Punching tools background

Maintenance of punching tools

Every owner of punching press consumes a lot of punching tools for his applications. And normally the proper maintenance and servicing of punching tools is one of the reasons to follow the permanent quality of the punched parts with the possibility for clever saving of costs of new punching tools purchasing.
Because of constant hit of metal it is normal to have the wear of punching tools, in particular punches themselves. For the production process it means the higher force of punching press to execute the hit and additional deformation of metal near the punching hole with appearance of burrs.
Punching tools grinding Moreover, more work with the weared tooling causes more problems and more wearing for the tool itself because the area if wearing increases. For sure, more improper force for punching press reduces the stable life of the machine.

What is the procedure of maintenance? The main cutting area of tool needs to be regrind. So the standard punch press operator's duties are to include the necessity of continuous verification about the quality of tool, fabricated part, presence of burrs, absence of improper increased noise of the machine.
There are a lot of parameters which affects the life of the tool and intervals for regrinding. Standard position for tool manufacturers is around 40000-50000 hits but for sure this number could be different depends of the hole, force and the material used. Every tool allows several regrinding procedures and it is important to catch the right interval in time, otherwise the size of the removing material will be higher and quantity of possible regrinding will be reduced, for example it could be started from 0,1-0,2 mm if the regrind is done in time but could be enlarged for 0,4-0,5 mm if the operator missed the time for regrind.

The punching tooling in a lot of executions allows the special adjustment for positioning of the punch after material removal. If punch has channel for lubrication, the quantity of hits before maintenance will be much higher. One of the best positions to verify the necessity for tooling to be regrind is to verify the cutting edge as the main area of tool for wearing and damaging because of the contact with the material.
The regrinding could be executed with the use of any grinding machine. From one way it is not a hard and complicated procedure, moreover the grinding machine is available in lot of workshops. From second side operator has a question to adjust the proper way for regrinding, create a program if it is NC or CNC machine and to make tight fixation of tool with the table of the machine.
That is why to prevent additional operations and to save time the market offers punch and die grinding machines for the main application to regrind the tooling for punch presses.
There are different and possible solutions from manual equipment till fully automatic regrinding machines to make programs for each tool. Depends of the machine, special adapters could be used, fabricated specially for tools for main producers and systems like Amada Thick Turret, Trumpf, Multitool etc. These adapters are the main important point if to use for example flat grinding machine. One more important point that regrinding itself needs to be only with the coolant supply and not as dry grinding process.

One of advantages to have in-house punch and die grinder is the additional possibility to make angle grinding (if possible with adaptors or the machine construction). It means to make proper regrind of shearing tools – forms “whisper” or “double whisper” which are used to make better penetration of the tooling with the reduction of force of punching press necessary to make the hit. These forms are used if the force is high or to make the contour outside the part, for example for standard slitting tools 5x80.

Everything is much more important when the turnover of workshop is big. For simple manual punching machine probably the maintenance of punching tooling doesn’t make a big sense but with big sheetmetal fabrication workshop with 4-5 CNC punching presses with 2 shifts operation the reasonable control can save a lot of money because the turnover for purchases of punching tools can be dozens of thousands Euro.


Punch and die grinder

Punch and die grinder

Semi-automatic effective machine for grinding of punches and dies for punching presses as the maintenance process for punching tools. ll possible types (Amada Thick Turret, Trumpf, Multitool etc.) as well as special punching tools could be proceed up to diameter of 180 mm.

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