Support > Knowledge Base > XL200 Series Controllers > Parameters > Shear Dwell Up
Shear Dwell Up
Help ID: 122
Initial Version: 1.0
Appears In: All Software Models Except XL208CL
As of the publishing of this webpage (09/21/10), the assumption of the software of every XL200 Series controller is that it controls a cutoff (shear) press, regardless of whether or not the cutoff is an actual shear, slug die, saw, etc.
The Shear Dwell Up parameter allows the user to define how long it takes the shear to exit the material after cutting or breaking through. Typically, this parameter is set to the same time as the Shear Dwell Down parameter, though most presses will not take as long to exit the material as they will to enter.
Regardless of the physical requirements for the setting, it is important to note that the XL200 Series controller does not dictate the speed of the press. Some users see a correlation between the parameter setting and the amount of time the press fires. The actual press speed is a function of the mechanics of the press, itself - stroke, hydrualic or pneumatic pressure, flow, mechanical linkages, etc. What this means is the controller does not control press speed, the parameter is so the XL200 can know how long it takes for the press to do its job.
Today, most hydraulic or pneumatic presses use spring-return-to-center valves. These valves do not need an Up signal - so long as the valve is not being fired, the press will automatically return to its Up position. Mechanical presses never need an Up signal as their motion is a cyclical process. Still, based on the specific machine application type the XL200 Series controller might need the time required to exit the material in order to properly calculate if it can acheive the next shear target at the current line speed.
Closed Loop Applications
In closed loop flying die applications, the XL200 Series controller must be programmed with a Shear Dwell Up time, regardless of the mechanics of the press being used. The controller must command the servo system to match speed and position with the cut point until the tooling has exited the material.
If the Shear Dwell Down is set to a value that is too short, the servo will begin to decelerate while the blade is still in the material, potentially causing material jam up and buckling, or creating excessive wear on the shear die. If the value is set too long, the die will travel too far, potentially running into the forward overtravel sensor or a hard, physical stop.