Re: [CAD_CAM_EDM_DRO] Re: Couplings

It's not so easy for some of us to make those work- a coupling with a little
compliance is easier to set up. I found the helical ones typically don't
have very high torque ratings (the ones I found) before they aren't really
backlash free (they distort under torsion).

I have become very fond of the somewhat pricy RW stainless steel bellows
couplings. No backlash, high torgue, axial and longitudinal compliant. I
know the OP was looking for cheap couplings and the RW for 640oz-in with
clamping hubs is about sixty bucks, but they are really sweet. They also
can't get jammed up with chips like a helical.

-Will

----- Original Message -----
From: "556RECON" <556recon@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Friday, December 11, 2009 5:09 PM
Subject: Re: [CAD_CAM_EDM_DRO] Re: Couplings


>I would tend to dis-agree here. There are a vast number of units out
> here that use the type pictured in the auction. mine ( a FIREBALL V90
> router) uses brass ones.
> It seems to me that if there is a danger of the lead screw mis-aligned
> so much that it might break the stepper motor shaft, then something is
> very wrong and should be fixed. My unit has worked 100's of hours with
> out a problem.
>
> OLD BOB
>
> Andrew Werby wrote:
>>
>> "Alfredo Sola" alfredo@... <mailto:alfredo%40sola.es> alfredosola
>> wrote: Good day Johann et
>> al, Following your advice on couplings, I found this. It's Chinese but
>> looks pretty decent:
>> <http://cgi.ebay.de/3x-Kupplung-Drehstarre-fuer-Schrittmotor-1-4-NEU_W0QQitemZ160382401978QQcmdZViewItemQQptZMotoren_Getriebe?hash=item2557893dba#ht_3281wt_912
>> <http://cgi.ebay.de/3x-Kupplung-Drehstarre-fuer-Schrittmotor-1-4-NEU_W0QQitemZ160382401978QQcmdZViewItemQQptZMotoren_Getriebe?hash=item2557893dba#ht_3281wt_912>>
>>
>> Also the price can't be beaten at 9,90 euros for 3 units! what do you
>> think?
>>
>> Hi Alfredo;
>>
>> If those are meant to couple a motor to a leadscrew, I don't think much
>> of them. Unless your alignment is absolutely perfect, a solid coupling
>> like that can break the end off your motor, or the stem off your
>> leadscrew. What you want for a situation like that is some kind of
>> flexible coupling, which will allow for some imprecision in the
>> positioning of the two shafts being joined. There are several basic
>> designs for this sort of thing; such as the "Lovejoy" type, which has a
>> pronged head for each shaft and a rubber "spider" that fits in between
>> them, or one that has a helical slot cut in the middle, which acts like
>> a spring, or one that has metal ends but a solid rubber center portion.
>> The Taig mills I sell have metal cylinders on the end of the motors and
>> leadscrews, which are bored with four facing holes with stiff nylon
>> tubes making the connection. Any of these solutions would be better
>> than what you're looking at on Ebay.
>>
>> Also, the simple set-screw attachment will tend to give you problems
>> over time. A better design is the clamp-type connection, which uses a
>> screw to compress the split end of the coupling over the shaft. This is
>> less likely to loosen, and if it does, it won't make a gouge in your
>> shaft that makes the coupling very difficult to remove. Yes, you can
>> save some money going with those cheap solid couplings, but you'd be
>> setting yourself up for losing a lot more down the line, not to mention
>> the frustration factor of ruining parts and having to tear your machine
>> apart to repair it and wait for parts to arrive before you can get back
>> to work. I'm not sure who sells couplings in Europe, but I'm sure you
>> can find some like this:
>>
>> http://www.anaheimautomation.com/products/coupling/flexible-coupling.php?tID=114&pt=t&cID=32
>> <http://www.anaheimautomation.com/products/coupling/flexible-coupling.php?tID=114&pt=t&cID=32>
>>
>> Good luck;
>>
>> Andrew Werby
>> www.computersculpture.com
>>
>>
>
>
>
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