Messages

91

General Mach Discussion / Re: Problem with the length of motor and encoders cable

« on: August 25, 2013, 12:09:29 PM »

Cable length is not a problem - mine are over 20 feet, and work perfectly.  How did you tune ther servos?  Sounds like they are massively out of tune, and runing CANNOT be done on the bench - it much be done on the machine, under load.

Regards,
Ray L.

92

General Mach Discussion / Re: Need help with pulse per inch math

« on: August 15, 2013, 11:52:21 AM »

Those aree weird screws....  I've never seen ballscrews with that odd pitch.  As they are 13/64" lead, they need to turn 64/13 turns to move one inch.  Gerry is absolutely correct that it is useless to use 40X micro-stepping.  Anything more than about 10X gains you nothing of value.  So, using 8X as Gerry suggests, you'd have:

    200 Steps/Turn * 8 uStep/Step * 64/13 Turns/Inch = 7876.923076923 Steps/Inch

Regards,
Ray L.

93

General Mach Discussion / Re: Odd stepper motor control issue.

« on: August 13, 2013, 12:40:42 PM »

Most likely your Mach3 XML file got whacked.  Look in the backup directory, and copy a version from before it stopped working.

Regards,
Ray L.

94

General Mach Discussion / Re: Mach3 Output For DC Motor Control

« on: August 04, 2013, 09:49:46 AM »

The PWM outputs, like all Mach3 outputs when using the PP, are limited by the kernel frequency.  The higher the output frequency, the less resolution you get.  With a 25kHz kernel, and 10kHz PWM frequency, you'd have less than 2 bits of resolution.  Some hardware motion controllers, like SmoothStepper, will allow higher frequencies, but I'd be surprised if even they supported 10 kHz.

Regards,
Ray L.

95

General Mach Discussion / Re: Mach3 Output For DC Motor Control

« on: August 01, 2013, 11:15:03 AM »

An H-bridge is the basic output circuit used in nearly any DC motor controller that supports bi-directional operation, and many that only support uni-directional operation.  But the H-bridge itself is only PART of a usable motor controller.  There is MUCH more required to make something that would be suitable for driving a machine spindle, including voltage and current feedback, I/R compensation, and protection circuits to prevent the H-bridge from going up in smoke if not driven correctly (and you CAN'T count on Mach3 to always drive the PWM output correctly.  Without all that other other logic, you can expect to have something that works very poorly, up to the point where it goes Pfffffffffffffft!  And that WILL happen in very short order.

Regards,
Ray L.

96

General Mach Discussion / Re: PWM to 0-10v voltage linearity problem?

« on: July 27, 2013, 11:07:57 PM »

Sounds like their circuit has a hefty DC offset.  I'd guess even at a very low duty cycle the output voltage would be far higher than it should be.  Not much anyone here can do to help, with no schematic for that circuit.  This is the problem with some of the "great deals" on inexpensive hardware from China - a lot of it is just cr@p, and not worth buying at any price.

Regards,
Ray L.

97

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: July 21, 2013, 10:04:03 AM »

Well, as you might agree, the software is the real challenge, especially now that I have completely lost my mind and decided to go forward with porting to the Kflop. I can tell you now that I used your name in vain more than a few times for recommending the Kflop as a 'plug and play' MACH accessory and using the word 'easy'. Note to self: When Ray uses the work 'Easy', be afraid . . be very afraid.

 The HimmyKabibble vernacular exchange rates:
"Easy = Doable, like walking on water or spinning straw into gold."
"Difficult = requires intervention and assistance from advanced civilizations"

Eventually, I did get things working. It is quite a powerful system, but they really need to hire you to write some manuals like you did for MACH. I will be starting on that port in a few days so if you hear your name on the wind with colorful adjectives attached  . . . that would be coming from the East, most likely . . . 

Steve,

That explains the odd burning sensation in my ears lately!  But, when did I ever say bringing up a KFlop would be "easy"?  :-)

Regards,
Ray L.

98

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: July 20, 2013, 09:28:17 PM »

Steve,

The video is cool!  I'm almost to that point with my new ATC for all the Novakon machines  - I've had the hardware built for several weeks, but been too busy with other work to make time to do the firmware.

Regards,
Ray L.

99

General Mach Discussion / Re: spindle load feedback to mach3

« on: July 19, 2013, 03:07:12 PM »

I'm a drives field service engineer and work on VFD's up to 5000 hp. AC drives today including cheap Chinese knock off use IGBT's in the power output sections. Clamp on amp meters on the motor t-leads will not give accurate readings. Drives setup in V/Hz mode as are most low cost drive used in CNC application (not vector mode) will output without a motor connected... motor impedance (xd') has very little effect on drive filtering. I could debate drive theroy with you but I think it would be beyond most of the forum readers. I've had a number of customers state their clamp on amp meters don't agree with the drive digital display...

I don't think anyone here mentioned clamp-on meters but you - When I say "analog ammeter" I'm talking about a true analog panel-mount ammeter, with a shunt and D'Arsonval meter movement.  Think 1930's technology.  Even most clamp-on meters these days will have digital internals - Hall Effect sensors feeding into a (probably sigma-delta) A/D converter, etc.

Regards,
Ray L.

100

General Mach Discussion / Re: spindle load feedback to mach3

« on: July 19, 2013, 01:44:04 PM »

Putting a amp meter in series, or using a clamp on type with a VFD 3 phase output to the motor is useless. The VFD voltage is not a true sine wave and the frequency varies the motor speed. This will cause the amp meter to read incorrectly. All amp digital displays on VFD's are a calculated value corrected to 60 or 50Hz. The only way is use the 0-10V analog output or modbus. 

An analog ammeter really doesn't much care what the waveform looks like, within reasonable limits, and they certainly don't care about the frequency, as it is FAR above the frequency the meter movement can react to - they'll still read a pretty good approximation of the RMS current.  And most modern VFDs will output something close to a sine wave anyway - after it gets filtered by the motor impedance.  Digital meters are pretty much useless with a VFD, whether you're looking at voltage or current.

Regards,
Ray L.