29.12.2012 Views

3 Fundamentals of press design

3 Fundamentals of press design

3 Fundamentals of press design

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

46 <strong>Fundamentals</strong> <strong>of</strong> <strong>press</strong> <strong>design</strong><br />

This <strong>of</strong>fers the diemaker and the machine operator the capabilities<br />

for optimization <strong>of</strong> the drawing process and for the reduction <strong>of</strong> die<br />

start-up times. The stretch forming process, for example, can be initiated<br />

by briefly raising the blank holder force, or the material flow correspondingly<br />

facilitated by reducing the <strong>press</strong>ure in certain areas <strong>of</strong> the<br />

blank holder (cf. Sect. 2.1.4). To improve part quality, output and tool<br />

life as well as reducing noise, the draw cushion can be pre-accelerated.<br />

This means that the draw cushion is already set in motion before the<br />

slide impacts the blank. This reduces the relative speed between the<br />

slide and blank holder considerably as compared to an uncontrolled<br />

draw cushion. Due to the reduced impact <strong>of</strong> the blank holder, the num-<br />

female die<br />

drawn part<br />

blank holder<br />

<strong>press</strong>ure column<br />

lifting bridge<br />

Fig. 3.1.11 Design <strong>of</strong> a hydraulic draw cushion<br />

lifting cylinder<br />

Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998<br />

punch<br />

moving bolster<br />

foundation<br />

displacement cylinder

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!