A kind of powder injecting molding die and using method thereof
The present invention relates to a kind of powder injection-molded mould, particularly relate to and a kind ofly prepare the powder injection mould of compact formed and apply the method that this mould prepares shaped article.
Powder Injection Molding Technology (Powderinjectionmolding, be called for short PIM) be that metal dust mixes with organic binder by one, die cavity internal shaping is injected in a heated state with injection machine, remove adhesive by the method for chemical solvent or heat resolve again, finally sinter the novel alloy production technology of densification product into.In recent years, along with the manufacture metal of complicated shape or the development of ceramic post sintering body method technique, PIM technology is applied in increasing field, especially MIM(MetalInjectionMolding, metal injection molded) and CIM(CeramicInjectionMolding ceramic injection forming) be applied in the moulding process of all kinds of structural member, shaped piece.Along with the development of PIM technology, each field proposes more and more higher requirement to the dimensional accuracy, structural homogenity, mechanical property, production cost etc. of product, this just requires that degreasing sintered front raw embryo product has high density and structural homogenity, to reach the more and more higher performance requirement to product.
In prior art, in order to promote the compactness extent of raw embryo product, the minimum powder stock of particle diameter is often adopted to suppress, the strict homogeneity controlling powder stock granularity simultaneously, if conventional powder metallurgical raw material granularity is 50-100 μm, once the particle mean size of powder stock be controlled to be about 10 μm, then the compactness extent of MIM product can promote 20%-30%.But carry out control to the granularity of material powder and can bring being doubled and redoubled of material powder cost, simultaneously under current technical conditions, the reduction degree of powder size is also very limited.
Also many technology are had to improve mould used in preparation technology, it is the Chinese patent of " method and the combination die for the manufacture of the metal powder parts of densification " by name of 200510138082.7 as application number, provide a kind of mould including relative to each other movable upper die and lower die from open position to closing position, also comprise upper punch and at least one that at least one and described patrix be connected and the low punch that described counterdie is connected, the method utilizes upper and lower mould and upper low punch to relatively move powder in compacting die cavity to obtain densification product.The method step is comparatively loaded down with trivial details, and the compactness extent for powder compacting product improves also limited.
Summary of the invention
In order to solve described the deficiencies in the prior art, the invention provides and a kind ofly prepare the powder injection mould of compact formed and apply the method that this mould prepares shaped article, by the improvement to mould, and the mould that utilization improves carries out twice matched moulds in an injection moulding cycle period, can when other conditions change, secondary compaction is carried out to the raw embryo product of dusty material, the density of powder compacting product is significantly promoted.
Technical problem to be solved by this invention is achieved by the following technical programs:
A kind of powder injecting molding die, comprise dynamic model die and cover half die, described dynamic model die is provided with inner chamber, the profile of described cover half die and the inner chamber of dynamic model die suitable, it is characterized in that, be provided with gap between dynamic model die and cover half die, the inwall of dynamic model die inner chamber is provided with step, the outer wall of cover half die is provided with the step suitable with dynamic model die inwall step.
In existing mold technology, Split type die is generally made up of dynamic model and cover half, dynamic model die and cover half die are parts necessary on dynamic model and cover half, and dynamic model part also can comprise the assemblies such as dynamic model header board, thimble, ejector retainner plate assembly, moving clamping plate except dynamic model die; Cover half part, except cover half die, also can include the assemblies such as cover half template, feed nozzle.Dynamic model die in the present invention program and cover half die can be loaded in any mould of the prior art.
The suitable necessary condition being mould and can using of profile of set inner chamber and cover half die on dynamic model die in Split type die.In the solution of the present invention, gap is provided with between dynamic model die and cover half die, on the one hand to allow the gas in raw material have passage to discharge when pressed powder raw material, arrange on the other hand this gap and thimble direction present certain angle can allow dynamic model die and cover half die load coordinate time more smooth and easy, during compacted products, pressure can put on molded samples more uniformly along the direction in gap, what can provide more sufficient space that the binding agent in powder stock is melted for the raw material in die cavity in first matched moulds and injection pressure maintaining period is more even simultaneously, and then make subsequent forming product sinter more even.Dynamic model die and cover half die have certain form and position tolerance when loading and coordinating, the impact on shaped article size that a little bias that rationally setting gap length therebetween can also suitably avoid die to occur in process is brought.The present inventor is drawn by great many of experiments, and between dynamic model die and cover half die, set gap thickness is that 0.1-0.5mm is advisable, and this gap and thimble direction are angularly 1-15 ° and are advisable.
