Supplier of Steppers

[wildgrav]

I agree. It took me two weeks to get a quote for NSK guides in Oz and the price is not good. In 6 hr I had a price from "marchantdice" in the UK for a screw assy. Will take a while to get here but JOB DONE.

[raynorj]

Originally Posted by Greolt Just to add to what Dave said two posts up. I asked HomeshopCNC about torque curve on those 500 oz steppers and they said that they drop off dramaticaly after 400 rpm. Depends on what rpm you are expecting at ipm you are aiming at. My purpose tops out at about 300 rpm so they will suit my needs. But your needs may require more rpm and may be better with say the 269 oz ones. So look at the info and try to make a good decision. Bigger is not always better.

I am at the point of looking towards ordering steppers now but I need to do the all important math to identify the likely torque requirements. Can you point me towards info on that exercise as i am hoping that you have already done it.
many thanks
RaynorJ

[wildgrav]

I got my steppers from homeshopcnc.com The service is great and the product is excellent

Noel

[Pete Stenabaugh]

I cant say enough good stuff about Homeshopcnc. Rick has been a really excellent source of materials for me, and he has stood behind his products very admirably.

I havent really done any torque calculations, as it makes some difference as to the motor manufacturer to some degreee. So I just went with large ones, besides it is really difficult to get that sort of information.

What are you planning on powering with these stepper motors, router, mill, or what?

I used 1780 oz in on my milling machine conversion, but I think now (after switching to servos) that I could have gotten by quite easily with 1200 oz in motors geared 2 : 1. With my servos that I have now (850 oz in peak torque) I have the motors geared 5 :1 and this seems to be fine so far.

If in doubt about the torque then go with larger ones than you think you will need. You should not have any issues with motors, until perhaps above the 900 oz in size (according to some people). The price difference is so small from one motor to the other, it makes more sense to have more power than you need. Besides if you end up reaching the point where the torque starts to drop off too much, if you have more than you need, you should still be fine.

If you need motor speeds in excess of 300 to 400 rpm, then you should be considering using servos. They are a bit more expensive, and the torque is less, but they are smooth and very quiet. You also need different drivers (gecko 340's as opposed to gecko 202's), but the servo drivers are a bit less expensive also, so that helps out a bit.

In either case, make sure your power supply will give you enough power to support the motor requirements both in voltage and amperage......

Pete

[raynorj]

Intend to route , cut out thin styrene, acrylic and alumin sheetprimarily up to say 4 mm max mostly for model making activities.
have asked Richard Homeshop cnc for prices on 425 oz/ich stepper from their web pages with the Gecko drivers. I am not to concerned with speed so reckon that will be an ok choice. Still I await details of the cost including the shipping. can get "used" ASNYO DENKI type 103-8075-6 5 volt 1.9 amp, 1.8 degree steppers for $80 (NZ) locally but cannot find any info on torque or whatever and i think that they are only NEMA 23s.
thanks
Raynor J

[Pete Stenabaugh]

Raynorj:

The best advice I have for you is to use Nema 34 motors, not Nema 23. You will be too limited in motor size choices. With Nema 34 (about 3" square or round) you can have motors down in the 500 oz range or up to over 2000 oz and they will all fit the same bolt patterns.

I recommend that you go with motors heavier than 500 oz in. The cost is very little more, and you will have a lot more margin for power drop off. I would recommend at least 600 to 900 range. The prices for the motors can be seen on the www.homeshopcnc.com web page. I also recommend gecko 202 drivers, not the older 201 drivers.

If you have not already checked, talk to Stephen at Logitrol, www.lowcostcncretrofits.com about his stepper controllers and power supplies, he is right in your back yard in Aussie.

You can also go with the Xylotex controllers, these are very good as well (I have one and I am very happy with it, but it is not heavy enough for me), but they are limited to 2.5 amps, unless Jeff has some new stuff, so the Xylotex will not drive the bigger motors. Even the 500 oz in motors will be limited in power as they draw more amperage than the Xylotex can deliver.

If you are going to be cutting thin plastics, you will need fairly high machining speeds, in the range of maybe 60 to 100 ipm, depending of course on the rpm of the router. With aluminum sheet, you can slow the feeds down to maybe 20 ipm, but you will have to experiment. At these feed rates, your little motors may not deliver enough torque. It is a bit of a crap shoot, you may be fine with little motors, but why not be safe, it is better to have too much power.....

Pete

[raynorj]

Thank you guys for all the replies,
Working on the basis of plastics needing of order 100 ins/min with the 5 mm ball screws from homeshopcnc that means I need about 508 rpm. Comment that torque drops "dramatically" above 400 rpms suggests that I may have a problem with NEMA 34 at 425 oz/ins rate. Maybe the actual torque requirement is minimal for the plastics anyway. i would think that would be the case.
What about the next one up the RS34-960 at 960 oz/ins. I guess I need to know what the torque drop off is with it.
At the moment I see the bulk of my cutting being acrylic and styrene sheet 1 thru 4 mm thicknesses, and thin ply like 1.5mm.
I would imagine the 100 ins /min is the max so other machining would all be significantly slower than that.
So if not the 425 oz unit the 960 oz model.
With the gecko 201 or 202. I see suggestions that the 202 is a better deal. the homeshop people offer a deal with the motors for the Gecko 201.
Still somewhat confused but getting there.
I am assuming that one can mix and match torque rated servos with the 3 pack controllers. With the geckos one for each motor that is no prob.
Thanks again all continue the input much appreciated.
Raynor J

[Pete Stenabaugh]

Raynor,

Homeshop will supply you with gecko 202's in place of the 201's if you ask him. The 202's are the new design and have some new built in safety features.

I think the 960 motors would be fine for you. The idea is that they will also start to drop off in torque at the higher speeds, but when they do, they have to loose 1/2 of their torque before they even equal what the smaller motors have for max torque. This is where you get some safety margin for torque loss.

I would recommend getting the stepper controller from Logitrol as I mentioned earlier, it will save you a lot of time. You should ask him though if he can supply gecko 202 drivers for the controller, as he may only use gecko 201 drivers by default. There might be a slight price difference to do that, but it would be worth it. You should also look at his new ver 3.0 controller pendant, it is a cool device, I use one on my milling machine, I wouldnt be without it now.

If you have not already purchased your ball screws, I would recommend that you go with the larger ball screws that homeshop has, they are .631 diameter and will give you more rigidity for the higher speeds. Once again the cost difference is not that bad either. Plan on using 2 ball nuts per axis, so that you can preload one against the other to remove any backlash.....one ball nut is mounted to the moving part of the router, and the second ball nut is preloaded against that one, such that it cannot rotate. You can preload them with a couple of setscrews between them (lightly) to remove backlash. You will get much more accurate machining that way.

Pete

[Nzoldun]

Originally Posted by raynorj I am at the point of looking towards ordering steppers now but I need to do the all important math to identify the likely torque requirements. Can you point me towards info on that exercise as i am hoping that you have already done it. many thanks RaynorJ

RaynorJ. There is an excellent set of articles in the Uk magazine "Model Engineers Workshop", approx. Oct 2005 to March 2006. As I am also based in NZ, central North island, you might like to contact me.

[raynorj]

Originally Posted by Nzoldun RaynorJ. There is an excellent set of articles in the Uk magazine "Model Engineers Workshop", approx. Oct 2005 to March 2006. As I am also based in NZ, central North island, you might like to contact me.

Yes a good idea idea , how do I do that? my email is raynor.johnston@clear .net.nz.
thanks
Raynor J