Re: [CAD_CAM_EDM_DRO] Re: HTD belts vs GT2 on Bridgeport

Scott,

The JET 8X36 mill I retrofitted with NEMA34 servos (14 lb-in) last summer used 15mm HTD belts and there is zero backlash. The mill uses the encoder interface. In manual mode it can plainly be seen there is zero backlash in the belt. Just barely move the handcrank and the DRO reflects it. The HTD belts are the best for that size transmission and application. It's been running almost a year now and not one problem.

Accrding to the eng info on the stock drive site, the HTD belts at 15 mm are stronnger than the 3/4" L-series I'm using on my Bridgeports.

Your results may vary, but I'd go with the HTD.

I noticed in an earlier post the intended reduction is 4:1, thats too much. 2 or 3:1 for X and Y is sufficient

Ron

Polaraligned <polaraligned@...> wrote:

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Les Newell wrote:
>
> I know it isn't a very scientific test but I am using 5mm pitch HTD
> belts on my mill and I can't feel any backlash. It strikes me that the
> 4x backlash improvement claim is more of an advertising gimmick than
> anything else.
>
> Les


This is from the "Gates Poly Chain GT2 Drive Design Manual":
"PowerGrip®HTD® Drives have improved torque carrying capability and
resist ratcheting, but have a significant amount of backlash.
Polychain GT2 Drives have considerably improved torque carrying
capability, and backlash characteristics in between that of PowerGrip
HTD and PowerGrip Timing Drives."


From Stock Drive Products (SDP) :
"Trapezoidal Timing Belt Drives are known for having relatively little
backlash. PowerGrip HTD Drives have improved torque carrying
capability and resist ratcheting, but have a significant amount of
backlash. PowerGrip GT Drives have even further improved torque
carrying capability, and have as little or less backlash than
trapezoidal timing belt drives."


Maybe it is a gimmick. But it makes sense that they needed
to add clearance to be able to carry all that torque with the
HTD (High Torque Drive) belts and pulleys.
It just does not make sense to me that the GT2 system has such
a limited selection of belt sizes.


Scott









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