Messages

1101

General Mach Discussion / Re: Replacing a Resolver of an AC Servo with an Encoder

« on: August 28, 2009, 08:01:42 AM »

Hood,

Once read somewhere (can't recall where exactly) :

AC servo and BLDC are basically two types of motors operating on the same principle - electronic commutation. The only difference between the two is that an AC servo doesn't have magnets at all, while a BLDC has magnets on the rotor. AC servo has windings on both the rotor and stator.

Daniel

1102

General Mach Discussion / Re: Replacing a Resolver of an AC Servo with an Encoder

« on: August 27, 2009, 03:17:29 PM »

Hood,

I need the motor for my Emco F1 spindle. The original one is a DC motor 4000RPM, 440W, 1Nm, geared down 2:1, so at the spindle I get max speed of only 2000RPM (not really enough for most of my work) and torque of 2Nm. The torque is a bit insufficient at times, but I think an AC servo with the same continuous stall torque rating would do much better, since it can ramp up to it's peak torque much faster and stay there for longer times.

Getting a bigger motor - that was what I was thinking to do before I took apart the F1's head. The timing pulley mounts on a 35mm shaft, setting the limit to how small a pulley I can use, and the head housing limits the max pulley diameter I can put on the motor - about 70mm. So gearing down 1:1.5 seems to be the best I can do. Thus using a 8,000RPM motor I should be able to get 12,000RPM at the spindle - which is what I am aiming for.

But may be you're right, I'll need to compromise on a lower speed. May be I can find a 6,000RPM and get 9,000RPM at the spindle.

Thought using a High Speed VFD spindle, but it would limit me to a lower speed of 4,000RPM (if geared down 2:1).

Daniel

1103

General Mach Discussion / Replacing a Resolver of an AC Servo with an Encoder

« on: August 27, 2009, 02:25:35 PM »

Hi,

I am considering to buy an AC servo motor. This one I found satisfies all my requirements (the main of which is top speed of about 8,000RPM) but one - it has a resolver. I found that it's really hard to find motors in the above speed range, so there is no much choice really. So I am considering to buy it and fit a commutating encoder in place of the resolver (the other choice is to find a servo drive that will support servo commutation, but it seems even harder).

I have two questions:

1. Has anybody done this before and is it worth the effort? Any special difficulties?
2. Any sources for reasonably priced commutating encoders? I found some at www.encoderprod.com , just called them but their prices are much more higher than I am willing to pay for an encoder. They are selling them for $250 for a single encoder!

Thanks,
Daniel

1104

General Mach Discussion / Re: Front & rear toolpost in Turn 42.020

« on: August 27, 2009, 01:57:58 PM »

Sorry for interrupting the discussion, but I don't think I understand Hood why you need the scale factor if you change from a rear tool post to a front one? Are you changing the direction of rotation of your spindle and you need to change the X values from negative to positive?

And why by a factor of (-2) and not (-1)? If you're in dia mode and have for instance X-10, wouldn't G52 X-1 convert it to X10?

Daniel

1105

General Mach Discussion / Re: Post processor for new CAM system

« on: August 26, 2009, 10:13:26 AM »

1.   I note the G43 expects tool length offsets to be positive. G44 for negative offsets. Should a choice be given for both? Is it common for users to use G44.

I had problems using only G43 for both negative and positive offsets, and I was not fancy about using both G43 and G44, since the CAM doesn't know the actual lengths of all the tools I use and it has no way to determine which command to use (G43 or G44) for each tool. Trying to fix it would mean a lot of unnecessary work and a lot of room for mistakes.

I edited my M6 macro by taking out the Z move after the conditional. Now I am successfully using the G43 command for all cases.

Daniel

1106

Forum suggestions and report forum problems. / Re: Mach 3 and Yaskawa Servos

« on: August 18, 2009, 10:51:08 AM »

William,

Don't know what breakout board you're meaning. If it's for the PP, then you have whole lot of them out there. Personally I use those from CNC4PC.com , I like the support Arturo gives. Many use the boards from PMDX.com which have a very good reputation and there are many more.

If you don't have enough I/O in a single PP for your application, you may want to add a second one. Or you can use some additional I/O device, like the USB based Pokeys, or some Modbus based (PLC).

Another possibility is to use the Smooth Stepper which is a USB based external pulse generator device that will give you two full PP I/O capability and one port to connect a differential encoder to.

Daniel

1107

Forum suggestions and report forum problems. / Re: Mach 3 and Yaskawa Servos

« on: August 18, 2009, 08:15:22 AM »

William,

If the manual says that the drive can take Step/Dir, then I see no reason why it won't work with Mach3. For the other drive, if it really takes only analogue +/-10V, there are boards that will convert it to Step/Dir. Have a look at this topic:

http://www.machsupport.com/forum/index.php/topic,10459.0.html

Daniel

1108

Forum suggestions and report forum problems. / Re: Mach 3 and Yaskawa Servos

« on: August 18, 2009, 02:43:54 AM »

Did you search the Yaskawa website for the manual of this drive?

Daniel

1109

General Mach Discussion / Re: Mach3 Customization/Macro Programming Documentation

« on: August 16, 2009, 11:35:22 AM »

Finally we'll have some normal document to guide us. May be then I'll understand a thing or two about macros and other custom programming

Daniel

1110

Show"N"Tell ( Your Machines) / Re: New Project for the shop.

« on: August 16, 2009, 02:07:47 AM »

I know, nothing very exciting but you guys share everything and I figured what the heck.

I am excited with every new machine I see some one is building... makes me want to build one myself.

Thanks for showing and don't forget to update as you're making progress.

Daniel