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Author Topic: choosing the right electromotor, please help.  (Read 3232 times)

Giel

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Re: choosing the right electromotor, please help.
« Reply #15 on: February 04, 2019, 07:52:52 PM »
Quote
you don't want something screaming at you while you are faceting, it would get tiring very quickly.

You got a point there!

I wanted to buy a motor that does not slow down when cutting or polishing (the way a dremel slows down), and I dont want to use a motor that is to big and heavy.
That's why I asked about the torque,

I have also seen the stepper motors on ebay, but I thought they were only used to drive spindles for linear motion, not for a drive shaft.
But maybe they are fine to use like that. I will check those out!

I am looking at the ER16 spindle because I already have a full set of collets fot the ER16 (mm and inch)
And I already have a small ER16 head with an 8mm hole for the shaft.

I also checked the carriages with guide rail, they would make the machine smaller, but cost a lot of money (if you want good ones)
I will buy them if I cannot make it with the 20mm linear bearings. The 20mm bearings that I have now just seem to good to toss aside. They are so tight that there is literally zero play on the linear shaft and they run smoothly!

thanx for the input!
I will spend some more time on ebay hunting for the right motor.




MakkyBrown

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Re: choosing the right electromotor, please help.
« Reply #16 on: February 04, 2019, 08:02:35 PM »
Giel, that link wasn't for a stepper. It was a brushless dc motor. I don't really like the idea of using a stepper due to the vibrations etc. The linear rails in that link were the ones I purchased and carriages are a very nice fit on the rails. I'll probably buy more from that seller.
Rusted, you should buy one of the 128x64 serial screens, really easy to use and wire up. If you want to know the exact one to buy and which library to use let me know they are only about $7-8. I've even found a very cheap bezel case to fit them.
 
« Last Edit: February 04, 2019, 08:04:16 PM by MakkyBrown »

Orange Pirate

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Re: choosing the right electromotor, please help.
« Reply #17 on: February 04, 2019, 08:13:05 PM »
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I thought the idea was to cut a tier or two concave not the whole stone.
I don't know, I think I would be roughing the stone as normal then swapping the mast to the concave machine to finish the concave facets.


I didn't know neither. So I YouTubed it. It wasn't as I imagined.


https://www.youtube.com/watch?v=L3JjGmbvyrk

Giel

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Re: choosing the right electromotor, please help.
« Reply #18 on: February 04, 2019, 08:47:49 PM »
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Giel, that link wasn't for a stepper. It was a brushless dc motor.

I see that now, maybe I assumed it was a stepper because the site was called stepperonline.com

MakkyBrown

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Re: choosing the right electromotor, please help.
« Reply #19 on: February 04, 2019, 10:42:22 PM »
Quote
I thought the idea was to cut a tier or two concave not the whole stone.
I don't know, I think I would be roughing the stone as normal then swapping the mast to the concave machine to finish the concave facets.


I didn't know neither. So I YouTubed it. It wasn't as I imagined.


https://www.youtube.com/watch?v=L3JjGmbvyrk
Thanks OP.
Might be a good bit of run out on the machine, I expected Ultratech to be better. Rpm looked quite low. Run out looked the same for both mandrels so probably coming from the motor/collet. Run out shouldn't matter as much at low rpm. Mandrel oscillation was faster than I expected and the motion is doing a lot of the cutting.

Not really that inspired by it to start concave cutting, maybe one day.


MakkyBrown

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Re: choosing the right electromotor, please help.
« Reply #20 on: February 05, 2019, 10:36:42 AM »
I quite like this machine, polymetric.
https://www.youtube.com/watch?v=Q1oBOCm0V-o

Orange Pirate

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Re: choosing the right electromotor, please help.
« Reply #21 on: February 05, 2019, 03:47:35 PM »
I too was surprised by the runout on that UT, MB


That polylmetric seems less complicated to use than the UT.
The Justin Prim who produced that video has been flying up the faceting 'ranks' over the last few years. Doing all sorts of things. Good on him.