Meanwhile, the inwall of dynamic model die inner chamber is provided with step, the outer wall of cover half die is provided with the step suitable with dynamic model die inwall step, make dynamic model die and cover half die effectively form closed cavity.In common mould, dynamic model die and cover half die can produce certain shape difference dislocation unavoidably when loading and coordinating, arrange step can not only effectively avoid the generation of this situation and cause occurring the situation that powder stock leaks outside (namely " running material "), and provide the path of continuing compacted powder material forming idiosome for follow-up secondary close press-fitting mould step.On the inwall of dynamic model die inner chamber, set step can be one or more levels, and on corresponding cover half die outer wall, prefabricated suitable step also can be one or more levels.If have higher requirement to the closure of mould molding cavity, then according to demand, step can be set to two-stage or multistage, step shape also can adjust according to real needs.
On the inwall of dynamic model die inner chamber, set length of bench is the 3-15% of injection-molded product thickness, namely theoretically, by product density being promoted 3-15% in the compacting process in the close press-fitting mould step of secondary.But draw from the practical experience of inventor; under the processing conditions of common clamping; not unconfinedly can carry out compacting to powder stock always; once the hypertonia used in the close press-fitting mould process of secondary, there will be comparatively serious raw material in die cavity and to leak outside the situation of (namely " run about material ").The present inventor found through experiments, and according to the granularity of powder stock and with the mixed proportion of binding agent, set length of bench upper on cavity wall in dynamic model die is decided to be the 3-15% of injection-molded product thickness for preferably to arrange.If raw material granularity is comparatively large, and binding agent is general to the wetability of material powder, then the above-mentioned length of bench of adjustable is 8-15%; If raw material granularity is less, binding agent is good to separation wetability, then the above-mentioned length of bench of adjustable is 5-10%; If the compactness of raw material and binding agent itself is just more excellent, then adjusting above-mentioned length of bench is 3-5%, system for different powders and binding agent makes suitable adjustment not only can maximize utilization rate to powder stock, and can ensure the stability that shaped article density promotes in mass production process.The present inventor is found by great many of experiments, to particle mean size be material powder within the scope of 10 μm-50 μm suppress time, the inwall arranging dynamic model die inner chamber length of topping bar is 10% of injection-molded product thickness, injection molding product density can be promoted nearly 10% at optimum conditions.
On cover half die outer wall set with the inwall of dynamic model die inner chamber on suitable length of bench can be consistent with the inwall of dynamic model die inner chamber length of topping bar.Further preferably, on the inwall of length of bench comparable dynamic model die inner chamber set by cover half die outer wall, set length of bench is short, makes dynamic model die and cover half die form closed cavity so that more efficiently.
Utilize above-mentioned powder injecting molding die to prepare a method for shaped article, comprise the steps:
(1) first matched moulds: dynamic model die is mobile to cover half die first time by clamping, closes dynamic model and cover half, makes dynamic model die and cover half die form closed cavity, keep one section of preset space between dynamic model and cover half;
Step (1) is first time matched moulds, and object is preliminary by powder stock compacting, makes mould-cavity temperature and pressure reach desirable value, discharges the gas in powder stock, allows product just one-step forming.Above-mentioned clamping may be selected to be any suitable commercially available injection machine or forcing press, if desired heats, and forcing press can use by Heating System Supporting.
(2) pressurize is injected: by injection feeding mechanism, be injected in mold cavity by powder stock by feed nozzle, after being full of raw material in mold cavity, keeping feed pressure.Injection feed system can select feed system of the prior art, as screw in injection molding machine feed system.Keep feed pressure can impel exhaust further, and effectively make product even.
(3) close press-fitting mould: after step (2) completes; by clamping, dynamic model die is mobile to cover half die second time; until the die joint of dynamic model and cover half closes completely, namely remove preset space between dynamic model and cover half completely, make the further compacting of product in die cavity.
This step is the second time compacting operation of mould, namely to have reached under the precondition of suitable temperature and pressure product compaction again at die cavity.Preset space between dynamic model and cover half is not more than length of bench suitable with set step on the inwall of dynamic model die inner chamber on cover half die outer wall.Corresponding, the preset space between dynamic model and cover half is the 3-15% that injection forms product thickness, can be preferably 10% of injection-molded product thickness further.Such length is arranged, both the closure of dynamic model die and cover half die cavity in step (1) can have been ensured, also the process that can be second time matched moulds compacting in step (3) provides the moveable path of dynamic model, effectively can promote the density of product in die cavity after secondary compaction has operated.
(4) die sinking pickup: by the cooling system cooling die of mould, remove feeding mechanism, open dynamic model, by the ejector pin component in mould, product is ejected.The cooling system of mould can use cooling-water machine general in industry.
The present invention has following beneficial effect:
1, effectively promote the compactness extent of degreasing sintered front shaped article in powder metallurgy, optimum can make product density promote 10%, thus the density of finished product after effectively promoting sintering.
2, do not need undue dependence reduction raw material powder particle size and Control granularity uniformity to improve density and the compactness of product, the cost of product can be reduced thus, enhance competitiveness.
Accompanying drawing explanation
Fig. 1 is the method flow schematic diagram that powder injecting molding die of the present invention prepares shaped article.
