CH664925A5 - MOLDED BRACKETS IN CAST IRON FOR THE MOLDING UNIT OF A PLASTIC INJECTION MOLDING MACHINE. - Google Patents

Description

DESCRIPTION

The invention relates to a mold carrier according to the preamble of claim 1.

Known mold carriers of this type are generally castings of small volume with a relatively large surface area, especially if they have cavities in the mold carrier body in order to save weight. As a result, a relatively high casting temperature is required for casting, but this is selected at a lower limit that is still possible in order to keep gas absorption, oxidation, cavitation, grain coarsening and the like undesirable phenomena and reactions with the molding material as low as possible. Nevertheless, different cooling rates have a significant impact on the microstructure and thus on the mechanical properties of the mold carrier casting. This also applies in particular to its structure in a surface zone with increasing bending strength and decreasing elongation in the direction of the surface, which surface zone is referred to below as “cast skin”. After the process of cooling, in which tensions between the rapidly cooling surface zones and the slower cooling interior of the casting are reduced, a state of tension remains in the mold carrier casting, which, however, generally does not initially result in any shape change thanks to the casting skin. However, this can change during the further surface treatment of the mold carrier casting if the cast skin is milled off in a relatively large, self-contained surface area.

The invention is based on the object of making the cast skin usable for the shape stability of the mold carrier in a mold carrier of the type mentioned at the outset without impairing the requirements for rational series production.

This object is achieved according to the invention by the features mentioned in the characterizing part of patent claim 1.

This means that changes in the masses of the mold carrier casting, in particular deviations with regard to the plane parallelism of the work surfaces, are largely avoided, but also the quality of the mold carrier with regard to the mechanical properties important for its function, in particular with regard to its flexural strength and its elongation, is improved . Such an improvement is not without influence on the dimensional accuracy of the molded part itself, because a permanent or a rhythmic impairment of the shape stability during the injection cycle can inevitably lead to a rhythmic and asymmetrical loading of the injection mold, with disadvantageous consequences for the quality of the molded part.

Due to the further embodiment of the invention according to claims 2-6, the dimensional stability is further improved with relatively little technical effort. The latter is based not least in the method according to claim 7.

The invention is explained below with the aid of exemplary embodiments.

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1 shows a plate-shaped, stationary and a frame-like, movable mold carrier in the mold-closing unit of a plastic injection molding machine,

Figures 2, 3 the stationary mold carrier in perspective and

4, 5 a variant of the stationary mold carrier in a representation corresponding to FIGS. 2, 3.

The mold carriers S and B, which are made of spheroidal graphite cast iron, are each provided with four through bores 24 for the columns 42 of the mold clamping unit. The passage bores 24 are arranged such that common horizontal tangents ht and common vertical tangents vt of these columns 42 enclose approximately a square or rectangle. The stationary mold carrier S with a plate-shaped mold carrier body 10 is rigidly connected to a mounting plate M for the hydraulic drive unit 52 for the movable mold carrier B via the four columns 42. The frame-shaped mold carrier B comprises a support wall 49, pressure-transmitting ribs 48 and a clamping wall 50 for the associated mold half 55. It is supported on guide rails 47 of the machine foot 46 of the plastic injection molding machine by means of support devices 53. The mold carrier body 10 of the plate-shaped stationary mold carrier S has working surfaces on the casting mold side and on the back which lie in plane-parallel planes, which are referred to below as working plane planes h-h and f-f. The stationary mold carrier S is firmly connected to the guide rails via bearing surfaces F which are approximately twice as long as the distance a between the working surface levels h-h and f-f. The bearing surfaces F are formed by angled bearing ribs 12, 14 and supporting ribs 15, 16 of the same cross-sectional profile. The connecting leg 15 of the supporting ribs 15, 16, which is inclined to the horizontal, each merge into a vertical stiffening rib 18 which tapers upwards and is integrally formed on the rear side of the mold carrier S. Both the clamping surface of the stationary mold carrier S and that of the movable mold carrier B extends approximately up to the horizontal tangents ht and the vertical tangents vt of adjacent through holes 24. The clamping surfaces of both mold carriers S and B are each penetrated by grooves 30 and 45, respectively Base areas are covered by the cast skin. These grooves 30 and 45 also extend to the horizontal and vertical tangents ht, vt and merge into one another. About a quarter of the surface area delimited by the tangents ht, vt is occupied by the grooves 30 and 45, respectively. The depth of the grooves 30 and 45, which end at a distance from the central through opening 23 and are arranged symmetrically to the vertical plane of symmetry of the mold carrier S or B, is approximately one sixth of their width. The central access opening 23 can be penetrated by the plasticizing cylinder of an injection molding unit connected in the axis of symmetry e-e of the mold closing unit by means of connection body 43. The passage opening 23 is surrounded on the casting mold side by a self-contained clamping surface area. The stationary mold carrier S has, in its rear working surface plane f-f parallel to the working surface plane h-h, high-speed milled contact surfaces 33 for abutment against abutments 54 and high-speed milled contact surfaces 35 for connecting the injection molding unit operating transversely to the parting line of the injection mold 55, 56. The mold carrier S is otherwise covered by the cast skin, which is located at the rear at the desired distance from the working surface plane f-f, which corresponds to the depth of the grooves 30.

Formation and spatial arrangement (groove pattern) of the grooves 30 in the clamping surface of the stationary Formträ664 925

gers S corresponds to the groove pattern in the clamping surface of the movable mold carrier B. The cast skin areas of both mold carriers S and B are sandblasted and covered by a plastic layer that comes from a powder coating or a lacquer finish.

