Hello Guest it is July 21, 2019, 05:42:31 AM

Author Topic: BT30 spindle from scratch - with power drawbar and ATC of course  (Read 402255 times)

0 Members and 1 Guest are viewing this topic.

Offline simpson36

*
  •  1,374 1,374
    • View Profile
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #450 on: January 24, 2013, 06:57:11 AM »
Meant to ask, what is the cost of the Mitsu drives? Say the 400watt ones.
Hood

Sorry for the late response. Been a busy boy.

New price is a bit under US$1,000 each for the drive and the motor. Ebay has a number of vendors who have good used stuff and usually you can get good clean pair (Drive and motor) for about $800 or thereabout. The 750's usually run close to $1,100 to $1,200 for a set. A caveat with the J3 series is that the cables are stupid expensive   . as in . . up to $100 for each cable and they have special unobtainable connectors so anybody shopping for J3 Mistu, make sure you address the cables as they can be a significant part of the cost. 

Offline simpson36

*
  •  1,374 1,374
    • View Profile
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #451 on: January 24, 2013, 07:19:11 AM »
Nice try stevo BUT " your" words proved my point .   IF you look back through your posts the main objective was to sell someone on the site your wares. AND it was hard to sell your wares to Tormach users as long as Tormach LOCKED you out of the picture.  Then you were pissed because Greg would NOT work with you so you could access his customer base

Then there is the ME syndrome. Basic genetic flaw in a LOT of engineers who think the world cannot revolve without their guidance.

I dought that Greg needs your help with anything concerning his CNC products. He is light years ahead of you already .

But you Have a good one anyway, YA hear

(;-)TP

Jeez, don't you get tired of being wrong?  ::)

I have no trouble selling to Tormach owners. If I did not sell to Tormach owners, I would not have any reason to work with Tormach on their MACH software mods. You don't have to be a conceited, narcissistic engineer (like myself, apparently) to make that connection. Just have some common sense.

Also, you are just delusional if you think putting together a stepper driven bench mill and using an entire tiny lathe as a 4th axis is 'light years ahead' of anyone. Perhaps those examples of engineering prowess are impressive to you, but honestly I think even the greenest newbie can get to that level in a few months.

Next correction; I was not and am not 'pissed' at Tormach or any individual there. Nor am I 'pissed' at you. You are entitled to make as many inaccurate, incorrect or even idiotic statements as you like. I am entitled be amazed at baseless and idiotic some of your comments are. I am firm believer in the serenity prayer and your Tormach fanboi affliction and your belief that your assumptions are facts is one of those things that I can do nothing about.

And to correct your last incorrect assumption, I am not 'locked out' of anything. Tormach's MACH implementation took about 5 minutes to crack and I did the QC myself in about 5 more minutes.  As I said, this stuff is not rocket science. Some people like to pretend that it is so that their knowledge of it seem oh so impressive to newbies.  If you simply copy a standard copy of the MACH .exe over Tormach.s, it come up with access to all parameters. Oh my - OOPS,. was that supposed to be a secret?  . .  Sorry Obi Wan. . .

Offline simpson36

*
  •  1,374 1,374
    • View Profile
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #452 on: January 24, 2013, 07:33:51 AM »
Hey Steve,

    So, give me a web site where I can get those Springs I REALLY, REALLY like that idea over Belviells, I guess my concern would be, how would you keep the spring centered so it would not wobble the shaft?
Scott

Sorry for late replay. Your question about the centering will be answered in the next few posts. I'm happy to give you the source and part# for the spring, but since it is a potentially dangerous part, please PM me so I can give you the standard disclaimer blurb along with the info.

I will address the air cylinder throttling separately. Thanks for your comments!

Offline simpson36

*
  •  1,374 1,374
    • View Profile
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #453 on: January 24, 2013, 07:37:28 AM »
Steve,

Thinking about it some more, I think a solenoid-controlled needle valve driven by a simple (even software) PWM would be the way to go.  Simple to implement, and should give very good control.

Regards,
Ray L.

Right on the money, as usual. The trick is to find something 'off the shelf'. I'm thinking there must be a computer controllable (PWM, analog, or whatever) orifice or regulator. Hopefully there are some industrial control gurus lurking around here that can provide an example.

Offline simpson36

*
  •  1,374 1,374
    • View Profile
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #454 on: January 24, 2013, 07:43:52 AM »
Hey Steve,
 
Also:  Having built a Prototype ATC, I would NOT try and use "Air Cylinders" for any type of speed control. It is very hard to get the flow valves right, and the instant that your pressure, or humidity changes at the source, then those speeds are not longer valid........ Other than Bang-Bang motion, they are not good velocity or positioning devices.  It would probably make MUCH more sense to do a Rack/Pinion or acme screw/nut for linear motion.

Scott

I have to agree with you from the aspect of control. While I was noodling around on ways to power the various actuators, I discarded rack and pinion because of the difficulty in keeping it clean. The environment is difficult because of the flying swarf, coolant, etc. My career was primarily fault analysis on mechanisms in industrial environments, so I am always thinking in terms of 'what would happen if someone shoveled gravel into this machine' .  :o

Offline simpson36

*
  •  1,374 1,374
    • View Profile
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #455 on: January 24, 2013, 07:56:26 AM »
Hey Steve,

Having said the above, another way, but more expensive, is to drive the entire contraption via PLC brain, you could use "High Speed counters" or Stepper/motion cards to drive or read, or drive/read your motors.  You can use inexpensive AC or DC motors, and put an Encoder on the motor or on the moving part, your choice, and read its distance via the High speed counter,  you can set all kinds of very good positioning that way. The next level up would be stepper (or servos), controlled via a motion card on the PLC (with Encoder feed back). Many of these cards you can select various "Motion Profiles" and set up motion/velocity tables, with set positions that can be called. (this applies to both linear and rotary motion).

