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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #490 on: February 04, 2013, 12:24:48 PM »
Steve,

I've never once had the need to rotate the head on my knee mill, and I really wish it was rigid.  I would expect anything you can do with a tilting head, you can do just as well by fixturing the workpiece differently, or using a 4th axis.

I agree completely about CNC-ing knee mills.  If I had it to do over again, it's not where I would start - too many compromises.  My new machine is a bed mill.  I think most of the reason there are so many CNC'd knee mills is just that there are so many knee mills out there, and often for very cheap.  Bridgeport probably just took the path of least resistance on their early machines.

Regards,
Ray L.
Regards,
Ray L.

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #491 on: February 04, 2013, 12:36:29 PM »

I also plan to have a macro that will automatically touch off all loaded tools (I can tell which slots are occupied, and which are not), and load the tool table automatically.  I think that will be a nice convenience, and time-saver.


This was my conclusion also, but it does not seem so easy to do, at least on BT30 where there are holders with very long 'noses' that could then have very long cutters in them. Conceivably the delta could be 6 or 8 inches from a short holder+short tool to an extended holder+long tool.  Seems like moving a touch-off pad (or laser) with a LOT of travel would be the only way to do it.

Quote

I spend much more time thinking about designs, and much less time actually building them. And, in most cases, they work almost perfectly on the first try. 


Well, my observation is that you built an entire ATC over quite a long period of time with prototype components that were later replaced with final design parts. Now you have designed an altogether different one which, as described, should be quite an improvement on the first. That process seems pretty normal to me . . . . . Just sayin'  ;)

Quote

The more common approach I've seen far too often is to rush into construction, then spend months putting on "Band-Aids" for all the things that were not well thought out up-front, and you end up with something more complex, and expensive, than it needed to be. 


Seems you have discovered my secret method. Except that after about three band-aids, I scrap the whole idea and start over . .   :D

Favorite saying;

"Trip of thousand miles begin with one step"
 - Asian probably - don't know who  - circa:  long time ago

"Evrybody is incopetent, just at differnent things"
- Will Rogers maybe?  cira: some time before he died

"I cut it off three times and it is STILL too short"
- my mentor . . . .  explains a lot, huh  :)

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #492 on: February 04, 2013, 12:40:46 PM »

 My new machine is a bed mill. 

OK, I can't take it any more!

WHAT machine are you getting?    Tell me or kill me . . .  either way . . stop the pain,  . . . please.
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #493 on: February 04, 2013, 12:46:48 PM »

I also plan to have a macro that will automatically touch off all loaded tools (I can tell which slots are occupied, and which are not), and load the tool table automatically.  I think that will be a nice convenience, and time-saver.


This was my conclusion also, but it does not seem so easy to do, at least on BT30 where there are holders with very long 'noses' that could then have very long cutters in them. Conceivably the delta could be 6 or 8 inches from a short holder+short tool to an extended holder+long tool.  Seems like moving a touch-off pad (or laser) with a LOT of travel would be the only way to do it.

Quote

I spend much more time thinking about designs, and much less time actually building them. And, in most cases, they work almost perfectly on the first try.


Well, my observation is that you built an entire ATC over quite a long period of time with prototype components that were later replaced with final design parts. Now you have designed an altogether different one which, as described, should be quite an improvement on the first. That process seems pretty normal to me . . . . . Just sayin'  ;)

Quote

The more common approach I've seen far too often is to rush into construction, then spend months putting on "Band-Aids" for all the things that were not well thought out up-front, and you end up with something more complex, and expensive, than it needed to be.


Seems you have discovered my secret method. Except that after about three band-aids, I scrap the whole idea and start over . .   :D

Favorite saying;

"Trip of thousand miles begin with one step"
 - Asian probably - don't know who  - circa:  long time ago

"Evrybody is incopetent, just at differnent things"
- Will Rogers maybe?  cira: some time before he died

"I cut it off three times and it is STILL too short"
- my mentor . . . .  explains a lot, huh  :)




Steve,

My approach to the touch-off macro is to have a "compliant" touch-plate - one you can approach at high speed without risk of damage to the tool.  So, you do an initial high-speed probe, to figure out the rough length of the tool.  Then, back off a short distance, and do a second, slow, probe to measure the length.

If I'd had an uninterrupted period of time to do the ATC, the total time would've been down to a few weeks.  The parts I re-made were more to refine dimensions that I could not measure accurately, rather than fundamental design changes.  The initial design is VERY close to as first drawn.  The new design has a completely different set of constraints, and the MAJOR advantage of being aimed at production, rather than a one-off.  That makes many things practical that were not in a one-off.  The basic carousel design, BTW, is nearly identical, except for the number of tools, reducing the maximum allowable tool diameter (both per the customers request), and the change to internal Geneva (this helped make it more compact).  So, a lot of the initial design has been carried over.  The major change was making the carousel fixed, and adding the transfer arm, which both helped make the whole system more easily adapted to other machines - an important consideration for a "product" I hope to make lotsa money from.  This added complexity, but n0ot much.  This is where all the major design changes are.

Regards,
Ray L.
Regards,
Ray L.

