This is one of the really intresting question that all our new customers have in their pocket.
We have replaced the traditional kinematics, consisting of shaft and crankshaft, with a screw. This allows to improve the accuracy and the speed of response of the press system thanks to the reduction of friction. Thanks to the screw press, the load and the force is constantly applied in the vertical direction, on the contrary to what happens in the crankshaft system, where the force is perfectly vertical only at 0° and 180°, in all other situations the forces are different.
So much different.
In fact each mechanichal press (that have a crankshaft) is provided with a graphic that will tell you how and when the nominal power (energy, capacity, ton) is available. The parameters that affects the real pressing power applied to the mold are directly depending from:
- Speed of the machine (lower is the speed lower is the power)
- Distance from the closing bottom position 180° (higher is the distance, lower is the power, as effect of crankshaft link)
- Mass of the flywheel
This is an example of a 130 Ton press graphic:
The green curved line represent the available pressing power assuming that the press is running at 55-60 strokes per minute.
It is quate clear that the power is really high, but only in the few last millimiters of the stroke. Against that, the blue and orange line are referred to a screw servopress, that have instantly the nominal and maximum pressing power in each position of the travel; the advantage is quite evident, no one single aluminium or paper tray have a depth of few millimeters, all the trays are in a range of 30 to 100 (or more) mm depth. The consequence is that the pressing power is requested so much earlier to mold the aluminium (or paper).
Let’s have an example: need to form a 50 mm depth alufoil container. Considering a “L” type edge and 2 mm rolled rim, the start point of forming can is apporximately at 60 mm from the closing position. At this distance, the 60 ton crankshaft mechanical press have a pressing power of 2,5 ton. A screw servopress, at same position has the full power of 20 ton (200 KN), it is 8x times higher!
So, let’s assume we wish to have a crankshaft mechanichal press with at least the same pressing power of a screw servo press, at least starting from 80 millimiters from the closing point:
Wow! That is the true comparization, the 20 t screw servopress have a same pressing power of a 550 ton crankshaft press, from 60 mm distance to closed position.
That’s how is possible that Anistek servo presses never got problems into forming any kind of container. If you still have doubts about power capacity of our machines feel free to write to us, we’ll be happy to show you all details and real applications.
Authored by:
Marco Capra
CEO and founder of Anistek Mechatronic GmbH
24/07/2018
