[TT350]

No I don't work for Tormach.

[philbur]

It is possible to design an automatic drawbar that uses an air cylinder, without the need to apply any forces to the spindle bearings, by transferring the reaction force to the spindle rather than the head.

Phil

Other than that concern (I'd be a lot happier with the air-wrench approach like Joe Vicars') your toolchanger looks excellent!

Best regards,

Randy

[philbur]

Repeatly screwing two threaded parts together, possibly even thousands of times, is not a very sympathetic for the components involved.

Phil

Other than that concern (I'd be a lot happier with the air-wrench approach like Joe Vicars') your toolchanger looks excellent!

Best regards,

Randy

[79rallysport]

Is the ATC's arm actuated by pneumatics or linear actuators? From the sound of the air compressor in the background I'm guessing its by pneumatics. If so, why did you go that route?

[deon]

Hi Scott

Havn't heard from you for a while..............Is it back to the drawing board before we can see those test videos.
My two cents on the air cylinder clamping force discussion.....Won't it be posible to offset the cylinder and then multiply the force with some kind of a lever mechanism.
Just a thought .....Keep up the good work.

Deon

[PoppaBear10]

Opps...........

Yea, I am sorry, I had to goto Mexico to do a job, was gone for a week. (Still gotta pay bills with the day job........).

I am designing or should say Re-designing the Spindle Lock Arm to incorporate it into the design. One memeber here brought up that in probing you should be able to lock the spindle, I agree, so, trying to get the Lock arm done with a SAFE and stable rest position. Not alot of Room in the Spindle head and not many mount points left.

I am going to get the cutting vids up, I have ordered a AL Roughing Mill like the one in the Tormach Vid so I can try and recreate what they did.

I have to leave again to do a machine in Venezuela, this coming sunday and will be gone all week again.

Scott

[zephyr9900]

It is possible to design an automatic drawbar that uses an air cylinder, without the need to apply any forces to the spindle bearings, by transferring the reaction force to the spindle rather than the head.

Yes, I realize that Phil, and that would be ideal. It would need to be a floating assembly, like a disk brake caliper mounting. I could imagine a ring that threads onto the spindle above the bearing preload lockwasher to act as a reaction surface, but I don't know about the repeated axial loads through the threads. It would not be as straightforward a retrofit as Scott's current design.

To answer your other point, drawbar and R8 collet are easily-replaced wear parts. Spindle bearings not so much...

Best regards,

Randy

[snowshovelbmx]

Great looking design, It is very obvious that you put a lot of work into it.

on a side note: Mexico one week Venezuela the next, Can I have your job? lol.

chris.

[philbur]

I'm not sure I understand your concern with the repeated axial load. The thread is either rated for the load or not. Agreed it's not as simple as the direct approach, but it does have the advantage of protecting those expensive spindle bearings. It could also be implemented without the need for a noisy air compressor, necessary for the air wrench alternative.

Phil

I could imagine a ring that threads onto the spindle above the bearing preload lockwasher to act as a reaction surface, but I don't know about the repeated axial loads through the threads.

[zephyr9900]

I'm not sure I understand your concern with the repeated axial load. The thread is either rated for the load or not.

Cut threads will always have a stress concentration at the root unless carefully machined. My concern would be for the cyclic/fatigue stress that was not factored in the original specs, stripping off the spindle threads. But as you said, if the stress is low enough the lifetime would be adequate.

It could also be implemented without the need for a noisy air compressor, necessary for the air wrench alternative.

Where would the air for the pneumatic cylinder come from if not a compressor?

Best regards,

Randy

[ataxy]

i think he ment the use of motor instead

[PoppaBear10]

snowshovelbmx:

If it was not work, it would be a nice trip........ I HATE dealing with the TSA and Airports, I have found that they hire the people who score the absolute Lowest on the Government service exam, then if they fail the common sence/Courtesy exam they are promoted...........

Others:

Spindle bearings, the bearings resist normally a down ward force from the stock Nut when you tighten the nut to lock in a holder. Thus the nut is pushing the Top Bearings down, which they are designed to resist. The Tool changer push rod also pushes down in the same direction as the force of the OEM nut. The lower bearings in both cases only experience the normal upward load of the top nut pulling the holder up. When the top nut, OR, the push rod pushes down, all that does is Push the Tool holder out.

My Draw bar design: As Discussed prior to build with Greg, the Price needed to stay as low as possible but yet stay industrial quality. So, the Design was keep as simple and functional a possible. I could have done many other ways, but all would have been more expensive. There comes a point where the Market will not bear the cost for an ATC no matter how snazzy it is. The Mill head is VERY tight, it was a request to keep as much or all components as contained within the head as possible, both for cosmetic as well as trying to keep moving parts within the Mill Head door, so the door switch could work for the moving components as well.

I have many other ideas to make it more compact and a lot of other mounting/functional options, BUT, they all entail increasing the overall cost/coplexity of the unit.

IMHO, there is a very limited number of mount points available in the Head that still allow motor movement for belt changing and all to be enclosed by the Mill head shroud.

I could have just as easily made a "Swap Arm" tool changer, like on Big Comercial Machines, but the last one like that I did with only 16 tools ran about 6k just for the physical ATC, did not include programming, mounting, debugging etc.

scott

[zephyr9900]

Spindle bearings, the bearings resist normally a down ward force from the stock Nut when you tighten the nut to lock in a holder.

