Deckel Maho DMU 60T Drops Tool During Tool Change

[ViKiNG64]

We have a Deckel Maho DMU 60T that we got second hand and have had in full time use for the past five years. It has never had any tool change issues until last week when it dropped a tool into the tool changer cabinet during an unmanned over night run. The machine was set up to run four identical programs on four identical parts with at total run time for around 20 hrs. It dropped the fifth tool on the first part, luckily the rest of the program/part was not affected by this tool not cutting at all. This was unusual and there was no obvious reason and no logical explanation as how it was even possible to drop the tool inside the tool cabinet. We ran the machine over the following night with the identical four parts and setup. It dropped the same tool on again the first part in the same part of the program, the only difference was that the tool was dropped into the machine cabinet. Amazingly in both cases the tool was unbroken and it did not cause any problem to the part except that some of the part was not finished.

So the place to start looking was there must be something wrong with the tool/holder/pull stud/tool change finger/tool change mechanism. There is no obvious damage, wear, build up of lube, foreign matter or other anomalies with any of these. The pull stud looked to be in very good condition but it was replaced with a new one to at least eliminate this possibility

Has anyone seen anything like this or have any ideas because myself and the machinists are totally baffled by this problem

 

[rpseguin]

We have a Deckel Maho DMU 60T that we got second hand and have had in full time use for the past five years. It has never had any tool change issues until last week when it dropped a tool into the tool changer cabinet during an unmanned over night run. The machine was set up to run four identical programs on four identical parts with at total run time for around 20 hrs. It dropped the fifth tool on the first part, luckily the rest of the program/part was not affected by this tool not cutting at all. This was unusual and there was no obvious reason and no logical explanation as how it was even possible to drop the tool inside the tool cabinet. We ran the machine over the following night with the identical four parts and setup. It dropped the same tool on again the first part in the same part of the program, the only difference was that the tool was dropped into the machine cabinet. Amazingly in both cases the tool was unbroken and it did not cause any problem to the part except that some of the part was not finished.

So the place to start looking was there must be something wrong with the tool/holder/pull stud/tool change finger/tool change mechanism. There is no obvious damage, wear, build up of lube, foreign matter or other anomalies with any of these. The pull stud looked to be in very good condition but it was replaced with a new one to at least eliminate this possibility

Has anyone seen anything like this or have any ideas because myself and the machinists are totally baffled by this problem

Did you measure fingers/position on other holders and compare to problematic one?

How soon into the program?
Can you dry run starting just before the bad tool change and [slow-motion] video it?

 

[Kees]

The vertical liniair guideway ( that allows the tool changer arm to go up and down) has devolped wear causing the toolchanger arm to tilt downwards at the spindle position and therefor sometimes takes the tool wrongly but still might be able to bring into the tool cabinet where placing into the storagewheel goes wrong. Or sometimes droppes the tool in the machine itself.

 

[Mtndew]

Not familiar with that machine,but on our Okumas the ATC arm has spring loaded gripper fingers that hold the tool when removing it from the spindle. If those get sticky you get a dropped tool. Just a simple removal of a snap ring/Eclip and a pin will allow for cleaning and re-greasing.

 

[ViKiNG64]

Did you measure fingers/position on other holders and compare to problematic one?

How soon into the program?
Can you dry run starting just before the bad tool change and [slow-motion] video it?

Unfortunately we have not been able to duplicate the issue, it has only occurred when running unmanned.

 

[ViKiNG64]

The vertical liniair guideway ( that allows the tool changer arm to go up and down) has devolped wear causing the toolchanger arm to tilt downwards at the spindle position and therefor sometimes takes the tool wrongly but still might be able to bring into the tool cabinet where placing into the storagewheel goes wrong. Or sometimes droppes the tool in the machine itself.

This is a possibility but I think that the plastic fingers on the carousel are flexible enough to take up any wear, but I will look into this

 

[ViKiNG64]

We have had the local DMG service guy to have a look. He is not sure what is causing the problem but has recommended lubricating the tapers on the tool holders with a specific light lithium spray. From memory the previous owner had seen problems with the sticking during tool changing and breaking the plastic carousel fingers. We have not seen any sticking during tool change, but this maybe the problem and we will now use the lithium spray on the tapers

 

[ViKiNG64]

Not familiar with that machine,but on our Okumas the ATC arm has spring loaded gripper fingers that hold the tool when removing it from the spindle. If those get sticky you get a dropped tool. Just a simple removal of a snap ring/Eclip and a pin will allow for cleaning and re-greasing.

Thanks we have an Okuma in the shop that has seen this problem that you are describing. The DMU uses one piece plastic fingers on the carousel which makes for a simple finger and spring so it has a different problem