FlashGP

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Re: choosing the right electromotor, please help.
« Reply #22 on: February 06, 2019, 09:02:19 AM »
Hi, just saw this post.

Have finished my machine, the little chinese 12v, 3500rpm fan cooled 775  motor from Banggood is quiet and draws no more than 3 amps.  My 25 amp power supply is a  it of overkill but can also br used for other projects as well.

The 30rpm worm drive motor is small but does the job. It is quiter is turned down, and I think this will make it last longer.

I have only been using the dial indicator on my faceting machine so the readings are in knotches, because the 0.00005 inch grads are not calibrated.

I was getting 5 graduations run out on the mandrel with the ER11A collet holder sitting straight on the shadmft of the motor.

An engineer I know suggested sleaving the ER11A and shrinking it on the motor shaft., but there may also be runout in the cone that holds the collet.

Not having a lathe I milled some copper shims until they fitted between the ER11A and the motor shaft.  The copper was about 0.025mm by this time.  E.g. there is about 0.05mm difference between motor shaft and the hole it fits in.

The hole narrows enough to stop the shaft going all thecway home when a tube of the shim is inserted all the way into the hole.  I cut the shim so it stopped just before the narrowing, meaning the shim tube was amout 9mm long.

I also placed the collet on a dop in my quill, wrapped 1200 sandpaper around it and at 90 degrees, ground the inside of the taper with the motor running, oscillator off, to smooth it.

This reduced the run out to 2 graduations on the dial indicator, about the same run out when sweeping a worn lap.

Am now waiting on some cutting mandrels to be made.  So I can start cutting.

Long story short.  I'm pretty happy with the result since including the 2 Darkside polishing mandrels I bought for about $100 with postage it has cost me under $500 to make.

Regards
Gordon.


« Last Edit: February 24, 2019, 08:50:42 AM by FlashGP »
Yours Sincerely
Flash (Gordon)

MakkyBrown

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Re: choosing the right electromotor, please help.
« Reply #23 on: February 06, 2019, 04:04:57 PM »
I wouldn't worry about your run out flash. Just use lower rpm and faster osculation. That ultratech worked ok with run out.


Just came across this motor.https://www.ebay.com.au/itm/M315-402-Continuous-Duty-Operation-Speed-Control-Motor-AC-220V-15W-1-5uF/301739437903?hash=item4641126f4f:g:fk8AAOSw~vpaSivb

 

FlashGP

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Re: choosing the right electromotor, please help.
« Reply #24 on: February 06, 2019, 07:06:41 PM »
Hi Makky, I would first check the motor is wired for 50hz.  At one point the Gyroc burnisher/vibratory tumbler was sold with a 220v 60hz motor.  They ran so hot the thetmal cut out would trip.

Regards Gordon.
Yours Sincerely
Flash (Gordon)

MakkyBrown

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Re: choosing the right electromotor, please help.
« Reply #25 on: February 06, 2019, 10:28:08 PM »
Flash, With my limited electrical knowledge I did realize there was a difference. I thought it would just run slower at 50Hz.I'm not planning to buy it just posted it as a possibility.

CheersMB


Giel

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Re: choosing the right electromotor, please help.
« Reply #26 on: February 07, 2019, 02:41:40 AM »
@Flash: I just read about your little chinese 12v, 3500rpm fan cooled 775 motor from Banggood. Any chance your got torque specs on that motor?

I have been trying to learn about electromotors, torque ect the last few days....turns out it can be a lifelong study!
Apparantly you cannot just talk about the torque of a motor, there is "rated torque", "peak torque", "torque constant" and "continious stall torque" So I kind of gave up to understand it all.

I did compare the torque of "similar applications" (I assume this is all "rated torque")
The OMF machine has 9.2oz/inch torque that is equal to 0.064N-m of torque. (cant find specs on the ultra tech)
A 500 watt cnc spindle(ebay) which is way to powerfull for the machine has 0.5N-m of torque
A 100/150 watt spindle(ebay) which I think is still stronger than I need has 0.15/0.2N-m of torque

So I think I will go for a motor with something like 0.12 or 0.15N-m of torque, 2,5 times the torque of the OMF machine should be allright, also if it needs to power a spindle with bearings and pulley. Its going to be 12 or 24 volts preferably brushless.

