLE
Was projected onto the release agent covering the formwork 9 and the various parts and accessories contained in this formwork as described with reference to FIG. 1 a first surface layer (gel coat), consisting of Araldite SW 419 representing 100 parts by weight added with the hardener Hv 419 representing 13 parts by weight, from the company CIBA-GEIGY, at the temperature of 160C to produce a first layer with a thickness of approximately 0.4 to 0.8 mm. As soon as this first layer became tacky, a second layer was sprayed. The second layer was sprayed essentially on the working parts of the tool not provided with metal inserts and not provided with attached working parts. As soon as the second layer became tacky, a thickness of approximately 0.5 to 1 mm bonding layer was extended by projection onto all of the internal surfaces of the formwork 9. The bonding layer consisted of Araldite SW 419 and the hardener EN of the company CIBA-GEIGY respectively for 100 parts by weight and 15 parts in weight.

As soon as the above bonding layer took on a pasty consistency, the formwork 9 was filled with resin concrete obtained as follows: First of all, the binder consisting of 8 kg of resin was prepared
Araldite CY 219 and 4 kg of the company's EN hardener
CIBA-GEIGY, then this binder was poured into a mixer into which successively poured fractions of 5 to 10 kg of G2 reference sand from the company SILICE ET
KAOLIN according to the composition set out in the above and fractions of 5 to 10 kg of F35 sand from the same company, also constituted by quartz silicas, but comprising 5% of grains between 0.8 and 1 mm, 35% grains between 0.630 and 0.80 mm, 35% grains between 0.50 and 0.630 mm and 15% grains between 0.40 and 0.50 mm.

 The quantity of each of the two sands used was 50 kg. The resin-sand composite was kneaded for 15 min and then poured in successive layers of regular thicknesses inside the formwork 9, while carefully packing. Wood rods were placed on top of the last layer of concrete filling to delimit recesses in the air passages at the end of the air-purge tubes 12-described with reference to FIG. 1, then a layer of Araldite resin was extended to perfect the planing of the surface of the tool which was then kept at rest for 48 hours at a constant temperature of 16C to obtain sufficient polymerization allowing its handling.

 In other examples which were carried out, it was found that the increase in the mixing time for the resin and hardener composition set out above led to a reduction in the compression characteristics of the resin concrete. Tests carried out made it possible to establish the data below.

Mixing 15 '
Max load kN 68.3 75.3 75.7
Lift N / mm2 37.3 44.9 44.2
Average load N / mm2 44.5 = 4.5 kg / mm2 = 454 / cm2
Mixing 30 '
Max load kN 66.3 69 67.6
Lift N / mm2 40.6 41.7 40.9
Average load N / mm2 41.1 = 4.1 kg / mm2 = 419 kg / cm2
Mixing 45 '
Max load kN 66.4 74.2 76.8 65.9
Lift N / mm2 40.8 45.2 41 39.8
Average load N / mm 40.5 = 4.1 kg / mm = 413 kg / cm
It was also found that it was advantageous to prepare only relatively small masses of resin concrete of the order of 10 to 15 kg, while working them at a temperature between 16 and 19 CC. Indeed, beyond the above mass and temperature, the polymerization tends to be accelerated by mass effect and exothermic reaction, which leads to further reducing the mixing time by harming the homogeneity of the concrete.

 The invention is not limited to the exemplary embodiments shown and described in detail since various modifications can be made thereto without departing from its scope. In particular, the Araldite resins set out in the foregoing may be replaced by similar resins provided that said resins provide suitable wetting of the filler and filling of the interstices separating the grains from said filler without said resins forming a bending mattress between said grains. Likewise, the entire tool can be made of resin concrete coated or not with a gel coat, that is to say including the working parts which are formed by the resin concrete by molding on models of reference arranged in the formwork and then constituting molding elements. The added parts or working parts can also be made of other materials than metal, synthetic resins, elastomers loaded or not with synthetic fibers, etc., can be used to be adapted to a particular job of a part of the tool.

Likewise, by siliceous filler stated in the foregoing and in the claims is meant a filler wettable by the resins used and having the characteristic of being incompressible at the working pressures of the tools concerned.

