PUNCHING AND STAMPING - DALCOS - #6

medium and long-term savings in tools. hat is why the cost of amortization and therefore the hourly cost of the stamping line will be considered as slightly lower compared to the coil punching machine.

he stamping press, as has been seen, produces one piece at each press stroke. Productions of 40, 60, 80, 120 workpieces and more per minute are therefore normal. he coil punching machine requires from 0.5 to 1 second for each operation. he production of one workpiece may require, for example, from a few seconds to tens of seconds.

To obtain the discriminant number of pieces N, which for the given definition indicates whether to produce with a coil punching machine or to make a special tool for stamping with the press, it is necessary to equalise the two production costs calculated from the equation: [production cost] = [raw material] + [tools] + [hourly cost] x [hours of production]. he raw material cost is the same and may therefore be eliminated from the calculation. Given the great difference between the cost for the punch press tools and the press die, the cost of the punch press tools are considered as practically nil compared to those of the special die. Also given the greater speed of the die press over the punch press, the necessary hours of production when manufacturing with press and die are considered at first analysis as zero. he necessary hours of production for com­pleting the production with the coil punching machine are equal to the number of pieces N multiplied by the hours required to make one piece (time-cycle). After a few passes, it can

Fig. 9

Examples of products made by punching from coil (door panels).

COMPARISON BETWEEN PUNCHING FROM COIL AND STAMPING BY PRESS

With these two technologies available, given the high cost of press tools, the aim is to determine the discriminant number of pieces N below which it is more economic to work with the coil punching machine. For pro­duction runs greater than N, it will be more economic make a special press die. Also in this case each of the factors making up the production cost will be analysed and the conclusions drawn.

Both machines work from the coil and the raw material cost is therefore identical.

The cost of special press tools is higher than the cost of punch press tools, which are standard and may be reused in various productions. The cost of setup time is inclu­ded in the tool cost; it is considered as being equal in the two machines and negligible compared to the cost of the special press tool.

Both machines need the constant presence of an operator and the labour cost is therefore negligible. The annual maintenance and electricity costs are similar for the two machines. The cost of amortization of the two machines also here depends on the type of system.

Basically the coil punching machine, with a slightly higher investment, offers great

Fig. 10

Products punched from coil (metal furniture panels and shelves).

1

WWW.MECCANICANEWS.COM

LAMIERA • OCTOBER 2005