Messages

1

Galil / Re: VFD Spindle control 0 to 10V (not -10 to +10V)

« on: April 18, 2011, 06:02:14 PM »

Yes, good point.  My spindle doesn't have an encoder, but I'm hoping to add one eventually for rigid tapping. 

With an encoder and the JG command, to make the Galil driver work without a diode on the output, it would have to change the encoder polarity using the MT command (MT 1 for forward, MT -1 for reverse polarity). 

Kenny, I assume the Galil driver use JG commands for spindles with an encoder, right?  If so, then in your update you sent me, we would have to add MT commands to the Custom Notify messages and M3/M4 macros as well for people with encoders.  But, your updated driver as is will still handle it.

I should mention, I don't like the diode because it creates a voltage drop which can skew the actual spindle speed (make it non-linear).  I know, maybe it's splitting hairs.  It depends on the current through the diode.  My VFD speed input is about 30K ohms, so at 10V, that's 0.33 mA at 10V.  A common diode will only drop about 0.1V at 0.33mA, so that's fine.  But VFD's with a lower input impedance (e.g. 5K or less will cause a 0.2V to 0.5V drop through the diode), and the voltage drop through the diode starts to become an issue for linearity (spindle speed will not be linear with respect to commanded voltage). 

But, using JG commands and an encoder on the spindle, this doesn't matter.  The Galil card will adjust the voltage to maintain the speed based on the encoder feedback.  That's useful. 

Mike

2

Galil / Re: VFD Spindle control 0 to 10V (not -10 to +10V)

« on: April 18, 2011, 12:42:39 AM »

Kenny, thanks for the test plugin.  Kenny set the driver to output 0-10V instead of -10 to +10V to test the idea.  He's got a few minor changes to make, and add the check boxes to enable/disable it, but it should work great.

NosmoKing, I'm using outputs 4 and 5 for reverse and forward control of the VFD, as you say.  I enabled them in the "Relay Control" box of the Ports & Pins dialog.  But, what do you mean by using the Jog+.

Mike

3

Galil / Re: VFD Spindle control 0 to 10V (not -10 to +10V)

« on: April 15, 2011, 04:43:06 PM »

Yes, the debug file. I should have tried that first.  Thanks much for your help.

Mike

4

Galil / Re: VFD Spindle control 0 to 10V (not -10 to +10V)

« on: April 14, 2011, 10:19:24 PM »

Understood. Thanks.

Can you confirm how the Galil driver sets the spindle speed?  Does it use SH to enable the axis, and OF commands to set the speed?  Does it check the result after the fact (i.e. read back the OF result or just blindly write it)?  My program will read the OF value, and if negative, change it to positive. But, if the Galil driver fights me and changes it back to negative, it won't work.  Also, this assumes the Galil driver only changes the OF value when the speed changes. If OF is updated constantly (even if the speed doesn't change), then it won't work very well.

I might be able to do it with Custom Notify too.

But, yes, if all else fails, I'll use a diode bridge. The VFD input only draws 0.3mA, so the diode drop won't be a huge concern. I don't have a spindle sensor, so Spindle Calibration won't help me. No feedback.  But as long as the diode drop is small, it will work fine.

Thanks,
Mike

5

Mach4 General Discussion / Re: New people welcome !! Come in here and introduce your self!

« on: April 14, 2011, 08:16:35 PM »

Hello,

Nice to meet you all. I've been following Mach3 for years, but finally decided to install a machine with it. My 3 axis  Acer knee mill was done with Camsoft.  Been fighting with it since I bought it. I finally gave up and installed Mach3 last weekend. I hope to upgrade the machine to 4 axis eventually.  I'm also considering another project with a 5 Axis Maho - a semi-retrofit. 

I'm an electrical engineer by trade, but I'm heavily into machining, and motorcycle engine development.  The motorcycle stuff is what promted getting into machining, but I have broader intentions.  I've been taking classes at De Anza College in Cupertino, CA for the last year. 

The Maho "semi" conversion is a project where I don't plan to replace the orignial controller (a Maho CNC532), but instead bypass it. My Maho already has a system to do exactly that - it's called a "Lemoine PC" upgrade, intended to add high speed machining capabilities to older machines.   But even the Lemoine system is old (ISA cards, and DOS based software).  It's an easy conversion because the wiring is already in place to bypass the CNC532 controller (it was a factory installed option in 1994).  I just need to wire in a Galil card and Mach3 where the Lemoine system used to be.  But, that's a project for another day. 

Regards,
Mike

6

Galil / Re: VFD Spindle control 0 to 10V (not -10 to +10V)

« on: April 14, 2011, 06:40:16 PM »

Thanks.  Unfortunately, it doesn't quite work.  The DMC-18x2 manual says.

For each axis, the SM jumper selects the SM magnitude mode for servo motors or selects stepper motors. If you are using stepper motors, SM must always be jumpered. The Analog command is not valid with SM jumpered.

According to Galil Support, The SM jumper doesn't apply an absolute value function to the output (e.g. like a diode bridge).  It compresses the -10V to +10V into 0 to 10V, with 5V as the center.  Max reverse RPM would be 0V, max forward would be +10V, and 0 RPM would be 5V, and that assumes the analog output even works - which according to the manual it does not ("The analog command is not valid with SM jumpered.").



I'm assuming the Mach3 Galil driver is using OF (offset) commands to output 10V for max forward spindle motion, and -10V for max reverse spindle motion. What I need is to always get 0 to +10V regardless of spindle direction (0V = spindle stopped, +10V = spindle max RPM).

A diode bridge sort of works, but issues with the diode drop are problematic.  Besides I hate to use electronics to do what software should be able to do much easier. 

In this forum post (http://www.machsupport.com/forum/index.php/topic,12652.0.html) from Sept 2009, Smuph suggests that more such options need to be added to the Galil driver to make this kind of spindle control possible. I'm hoping those options were added and I'm just missing it. 



I should point out, my machine is a Camsoft to Mach3 conversion. The spindle in Camsoft works fine. It's handled using SHW and OFW commands to enable and set the spindle voltage. All OFW commands are 0 to +10V, not negative. 

If the Galil driver doesn't do this, I'll try writing a Galil built in program that monitors the spindle voltage and converts any negative voltages to positive voltages (if _OFW < 0, OFW = @ABS(_OFW) sort of thing).  This only works if the Galil driver does not monitor the _OFW value.  I hate to mess with the Galil driver like this without knowing exactly how the driver handles this. 

Thanks,
Mike

7

Galil / VFD Spindle control 0 to 10V (not -10 to +10V)

« on: April 13, 2011, 06:58:15 PM »

I have a VFD drive on my spindle, controlled through the W axis on the Galil card. I set my direction using outputs 5 and 6, and the spindle speed is set using an absolute value (0 to 10V), regardless of direction.

What I see, however, is for reverse spindle (M4), speed control works fine (10V = max RPM, 0V = spindle stopped).  For forward spindle (M3), the spindle runs, but at a constant RPM (about 500 RPM) regardless of the set spindle speed.  I assume this is because the Galil controller is using -10V to +10V where negative is spindle CW, and positive is spindle CCW. How can I force it to output positive voltages regardless of the spindle direction.

I saw this discussion:  http://www.machsupport.com/forum/index.php/topic,13901.0.html 

If I have to create a special Galil program to do it as suggested in that topic, I will, but I assume I'm missing something.  There must be a way to tell Mach3 to do what I need without a custom Galil program, right?

Also, how is the Galil driver controlling the spindle?  Is it using SH to enable the output, then OF commands to set an offset voltage, and MO to turn off the spindle?  Or does it use another method.

Thanks,
Mike