Boosting performance and worker safety should always be a priority in any operation, and preventing punch failure is an important part of that process at metalworking facilities.
Everything wears out eventually – even punches made of hardened steel. But punches shouldn’t break. A broken punch always has a root cause, but that’s very rarely a manufacturing defect. More often than not, punches break because of set-up issues or improper operation.
Most punch failures fall into one of several categories:
- Punch head failure
- Compressive failure
- Ringing
- Chipping and galling
- Stripping failure
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American Punch Company recommends the following tips to help sort out the reason for your punch failures and to prevent them in the future.
Punch Head Failure
There are two main culprits if the punch head breaks off or fractures:
- The coupling nut is worn or loose
- The punch stem is worn
Either of these issues will allow the punch to move during operation, creating uneven pressure on the punch. If the coupling nut is worn, the punch has space to move in multiple directions, which prevents proper load during operation. If the coupling nut is loose, the punch won’t seat properly seat against the stem in the machine.
You can help prevent this failure by regularly inspecting the coupling nut. Make sure the nut is tight and check the inside diameter to maintain proper specifications for your punch style.
It’s also important to confirm that the punch stem is smooth and flat and not worn in any area.
Compressive Failure
This failure occurs when the compressive strength of the punch is exceeded, and the entire working end of the punch shatters.
Compressive failure is occasionally caused by the total misalignment of the punch and die, so you’ll want to make sure the punch and die are properly aligned.
If the alignment is correct, the material is likely too hard or thick for the punch. In these cases, you’ll want to use an “alpha” punch, which provides the necessary strength and durability to punch through the material.
Ringing
When the material being punched deforms with each stroke of the press, ringing can occur. This generally happens when the material is thicker than the working length of the punch or the punch is entering into the die too far.
To avoid ringing, make sure you have the right size punch for the job. You can also adjust the stroke length to enter into the die a maximum of 1/16”.
Chipping and Galling
Punch face chipping or heavy galling on one area of the punch usually occurs because the punch is allowed to drag, due to poor alignment between the punch and die.
Resolving this issue usually requires adjusting the alignment to provide equal clearance all the way around the punch. You should also make sure the punch stem and die block are clean and clear of debris that could create an uneven surface for tooling.
Stripping Failure
The stripper on your ironworker plays an important role in keeping material in place during punching. The material can move, causing the punch to bind and break, if the stripper clearance is set too high. An angular fracture is a classic visual clue that stripping failure is an issue.
Adjusting the stripper closer to the material will help prevent this failure.
The importance of preventing these issues runs beyond the simple replacement of a broken punch. These common causes of punch failure can also put operators at risk of injury. Proper setup and operation will help avoid these issues, keeping your workers safe, extending tool life and often increasing throughput.
If you’re faced with punch failure, send the broken tool and a sample of the material being punched to American Punch, and the company can provide recommendations to solve your issues. Contact them today for assistance.