[m1carbine]

A question for those with tool changers.

I just went through the exercise of trashing 2 lakeshore 1/2 endmills, 2 collet tool holders and a spindle collet. I am hogging out the inside of an aluminum cover, and for both the tool holder pulled out of the spindle. They made an attempt to reach China ruining the part and putting a new drainage slot in the fixture.

I read the Tormach white paper and watched the NYCNC video on cleaning tools and lubing the R-8 collet. Subsequently I broke everything down, cleaned and carefully relubed where needed. When I got everything ready to run again I went to clean the tools still in the changer, I found that all of the shanks were coated with coolant residue. I cleaned them with a paper towel and acetone and the first test run went smooth, no issues.

How do you all deal with the coolant getting on the tools in the changer?


Ray

[SCzEngrgGroup]

The problem is not enough tension in the drawbar. With adequate drawbar tension, pull-out simply does not occur, even with wet toolholder shanks. Trouble is, the Tormach PDB seems to be kinda marginal in this respect. It really needs to provide an additional 500-1000# tension to eliminate the problem. The best you can do is make sure you have everything clean, and adjust the drawbar so the air cylinder can just barely release the tool. Higher air pressure will also help.

Regards,
Ray L.

[FuriousGeorge]

The best you can do is make sure you have everything clean, and adjust the drawbar so the air cylinder can just barely release the tool. Higher air pressure will also help.

Regards,
Ray L.

I think the is the crux of the question, not tensioning the drawbar. He HAS done everything he can to set up properly and keep the shanks clean and dry, but they get soaked while sitting in the ATC when coolant is running.

So how do you keep your tools dry when they are sitting out in an environment exposed to coolant splashing?

[SCzEngrgGroup]

So how do you keep your tools dry when they are sitting out in an environment exposed to coolant splashing?

The obvious solution would be the extend the "skirt" on the carousel, so it extends lower down. But, given how close the carousel is to the spindle, that may have limited effect.

Regards,
Ray L.

[popspipes]

My motto is "no chatter no pullout".

I have a power drawbar and mine is tight enough that it takes about 130 psi to release it.
I had chatter on a .250 4 flute and it pulled out a few months back.

I think some guys are lucky with the pullout thing, I have had it on occasion, with every mill I have ever run, and the drawbars were tight.

I have always been curious about why the cutter never pulls out of the holder, it always pulls the holder out of the R8 collet, kind of makes one wonder if the spindle taper and collet arent mating up correctly??

edit: clean and dry shanks do help, but in some cases thats hard to accomplish.
Proper lube on the collet, spindle taper, and drawbar threads helps as well, as has been stated in a previous post

[handlewanker]

Hi, I've seen that problem a few times on here, and it isn't going to go away if your drawbar tension is not heavy enough......coolant or no coolant coating.......the tool won't pull out if it's held in tight enough.

My personal opinion is that when you need to have a huge force just to ensure the parallel shank gets gripped tightly, there has to be a better way......a spring loaded force is not the best way to ensure too retention tightness.

Perhaps we need to re-design Tormach's TTS retention system.....LOL.

The worry is, if the tool shank doesn't pull out completely, it might just pull out a few mill to make the Z axis position null and void, and that would occur on a roughing cut, leaving it undersize with nothing to finish the part with.
Ian.

[popspipes]

I tightened the Bridgeport enough that I could feel the drawbar stretch, you cant get tighter than that...........

[SCzEngrgGroup]

I tightened the Bridgeport enough that I could feel the drawbar stretch, you cant get tighter than that...........

You're not saying you got pullout with that are you? If so, then something was wrong somewhere.

My PDBs actually torque the drawbar to 30 ft-lbs using an electric motor. In over fours years of daily use, I have never once seen pullout, even when the tool shanks are dripping with soluble oil coolant (coolant gets up onto the shanks through the slits in the ER20 collets). Nor have any of my customers ever reported any pull-out problems to me, except when they have failed to properly clean/lubricate the spindle taper, collet, and drawbar thrust washer on a regular basis. With adequate drawbar tension, TTS is MORE than capable of handling anything a 1.5HP machine can possibly throw at it with zero pull-out.

Regards,
Ray L.

[handlewanker]

Ooohhh.....that's tight.....gotta be a better way......I can't imagine how much pressure you'd need to release the tooling.....something like 800 lbs + I've been told, and that's just to hold it in......more to compress the Bellville washers to make it release.
Ian.

