[DiverBob]

[QUOTE=I solved my problem by building a PDB that uses a 400 oz-in stepper motor and 50:1 planetary gearbox to directly tighten/loosen the drawbar. This gives me a consistent 25 ft-lbs tightening torque (and ~2500# drawbar tension), and up to 75 ft-lbs loosening torque. In about 5 months use, I have NEVER had a TTS holder pull out on my 3HP knee mill. As an added bonus, I can just as easily swap R8 tools in and out with the PDB, by just loosening 10 turns instead of the 1.5 turns I use for TTS, all under software control.

Regards,
Ray L.[/QUOTE]

That sounds great! Do you have any photos or drawings? I've been thinking of adding a similar type of system to my Tormach 770, it would be nice to see one that works!

Bob S.

[Spinnetti]

I highly recommend G-Wizard. It has saved me more than it's cost in broken bits. It got me through to voodoo phase to where I can have a good guess myself on proper feeds.

Yeah, good idea, but loathe "renting" software. Great for the developer, lousy for the customer. I'd rather pay for a new version if upgrades are worth it to me, otherwise, I'd be happy to keep an old version. Time to dig up the machinists handbook sounds like!

I also used brake cleaner on the collet and TTS holder, and tightend the drawbar so it just releases, but still won't handle much of a cut seems like. Right now I'm sitting at 850rpm and 5.5 ipm but haven't fine tuned. Issue is that this is just too slow - 1hr per part which "won't cut it" so to speak. I assume Carbide would let me crank it up? Any recommendations for the best reasonably priced tooling to to cut iron? (brake rotors)...... . Right now I'm doing (2x) .4 DOC and (4x) .050 Axial DOC 16 times which makes for some loooong cycle times.

[DiverBob]

Yeah, good idea, but loathe "renting" software. Great for the developer, lousy for the customer. I'd rather pay for a new version if upgrades are worth it to me, otherwise, I'd be happy to keep an old version. Time to dig up the machinists handbook sounds like!

I believe that once you purchase the software, if you do not renew the license then the software just downgrades to become a 'lite' version. The only limit i know is you are lomited to 1 HP for all the calculations. Since the 770 is a 1 HP motor, my one year subscription continues to be good for me. Check the website to verify my 'facts', I've been known to be wrong occasionally!

Bob S.

[Spinnetti]

I believe that once you purchase the software, if you do not renew the license then the software just downgrades to become a 'lite' version. The only limit i know is you are lomited to 1 HP for all the calculations. Since the 770 is a 1 HP motor, my one year subscription continues to be good for me. Check the website to verify my 'facts', I've been known to be wrong occasionally!

Bob S.

Good call Bob.. I'll check that. I have an 1100, but still, that softens the blow somewhat. What would be really handy is for it to recommend tooling diameter, depth of cut and axial engagement - it would save a lot of "what ifs" messing with tooling diameter.

I also found "ME Consultant" which is much cleaner on the UI and seems pretty good. I also see there are iphone apps which I'll check out shortly.

[SCzEngrgGroup]

That sounds great! Do you have any photos or drawings? I've been thinking of adding a similar type of system to my Tormach 770, it would be nice to see one that works!

Bob S.

Pictures below. The stepper is a NEMA34, 400 oz-in. The gearbox is a 50:1 NEMA34 I bought on E-Bay for about $150. The gearbox and stepper ride on a floating plate, supported by the two air cylinders, which push to down to engage the hex head on the stock drawbar. The drawbar coupling is an aluminum sleeve, split-clamped to the gearbox output shaft by a couple of clamp bolts. A 3/4" 12-point socket is pressed/shrunk into a bore in the coupling. The very small air cylinder near the bottom of the second photo actuates the spindle brake, to lock the spindle when the drawbar is active.

The stepper is driven by a Gecko G201, with the current-limit resistor selected by a relay, to provide either full torque (when loosening the drawbar), or reduced torque, corresponding to 25 ft-lbs drawbar torque (when tightening the drawbar). The software is trivial - for TTS, it simply turns the drawbar CCW 1.5 turns, and tightens it 2 turns, to ensure the stepper stalls before moving he full 2 turns. For R8, it loosens 10 turns, and tightens 11 turns. Both modes work have worked absolutely flawlessly for months now.

