Machine-guarding problems—one company's solution
Editor's Note: Safety expert Cheryl Henderson is a member of the FMA/CNA Safety Committee. Watch for other committee-authored articles in upcoming issues of thefabricator.com.
What would it take to have press guards in place, adjusted, secure, and working properly every day, through every part cycle? We've come a long way since the days of running unguarded presses, but never a day goes by that a press isn't found with a guarding problem.
Pneumatic controls significantly reduced dedicated-line nonconformities. Guarding lines that are subject to frequent changeover and setup are more challenging. Vertical or horizontal bars commonly are used because of their relative simplicity and flexibility. However, during a parts run, the bars can snag and bend. Screws can loosen, and adjustments can change. Unless you monitor the guard's condition closely, you might encounter guarding problems.
Step 1: Install window brace to increase performance of the bars and reduce setup time.
At the Shape Corp., we looked for ways to address machine-guarding reliability on nondedicated lines. As we problem-solved, we looked for a root cause and determined that the bar length directly impacted the guard's robustness. To reduce that impact, we added windows (see Figure 1) built from the locking frame material to the guard. This allowed for closer adjustment but increased the adjustment time, because, two frames had to be adjusted. The average time to prepare a guard of this type was two hours.
The Next Step
As we reviewed the first step's implementation, we questioned why the windows couldn't be standardized. If we settled on a standard window, we could attach the outside rods permanently and add a smaller guard to the standard window using only the smaller rods. The idea was presented to the team and quickly revised to develop a profile of each part's opening. The appropriate guard could be set up offline and attached to the frame for a particular part. Final adjustments could be made quickly.
Our fabricator used this idea and added his twist by completely eliminating the rods on the smaller guard section. He replaced them with a LEXAN® material. He formulated the templates with a standard identification plan. The templates then were added to the in-process control manual.
The unused LEXAN guards are stored in a rack similar to a printing die rack. If one of the guards has a broken component, within a few minutes a replacement can be completed and attached to the standard window. The guard slides into the window and is secured with a padlock at the top (see Figure 2).
When the part is run on a different press, the window still fits because it is standardized. Best of all, what used to take a couple of hours to set up with every change now takes less than 15 minutes. The guards are in place, adjusted, and secured – accomplishing reliable press guarding.