I have a pair of Mitsu servo motors actuating the carousel and the arm. The whole thing is controlled by a processor running C code. After thinking about Hood's excellent suggestions, I reasoned that writing some code to generate a step stream and run the servo drives would be shorted time-wise than the learning curve for a new type of industrial drive. The AB seems quite a lot more intuitive that the Mitsu, which is extremely complicated to use in that way, but the code to run the drives was relatively simple and I have the carousel routines finished and tested. The arm is the same servo drive (just a newer model) so the same code, slightly modified will do that job as well.

Ultimately I am thinking about following HimyKabibble's lead in implementing a Kflop and connecting 'satellite' task specific processors to it, but that's a big meal that I don'thave time for at the moment, so I elected to pile the ATC code on top of my existing InTurn™ 4th axis motor controller since it is already tied in and talking to MACH. The little processor has it's hands full as it is, but a tool change happens 'in a vacuum' so to speak when everything else is on hold, so it will probably be fine.

Quote
IF your real, real hell bent for leather, then you could just use analog cards, with linear rheostat for feed back coupled with a PID loop per motion axis/device...
Many, Many ways to kill that cat, even do PID loops in a plugin if you like the pain....

Scott

Running in the dark .  with scissors . . and my hair on fire . .  is pretty much normal condition for me . .

Offline simpson36

*
  •  1,374 1,374
    • View Profile
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #456 on: January 24, 2013, 08:03:33 AM »

Simpson better get cracking on his ATC! I'm already working on my second one, for my new machine!

Regards,
Ray L.

Hey, haven't you won this thing yet? I caught you sand bagging one sensor as I recall. Is that done?

Offline mc

*
  •  381 381
    • View Profile
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #457 on: January 24, 2013, 08:08:52 AM »
Steve,

Thinking about it some more, I think a solenoid-controlled needle valve driven by a simple (even software) PWM would be the way to go.  Simple to implement, and should give very good control.

Regards,
Ray L.

Right on the money, as usual. The trick is to find something 'off the shelf'. I'm thinking there must be a computer controllable (PWM, analog, or whatever) orifice or regulator. Hopefully there are some industrial control gurus lurking around here that can provide an example.

In hydraulics, you get electrically controlled variable flow control valves, and I'd guess someone will do something similar for air.
However the usual way for controlling cylinder speed with air is by controlling how quickly air escapes from the non-powered side of the cylinder. The flow restrictors are usually plumbed in with a one way valve, so you get full flow into the cylinder, but any flow out goes through the restrictor.

Offline simpson36

*
  •  1,374 1,374
    • View Profile
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #458 on: January 24, 2013, 08:24:09 AM »
OK, I think I have answered all of the questions. Couple general comments;

* Not interested in introducing hydraulics.

* PWM out and analog in and out are standard feature of the current crop of tiny processors so extra boards are not needed.

*Anything that requires operator intervention is contrary to the design goals here.

* cost is always a consideration except where safety is concerned, but it is not high on the menu here as this device is not intended for hobbyists . . per se.

* Bang-bang is not the concern and is easily handled by cushions built into the cylinders. It is a standard option with Fabco, for example.

* fixed speed control of the air cylinders id not a concern as that is easily accomplished with available adjustable orifice valves specifically for that purpose. I have one of those on the drawbar actuator in the 'grip' direction to reduce the shock load on the gripper. Shock load is beneficial and perhaps even needed on the release cycle, so there is a small acceleration gap and no restricts.

* the challenge is to be able to computer control the speed of the air cylinder that raises and lowers the arm.  Given that for any specific part, the overall thoughput can be significantly effected by optimizing each operation, it makes sense to run the ATC as fast as possible with small low mass tools and slow down for very heavy or large tools. I have read volumes of concerns over drawbar release pressue being taken by the spindle bearings, but in most cases that is really a needless worry as the static load on the bearings is typically far above the drawbar pressure. However, taking a very heavy tool and slamming it into the spindle taper is not a good plan. Note that industrial robotic loader/unloader mechanisms almost always decel just off the target and gently deliver the load.

Offline simpson36

*
  •  1,374 1,374
    • View Profile
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #459 on: January 24, 2013, 08:26:47 AM »
Steve,

Thinking about it some more, I think a solenoid-controlled needle valve driven by a simple (even software) PWM would be the way to go.  Simple to implement, and should give very good control.

Regards,
Ray L.

Right on the money, as usual. The trick is to find something 'off the shelf'. I'm thinking there must be a computer controllable (PWM, analog, or whatever) orifice or regulator. Hopefully there are some industrial control gurus lurking around here that can provide an example.

In hydraulics, you get electrically controlled variable flow control valves, and I'd guess someone will do something similar for air.
However the usual way for controlling cylinder speed with air is by controlling how quickly air escapes from the non-powered side of the cylinder. The flow restrictors are usually plumbed in with a one way valve, so you get full flow into the cylinder, but any flow out goes through the restrictor.

Exactly correct, however, the objective is to find a computer controlled restrictor. Must be something out there. I'm just being lazy really  . . don't want to do the research  :-[