Page 42 - MetalForming Magazine March 2022

to eject can blow out entire die sections, send metal shards flying and even cause the press to stick at bottom, dies to be ripped from the clamps, and any number of other undesirable events.
In progressive dies, optical sensors typically find use for monitoring part ejection, although other solutions also may work depending on the applica- tion. As with feed progression, several process variables including part shape, tooling design, and press stroke and speed prevent a “one-size-fits-all” solu- tion. Transfer operations also apply sensors on end effectors to ensure that they maintain control of the part until it is deposited onto an exit conveyor or chute.
Part ejection also plays an important role in hand-fed operations, with the press operator protecting the die and press from damage by removing the last formed part before inserting anoth- er. Beware, however, as I’ve surprisingly heard of numerous occasions where, with compound knockout dies, the last part fails to be knocked out of the upper die half by the knockout bar, rather than fall onto the lower die section during the press upstroke. In these cases, it is imperative that the operator remove that jammed part from the die before loading another blank and stroking the press to avoid jamming two parts in the upper die. Otherwise, you risk blowing up the die or the press sticking at bottom because it cannot force its way through the bottom of
the stroke.
Yet another event to monitor: Slug
ejection. Here, certain die designs may have constraints such as limited shut height that can prevent the press from consistently shedding scrap. In other cases, the scrap itself will stick together and fail to exit the tool with each stroke. In these instances, sensors get the call to ensure proper scrap ejection and prevent crashes.
In all cases, we recommend that stampers perform a die-protection risk assessment with each tool, much like those performed to ensure pressroom safety. Include the toolmakers and setup team and have them identify any incidents that could occur, eval- uate the likelihood of each incident and the severity of the possible dam- age, decide which incidents can be “engineered out,” and establish how much risk they can accept or if sensors should be implemented to prevent each type of incident. In a perfect world, conduct these risk assessments during the die- and process-develop- ment phase.
While stampers well-understand the benefits to production from eliminat- ing crashes, these benefits extend into other departments as well. Avoiding crashes eliminates hours of labor for an already busy and likely understaffed tool room, as well as for the press tech- nicians. Time spent repairing broken tools and presses can be better spent working on value-added projects such
This advanced press control monitors and controls press-line parameters that previ- ously would require manual intervention. In this example, upon recipe recall the press control changes the shut height and counterbalance force to the set- points stored in the job recipe. This reduces setup time and ensures use of the proper settings with each job.
as improving existing and upcoming tools, automating manual processes, and performing preventive-mainte- nance inspections.
Improvements Up and Down the Press Line
The value of sensor applications does not stop where the tooling ends. Sensors also find use for monitoring press-line auxiliary equipment. Exam- ples include scrap systems that must continue to run as the press strokes; scrap backups can cause huge prob- lems. End-of-coil sensors on coil lines can trigger a press stop before it is nec- essary to tail-out in a more deliberate way. Sensors also can ensure that lubri- cation systems have oil in their reser- voirs, so that tooling does not run dry.
Finally, stampers rely on sensors to continuously monitor for part quality during production. Relatively simple examples include deploying stripper level sensors that stop the press if slugs or other foreign objects make their way to the top of the strip or part, or sensors that directly measure part features dur- ing the process. Using analog sensors for part measurement, in vision sys- tems and at gauging stations in the tooling can add a whole new level of capability to the pressroom.
All of this allows stampers to operate their press lines safely and without constant, direct operator monitoring. When installed and used properly, especially in applications where small parts are bulk-packed into bins, process automation using modern press con- trols and sensors can allow a single operator to effectively run multiple presses. MF
40 MetalForming/March 2022
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