I am still contemplating though if I am gonna put the collet straight on a motor, or make a separate spindle with pulley system.
And its chinese new year so no orders for now....

I just cannot figure out how to make the oscilater with a wormwheel, I am using a 100 RPM motor that drives a piston like arm, I can adjust the arm on the shaft of the motor to make it swivel longer or shorter strokes. I'll upload a photo when its done, I am waiting for some parts to arrive.

Rusted

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Re: choosing the right electromotor, please help.
« Reply #27 on: February 07, 2019, 05:55:36 AM »
Would a windscreen wiper motor be overkill for your oscillator drive?

MakkyBrown

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Re: choosing the right electromotor, please help.
« Reply #28 on: February 07, 2019, 08:39:05 AM »
I think I found a motor similar to the OMF one on Aliexpresss yesterday, just can't find it again for you.


I had a look at the 775 motors. They have a ball bearing on one end, I noticed an 895 motor in the same listing with ball bearing both ends and slightly lower rpm. Other 895 have bearing on one end. This listing has some info.

https://www.aliexpress.com/item/885-DC-motor-12-24V-high-torque-895-high-speed-motor-high-power-bench-drill-electric/32880222654.html?spm=2114.search0104.3.127.422670435BOALY&ws_ab_test=searchweb0_0,searchweb201602_5_10065_10068_10130_10547_319_317_10548_10696_453_10084_454_10083_10618_10307_537_536_10131_10132_10902_10133_10059_10884_10887_321_322_10103,searchweb201603_55,ppcSwitch_0&algo_expid=d874a36f-0cfe-4ca5-a6d8-f625edc03b9b-18&algo_pvid=d874a36f-0cfe-4ca5-a6d8-f625edc03b9b&transAbTest=ae803_4

Found theses search MY6812 on Ebay and AliexpressThis link describes the motor and how to remove the pulley.
https://www.motiondynamics.com.au/united-my6812-12v-dc-100w-2750-rpm-electric-motor.html
8mm shaft, low down torque being a bike motor, runout no info.

And lastly I wonder if end play is important due to the motor being oscillated.That printer motor I have had preloaded end play.
« Last Edit: February 07, 2019, 08:44:50 AM by MakkyBrown »

FlashGP

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Re: choosing the right electromotor, please help.
« Reply #29 on: February 08, 2019, 08:57:49 AM »
Hi Giel,

I dont have the specs on gand, but the more info tab under the picture of the motor on Banggood gives these specs.

Torque is also a function of motor speed, so you need one with good torque for cutting at low speeds.

Noise will also be a factor.  Motors for battery drills are quite noisy, too noisy for faceting.

The worm wheel drives the output shaft of the gearbox.  On my gearbox the shaft is 6mm od with a flat.  I drilled a 6mm hole in the end of a 10x10x60mm piece of mild steel, rotated 90 deg and drilled an offset hole for a tightening screw and split the end so it looks a bit like a battery terminal. 

Next time I wont do this, it requires too much pressure to clamp the arm to the shaft. Instead I'll just drill and tap a hole in the end, so I can screw a bolt straight down onto the flat on the shaft.

Then I split the rod so ut was 5mm wide except for the end with the hole, it stays as a 10x10x10mm bloc, and drilled and tapped 3 holes for 5mm bolts at, 15mm, 20mm and 25mm from the centre of the 6mm hole. These are mounting holes for the 5mm tie rod ends I use as a shaft.   They give a throw of 30  40, and 50mm respectively.

The tie rod ends are from Banggood, 1 male and 1 female + a tightening nut so I can adjust the length and position the end point of the oscillation.  They have a swivvel bearing at their end.

Makky,
I'm wondering if bush bearings would be better than ball bearings when accuracy is required,  a small amount of oil on the bearings would remove the play.

Motion Dynamice make
Yours Sincerely
Flash (Gordon)

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