Review: IPMD 14th Edition 2010-2011, 14 Pages, 6684 words

Author: Prof. Dr.-Ing. Paul Beiss, RWTH Aachen, Germany

RWTH Aachen, Institute for Materials Application in Mechanical Engineering, Augustinerbach 4, D-52062 Aachen, Germany

Continuing developments in process technology and production equipment are providing the global PM industry with the tools to produce ever larger, more complex and competitively priced PM shapes with improved properties. This review by Prof. Dr.-Ing. Paul Beiss, RWTH Aachen, Germany, looks at trends in equipment and processes for powder compaction.

Introduction

Axial die compaction is by far the most important shaping technology for powdered materials. To achieve the extreme height precision required in compaction of hardmetal inserts or for the complex multilevel geometries which are typical of newly developed structural parts, presses are needed to actuate the various tool elements. Usually the tools are not assembled in the press but in a die set or adaptor, an easily changeable type of tool cassette which is prepared outside the press for the next component to be manufactured.

When compacting multilevel parts the different axial punch movements are partially executed by the press frame and in part actuated by the adaptor. The simplest forms of die and lower punch sections of die sets are shown in Fig. 1. Most powder presses demould the green compact by withdrawing the die platen over the lower punch, which is connected to the base platen. The base platen with the stationary lower punch is fixed in the press frame and serves as the reference plane for all tool movements. The die platen is connected to the lower machine actuating mechanism by a T-slide and pillars, which are tightly guided in the base platen.

Newer, mainly hydraulic presses work sometimes with fixed die platens and the lower punch is lifted for compaction and ejection. Depending on the design of the press frame die sets can look different than the examples in Fig. 1, but the principle - withdrawal or ejection - stay the same. In this elementary form the upper part of the adaptor consists of an upper punch mounting platen sliding over the T-piece of the upper crosshead. The upper punch platen is guided versus the die platen via pillars............

Further sections of this article include:

• Press frame
  - Powder filling
  - Press drives
• Hardmetal presses
• Presses for structural parts
  - Production controls
  - Striving for higher densities
• Isostatic pressing
• High speed rotary pressing
• References

Figures and Tables:

Fig. 1 Principle design of simple adaptors for die withdrawal, left and lower punch lift for ejection, right

Fig. 2 Examples of centre pin applications: outer lower punch lift, left, core rod withdrawal, middle and opening filling room for a second powder, right

Fig. 3 Upper auxiliary piston and possible uses: Powder transfer with inner punches, upper punch hold down load and retraction of inner upper punch in demoulding

Fig. 4 Fill shoe design principles: Hose connection to hopper, left and predosage of powder, right

Fig. 5a Fill shoe rest upon overfilled die cavity

Fig. 5b Suction filling of parallel walled dies with less readily flowing powders

Fig. 5c Feed shoe shaking for better weight uniformity

Fig. 5d Contour filling to improve concentricities

Fig. 6 Grooving insert with profiled cross hole (Courtesy Fette, Germany)

Fig. 7 Core pin arrangement for profiled cross holes (Courtesy Dorst Technologies, Germany)

Fig. 8 Radial compaction die with up to six punches (Courtesy Osterwalder, Switzerland)

Fig. 9 Hardmetal milling cutter with radially compacted chip breaker in the rake face and demonstrator component to illustrate the capabilities of radial compaction (Courtesy Dorst Technologies, Germany)

Fig. 10 Demonstrator component for radial compaction (Courtesy Osterwalder, Switzerland)

Fig. 11 Compaction die with radially split die wall for the demoulding of difficult undercuts (Courtesy Fette, Germany)

Fig. 12 So-called mono-column adaptor for better accessibility to the tool area (Courtesy Fette, Germany)

Fig. 13 Direct electrical drive press for hardmetal compaction (Courtesy Osterwalder, Switzerland)

Fig. 14 Quick-clamping system for five levels, schematically (Courtesy EROWA, Switzerland)

Fig. 15 Press for indexable inserts, protective panels removed (Courtesy Komage, Germany)

Fig. 16 Selection of die compacted structural parts (Courtesy Dorst Technologies, Germany)

Fig. 17 Row of hybrid presses with overhead eccentric driven by two worm gears (Courtesy SMS MEER, Germany)

Fig. 18 Axial split die compaction with multiplaten adaptor; 1: Filling of the lower die cavity; 2: Closure of the die with the outer upper axis; 3: Powder transfer into the upper die cavity; 4: Double-sided compaction; 5: Withdrawal of the upper die under upper punch hold down load; 6: Ejection with lower punch; 7: Core rod retraction, lowering of the lower punch in filling position and removing of compact

Fig. 19 Double raced sprocket with circumferential groove (Courtesy Nissan, Japan)

Fig. 20 Plug in panel for the hydraulic supplies in a fixed base platen (Courtesy Dorst Technologies, Germany)

Fig. 21 Turning station to strip and reassemble the upper part of a multiplaten adaptor (Courtesy Dorst Technologies, Germany)

Fig. 22 Pitless design with two lateral pistons actuating the die platen (Courtesy SACMI Matrix, Italy)

Fig. 23 Structural part press of 630 kN capacity for eight tool levels; set-up flush with the floor without pit; the adaptor has only mechanical guiding functions, all hydraulic pistons are located in upper ram and lower crosshead of the press frame (Courtesy Lauffer Pressen, Germany)

Fig. 24 16.000 kN press with robotic handling of the green compacts; the robot is programmed from the press control panel (Courtesy Dorst Technologies, Germany)