Regards,
Ray L.

[Spinnetti]

Pictures below. The stepper is a NEMA34, 400 oz-in. The gearbox is a 50:1 NEMA34 I bought on E-Bay for about $150. The gearbox and stepper ride on a floating plate, supported by the two air cylinders, which push to down to engage the hex head on the stock drawbar. The drawbar coupling is an aluminum sleeve, split-clamped to the gearbox output shaft by a couple of clamp bolts. A 3/4" 12-point socket is pressed/shrunk into a bore in the coupling. The very small air cylinder near the bottom of the second photo actuates the spindle brake, to lock the spindle when the drawbar is active.

The stepper is driven by a Gecko G201, with the current-limit resistor selected by a relay, to provide either full torque (when loosening the drawbar), or reduced torque, corresponding to 25 ft-lbs drawbar torque (when tightening the drawbar). The software is trivial - for TTS, it simply turns the drawbar CCW 1.5 turns, and tightens it 2 turns, to ensure the stepper stalls before moving he full 2 turns. For R8, it loosens 10 turns, and tightens 11 turns. Both modes work have worked absolutely flawlessly for months now.

Regards,
Ray L.

Very nice!

[tbaker2500]

I know this is an question only Tormach can answer, but is there any good reason to go with a spring style system like their vs a twist system like this and many other PDB designs out there?
I was considering a PDB, but am getting scared off by this thread.

[neilw20]

It is quite a challenge to get sufficient pressure with a spring system, all the time not exerting the releasing force on the bearings, while just using normal factory air pressures below 100PSI. The release pressure is considerably higher than the holding tension required. The twist system is more complex to drive due to sequencing and control, but is culpable of consistent repeatability of getting the same tension, and no belville washers needed. Some machine configurations have very little space for the mechanism as the motor axis is very close to the spindle axis.

[SCzEngrgGroup]

I know this is an question only Tormach can answer, but is there any good reason to go with a spring style system like their vs a twist system like this and many other PDB designs out there?
I was considering a PDB, but am getting scared off by this thread.

Bellevilles are how PDBs on VMCs usually work - albeit with a stack of 100-150 Bellevilles. And, VMCs don't require quite as much drawbar tension as TTS, due to their use of CAT/ISO tool holders. I think the attraction of Bellevilles is the mechanical simplicity, and low cost. My approach is more expensive, though not by much if you get a deal on the gearbox as I did. But, it is also much more flexible, as changing out an R8 tool with a Belleville drawbar requires moving the PDB out of the way, and doing the change manually.

Regards,
Ray L.

[tbaker2500]

Thanks for the info. Makes sense.

[Spinnetti]

Well, after many hours of research today, with your help, as well as tooling suppliers (Dormer and Niagara sites were helpful), books and about 5 different feed and speed calculators, I learned an important lesson: My tendency when the cut doesn't feel right was to keep backing off until it worked ok, but this was totally backwards. For one instance of the profile I was cutting, I was taking .050 radial cuts and .100 axial which was no good. After correlating all the sources of data I had, I found that "ME Consultant" had the numbers that worked best for me, which was to increase the radial cut from .050 to .100, and the axial from .100 to .400,at 737 rpm and 3.4 feed in the deepest part of the cut (16 cuts down to 4). So I went from a cycle time of 6min to 2.5min total elapsed time with much less load on the machine. Interesting bit is, the deeper the cut, the better it worked. I'm half tempted to try to cut full depth radially and do the full profile in two passes instead of four (.200 radial x .400 axial per cut). The load meter doesn't even move from static, so its not a HP issue. I'm thinking of getting a carbide cutter and see if I can speed up a bunch, as each part has 16 of these cuts.

Anyway, with the current settings, the tools stopped pulling out too, though it seems to me that the PDB is on the weak side still.

[neilw20]

My belville spring PDB holds the normal holders.
Press release, unscrew the collet by rotating shaft, insert R8 tool and rotate spindle until it is just nipping up, the lock with PDB. Same 25 ft.lbs. I have 20 washers, (())(())(())(())(())
To reinsert collet, rotate spindle with released so the TTS just releases, and lock the PDB. Full reaction only within the shaft, and soon I'll have one that works on the movable SX3 quill.
I'll post something when it is all good. Don't ask until then. Development almost finished. Doing some assembly today.

