In Lights-Out Machining, Part Loading Is Not the Problem — Here is How This Shop Handles Unloading
Correct unloading of the parts affects part quality as well as the capacity of the unattended machining system. Here is more of the experience from our “168” shop.
Precision Tool Technologies of Brainerd, Minnesota, is a shop that uses bar-fed multitasking CNC lathes and bar-fed five-axis machining centers to run unattended not only through the night but through weekends as well. We recently covered this shop’s journey to what it calls “168 machining,” or machining so the shop keeps producing well beyond the one staffed shift and through all 168 hours in a week.
The bar feeders serving these automated machines come from LNS, and all perform well for the shop. Trusting them to deliver work into the machine is no problem. The more difficult challenge relates to the other end, the finished parts. What happens to the part after the machining is done can affect the capacity of the unattended process or the quality of the pieces.
Here are two examples of part unloading challenges the shop has dealt with successfully:
Unloading with Water and Plastic
In one job involving turned brass, the workpieces dropping from the DMG MORI lathe after machining sometimes struck one another in the bin, dinging the work. The part might be machined beautifully by the lathe, but then the ding to the soft part due to gravity could make the part unacceptable to the customer. After various attempted solutions failed to address this problem, here is the system that worked: a bin of water full of ground plastic creates a surface that temporarily catches the part when it falls, until the part slowly sinks through the floating plastic to gently settle with the rest of the parts. Here is that solution in action:
Unloading with Automation
By contrast, on one of the shop’s Willemin-Macodel machining centers, a robot provides for gentle unloading of the finished work. The robot stacks work within in its own enclosed work area as the parts are completed. But Precision Tool runs this machining so long without an operator that the finished parts threaten to overfill the enclosure. The solution: The shop opened a hole in this enclosure and added a conveyor for transporting parts out of the machine.
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