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Author Topic: How do I control spindle brake and gear shift?  (Read 4989 times)

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How do I control spindle brake and gear shift?
« on: September 09, 2009, 03:42:28 PM »
Hello!

I am about to start the retrofit of an old Tree CNC milling machine.  I am at the point where I need to start purchasing the necessary equipment.  I am planning to keep the original DC servo motors and the AC spindle servo.  The plan is to use some of the new Granite drives to run the 3 axes and either a VFD or the original spindle drive for the spindle motor.  Another forum member mentioned that the original spindle drive (Fanuc) is a nice unit, but I'm not sure how I would get it set up on a PC-based system.  My goal is to come up with something that is fairly simple and very reliable.

Anyway, the main reason I started this thread is to find out the best way to control the spindle brake and two-speed geared head on the mill.  I believe that both of them use relays/selenoids that control compressed air.  Typically, are those sorts of things controlled through the I/O relay controls of a breakout board?  I'll have to take a closer look at the  head to see just how it changes gears, but I'm pretty sure it uses air lines.  The last time I ran the mill through its gear change, it did it on the fly and made an awful racket.  However, I don't think that anything was damaged (hopefully).  I've just been wondering if it would be better to just have it in high gear and use a VFD to cover the entire speed range.  I believe the original control changed from low to high around 1200 RPM (with a top speed of 6000).

Well, if anyone can give me any pointers in regard to this matter, please let me know.  As I mentioned, I've been under the impression that I could control such things through the breakout board, but I figured I'd ask to be sure.  I don't know too much when it comes to the amalgamation of electronic and mechanical systems, but I'm trying to learn!  Thank you for taking time to read my post and for any pointers you can give me.

Offline Hood

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Re: How do I control spindle brake and gear shift?
« Reply #1 on: September 09, 2009, 05:14:11 PM »
First thing to say is if its a servo motor on the spindle then a VFD is no use.
Whether you can use the old drive or not will depend on the signal it needs, if its 0 to 10v then some of the spindle boards may work, if its -10 0 +10volts then thats no use.

As for gear controls then it may be possible to use the parallel ports but that will depend on how much I/O you need. Other options are PLC, ModIO or Pokeys or similar I/O devices. My preference would be a PLC.

Hood
Re: How do I control spindle brake and gear shift?
« Reply #2 on: September 09, 2009, 08:02:39 PM »
Hm.  Now I'm confused.  Up until now, I wasn't aware that a VFD won't even work with my motor!  It's a good thing I didn't throw the spindle drive away.  I believe I have some schematics for the spindle drive (very basic ones).  Maybe that will tell me what voltages it runs at.

As for controlling gear shifts and spindle brake with PLCs...  I'll have to research that idea, as well.  I had to look up PLCs on wikipedia just to get a better idea of what exactly they are!  I am starting to think that attempting this  retrofit may've been a bad idea.  My friend bought an entire kit from MachMotion and said it was a breeze to install.  So, I figured it can't be all that complicated.  However, I might be better off just getting ANOTHER crusty old CNC mill that actually works!

Offline Hood

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Re: How do I control spindle brake and gear shift?
« Reply #3 on: September 09, 2009, 08:14:32 PM »
It all sounds complicated but its not really that bad, the good thing is in the end you will have something that you know how to fix.
Hood

Offline cnc-it

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Re: How do I control spindle brake and gear shift?
« Reply #4 on: September 09, 2009, 08:26:15 PM »
Ions I think you could still control that spindle drive with a Galil motion card in analogue mode..Has it got an encoder on the spindle motor..? You did say it was 0-10v analogue when you checked in the manual..is that correct.?

If you would like to send me a copy of the manual I can check it out for you..

John

Offline cnc-it

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Re: How do I control spindle brake and gear shift?
« Reply #5 on: September 09, 2009, 08:28:18 PM »
Click on my member name to get my email!

John.

Offline poppabear

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Re: How do I control spindle brake and gear shift?
« Reply #6 on: September 11, 2009, 09:41:58 AM »
Ion,

     chances are probably good that your control voltages for that machine is 24V, (look at the solinoids for your air valves). Plus older solinoids can sometimes pull upto 0.5 amps per coil.  Having said that, if you do the retrofit with just PP boards, you going to have to go through Relays. Your other option is
some of the modbus boards, some of them offer secondary "Relay" boards as well.

The best option as Hood said, is PLC's since you get a device designed to work day in, and day out in an industrial enviroment. If you IO needs are small less than 8in and 6 out, grab a DL05 they are around 100 bucks or so, if more than that but less than 20 in, and 16 out, grab a DL06 (they sell a model that has all the outpus already as relays, it runs around 220 or so. If you dont have many rungs of logic in the plc, then the Demo software that you can download for free if your program is less than 1000 bytes, more than that you have to buy the programming software, and it runs about 300. I use Automation Direct since they are economical, BUT, you can pick what ever you want to use/afford, just make sure you can get your hands on the programming software for what you choose.

Gear Shifting:  Look at what the logic sequence is on your Air for the Gear positions, and look at the logic sequence for the "Change gear" (if any, I suspect it just changes from one state to the other without a Transition state).  What you can do, is watch your Current Spindle Speed in mach3, and depending on that value, send out the changes to your gears once it crosses the change point in your speed. You can run that from the Macropump, or Brains.

scott
Commercial Mach3 & Mach 4, Design/Build/Retrofit CNC and Industrial machines.
http://www.ss-systems-llc.com/