[MichaelHenry]

Good call Bob.. I'll check that. I have an 1100, but still, that softens the blow somewhat. What would be really handy is for it to recommend tooling diameter, depth of cut and axial engagement - it would save a lot of "what ifs" messing with tooling diameter.

I also found "ME Consultant" which is much cleaner on the UI and seems pretty good. I also see there are iphone apps which I'll check out shortly.

The Lite version of G-Wizard gives you 1 HP for every year of the retail license you "lease". I bought the 3-year "lease" so will get 3 HP in my Lite version when the lease expires in a year or so. The author claims that you will still receive upgrades and forum-based tech support on the Lite version.

I also have ME Pro and actually like the simpler interface more and appreciate the printable specs for thread forms but G-Wizard has a better selection of materials.

G-Wizard is being offered with some sort of discount for > $100 at present and a 3-year license might qualify for that discount. It's worth checking out if you are on the fence.

Mike

[Spinnetti]

The Lite version of G-Wizard gives you 1 HP for every year of the retail license you "lease". I bought the 3-year "lease" so will get 3 HP in my Lite version when the lease expires in a year or so. The author claims that you will still receive upgrades and forum-based tech support on the Lite version.

I also have ME Pro and actually like the simpler interface more and appreciate the printable specs for thread forms but G-Wizard has a better selection of materials.

G-Wizard is being offered with some sort of discount for > $100 at present and a 3-year license might qualify for that discount. It's worth checking out if you are on the fence.

Mike

Thanks Mike. I'm on the fence between ME pro and Gwhiz. ME pro outputs correlate well to tooling mfgs. recommendations and uses pretty conservative recommendaions suitable for our smaller machines. Materials in ME are fine for me, and the app doesn't look so thrown together, but I appreciate the support Bob gives and participation in the formums.. might end up getting both and comparing results with my real world findings, then sticking with the better of the two long term.

[tbaker2500]

I don't know ME pro- Does it give tool deflection? This is the single most handy feature to G-wiz. If the deflection is in orange, I'm going to break the bit. I use it commonly to figure out how much chatter I will get from the tool before I even do the cut. Well worth it.
My 2c.

[AiR_GuNNeR]

I also found that if your feed is too small, and the cutter starts to squeal, the high frequency vibration can cause the cutter to work it's way out.

[MichaelHenry]

I don't know ME pro- Does it give tool deflection? This is the single most handy feature to G-wiz. If the deflection is in orange, I'm going to break the bit. I use it commonly to figure out how much chatter I will get from the tool before I even do the cut. Well worth it.
My 2c.

Sorry, I don't remember if it does or not and can't check for a few hours. You should be OK if you use the recommended feeds and speeds, though. PM me if you want a definitive answer and I'll check when I'm near the right PC.

[Spinnetti]

Sorry, I don't remember if it does or not and can't check for a few hours. You should be OK if you use the recommended feeds and speeds, though. PM me if you want a definitive answer and I'll check when I'm near the right PC.

Thanks. I checked with the developer. It has chip thinning (check box on bottom of window) but not deflection. He said too many variables to accurately predict.

[Spinnetti]

So I bought Gwhiz 3 year deal. Seems to work good, though I'm still seeing pullout. After spending the money on the PBD, I don't want to chuck it just to get a reasonable cut, but dunno. I read the Tormach feedback and made sure the holder is clean and dry, used the recommendations out of gwhiz, but had to slow down the feed to avoid pullout in a radial cut right at the tooling mfg limite for depth of cut and 53% of radial load. One flaw in the Tormach pullout test is that they test strictly in a linear pull, where in actual use its radial deflection causing the collet to give up; I suspect if you put a few lb of side load on a standard cutter at the bottom of the stick out, then do the pull test, it will pop out at a MUCH lower load... I suspect there's more engineering that needs to be done here.

[tbaker2500]

Spinnetti, I beginning to think there is something wrong here. You just shouldn't be seeing this much pullout.
My suggestion at this point is to contact Tormach with the specifics of what you are seeing, pictures and video always help. I am sure they would be happy to help resolve this, before it becomes too big of a deal.