Messages

1

General Mach Discussion / Re: Mike Beck vs Xylotex

« on: September 18, 2013, 12:03:03 AM »

For larger motors I agree, Gerry.  But I have used Xylotex boards for years on NEMA23 and NEMA17 motors (anything up to 2.5A/phase) and they work very well.  For those smaller motors G540 is way overkill, IMHO.

Randy

2

Show"N"Tell ( Your Machines) / Re: Adding a 4th axis to my mill

« on: May 17, 2012, 10:12:22 PM »

To complete the design reference, http://www.sdp-si.com/D265/PDF/D265T016.pdf gives pulley O.D.'s for the various belt types and sizes up to crazy groove numbers.  Those O.D.'s and the above-referenced patent give all the information needed to draw up any GT2 pulley you need.

Randy

3

Show"N"Tell ( Your Machines) / Re: Adding a 4th axis to my mill

« on: May 17, 2012, 01:48:50 PM »

D'oh, I realized that patent 4515577 expired a decade ago.  Based solely on the information in that patent, anyone is free to make appropriate pulleys...

Randy

4

Show"N"Tell ( Your Machines) / Re: Adding a 4th axis to my mill

« on: May 17, 2012, 12:31:52 PM »

...they hold the new GT2 series TIGHT

Ah, but that's where the patent I linked earlier comes in.  They show the dimensions for an 8mm pitch belt tooth and pulley groove, and you can get the other sizes just by ratioing the pitch.  I drew up a 90-groove 5mm pulley last night.  Just for educational purpose to verify their numbers, of course.

I wouldn't even think of attaching a DXF--given the patent situation that's something you'll need to draw in the privacy of your own house.

Randy

5

Show"N"Tell ( Your Machines) / Re: Adding a 4th axis to my mill

« on: May 16, 2012, 11:55:52 PM »

You make a convincing argument, BR549.  I need to do more research (though your real-world experience counts for a lot! )

I'm attaching a screenshot (highlighing mine) from the Gates PowerGrip GT2 Design Manual which has helped color my opinion (though since GT2 is proprietary to them they have a vested interest in pushing it...)

In lightly-loaded mechanisms I have traditionally used 80DP belts and pulleys with good result.  But this thing will need to withstand machining forces and will be very low speed (quasi-static) vs. power drives that GT2 is aimed at.

Thank you for making me dig deeper!

Randy

6

Show"N"Tell ( Your Machines) / Re: Adding a 4th axis to my mill

« on: May 16, 2012, 10:28:47 PM »

Man, it's not like I haven't done this a time or two....

You and me both, brother.  But it's a lot easier to spot other peoples' mistakes  I see that SDP/SI only goes up to 72 teeth on their 5MGT pulleys.  And, they are inconveniently recessed on the sides, unlike their T5 pulleys.  (Not to hijack your thread, but I snagged a Harig 5C spin indexer that I'm motorizing, which led me to your thread)  BTW, the patent that defines the GT2 tooth and groove profile is  http://www.google.com/patents/US4515577   There's a guy with a wire EDM machine who owes me a favor, and I'm thinking of drawing up a large 5MGT pulley for him to carve out for me...

I would use the trapezodial profile if you want tight backlash tolerance from the drive.

BR549, that is an interesting observation.  From everything I've read (from the above patent to all of Gates' literature on the GT2 belt/pulley system) the GT2 has lower backlash in biderectional/reversing drives than the trapezoidal system, when the pulleys are properly made for the belt (i.e. the belt's tension members are on the pitch diameter and the teeth are only "cleats" for traction).  Is your experience with off-the-shelf pulleys?

Randy

7

Show"N"Tell ( Your Machines) / Re: Adding a 4th axis to my mill

« on: May 14, 2012, 06:41:09 PM »

Thank you for the quick reply, Mike.  That's interesting--Designatronics is the parent company of SDP/SI (used to be called Stock Drive Products) so Econobelt is essentially the same company as SDP/SI.  But you answered my question in that they're calling the pulleys "T5".  Are you entirely sure they are GT2 pulleys?  The Econobelt catalog page for the part number you quoted says "T5 profile per DIN 7721-2 Rev 6/89" which is a regular trapezoidal-tooth contour.  A 5mm-pitch GT2 pulley would be called "5MGT".

Randy

8

Show"N"Tell ( Your Machines) / Re: Adding a 4th axis to my mill

« on: May 14, 2012, 12:01:25 AM »

The pulleys came from Econobelt.

Mike, my google-fu is usually not lacking, but for the life of me I can't find GT2 pulleys on the Econobelt website, nor in their downloaded PDF catalog.  Do they call them something else?  Their prices are very attractive.

Thanks for any enlightenment you can provide,

Randy

9

General Mach Discussion / Re: Lost code.

« on: April 04, 2012, 02:39:11 PM »

Mach3 will cut off at 500 lines of gcode if it isn't licensed (i.e. trial version), or if it doesn't properly recognize your license.  How much of the gcode is showing?  If you're doing 3D with MeshCAM it won't be much at all if only 500 lines get through!  

Randy (mod at the MeshCAM board)

10

General Mach Discussion / Re: Digispeed not working

« on: March 20, 2012, 07:03:21 PM »

...there is no Reverse wire to the VFD. How will the M3 and M4 work?

I use a TECO FM-50 VFD on my lathe, and you can set it to either run forward by energizing FWD and reverse by energizing REV, or select forward/reverse by toggling REV (I use this scheme).  It's a parameter I set from the VFD's front panel.  Maybe your VFD has a similar setup.

Randy