Product category:
Abrasive machining - manual and CNC machines
News Release from: Burrhart Machinery | Subject: VTG-01 grinder
Edited by the Manufacturingtalk Editorial
Team on 13 May 2003
Semi-automatic unit sharpens punches
accurately
A subcontract sheet metalworker has transformed a tedious, imprecise job into a fast, accurate process using a semi-automatic grinding machine for resharpening turret punch press tooling.
At the Kings Lynn factory of Ebbs and Dale, which specialises in subcontract sheet metalworking for the food industry, a semi-automatic grinding machine for resharpening turret punch press tooling has transformed what used to be a tedious and imprecise job on a manual swing-arm grinder into a fast, highly accurate process Manufactured by Mate and supplied through sole agent, Burrhart Machinery, the new VTG-01 grinder is able to restore the worn profile of any make of tool although on this site, the punches and dies are also from Mate
This article was originally published on Manufacturingtalk on 10 Apr 2003 at 8.00am (UK)
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They are used in the 20-station turret of an Italian-built Rainer 30-tonne capacity punch press, purchased in 2000, and in a similar but more modern, automated Rainer 30-tonne PRO 15.25.
Installed in April 2003, the latest press has a 19-station turret accommodating two multi-tools capable of working at the full rated tonnage, and three E-stations, one of which is adapted for up-forming.
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He said, "Unlike our previous manual machine, which could only regrind flat punches effectively, the VTG-01 is able to grind rooftop shear profiles.
This reduces noise, as the punch is not slapping into the sheet but making a gradual entry; and for the same reason, tonnage is lower for a given punch diameter and material, reducing wear and tear on the press as well as saving energy.
"Consequently, whereas the vast majority of tools purchased for our first punch press are flat and only a couple are shear, those purchased for the second press will include a higher proportion shear, particularly for the larger diameters." He went on to explain that some of the larger D-station tools could not be reground at all on the old swing-arm machine and had to be put out for resharpening.
Now all tools can be profiled in-house, including even larger E-station tooling, saving further expense and inconvenience.
Another benefit is that as the grinder is compact enough to be positioned immediately next to the presses and tool resharpening is automatic, the operator is able to complete the task while carrying out other jobs.
He clamps the tool on the turntable and datums it manually, selects the program to set feed rates and how much stock is to be removed, closes the guard and walks away, returning a few minutes later to find the automatic grinding cycle complete.
The result is that all the punches and dies in the machine, as well as those in the drawer waiting to be used, are sharp.
Previously, there was a tendency for Ebbs and Dale operators to run tools until they were dull, which increased noise, caused burrs and risked snagging and destroying the sheet.
Moreover, such blunt tools took a long time to regrind and to avoid press downtime, it was necessary to have back-up tooling.
This expense has been eliminated by the availability of efficient regrinding.
A consideration when grinding tool steel is the large amount of heat generated, which if allowed to build up is capable of altering the metallurgical properties of the tool steel punch or die.
To avoid this, the Mate VTG-01 grinder delivers copious quantities of coolant to the machining area.
Ebbs cited an example where one of his larger tools was put out to a toolmaker for resharpening and had obviously been overheated, as when it was returned to the press it lasted only a very short time before it had to be scrapped.
Such an occurrence is impossible with the new grinding machine, which is also available in fully automated version with laser datuming of the tool.
On the subject of the tooling itself, he continued, "At the outset we opted for Mate's Ultra holders, punches, slug-free dies and hardened and ground guides because they are the most convenient to use, particularly with regard to the ease with which they can be reset within seconds after grinding to compensate for stock removal.
It means the tools can be back in the press producing components faster.
"Moreover, a counterbore on the reverse of the stripper disc allows the shoulder of the punch to penetrate further and give an extra 3mm of grind life, resulting in an additional 10 to 30 resharpenings before the tool needs to be replaced.
The tools are also accurate in operation, allowing us to hold tight tolerances down to +/-0.04mm." In fact, so successful was the use of Mate tooling on the first Rainer punch press that the second machine was fully equipped with the same manufacturer's tools.
As Ebbs and Dale specialises in refrigeration components and other sheet metalwork that can come into contact with food, for a large proportion of the time the tools are subjected to the demanding task of punching and nibbling pre-coated stainless steel ranging in gauge from 0.7 to 3.0mm.
Most of the remaining work is in mild steel from 0.5 to 6.0 mm thick.
Component size ranges from small hinges to panels over 4 metres long and part numbers, already in the hundreds, will soon be in the thousands when a new project starts soon for a principal customer.
Ebbs concluded, "The fact is that with the old tool grinder, our punches and dies were rarely spot-on, which lengthened the turnaround time for jobs and risked supplying our customers with components that were of lower quality than they could produce themselves using their in-house punch presses.
This situation has been reversed following installation of the Mate grinder.
"Service from Burrhart has been good; so much so that we have extended our relationship with the supplier recently by taking delivery from them of Italian-made Rolleri tooling for our 6-axis CNC Edwards Pearson 4m x 2000kN press brake.
The tool has a narrow die to allow us to produce a tight Z-fold for a new contract we are about to start.".
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