Messages

641

General Mach Discussion / Re: Power Supply Unit

« on: January 08, 2011, 05:36:08 PM »

"Do you see any problem with the power unit I purchased?" - Yes.  What you really want is about a 37V/10A supply.  12V is nowhere near enough to get decent performance from those motors.  The ideal voltage for the motors is given by 32 times the square root of the motor inductance (in mH), which gives about 47.5V.  This is assuming bipolar parallel mode, which is what you want to use.  But your drivers are rated for 42V maximum, so you want to stay a bit below that maximum rating, so knock it down to 37V.  The current rating of the supply should be about 70% of the sum of all the motor currents, or about 8.5A.  Round that up to 10A.  You won't get best performance out of this setup, as the drivers are not well matched to the motors.  You will be losing about 25% of the potential torque, since your drivers won't allow you to run full rated current on the motors (4.2A for the motors, vs 3A for the drivers).

Regards,
Ray L.

642

General Mach Discussion / Re: Step Morphing Question

« on: January 01, 2011, 11:28:34 AM »

No, the step morphing is completely transparent to the CNC controller.

Regards,
Ray L.

643

General Mach Discussion / Re: YAHOO GROUP MESSAGES ARCHIVE

« on: December 26, 2010, 05:11:48 PM »

Terry,

What makes you say Yahoo groups are going away soon?

Regards,
Ray L.

644

General Mach Discussion / Re: polished aluminum

« on: December 25, 2010, 02:00:47 PM »

What tool would at least give a not rough but smooth surface on the aluminum? Would a round nose bit be better than a 4 flute end mill?

THANKS!!!!

It has FAR more to do with the type of cut, and the quality of the machine, and especially the skill of the operator, than the specific tool in use....

Regards,
Ray L.

645

General Mach Discussion / Re: polished aluminum

« on: December 25, 2010, 01:38:36 PM »

You get a polished look by polishing using abrasive and a cloth wheel, not by cutting with a tool.  And it's a LOT of horrible, messy, unpleasant work, especially if the as-machined surface is rough!

Regards,
Ray L.

646

General Mach Discussion / Re: My ShuttleRu pendant

« on: December 19, 2010, 04:02:41 PM »

That sounds very reasonable, I even may take you up on the LCD version 

Thanks,
Dave

That's not reasonable - it's downright CHEAP!  I don't know of a single decent pendant you can buy for that kind of money, and this one seems to have a quality of build and functionality that is unmatched.  Very nice work!

Regards,
Ray L.

647

General Mach Discussion / Re: Using M-Codes to send signal to Arduino that controls solenoids

« on: December 01, 2010, 11:12:09 PM »

There is a Mach VB function to write to a serial port, but it's not well supported, and may well go away.

Regards,
Ray L.

648

General Mach Discussion / Re: Need help with Bridgeport Series One CNC Retro Fit

« on: November 06, 2010, 10:14:24 PM »

Terry, Hood    What I have is 1970 Bridgeport Series 1 Cnc updated to BOSS 5
                     I installed a AN TEK 800VA Toroidal Transformer 10 Amp and built the rest of the power supply from parts
                     The original steppers are Superior steppers (90 VDC 8Amps)
                     I replaced one with a Kelling KL42H2150-42-8B 
                     All 3 drives are Gecko 201 they are set microstepping the way I read the set up sheet
                     Sound Logic BOB Rev 1.9 (Bob Campbell has been a grate help)
                     Added a Sumitomo VFD and a sound Logic inter face board
                     Current motor setup
                     Steps Per            Velocity                Acceleration           Step Pulse               Dir Pulse
                        10000                70.0                       2                         5                          5


I run a progran to make a 6" square with a 1.5 pause at each corner as to read indicator before next axis move, it misses steps at all speeds worst at 31 IPM.                 

Coke

The power supply for stepper motors should be sized at roughly 70% of the total rated current of the motors.  So, if you're using Geckos set for 6A, and you have three motors, the supply should be rated for at least 18 * 0.7 = 12.6A continuous.  AND, you must have sufficient capacitance in the filter as well.  For 3 6A motors, you should have probably on the order of 20,000-30,000uF of filtering.

Regards,
Ray L.

649

General Mach Discussion / Re: Breakout boards

« on: November 03, 2010, 11:59:09 PM »

For use with Geckos, the cheap, simple, buffered (not opto-isolated) boards from Homann Designs work great.  And at about $30, they're dirt cheap.  Add one of his spindle speed controllers, and you've got everything you need.  And Peter Homann is a member of this forum, so if you need help it's just an e-mail or PM away.

Regards,
Ray L.

650

General Mach Discussion / Re: Huge Threading Problem Help

« on: October 23, 2010, 03:18:24 PM »

@ Himy, I can't go slower even geared down motor with a VFD if I go to 100 RPM the motor will be very weak. I assume Himy, that you have a CNC lathe that you can actually gear down to 100 RPM? I usually don't have a problem at 500-700 RPM. I was trying 1000 RPM because my motor lowered to 500 RPM was losing RPMS during threading, but last night I changed to my 2 HP motor with gearing so the highest RPM I can get is 742 rpm, so that will give me full HP at that RPM.

RPM should be determined by recommended SFPM for the specific tool being used, and the material being cut, whether it's turning or milling.  Excessively high RPM will destroy the tool very quickly, and with stainless can easily lead to work-hardening, which will make the material near impossible to cut.  Most carbide tools recommend SFPM in the 1000-3000 range, but you're up at around 15,000.  You may get away with it, but it'll be really brutal on the tool.

Regards,
Ray L.