Design And Research On Precise Powder Compaction Forming Equipment With Integrated Mold Base

In the Powder Metallurgy (P/M) production, P/M equipments are vital important indetermining the formed P/M parts’ precision and density. Domestic produced P/Mequipment now is large, complex and expensive, so an advanced P/M precisionforming equipment is designed, the new equipment have two upper and three lowermulti-plate mold base, drived and closed-loop controlled by integrated cylinder, thehigh-precision, high-density, uniform density P/M complicated production can beproduced.The integrated mold base P/M precision forming equipment is developed. Due tothe integrated mold base structure, the equipment can be specialized in P/Mproduction, which makes it simpler, cheaper and easier to debug, furthermore theformed parts are more precise. To ground the design of integrated mold base in reality,the constitutive model accurately describing the specific deformation behavior of thepowder compacted in the equipment is established, in which the flow stress relationfits experimental results better is used, then numerical simulation m odels of the P/Mparts’ forming process and the whole equipment’s simultaneous activity areestablished, by which the influence of equipment structure, parts structure andforming process on equipment are analyzed, and the overall design plan is checkedthen. Electrohydraulic proportional control system of equipment is studied, thecontrol software is programmed considering the specific characteristics of the pressesand their hydraulic system used in the equipment, the prototype is successfullydeveloped, related research results achieved are listed as follows.By numerical simulation method based on the ellipsoidal yield criterion, thepowder’s mechanical behaviors in the compacting process are studied, through thecomparison of load-stroke curve of model with that of experiments, the change of thepowder’s flow stress in the whole compacting process is analyzed. The powdercompacting experiments with different apparent density are carried out, theexperimental results are analyzed and arranged, combining with the dimensionalanalysis of the Doraivelu’s flow stress model, the flow stress model δ(ρ)which canbetter apply to the integrated mold base P/M precision forming equipment.The compacting process of the powder cylindrical specimens is analyzed by themodel established, the load-stroke curves of model agrees with that of experiments quite well, which means that the model is better in describing the powder’smechanical behaviors in the compacting process. The relative density distribution ofmodel is compared with that of experiments and they agree with each other quite welltoo, which supports the conclusion that present model is better than the past models.Based on the model established, the numerical simulation of the compacting processof some classical parts are carried out systematically, which supply the design ofintegrated mold base P/M precision forming equipment with a theoretical basis.Using multibody dynamics numerical simulation method, finite element model ofthe entire equipment is established, which can be used to analyze the contact statusbetween every equipment’s composing parts, also the deformation, stress distributionof all composing parts can be seen from the nephograms given by the model, whichshows that the deflection of mold plates area are within the safe levels. Compare themaximum stress of each composing parts with its yield limit, it can be seen that allparts are in the elastic limits, no yield behaviors are exhibited. The simulated resultsprovide the optimization design of equipment with a scientific basis.The modal analysis of the equipment is performed, every natural frequencies andcorresponding vibration modes can then be predicted, and the first to the tenth ordernatural frequencies are derived. The modal analysis shows that all natural frequenciesof the equipment have no overlap with each other, no resonance occurs and thedeformation tendency is quite small. From the vibration shape in every naturalfrequency calculated by modal analysis, the vibration amplitude distribution and theanti-vibration weak area are displayed, the study provides a reliable basis onsuppressing the vibration and noise of the entire equipment, and also providesnecessary a theoretical basis for the structure dynamic optimization of the entireequipment.The key technologies being proposed and implemented in the equipment includesthe cartridge valve circuit, electrical and hydraulic proportional valve and the gratingscale used in the hydraulic transmission system, accurate and independe nt continuouspath control to every punch through combination control by different sensors,assurance of height change rate’s uniformity of the mould’s pressing plane whencompacting multi-plane P/M parts with big height differences, and then compactinghigh-precision, high-uniformity density P/M parts with higher level of productivityand quality.The equipment successfully developed and the integration of the mold base structure with the P/M forming equipment, with independent intellectual propertyrights, utterly change the traditional P/M equipment’s structure, which makes itsimple, easy to debug and can make best of the characteristics of integrated equipment.The mold base is driven by symmetric integrated hydro-cylinder with theindependently control of all the presses, then the compacting of P/M part with twoupper step faces and three lower step faces are achieved. Using the grating scale,sensors and the hydraulic system, the location and pressure of the presses can beaccurately closed-loop controlled, the attainable precision of the equipment is±0.03mm.