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Author Topic: Adding a 4th axis to my mill  (Read 18617 times)

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Re: Adding a 4th axis to my mill
« Reply #20 on: March 24, 2012, 05:15:14 AM »
The 80, 32, and 16 groove GT2 pulleys came in today. The belt was the wrong length. After looking at the calculator I am suspicious of it's accuracy. So I have drawn the belt path in cad. That showed I need about a 90 groove belt. Maybe longer would be better since I have 2 drive pulleys of differing diameters. The pulleys came from Econobelt. And the belt came from SDP/SI. At least I have lots to do before I need the belt.

My horizontal band saw takes at least and hour to cut about half way through the 1 inch al plate. I may have to use the skill saw with the metal cutting blade.
Re: Adding a 4th axis to my mill
« Reply #21 on: April 15, 2012, 10:42:21 AM »
heat the bearing in hot oil and it should slide on
Re: Adding a 4th axis to my mill
« Reply #22 on: April 15, 2012, 07:48:19 PM »
Certainly a temperature delta would help the press fit.

I had a tough time getting the basic parts cut from the 1 inch thick stock that I picked up from the recycling center. The horizontal bandsaw only cuts about 48% through the width of a piece. So when I flipped it over they were 1/4"  apart. The band saw blade broke. My spare was broken when I slid the material in from the side and banged into it. I ordered a pair of blades from Amazon. They were from Starrett. The new blades cut quite a bit faster. But they now curve through the material instead of cut a straight line like the band saw used too. The blade maybe thinner as I noticed there was a gap between the bearing guides that seemed excessive. This saw cut dead straight for 10 years. So an alignment is in order. Also the weld on the Starrett blade was thicker than the blade itself. It would thump every time the weld passed through the material.

Now at least all of the pieces are rough cut. Each one just needs to be milled true then I can start machining the 4th axis parts.
Re: Adding a 4th axis to my mill
« Reply #23 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
Re: Adding a 4th axis to my mill
« Reply #24 on: May 14, 2012, 06:12:43 PM »
One of the tags that came with a pulley I ordered says this on it:

Quality Transmission Components
Division of Designtronics, Inc.
55 South Denton Ave., New Hyde Park, New York 11040
516.437.6700

One of the pulleys was part number QPMT5A16032F08 T5 Timing Pulley.


I don't remember which web site it was affiliated with.
Re: Adding a 4th axis to my mill
« Reply #25 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
« Last Edit: May 14, 2012, 06:49:16 PM by zephyr9900 »
Re: Adding a 4th axis to my mill
« Reply #26 on: May 15, 2012, 10:13:18 AM »
Yikes! You found an error for me. The tooth profiles that I have here are trapezoidal. I'm short of time this week to do much about it. At least the belt has the right tooth profile, but it was too short. Sigh.

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

Mike

Offline BR549

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Re: Adding a 4th axis to my mill
« Reply #27 on: May 16, 2012, 03:54:00 PM »
I would use the trapezodial profile if you want tight backlash tolerance from the drive. I use the Gt2 profiles for Kart racing final drives and they are not as tight on backlash as one would want for a 4th axis drive.

Just My experence here your mileage may vary due to local conditions,

Just a thought, (;-)
Re: Adding a 4th axis to my mill
« Reply #28 on: May 16, 2012, 10:28:47 PM »
Quote from: mikep_95133
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...

Quote from: BR549
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

Offline BR549

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Re: Adding a 4th axis to my mill
« Reply #29 on: May 16, 2012, 11:13:31 PM »
Look at the drawing in the patten app. Notice the air spaces between the tooth and the sprocket. With the Height of the tooth that space is required to reduce the friction on the belt as it slides in and out of the sprocket form. The Gt2 is a derivative of the older HTD and is a modified curvelinear design with MORE contact angle on the circular tooth than the old HTD but not as much as a trap design.

Minimum Backlash is a relative term(;-) Yes it IS less than the HTD that it replaced

Just my experience, Your milage may vary

(;-) TP