The geometry of the groove pattern on the clamping surface and the geometry of the cavities in the mold carrier body 10 are matched to one another such that at least one groove section 30 ′ or 30 ″ is arranged in front of each cavity as seen in the closing direction of the mold clamping unit.

Vertical legs 13, 17 of the mold carrier S serve to center it on the guide rails 47. A protective flange 11, which projects over the mold carrier body 10 on three sides, is flush with the back of the mold carrier S. The protective flange 11 is stiffened on the casting mold side by horizontal webs 19.

Mold-side core bearings 29 and back-side core bearings 29 'of the stationary mold carrier S serve to hold cores to form cavities in the mold carrier body 10. Bores 25 serve to hold clamping bolts for holding the associated mold half 56 (or 55 in the case of the movable mold carrier B). The clamping bolts can be tensioned with the aid of hydraulic cylinders which can be centered in bores 26 which are perpendicular to the bores 25 on the mold carrier body 10. Fastening surfaces 28 serve to accommodate loading and unloading devices. Threaded bores 31 are distributed evenly over the clamping surface for form fixing screws. A hanging pin 39 enables the casting to be easily gripped by the gripping members of the transport device when it is transferred to the machining center.

Since about a quarter of the surface area delimited by the tangents ht, vt is occupied by the grooves, there is a correspondingly smaller contacting clamping surface. As a result, the temperature compensation between the clamped casting mold and the mold carrier is desirably reduced. In this respect, the design of the mold carrier according to the invention also has an insulating effect.

The reduction in the contacting clamping surface also facilitates the machining required for their production, in particular the high-speed milling which is carried out in the process; because the reduced contacting clamping surface is synonymous with a reduced processing area that can be processed with a correspondingly lower surface pressure.

The process for the production of the mold carrier S or B comprises the following essential process steps: A cast piece corresponding approximately to the shape of the finished mold carrier is produced with the proviso that the regions between the grooves 30 and 45 and, in the mold carrier S, the regions of the contact surfaces 33 and 35 protrude the respective work surface level hh or ff forward or backward. Then, after sandblasting, the casting is completely covered with a plastic layer, e.g. by painting or by powder coating. Then the casting is clamped onto the machining table of a machining center for machining and the areas that project beyond the work surface levels h-h and f-f are carried out until the finished clamping surface and the finished contact surfaces 33; 35 exclusively by high-speed milling. The through bores for the columns 24 are also introduced.

The casting remains in its initial clamping position during machining until the finished mold carrier.

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3 sheets of drawings

Claims (8)

664 925 PATENT CLAIMS 1. Cast iron mold carrier, for the mold clamping unit of a plastic injection molding machine, with four through holes for the columns of the mold clamping unit, with a square or rectangular area enclosed by common, horizontal and vertical tangents applied to these columns from the outside, and with one In this area, in a plane perpendicular to the closing direction of the mold clamping unit, the finely machined clamping surface, in which the cast skin covering the mold carrier as a casting is milled off by a statistical mean higher bending strength and less elongation, characterized in that the between the through bores ( 24) through which the clamping surface extending approximately to the tangents (vt; ht) is penetrated by grooves (30 or 45), on the base surfaces of which the cast skin is preserved. 2. Mold carrier according to claim 1, characterized in that merging horizontal groove sections (30 ') and vertical groove sections (30 ") of the grooves (30 and 45) extend to the tangents (vt; ht) and about a quarter of the clamping surface. 3. Mold carrier according to claim 1 or 2, characterized in that the depth of each at a distance from a central through opening (23) and symmetrical to the vertical plane of symmetry of the mold carrier arranged grooves (30 or 45) is about a sixth of their width, wherein the passage opening (23) is delimited by a self-contained clamping surface area. 4. Mold carrier, which is designed as a stationary mold carrier and has internal cavities, according to one of the preceding claims, characterized in that in a plane parallel to the working surface (hh) of the clamping surface, rear working surface plane (ff), high-speed milled contact surfaces (33, 35 ) are arranged and that the mold carrier (S) is otherwise covered by the cast skin, which is located on the back at a distance from the working surface plane (ff), which corresponds to the depth of the grooves (30). 5. Mold carrier according to one of the preceding claims, characterized in that the groove pattern of the grooves (30) in the clamping surface of the stationary mold carrier (S) corresponds to the groove pattern of the grooves (45) in the clamping surface of the movable mold carrier (B), all areas of the cast skin of both Mold carriers (S; B) are sandblasted and covered with a plastic layer. 6. Mold carrier according to claim 4, characterized in that the geometry of the groove pattern on the clamping surface and the geometry of the cavities in the mold carrier body (10) are coordinated with one another in such a way that, seen in the closing clearing of the mold clamping unit, at least one groove section (30 ') in front of each cavity. or 30 ") is arranged. 7. mold carrier according to one of claims 1 to 6, characterized in that the cast iron is a spherical cast iron with nodular graphite. 8. A method for producing a mold carrier according to one of the claims 1 to 7, characterized in that a casting approximately corresponding to the shape of the finished mold carrier is produced with the proviso that the areas between the grooves (30; 40) and the areas of the contact surfaces (33, 35) protrude the associated work surface level (hh or ff) forward or backward, that you then completely cover the casting with a plastic layer and then clamp it on the processing table of a machining center for machining and then the Work areas (hh; ff) outstanding areas to form the finished Clamping surface and to form the finished contact surfaces (33; 35) is removed exclusively by high-speed milling and also drills the through holes for the columns of the mold clamping unit, the casting remaining in the first clamping position in all machining operations up to the completely finished mold carrier.