Feature article: PIM International, Vol.2 No. 3 September 2008, pages 23-32, 3736 words

Author: Dr. Georg Schlieper, Ingenieurbüro Gammatec, Germany

Ingenieurbüro Gammatec, Alleestr. 101, D-42853 Remscheid, Germany 

Introduction

In the following feature, Dr. Georg Schlieper reviews the currently available PIM feedstocks along with the main raw materials used. The manufacturing technologies applied in feedstock preparation and methods for feedstock characterisation are also covered. All the main players in the feedstock industry have also been profiled.

According to Wiktionary, the internet dictionary, the term ‘feedstock’ refers to ‘any bulk raw material constituting the principal input for an industrial process’. In powder injection moulding (PIM) we use the word in a more restricted sense. For PIM, feedstock is a highly loaded compound of metal or ceramic powder with a plastifiable binder phase that can be processed into complex, high precision components by plastic forming, followed by debinding to remove the plastic binder and sintering of the remaining powder body. Therefore, when we look at feedstock for PIM, we have to keep in mind that powder, binder and the processing conditions are mutually dependent, even if we do not mention this explicitly each time.

Feedstock ingredients: metal & ceramic powders

The raw materials for PIM feedstock are the metal or ceramic powders and the binder which is required to form a mouldable feedstock. While the binder is only an intermediate processing aid and removed from the products after injection moulding, the properties of the powder determine the final properties of the PIM product.

Let us first consider the metal powders. These are typically sintered to a high density (usually > 95% of full density) without using external pressure. Without going into details of the sintering theory it can be said that basically two ways can be pursued to achieve this: liquid phase and solid state sintering. .....

Feedstock supplier profiles

This article includes detailed profiles of all known commercial MIM and CIM feedstock suppliers at time of publication.

Further sections of this article include:

- Feedstock ingredients: binders
- Feedstock preparation
- Feedstock characterisation
- In-house feedstock production vs. commercially produced feedstock
- Conclusions

Figures and Tables:

Fig. 1 Carbonyl iron powder (SEM, above) and cross-section of a powder particle (Courtesy BASF AG)

Fig. 2 Gas atomised stainless steel powder (SEM) (Courtesy Ryer Inc.)

Fig. 3 Ceramic alumina powder for PIM (SEM) (Courtesy Inmatec GmbH)

Fig. 4 Golf club made by MIM (Courtesy Latitude Manufacturing Inc.)

Fig. 5 Schematic of the in-line PowderFlo® injection moulding process (Courtesy Latitude Manufacturing Inc.)

Fig. 6 Sigma blade kneader extruder (Courtesy Patterson Industries (Canada) Limited)

Fig. 7 Twin screw extruder (schematic) (Courtesy Chris E Scott)

Fig. 8 The feeder and shear rolls of a shear roll extruder (Courtesy Bellaform GmbH)

Fig. 9 Metal (left) and ceramic (right) feedstocks produced by Dai-Ichi Ceramo Co., Ltd., Japan

Table 1 Carbonyl iron powder grades produced by BASF