Fig. 2 is powder injecting molding die of the present invention first matched moulds step schematic diagram.
Fig. 3 is powder injecting molding die of the present invention close press-fitting mould step schematic diagram.
Fig. 4 is powder injecting molding die die sinking pickup step schematic diagram of the present invention.
Number in the figure illustrates:
1-dynamic model die 2-thimble 3-moving clamping plate 4-ejector retainner plate lead 5-ejector retainner plate assembly
6-dynamic model header board 7-cover half die 8-feed nozzle 9-cover half template 10-push rod
Gap 13-step (oval frame mark place) 14-die joint 111-dynamic model 112-cover half between 11-product 12-dynamic model die and cover half die
A place distance is in first matched moulds step, the preset space kept between dynamic model and cover half.
Detailed description of the invention
Below in conjunction with drawings and Examples, the present invention will be described in detail.
Utilize injection machine conventional in Powder Metallurgy Industry and corollary system in the present embodiment, the powder stock granularity average out to 10 μm selected, is installed on mould on injection molding machine.This part is prior art, at once common technology in the industry, does not add to repeat at this.
As shown in drawings, mould comprises dynamic model 111 and cover half 112.Dynamic model 111 comprises dynamic model die 1, thimble 2, moving clamping plate 3, ejector retainner plate lead 4, ejector retainner plate assembly 5, dynamic model header board 6.Cover half 112 comprises cover half die 7, feed nozzle 8, cover half template 9.Wherein dynamic model 111 is connected by push rod 10 with cover half 112, and dynamic model 111 moves along push rod 10.Dynamic model header board 6 fixed bearing dynamic model die 1, thimble 2 fixed by ejector retainner plate assembly 5, and ejector retainner plate lead 4 connects dynamic model header board 6, ejector retainner plate assembly 5 and moving clamping plate 3 in turn.In cover half 112, cover half template 9 fixed bearing cover half die 7, the opposite side do not connected with dynamic model die 1 at cover half die 7 is provided with the feed nozzle 8 matched with cover half die 7.
Above-mentioned die assembly is the common implementation method of mould of the prior art, it should be noted that, though the mould in the present invention is applicable to the method in the present embodiment, but be not limited only to mould in the present embodiment uses, such as, although the mould used in the embodiment of the present invention is horizontal type structure, the mould in the present invention and method are equally applicable to the mould of vertical structure.
Be provided with gap 12 between dynamic model die 1 and cover half die 7, in dynamic model die 1, cavity wall is provided with step 13, and length of bench is 10% of shaped article thickness, the outer wall of cover half die 7 is provided with step suitable with it.Step on cover half die 7 outer wall is slightly shorter than the step on inner wall in dynamic model die 1.Gap 12 thickness between setting dynamic model die 1 and cover half die 7 is 0.1mm, and gap 12 and thimble direction are angularly 5 °.
Utilize above-mentioned powder injecting molding die to prepare the method for shaped article, step is as follows:
(1) first matched moulds
As shown in Figure 2; by the clamping of equipment, dynamic model die 1 is mobile to cover half die 7 first time; dynamic model 111 is closed with cover half 112; form closed cavity, the length retaining one section of preset space (as in Fig. 2 shown in A) this preset space between dynamic model 111 and cover half 112 is 10% of injection-molded product thickness.By powder stock compacting, make mould-cavity temperature and pressure reach desirable value, discharge the gas in powder stock, allow product 11 just one-step forming.
(2) pressurize is injected
By the injection feeding mechanism of equipment, powder stock is injected in mold cavity by feed nozzle 8, after being full of raw material in mold cavity, keeping feed pressure.
(3) close press-fitting mould
After step (2) completes; the clamping of equipment is mobile to cover half die 7 second time by dynamic model die 1; product in further extrusion die profile; until dynamic model 111 closes completely with the die joint 14 of cover half 112; namely remove preset space between dynamic model 111 and cover half 112 (as in Fig. 2 shown in A) completely, make the further compacting of product in die cavity.
(4) die sinking pickup
By the cooling system cooling die of mould, remove feeding mechanism, open dynamic model 111, by the ejector pin component in mould, product is ejected.
Owing to there being the process of the close pressure of secondary, obtain by above-mentioned steps the product that the shaped article after compacting obtains than conventional method more closely knit, density promotes nearly 10%.After sintering, the compactness of product and mechanical property can significantly be promoted the product obtained in this way.
Finally it should be noted that, above embodiment is only in order to illustrate the technical scheme of the embodiment of the present invention but not to be limited.Although be described in detail the embodiment of the present invention with reference to preferred embodiment, those of ordinary skill in the art is to be understood that and still can modifies to the technical scheme of the embodiment of the present invention or equivalent replacement, and these are revised or be equal to the scope that replacement also can not make amended technical scheme disengaging embodiment of the present invention technical scheme.