Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: EJParrott on July 26, 2012, 05:09:08 AM
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Apologise if this is in the wrong section but I couldn't find anywhere better.
I'm looking to purchase one of the Nema 34 8.5Nm steppers I plan to use on my Bridgeport clone, as I'd like to have one in my hand while building the mounts and everything. Zapp is currently coming up as the cheapest supplier, has anyone used them before? Any experinces to share?
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I have used them numerous times and they have always been spot on.
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Used a few times and once they said they had a small ballscrew in stock but it took well over a week and quite a few emails, otherwise they have been ok the few times I have used them.
Curious though as to what type of machine you are putting such a big stepper on?
Hood
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My Bridgeport clone...was actually thinking about going up to a 12.2Nm....Motion control have a package of 3 12.2 motors, 3 drivers, 2 PSU's and a BOB....
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I had 916 oz in steppers on my Bridgeports with 2.5:1 on the old Boss and 2:1 on the converted manual and there was more than enough torque. Not saying that is the way to go though was just what worked for me, now have servos on it and what a difference :)
Hood
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I'm putting 4:1 on the X and Y, the Z I can only get about 2.5:1, there isn't room to get a bigger pulley on the end of the ballscrew.
So you think 8.5Nm is plenty big enough then? I searched and searched Google but could not find any way to calculate what I needed. Never having designed stepper motors for a CNC machine I've got no gut instinct on what's man enough for the job!
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They will give more than enough torque at 4:1 reduction but your rapids will suffer quite a bit.
Hood
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Thanks for the reasurance Hood!
As far as the rapids go, its not an industrial machine anymore, and its not like its costing me the same £40/hr as the machines at work do. What I want is accuracy, and longevity, so oversized and reduced down is good for me, as it means they'll not be working hard all the time, and are hopefully going to last longer.
Anyway, I might try and see if MCP will do an offer on 8.5's instead...
In answer to the original question to get back on track, I've been having email discussions with Gary Higgins of Zapp about MPG's. He's been really helpful, and has tipped me off about a rather nice looking pendant designed for Mach3 which will be going on the new website hopefully during the next month. I think I'll give them a try!
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Regarding the rapids, I have heard that many times before and indeed it was one thing I said. I will ask you again in a years time and more than likely you will have changed your stance ;D
Rapids are nice to have but a more important thing however in my opinion is acceleration.
With the size of steppers you are considering I would think 1:1, 1.5:1 or even 2:1 would be a better choice. As mentioned I had 916 OzIn (6.4Nm) steppers on the Bridgeport geared 2:1 (manual conversion) and 2.5:1 (Boss 6.1 conversion) and there was more than enough torque. I was actually considering making them 1:1 but then decided to go with servos instead as using the Bridgeport after using the Beaver NC5, which had servos, was a chore.
As for the motors lasting longer with higher gearing, I dont think that will make any difference to them, I ran the Bridgeport almost daily for 4 or 5 years and there was not an issue. I still have the geckos and motors here, just have to find something that I can fit them to, was going to put them on the wee lathe but decided to go servos on that as well, maybe another coil winder would be a good idea, one made specifically to wind small spools of Alu wire for the mig's spool on gun ;D
Hood
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Also worth thinking about is as steppers spin faster the torque drops off very rapidly so if you have a high gearing you are having to spin them fast to get anywhere and you may actually have less torque than you would with a lower gearing. You would have to look at the motors torque curves and the normal cutting speeds you will be using to determine what is best.
Hood
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8.5Nm stepper ordered this afternoon....I'll let you know what sort of service I get!
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Arrived this afternoon, well packaged, and sent with a trackable courier.
I think its safe to say, it was a good punt!
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Just so happens, while setting up at the Midlands Model Engineering Exhibition, I noticed the stand next door was labelled 'Zapp Automation'. I assume its the same company, hopefully they turned up, I'll be having a good look at their stuff at the weekend, maybe even get the next stepper motor if they've got one with them.
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Robinson.
I used Zapp Automation to convert an old Henry Milnes mill They were very helpful and pretty prompt in dealing with deliveries.
The Milnes was a very heavily built machine. I put ballscrews on x & y reasoning that the tremendous weight of the carriage and slides would more than nullify the backlash! So far so good. I used the heavy stepper mentioned for the z due to the weight and so far it has coped and run satisfactorily.
Dave.