Tool Changer Problem (with video)

Hello all,

I mentioned this in one of my post (in the DMG forum) already, but then I thought it may not be a DMG-specific issue. So I thought I'd try my luck here and see if anyone else has seen this?


Notice the tool holder will "shake" before the spindle engages it. However, this behavior is extremely random. We can call the same tool 10 times and only once or twice it will show this. (I filmed 30-40 tool changes to put that video together.) We've also seen this "shake"/"vibration" from almost every tool and from every tool-changer position. The best I can put my finger on it is maybe the power draw bar doesn't fully open the "claw" inside the spindle? So if the tool is not 100% perfectly aligned, the claw will hit the pull stud? And most of the time the pull stud pops in-place but one in a hundred tool-change we will get one so bad that the spindle literally pushed the tool holder off the tool pocket and it fell to the floor.

Any help will be greatly appreciated!!



Wallace

You can see the tool move side ways in the last bit, is this not just a alignment issue? Film it again from 90 degrees and see what that shows, best guess if its just random you probally have a tool changer indexing issue.

I reviewed all the other footage and yes, it does seem like every tool get pushed to the right very slightly while the spindle is coming down. Is that enough to cause this issue? If so, my next challenge will be to figure if we can even realign the tool-change position without DMG's help... since I don't think we will be getting any.

I want to say I've come across machine constants that store the X/Y axis value for tool change...

Thanks,



Wallace

WallaceLau said:

I reviewed all the other footage and yes, it does seem like every tool get pushed to the right very slightly while the spindle is coming down. Is that enough to cause this issue? If so, my next challenge will be to figure if we can even realign the tool-change position without DMG's help... since I don't think we will be getting any.

I want to say I've come across machine constants that store the X/Y axis value for tool change...

Thanks,



Wallace

Click to expand...

How does that tool changer work? As far as the positioning of the tools.. I'm not familiar with
a DMG and it doesn't look as simple as a carousel or a swing arm(which can get stupid complicated)..
Is T1 ALWAYS grabbed by the same set of finger?

Fix that issue where its pushing the tool to the right, and I'd guess 90% of your problems will go away.
Could be parameter driven as to where the head parks itself, or you could be playing with some mechanical
stuff, like adjusting a sensor or something.

Nothing pisses you off more than when a tool holder ends up in the chip pan, and its ALWAYS with
the most expensive endmill you have in the machine. And then you don't catch it and the second
most expensive endmill in the machine rapids into material that should have been removed.

I'd be looking at the retainer claw, maybe with a bore scope to see if there is a distorted hole or something that keeps a ball or finger from fully retracting in its holder.

Bobw said:

How does that tool changer work?

Click to expand...

It's a chain-style system but it works very much like a carousel tool changer (at least in principle). A loaded spindle will move side-way into the tool changer, those white-colored tool holders (some kind of injection-molded plastic) will hold onto the grove, then the gripper/claws (what's the correct term?) releases and spindle moves up. Thereafter the chain/conveyor rotates to the new tool you are calling, spindle comes down, claws tighten, and spindle moves side-way out the tool changer with the new tool.

Bobw said:

Is T1 ALWAYS grabbed by the same set of finger?

Click to expand...

If I understand your question, yes - the machine always put the same tool back to the original pocket it came out of. So if T1 came from tool-holder pocket 5, it will be put back into pocket 5, so the same "finger" in the tool holder (that white plastic thingy I mentioned above) will be grabbing that tool. Unless you are talking about the finger that grabs the pull stud, in which case the answer will be yes as well - there is only one pull-stud gripper and that's in the spindle.

Bobw said:

Fix that issue where its pushing the tool to the right, and I'd guess 90% of your problems will go away.
Could be parameter driven as to where the head parks itself, or you could be playing with some mechanical
stuff, like adjusting a sensor or something.

Click to expand...

I am hoping that's the ticket. I believe I saw some value in the machine-constants that refers to tool-changer positions, and it might just be a small adjustment there. The two question is, can I even change the machine-constants without calling DMG (since they won't help), and how do I actually align them... (trial and error?)

Bobw said:

Nothing pisses you off more than when a tool holder ends up in the chip pan, and its ALWAYS with
the most expensive endmill you have in the machine. And then you don't catch it and the second
most expensive endmill in the machine rapids into material that should have been removed.

Click to expand...

Let me one up you on that. Last week our machine dropped the !#$%^&* probe into the chip pan. My initial thought was "there goes the stylus" and then subsequently find out the probe no longer works (shows red blink of death as soon as it received the power-on signal). Contacted Renishaw and was told they can no longer fix it. Now we have to buy a new probe ($3,000+). Talk about ouch.



Wallace

HuFlungDung said:

I'd be looking at the retainer claw, maybe with a bore scope to see if there is a distorted hole or something that keeps a ball or finger from fully retracting in its holder.

Click to expand...

It uses a collet style gripper (with fingers), and I sort'a did that in the most redneck way possible (put my head under the spindle and shine a flashlight up through the bore - yeah bad idea, I know). From what I can see, the fingers look OK (all 4 seems to have opened to the same position away from the center). But that brings up another question. If the machine was stored with no tools in the spindle (for months), the gripper collet would be in the retracted position without a pull-stud in the center to counteract the collapsing force. Would that permanently deform the finger/gripper because they are "over-collapsed" for extended period of time? I asked that because we bought the machine used, and when it came there was no tool in the spindle (and we have no idea how long it's been sitting in the dealer's warehouse.) We also had a similar problem with our Tormach but I chuck it up to cheap Chinese tooling; maybe that happens to German machines too?

Thanks,



Wallace

" If the machine was stored with no tools in the spindle (for months), the gripper collet would be in the retracted position without a pull-stud in the center to counteract the collapsing force. Would that permanently deform the finger/gripper because they are "over-collapsed" for extended period of time?"

From what I've always been told, the opposite.
You take the tool out of the spindle when not being used for extended periods of time to give the springs a chance not to "set"

Ok the plot thickens. (Maybe.) I spoke to the dealer who sold me the machine, he suggest I spray WD40 into the spindle to make sure the "fingers" (grippers) moves freely. As I did so, I noticed NONE of the grippers are spring-loaded. i.e. They DO NOT "open" when the draw-bar engages; they basically just loosen themselves and literally "hang" there. i.e. If there is no tool in the spindle, the engagement of the draw-bar simply "raise" and "lower" the grippers inside the spindle.


It sounded like the grippers are basically relying on the 45-degree cut on the top of each pull-stud to open it, which I can see how if we even have the tiniest misalignment it could push the tool off the holder.

So questions... Does ANYONE know how to modify the tool-change position on a Heidenhain Millplus controller (V500)? Perhaps I will ask the same question on my thread in the DMG forum. Secondly, how often have you guys seen grippers that are NOT spring-loaded?

Thanks in advance!



Wallace