Having issues with my TTS & Power Drawbar

[mooreaa]

Hi guys,

I've been trying to work though some tutorials on setting up my tool table and ran across a problem with my TTS/Power Drawbar setup. Being a total newbie, I though I'd try to get some thoughts on what I might be doing wrong.

I starting off setting the tool height of my Heimer 3D probe using the mill table as a reference. To verify the length I tried to measure the distance from the table to the spindle face using my Edge Technologies tool setter and realized that something was off( about 0.015" ). It took a while (as I am new to this) to realize that my TTS tools were not sitting flush again the spindle face. Looking at the manual, I figured things were installed incorrectly so I went about checking things.

I opened my spindle cabinet and went to loosen the drawbar bolt but realized that the screw was already very loose (issue #1). So, following the setup instructions again (a video online by NYCCNC), I went about tightening the whole thing down again. (about 2 full turns with a TTS tool in the collet). When I did this and reinstalled the power drawbar unit, I realized that it wasn't able to eject the tool (issue #2). So it took a while but I realized that the factory installed air lines on my cylinders seemed to differ from all the photos I've seen.



Looking at the physics of it, the airliens were installed all wrong so I fixed this issue and low and behold it could now properly eject my tool even with the bolt tightened all the way down. (Note: The first time I installed this, I remember backing the nut out 1/4 turn at a time till the point I could relase the tool. This is what caused this bolt to be loose in the first place. This was because the cylinder wasn't running properly and didn't have the right power to eject the tool. Hence needing very little pressure on the nut to release the tool. The only thing holding the tool in was lateral pressure.

So with the machine setup again, I looked at the collet and saw that without a tool the collet retracted nicely into the spindle head.



Still, when I inserted a tool, there was a visible gap.



I tried adjusting the tension on the collet nut and such but no luck. I then inserted a TTS tool part way in and retracted the head to see how far it would retract and bam, there it was, the collet sticking too low again.



At this point I am not sure what the root cause is, but somehow, the collet isn't retracting in all the way when there is a tool in it, even though it retracts nicely when there is no tool. One theory is that I have a bad TTS collet that has bad geometry. This is a shot of the TTS collet from the bottom without a tool. Doesn't look very round, but then again I am not sure what its supposed to look like.



If this is a setup issue, what am I doing wrong?

Sorry for the long post, thanks all!

Aaron

[Jeff E.]

Aaron,

The collet doesn't necessarily have to retract all the way in. Mine doesn't when there is a tool in it. What your are looking for is the top surface of tool holder to be flush with bottom of the spindle. There is a small recess on the top of the tool holder to compensate for the collet not being completely flush with the spindle.

Jeff E.

[mooreaa]

Hey Jeff,

Thanks for the comment. The problem I am having is that the collet will not retract in far enough with a tool in it. Hence when the tool is pushed in all the way, and the drawbar retracts there is a noticeable gap between the tool and the spindle face. Meaning that the holder is not sitting flush again the bottom of the spindle and is only supported by the lateral clamping force.

I've tried tightening and loosening the drawbar nut to try and see if this has an effect on the collet spacing, but it just won't retract any further in with a tool in it.

Appreciate the input.

[Don Clement]

It doesn't matter so much about the collet protruding. What is important is that the TTS shoulder have contact with the spindle face making a dual-contact.

How does TTS work? The TTS shoulder is undercut so it contacts the spindle itself, not the end of the collet. As the drawbar is tightened the collet will simultaneously squeeze the shank and move upward into the spindle taper. It is this simultaneous action, grasping while moving up, that pulls the toolholder tightly against the spindle face. The high pressure contact between the shoulder of the toolholder and the spindle is the equivalent of a zero tolerance fit; the vertical location of the tool is exact. The initial placement, created by simply sliding the toolholder up until it stops, is normally within a few thousandths of an inch. The final location, after tightening the collet, is exact, highly repeatable, and not affected by the variable tension of the drawbar or wear on the collet. And what’s more, the zero tolerance fit in combination with the wide base of the shoulder provides a significant increase in toolholder rigidity.
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[Gerry Sweetland]

I don't know if this is relevant or not, I don't have a power draw bar and I'm not familiar with what relationship the collet needs to be at when used with the PDB but I had an issue where I was tightening my DB and noticing a gap between the top of the TTS holder and the bottom of the spindle and some inconsistencies in my Z depth on some parts. I emailed Tormach support and they responded that at the time I bought my 770 that some machines shipped with incorrect length collet's and sent me a new one under warranty.
I would get in touch with Tormach, they are always very helpful.
Gerry

[TXFred]

I suspect that Gerry's found the issue. Your collet looks exactly like his old collet.

The tool holder is bottoming out, and it's probably due to the collet depth.

The other possibility is that the tool holder is bottoming out against the bottom of the drawbar. This would happen if the drawbar is too long, or if you didn't have the correct spacer underneath the spring washers.

Can you post a closeup picture of the spring washer stack on top of your spindle?

Frederic

[philbur]

I don't think you should have drawn the collet up without a toolholder in the collet. This can damage the collet.

Inspect a few toolholders to ensure you are not using one that lacks depth in the recess. Then with the drawbar removed it should be possible to push a toolholder into the collet by hand such that the toolholder bottoms out on the spindle. If it bottoms out before the shoulder of the toolholder makes contact with the spindle then clearly the nose of the collet is too long. In which case you should obtain a replacement collet or machine some off the end of the collet you have.

Phil

[mcphill]

Are you using a Tormach TTS R8 Collet, or did you get your own 3/4" R8? If you got your own (or even it if is from Tormach) it looks like the collet face protrudes too far. This is covered in the TTS manual. If that is the case you just need to grind off the face of the collet enough so that the TTS pulls up to meet the spindle.

Go here: http://www.tormach.com/uploads/51/DS...oling-pdf.html

Section 2.2

[DiverBob]

I had a similar problem myself and it turned out the collet was too long. The problem was solved by carefully grinding down the face of the collet until a mounted tool showed no gap against the head.

Bob

[mooreaa]

Gerry/TXFred: This was the conclusion that Daniel from Tormach came up with as well. They think the collet was "out-of-spec" so they are sending me a replacement. I will get a photo up as soon as I get the new unit and share my results.

I do believe that grinding the face of the collet down could resolve this as well, I just don't have a method of doing this at the moment (waiting on some lathe tools to test out vertical turning soon). Also heres a picture of the sping washer stack:




Philbur: Is it really bad to let the collet retract with no tool? Many times during a tool change, the collet will get pulled up without a tool. Can anyone confirm if this is bad?

I did you test and I cannot get the toolholders to touch the spindle face even without the drawbar. I would need to remove quite a bit off the collet in order for the toolholder to sit snugly against the spindle face (Maybe about as much as a 1mm in order to clear any variances in toolholder cut-outs).

How are you guys grinding your collets down? This may be a stupid question but doesn't that affect the balance / holding precision? I don't have access to a lathe so I don't think I could grind this down very well unfortunately.

Thanks for all your replies.

[TXFred]

Philbur: Is it really bad to let the collet retract with no tool? Many times during a tool change, the collet will get pulled up without a tool. Can anyone confirm if this is bad?

It will close the collet all the way, which may eventually bend it to the point that you cannot insert tooling.

I try to avoid doing it during tool changes. I grab the new tool, hit the pedal, swap tools, then release the pedal. Without a foot pedal, it's harder to do.

By the way, the spring stack looks fine.

Frederic

[David Bord]

Have you called Tormach? I bet they would be able to solve it with no issue. Maybe you have the wrong, or defective collet?

David