[mrquacker]

I really hate the power drawbar on the 770. It has been **** and nothing but trouble. I've broken hundreds of dollars of carbide because of it.

All the gcode and programs I write in Sprut7 simply just work with the manual drawbar. You put the tool in, hit go, and it does what its told.
But as soon as I install the PDB, everything goes to ****. As soon as the endmill touches metal, the entire toolholder pulls out of the collet by 1/16" to 1/8". Sometimes halfway through a program, destroying the part, the tool, the fixture, and the toolholder itself when it touches a fixture bolt and starts melting.

I have the compressor set to its max psi (~120) and the drawbar nuts torqued to the point where the 4stack of belleville washers just barely releases when the compressor is at max. And the suma***** still pulls out. None of them are broke, I check every freakin time.

1/4" 2F carbide, 0.02" WOC, 0.5" DOC, 30ipm

The really fast toolchanges are nice, but this is starting to piss me off.

How do I make the damn thing hold the tools as well as the manual drawbar?

[astro_eng]

Sounds frustrating. I would check the gap between the top of the drawbar and the PDB. Make sure that gap is per the manual. It amounts to about 1/8" collet stickout when the PDB is released.

It sounds like you have more than enough torque on the drawbar to prevent tool pullout with a 1/4" 2F carbide tool. My thought process is that if you have super high torque and bad engagement your collet may be biting as a point contact on the TTS shank. Proper stickout makes sure that the collet closes around the TTS shank with *hopefully* surface to surface contact.

[WOTDesigns]

Anti seize per white paper makes a BIIIIIIIIIGGGGGG difference

Sent from my SM-G900V using Tapatalk

[mattz0r]

Here is the white paper mentioned above - link

[SCzEngrgGroup]

First thing to do is get some Dykem, and see what the contact pattern on your TTS collet looks like, both inside and outside. There have been a number of reports of badly made collets that make only a very thin line of contact to either the spindle taper, or the tool shank. Second thing is to read and follow the instructions in the Tormach paper others have linked to. The fact of the matter is (and this always upsets some people here....), IMHO, the Tormach PDB provides rather marginal drawbar tension. Even when working at its best, there are many reports of tool "pull-out" if heavy milling is attempted, so many users simply don't do heavy milling when using the PDB. Some people write this off as an inherent limitation of TTS, but I can tell you for a fact it is not. I manufacture and sell PDBsand ATCs for TTS tooling (not on Tormach machines), and I have NEVER had pull-out, nor have I ever received a single report of pull-out from any of my customers. The difference is, my PDB provides considerably more drawbar tension - >3500# vs <2500#. You can increase the spring tension on the Tormach PDB, but then you'll need to either put in an even larger air cylinder, or provide even higher air pressure to make it release, or replace the pneumatic cylinder with an air-over-pneumatic system capable of higher force. There are several designs out there that could be adapted to a Tormach, but building a good PDB is not a small project. There are also designs out there for manual drawbars that use a long lever arm, and give the same speed as a PDB, albeit with slightly less convenience.

So, check your spindle and collet, perhaps evern replace your collet, then follow the cleaning/lubrication procedure, and hope for the best. If that isn't enough, then you need to decide how much you really want a PDB.

Regards,
Ray L.

[Steve Seebold]

It looks and sounds to me like you just don't have your PDB set tight enough.

I have a PDB on my 1100 which will be 5 years old next month, and I have had trey few issues with cutter pull out. When I do, it's usually operator error.