Scott, that is just not so. You could take the spindle out of the head and sit it on the bench. Place a toolholder in the collet, place a wrench on the spindle flats to replace the lock bar, and tighten the drawbar with another wrench. There is no force pushing lengthwise on the spindle at all and it will not scoot across the bench. The tension from the drawbar is resisted by compression within the spindle itself. The force path is drawbar-collet-spindle-drawbar.

You are applying a vertical force external to the spindle with your air cylinder. The cylinder is mounted to the head casting as is the spindle. When you actuate the cylinder the force path is air cylinder-drawbar-belleville springs-spindle-spindle bearings-head casting-air cylinder. The spindle bearings are now called on to resist a thrust that is much greater than any vertical machining thrust, and are bearing this thrust while static. (Of course, after the toolchange the situation is no different than the standard drawbar.)

That is why I ask whether there is a full buy-in from Greg in your drawbar actuator design. All design modifications come with a cost, and it would be a reassurance that the cost in this case is not shortened spindle bearing life.

Scott, please note that I don't intend this as a criticism of your design. If I'm coming across that way, I apologize. It is well thought out and overall balanced design. It's only this one aspect that I'm concerned about.

Best regards,

Randy

[PoppaBear10]

I will agree to disagree with you,

I just dont see it the way you do, I look at the spindle Insitu of the head. the only force across the draw bar with activation of the plunger, is straight down in the direction that the bearings are designed to resist. When tightning the Spindle on a standard tool, the nut vs. the R-8 is still a compression force towards the mid point of the spindle shaft., The draw bar just push downward ONLY in the same dirction of the standard compression force anyway. At this point, it is really a moot point anyway, since the changer is the way it is, and will not be changed.

But in eighter case, the bearing are made to take the large multivector loads that machining excerts.

scott

[zephyr9900]

I will agree to disagree with you [snip] At this point, it is really a moot point anyway, since the changer is the way it is, and will not be changed.

:rainfro: You've done an excellent job of packaging the changer within the contstraints Greg has specified. I hope that it's a very successful product for you.

Best regards,

Randy (good at disagreeing )

[philbur]

I have to agree with Randy. When tightning a standard drawbar setup the compression load is taken through the shaft of the spindle, there is no load on the bearings. When you activate the air cylinder of a powered drawbar (fixed to the head) it is trying to push the spindle out of the head, the spindle is connected to the head through the bearings, so the force resisting the spindle from being pushed out of the head must pass through the bearings.

Yes the bearings are designed to take axial loads during operation, but they do have a limit and you need to know what that limit is. Overloading a bearing either dynamically or statically may not only limit the life of the bearing it can also kill it stone dead, instantly.

Just some points to consider
Phil

I will agree to disagree with you,

I just dont see it the way you do, I look at the spindle Insitu of the head. the only force across the draw bar with activation of the plunger, is straight down in the direction that the bearings are designed to resist. When tightning the Spindle on a standard tool, the nut vs. the R-8 is still a compression force towards the mid point of the spindle shaft., The draw bar just push downward ONLY in the same dirction of the standard compression force anyway. At this point, it is really a moot point anyway, since the changer is the way it is, and will not be changed.

But in eighter case, the bearing are made to take the large multivector loads that machining excerts.

scott

[sharpshooter90]

What may be killed stone dead is the whole concept of the ATC for a Tormach. ATC's are the province of high production shops, where the operator may have multiple tasks to complete while the machine is running its program. Therefore the hourly cost of the operator is utilized. I see the Tormach as a small business-home shop machine, most likely to be run by a single operator doing small runs. Investing in an ATC essentially just makes things more convenient for the operator, who may now stand around and just watch the machine run. In an economy where people are scrambling for every dollar and jobs will go to the lowest bidder, many owners may choose to hang on to their $$, hustle harder and do the tool changes manually.

[PoppaBear10]

Phil, and Randy,

Again, I will agree to disagree, and at this point there is nothing to be gained on this subject, the Draw bar release stands as it is. There really is no other Cost effective way
to do it within the constraint provided. Thank you both though for your Opions!

Sharpshooter90,

As I said in the origianl postings, the ATC kit IS targeted to production/commercial/engineering/school enviroments. If a Hobbiest wants to buy one, that is fine also........
There is Nothing Wrong with the Tormach as a Milling machine in my opion, I have cut many parts with it in the shop for making some of the ATC part that need to be modified or changed a little. Each and every time the Tormach has cut the part dead on, so I really have no complaints against it. It is Orders of Magnitude better than my first machine a Shoptask Elderado, and it can hold a very even match with my Bridge Port 2, (with in the tormachs design parameters).

Economy: Yeap, I agree with you there, no dought we are all feeling the effects of the Criminal Polititions in Washington who caused the finacial mess in the first place and now they want to "Oversee" the "Fix". I might as well as put the Fox over my Hen House.

scott

[BlueFin]

Investing in an ATC essentially just makes things more convenient for the operator, who may now stand around and just watch the machine run.

There is no way I would stand around and watch the thing run, the minute I was comfortable with the G Code running on it's own without boring a hole through it's own T Slot table I would shut out the shop lights and head down to the local Mexican resturant for Enchilada's and Corona's or better yet I would leave the lights on, point a webcam at it and go hiking in the hills with my kid, every now and again I could fire up the Verizon wireless PDA and see how things are going back at the shop

[Jim G]

[QUOTE=highspeedmazak;507741]...it should be made of SS heat treated and milled on a very solid machine.QUOTE]

FWIW, we just had to replace our carousel for our Haas VF-1.
11 years of coolant on tools 1-7 have corroded it sufficiently.

It's a 1/2" thick Aluminum dial plate. Stamped steel retainers for the tools.
Nothing too fancy but does the job just fine.