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #494 on: February 04, 2013, 03:18:16 PM »
Ray,

Are you going to spill the beans about your new milling machine voluntarily, or do I have to send Carmine over to see you?  >:(

Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #495 on: February 04, 2013, 06:11:06 PM »
Steve,

No secret - I ordered a Novakon Torus Pro Servo bed mill - 25"X x 15"Y x 12"Z travels, 2HP 3-Phase, AC servos, 500 IPM Rapids, ground ballscrews, linear rails on Z.  Best of all, it's EASY to fully enclose, so first project will be fully enclosing it with 8020 and Plexi, and finally get to use the high-pressure (60 PSI) coolant system I've had sitting in the corner since I built it last year - WAY too messy on the knee mill.  I will, very shortly, rip out the BOB and 86 Mach3, and put a KFlop in it so I can run my CNC controller app.  This is the biggest machine I could find at a reasonable price, and the guys I've talked to that have them are VERY happy.  It seems to be quite rigid, and very accurate.  I hope to also add linear scales, fed into the KFlop, to get a bit more accuracy out of it by compensating for thermal errors.

Regards,
Ray L.
Regards,
Ray L.

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #496 on: February 05, 2013, 06:03:37 AM »
Nice looking machine!  Had not seen this guy before.

The Kflop is here and I *might* have some minutes to play with it today. Initially, I just want to get it running with MACH and get rid of the smoothstepper, but I had in mind to run the ATC on it, or to it, or around it or whatever. But now Arduino has just come out with a new board with a much higher end processor that is almost a direct swap out for the MEGA board that I use in the InTurn™ motor controller, so I may go with that. The new processor is also Atmel and it similar to the processors on Atmel's industrial development boards, of which I have a couple. Up from 16 bit to 32 bit and up from 16mhz to 84mhz, DMA, native USB, blah blah blah. Couple comparos I've seen show 4x to 5x improvement. Just available in the last couple months. I have one on its way and I'll probably put my balancer software on it first, then the InTurn™ controller with the ATC code. Calculating the command params for the Digital Signal Synthesizer requires floating point math which really bogs down the MEGA.

An IH bench mill is being shipped to me today. It gets a conversion with ground ball screws and the new head along with ball slides on the Z.  Seems like a pretty nice machine. Owners like them. Very difficult to actually get one though, especially a manual version.

I wanted to mention that the new head will NOT rotate. Feedback I got here and elsewhere was all the same; nobody uses the rotating head and several people said it was actually a problem occasionally. Most likely the mount will be 12" x 12" x 1.25" surface ground plate with the slide bearings bolted to the back and the head to the front.

Finally, I have some data on a filled column vs cast iron, so I may be able to compare the two and satisfy myself that a steel tube full of epoxy or concrete is equal to (or better by some accounts) than grey cast iron.   'Course, now I have to start all over and build another head . . .






Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #497 on: February 05, 2013, 11:36:36 AM »
Steve,

Feel free to call or e-mail if you need any help with the KFlop.  I'd also be happy to send you all my code as a starting point/educational tool.  I"m sure there's a lot there you could use, with straight-forward modifications.

This really is the golden age of cheap, powerful little MCU boards, isn't it?  Seems like every couple of weeks there's a new board that's better, stronger, faster, cheaper than the best of the previous week.  My PDB and toolchanger will be built around a lowly Arduino ProMini.  At about $6 each, it's hard to pass up.  I've been wanting to try the Propellor. Not so much because I need 8 processors on a chip, but I'm a multi-processor guy from way back - I was doing HyperCube research at CalTech/JPL back in the '80s, and helped build what was, briefly, the worlds fastest computer, the CalTech/JPL Mark III Hypercube.

I think you've made the right choice re: rotating the head.  But how are you going to drive the Z axis if you fill the column?  Where will the ballscrew go?

Regards,
Ray L.
Regards,
Ray L.

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #498 on: February 05, 2013, 01:40:23 PM »

I think you've made the right choice re: rotating the head.  But how are you going to drive the Z axis if you fill the column?  Where will the ballscrew go?


I am not a fan of slotted columns. As an engineer, I'm sure you know what it does to the torsional rigidity of the structure.

When you have ball slides, the overall depth of the slide is (generally speaking) the space you have between the back of the head and the front of the column. The screw is in that space.

On this IH machine I will be mutilating, until I have my hands on it in a week or so, I won't know what is doable, but I can tell you for certain, the screw will not be inside the column, so if the owner wants to fill the column with something, he will have that option. At this moment in time, it looks like it will be treated to a Mitsu 350 series drive and motor for the spindle so filling the column might be a requirement in order to keep the head in the same county as the rest of the machine   :o

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #499 on: February 05, 2013, 02:01:01 PM »
Feel free to call or e-mail if you need any help with the KFlop.  I'd also be happy to send you all my code as a starting point/educational tool.  I"m sure there's a lot there you could use, with straight-forward modifications.

THX, Ray.   Much appreciated, really.

I have the Kflop working with MACH  . .  well . . .  on my desk anyway. Took a bit to figure out how to get it to spit out a TTL step, but it's clicking along now. I though it had differential signals for some reason, but it does not seem to. No matter, I'll just throw line drivers on the outputs. There are some odd quirks that are probably caused by operator error :-[  but I'll send you an e-mail about that. Not really germane to this thread.

Surprisingly, it seems to get along OK with 64bit Windoze 7 Pro . . .  so far.  It is going to live on XP and Win7 32 bit, but for now it's in my office.