Claims (15)

 1 - Process for the manufacture of forming tools, in particular stamping, trimming and the like of sheet metal parts, the tools containing a resin concrete, characterized in that at least one resin and its hardener are mixed, in that a siliceous pulverulent filler is added to this mixture, the weight ratio between the resin and its hardener, on the one hand, and the filler, on the other hand, being determined so that during kneading, the duration of which is determined as a function of the working temperature, said resin is still at least partially free of macromolecules, but that it wets the grains of the filler and fills the interstices separating said grains without creating a bending mattress between them ci and in that the concrete is poured into a formwork containing working parts or molding elements.  2 - Process according to claim 1, characterized in that an ethoxyline resin is used, preferably Araldite and sands constituted by quartz silicas.  3 - Method according to one of claims 1 and 2, characterized in that a binder containing about 8 kg of Araldite resin CY 219 and 4 kg of HM hardener from the company CIBA-GEIGY is used, or their equivalents for be mixed with 100 ka of a load of quartz silica sands having a particle size between 1.25 and 0.5 mm.  4 - Method according to one of claims 1 to 3, characterized in that the filler comprises half a sand comprising 5% by weight of particles with a particle size between 1.25 to 1.6 mm, 25% by weight of particles with a particle size between 1 and 1.25 mm, 45% by weight of particles with a particle size between 0.8 and 1 mm, 15% by weight with particles with a particle size between 0.63 and 0.8 mm, 10% by weight of particles with a particle size between 0.5% and 0.63 mm and a sand comprising 5% by weight of particles with a particle size between 0.8 and 1 mm, 35% by weight of particles with a particle size between 0.630 and 0 , 80 mm, 35 t by weight of particles with a particle size between 0.50 and 0.630 mm and 15% by weight of particles with a particle size between 0.40 and 0.50 mm.  5 - Method according to one of claims 1 to 4, characterized in that the sands constituting the load have the following physical characteristics Actual density 2.65 to 2.7 Bulk bulk density. 1.3 to 1.5 Melting point ...................... about 1,750 C Mohs hardness .......................... about 7 Humidity recovery at 98 8 relative humidity below 0.03 pH 8 Milky color to pinkish beige  6 - Method according to one of claims 1 to 5, characterized in that the sands have the following chemical properties SiO2 98.5 to 99 A1203 0.3 to 0.5 Loss on ignition at 800 ....... ........... 0.1 to 0.2 Feȏ .............................. 0.2 CaO + MgO .......................... 0.15 K0 + NaȎ ............... .......... 0.20  7 - Method according to one of claims 1 to 6, characterized in that for the production of a stamping tool, die, punch or the like, a reference model is put in place on a marble (1) 2), working parts (6 and 6a), retaining tubes (7) and other accessories specific to this type of tool or molding elements, in that the formwork, the model and the accessories are coated or the molding elements of a demolding product of the wax type and then in that o # n forms a surface layer or "gel-coat" from a resin of the same nature as that used as a binder for the constitution of the resin concrete and in that this surface layer is connected to the resin concrete when said surface layer reaches a tacky state indicative of a start of polymerization.  8 - Method according to one of claims 1 to 7, characterized in that connects the surface layer to the filling concrete by means of a bonding layer formed from a binder containing a resin of the same kind as that of the surface layer and that of the binder of the filling concrete but whose charge is constituted by a slate powder whose quantity by weight is approximately 25 + 10 parts by weight per 100 parts by weight of bonding resin .  9 - Method according to one of claims 1 to 8, characterized in that the filling resin concrete is put in place in successive layers to completely coat the working or molding parts that the tool comprises and in that reinforcing elements (14) of the concrete irons type and the like are put in place as the filling resin concrete is poured.  10 - Method according to one of claims 1 to 9, characterized in that the working parts (6) of the metal inserts (4) of the sealing lugs (5, Sa) and other accessories are machined or prepared to present no edge in their parts in contact with the surface layer and / or the resin concrete.  11 - Method according to one of claims 1 to 10, characterized in that the surface layer or "gel-coat" (13) is produced in at least two thicknesses on that of the working parts that the tool contains. with the exception of said metal parts or other materials which constitute working parts.  12 - Method according to one of claims 1 to 11, characterized by the application of a layer of planing resin deposited on the free surface of the resin concrete at the end of the casting thereof.  13 - Method according to one of claims 1 to 12, characterized by air exhaust tubes (12) placed between the working parts of the tool and the surface thereof remaining free after pouring the concrete resin and any planing layer.  14 - Method according to one of claims 1 to 13, characterized in that at least some parts of the reported working parts are made of syntheticelastomeric resins loaded or not, synthetic fibers and other materials suitable for a particular work of a part of the tool.  15 - Method according to one of claims 1 to 14, characterized in that the resin concrete is prepared taking into account the ambient temperature in quantities allowing the wetting of the grains of the filler during kneading before a reaction occurs. mass causing an exothermic reaction leading to partial polymerization.