Press tool

Applications Ion implantation is widely employed to improve the life of tools. Thus press tools, dies and gear cutters can be treated to increase their durability by three times or more. Nitrogen-implanted tungsten carbide drawing dies for copper and iron wire can be improved up to fivefold. By implanting chromium, aluminium or silicon a considerable increase in the corrosion resistance of steel can be obtained. Implantation of chromium into aircraft bearing alloys has improved their durability in marine environments . 

All operations take place simultaneously in different stations. Sixteen stations were commonly used in earlier machines with outputs between 500 and 1000 TPM and tablet diameters up to 15 mm. Presses with outputs orders of magnitude greater than the above are now widely available. The dies are filled as they pass beneath a stationary feed frame, which may be fitted with paddles to aid material transfer. The die cavities are completely filled and excess ejected prior to compression. Compression involves the movement of both punches between compression rolls, in contrast to single station operations where only the upper punch effects compression. Ejection occurs as both punches are moved away from the die on cam tracks until the tablet is completely clear of the die, at which point it hits the edge of the feed frame and is knocked off the press. Tooling pressure may be exerted hydraulically, rather than through the use of mechanical camming actions, as is the case with machines produced by Courtoy. 

J. A. Waller, Press Tools and Presswork , Portcullis Press, London, 1978. 

It is important for those working with a tablet press to be familiar with the terminology used in the industry concerning the punches and dies. Table 1 describes the commonly used terms related to press tooling. Some of the press tooling parts can be identified in Figure 5. 

For a clear understanding, the Thomas Engineering Press Tooling Manual [24] states the following ... 

In addition to the possible causes of capping and lamination discussed previously, one should also consider the possibility that shape of the tooling and tooling defects are sources of capping. In such cases the problem can simply be alleviated by repairing or altering press tooling. 

Various approaches can be used to solve picking and sticking problems during tablet manufacturing, namely optimization of press tooling, process parameters, and formulation. Generally, it is important to find the optimal combination of formulation and process parameters, particularly when market image tablets are to be produced. 

Press Tooling Manual (2003), Thomas Engineering Inc. Hoffman Estates, IL, USA. pp. 1-38. 

The diameter of a pelleting die may be maintained to almost any tolerance specified. Similarly, the distance between the top and bottom punches of an automatic pelleting machine, or the punch-to-heel distance in a stop pressing tool, can be held to any desired tolerance. Thus, the dimensional variations are essentially the variations in expansion of the material, during and after ejection from the die. The immediate expansion upon ejection for a typical expl used for pressed pellets is about 0.3%. Feiiet-to-peilet variations are usually less than 0.1% but the expansion continues... 

The making of these tools will prove both interesting and instructive, and to many may be an introduction to better and more elaborate press-tool work. The results in anj case will repay the labour, and the writer loiows a firm who during the Avar being unable to secure Avashers or presses, resorted to the tool as slmwn by big. 23. 

Tool condition The condition of press tooling should always be evaluated when picking occurs. Polishing the punches and application of various coatings to the tools may help to eliminate picking for certain materials. 

In single-punch tablet presses (reciprocating tablet presses), the punches are fixed to the punch holders which travel up and down, and in many cases fixation screws are used. Each make has its own holder design for punches and dies, and consequently for the tooling sets as well. Therefore little can be said in general terms, but it would appear that on the whole the remarks on the rotary press tooling apply correspondingly. 

Is considerably reduced by lubricating the die walls or pressing tools. 

Figure 265. Photograph of a roller press with hinged frame in the field, opened for roll removal/maintenance. (Courtesy of Koppern/Berzelius, Hattingen, FRG.) Note that the uneven wear on the roller (concave shape of working surface) is a reason for the need to exchange or, respectively, remachine the pressing tools...

Roller cores with integral journals fitted with replacable rings or sleeves as pressing tools. 

The perforated support (die) can be either a flat disc (Figure 320(a)) or concave (Figure 320(b)) and convex (Figure 320(c)) rings. Either the pressing tools or the die or both may be driven. 

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