PUNCHING AND STAMPING - DALCOS - #2

tools and hourly cost of the machine, the last value being multiplied by the hours necessary for production.

To calculate the hourly cost of the machine, another four component factors will be analysed: labour cost connected to machine operation, maintenance cost, energy cost and lastly the cost of plant amortization. Lastly, the production costs either with sheet punching machines or coil punching machines will be compared. Likewise for the production costs with coil punching machine and press with die. his last part will also provide useful formulas, given the type of product and required quantity, for identifying the technology to obtain production at the lowest cost.

THE TECHNOLOGIES

he technologies analysed for flatbed blanking of the workpiece are: punching from coil, punching from sheet metal and stamping with press. Punching with sheet feeding is the technology that allows maximum flexibility (fig, 2). Complex shapes may be obtained within the space of the sheet and the system is also suited to the manufacture of a single piece. here are machines with manual or automatic loading and unloading; in either case the machine must stop when the sheet is loaded and the finished product unloaded (fig. 3). Punching with coil feeding capability is a technology suited to medium and small quantity production. he machine loads the metal strip directly from the coil; the machine therefore always works in the automatic cycle with good flexibility (fig. 4). Stamping is the technology suited to mass production. In this case the speed is maximum, but flexibility is low: a die is made for each product and its cost must be amortised in production (fig. 5).

PRODUCTION COST: THREE FACTORS

he guiding principle behind the choice of technology to be used is that of the lowest production cost.

his is given by adding up three factors.

he first is the cost of the raw material, which

may be in sheets (for the sheet fed punching

machines) or coil (for the coil punching

machines and press stamping).

he cost for all the raw material necessary for

completing production is considered.

To this should be added the cost of the tools.

he tools for the punch presses with sheet

metal or for the coil punching machines

are standard punches available from various

manufacturers (e.g. thick turret punches).

he latter produce a standard shape (round

or square holes and so on) or special shapes at

every stroke of the punching machine.

he tool for the stamping press is made to

measure for the product to be manufactured.

he standard punches undoubtedly have lower

costs than the special press tools.

he last factor is the hourly cost of the

machine, which is multiplied by the hours

that the machine will require to complete

Fig. 2

Sheet-fed punching machine

Fig. 3

Sheet-fed punching machine with automatic

loading and unloading.

WWW.MECCANICANEWS.COM

LAMIERA • OCTOBER 2005