[shred]

Check your bellvilles on the drawbar. I've had a few crack.

[handlewanker]

Ray......30 foot lbs is applied against the pitch and thread angle of the draw bar, so the actual dynamic pressure on the bar itself would be up in the hundreds therefore....extremely hard to measure if at all with normal means........ you'd also have a hi tensile steel draw bar like I have on my Ajax mill.
Ian.

[m1carbine]

Shred,

The washers are new. After the first pull out ruined the collet, I swapped in a new drawbar and washers while I was placing it.

I have the air set at 110 psi.

Ray

[wtopace]

Just to add in my own findings (with a PCNC1100): I have only ever experienced pull-out when I heard chatter.

This was most likely due to a few things:

• Drawbar wasn't tight enough (occasionally I have manually tightened it past the PDB capabilities to make cuts with a corn cob style rougher)
• Drawbar wasn't as tight as it could be (R8 collet needed to be cleaned and the outside re-lubed)
• Tools were chattering (too aggressive of a cut, gibs needed tightening)

Recently I was seeing chatter consistently in a few locations, re-adjusting all of my gibs solved the issue and all chatter is now gone. I would recommend you check yours if you haven't already done so.

[m1carbine]

wtopace,

I will check the gibs when I get a chance.

Ray

[wtopace]

wtopace,

I will check the gibs when I get a chance.

Ray

I haven't seen any mention of it from you yet, but are you getting any chatter while cutting before your pullout?

Here is a link to my notes from adjusting my gibs last weekend: http://www.cnczone.com/forums/tormac...djustment.html (it may seem really long and boring, but it's pretty quick once you get the process down)

[CadRhino]

It sounds like you may he doing too aggressive of a cut or don't have your pdb maxed out.
Coolant will get on the tools and that has never been the problem with my atc.
Lube, on the other hand will be a problem if it gets on your tts.

wtopace,

I will check the gibs when I get a chance.

Ray

[SCzEngrgGroup]

Ray......30 foot lbs is applied against the pitch and thread angle of the draw bar, so the actual dynamic pressure on the bar itself would be up in the hundreds therefore....extremely hard to measure if at all with normal means........ you'd also have a hi tensile steel draw bar like I have on my Ajax mill.
Ian.

Try in the thousands - on the order of 3500 pounds drawbar tension at 30 ft-lbs, which is still well within the capability of a standard 7/16" mild steel drawbar. I've NEVER seen or heard of thread failure at that torque. But, that is what it takes to keep TTS holders from pulling out under worst-case conditions. I can run my machine all day long with the 1.5HP spindle running very near stall, and never see pull-out.

The Tormach design targeted 2500# tension (there is an old Tormach video on that somewhere...), which is, apparently, kinda marginal, as evidenced by the not-infrequent pull-out issues reported in this forum. The extensive testing I did before designing my first PDB confirmed that 2500# was about the bare minimum required. Getting up to 3500# requires either a truly huge multi-stage pneumatic cylinder (and the one on the Tormach PDB is far from small), or, better still, an air-over-hydraulic system, as used on most VMCs. And as pointed out here, chatter can play havoc with the compliance of a Belleville-based design, making it fail when it wouldn't under the same load minus chatter. With the essentially rigid drawbar I use, I've never even had pull-out under conditions of really extreme chatter (chatter bad enough it was actually painful to listen to).

Regards,
Ray L.

[MichaelHenry]

I've read somewhere (possibly in Tormach's documentation) that the master collet and draw bar should be considered wear items and replaced periodically. I think that the pair run something like $40 so I always keep a spare set on hand.

[SCzEngrgGroup]

I've read somewhere (possibly in Tormach's documentation) that the master collet and draw bar should be considered wear items and replaced periodically. I think that the pair run something like $40 so I always keep a spare set on hand.

Drawbars are typically wear items, the collet should not be. I've been using the same one for over 5 years, and it still works just fine.

Regards,
Ray L.

[CadRhino]

If a tool holder ever spins in my spindle collet, I replace it. I don't want any bur inside the collet scratching the tops of my tts tool holders.

Drawbars are typically wear items, the collet should not be. I've been using the same one for over 5 years, and it still works just fine.

Regards,
Ray L.