Aussie Lapidary Forum
LAPIDARY => Gemstone Faceting => Topic started by: Giel on February 03, 2019, 07:00:34 PM
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I am building a concave cutting machine. (or I am trying to build one ;D)
But I have trouble choosing an electromotor for the cutter.
I am buying a reversible DC motor but I dont really know how much torque I need.
I have been looking at torque conversion tables but I am kind of stuck.
I was thinking to buy this motor (24 volt, 36W, 3000 RPM):
https://www.ebay.com/itm/36W-Permanent-Magnet-DC-Motor-2000-4000RPM-High-Speed-Large-Torque-Motor-12V-24V/302564825509?hash=item467244d9a5:m:m5uIJ9PnJ47Tm0HqWOMKUSQ:rk:36:pf:0
Would this be sufficient or would it be overkill?
thanx in advance for the advice!
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Hi Giel,
I be pretty temped to use a cnc spindle with the collet already attached to it. Have you read FlashGP thread, he was having trouble with run out.Maybe belt driving the collet shaft might not be a bad option.
http://aussielapidaryforum.com/forum/index.php?topic=6456.msg56588;topicseen#new
Plenty of cnc spindles on ebay. Interested in how you go with it.
CheersAndrew
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Thanx for the reply Makky.
Yeah I read the other post about the concave cutter, didn't know if I should have asked on that thread or create a new one.
I have already been looking for a cnc spindle on ebay, but most seem to run 12000 RPM and up.
They are also just the motor with a separate colletholder. (the affordable ones)
I also considered to make a separate collet shaft driven by a small belt, but I need extra room on the machine for that, meaning that option makes the whole setup bigger, thus creating other problems.
For now I cant makeup my mind....
Just considering the torque of the motor, do you think its sufficient, to little or overkill?
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From memory might have been Ultratech or Polymetric spindles speeds weren't slow might have been 8000rpm.
Not sure on torque. Also worth making the machine really rigid so it doesn't flex much when you push the stone on the mandrel. I suppose the more rigid the machine the more torque you could use when cutting.
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polymetric 5000rpm
http://cyberrockhound.com/polymetric.htm
Ultratech 3000rpm
http://ultratec-facet.com/Fantasy-Main.htm
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Regarding the torque I'd be tempted to go with more if I built one. I'll have a think over the next day or so and compare it to some motors I have.
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Regarding the torque I'd be tempted to go with more if I built one
yeah I know, the project is already spiraling out of control! Might as well get good linear bearings...precision machine parts....etc etc.
Someone sold me a bunch of 20mm linear bearings and thats where the problem started..... :o
The bearings are very good quality and very tight but big and heavy, so I need 20mm linear rods and the whole machine gets bigger that way.
I prefer a robust machine, but it needs to fit on a workbench.
I want to make it so you can turn the spindle 90degrees but that takes a lot of space on the workbench. (difficult to explain wihout drawings)
I am drawing the machine in 3d in tinkercad, I m used to drawing in tinkecad because I am into 3d printing.
But I am not familiar with solid works or autocad. So I cant show the drawings...unless you can open an stl or obj file.
thanx anyways for willing to help out!
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would you like something like this? ;D
https://www.ebay.com/itm/ER16-Spindle-Unit-Power-Head-3000rpm-5Bearings-for-CNC-Drilling-Milling-Grinding/192021811919?hash=item2cb56452cf:m:mH1qSUiLxV4Yx9NfIJCBoFQ:rk:2:pf:0
big and burly heavy duty
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Instead of the linear rods, I purchased some on these for my new faceting machine, they seem pretty nice. I reckon they'd be pretty good. Or this style in better quality but they are expensive.
https://www.aliexpress.com/item/2pcs-12mm-Linear-Guide-MGN12-150-200-250-300-350-400-450-500-550-600-mm/32912475672.html?spm=a2g0s.9042311.0.0.27424c4duhiDIh
Yeah that power head looks nice, but you only probably need ER11
Try Fusion 360 it is pretty good and you can get a free license. I've been using it for awhile but I'm still a bit of a novice with it. My sons pretty good with it so I can get help :)
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I don't think you would need all that much torque, look at the area of contact, just a few square mm max, there's no way you are going to be leaning on a stone enough to slow the shaft.
RPM, a bit of maths could give you what your expected RPM should be, look at the surface feet per minute (dropping back to imperial) on a normal lap then calculate what RPM you would need to get similar on whatever diameter you are using in your concave cutter.
I think the biggest consideration for this motor considering how rapidly it's spinning is noise, you don't want something screaming at you while you are faceting, it would get tiring very quickly.
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Rusted what about for roughing/coarse cutting on a big stone. If your doing that on the machine I'm thinking you could potentially use quite a bit of torque.
Good point about noise.
With motors if I did one I'd probably go for a motor with an 8mm shaft.I was just looking at these, not sure though.
https://www.omc-stepperonline.com/brushless-dc-motor/24v-3500rpm-047nm-172w-104a-%D1%8457x69mm-brushless-dc-motor-57blr70-24-02.html
I purchased a fair few steppers from them and always really good motors.
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I've got one of this out of a huge HP printer.Model number is 1.13.044.246.50
Says 15vdc
Shaft is only 6mm but.
Dead quiet and very hard on the fingers trying to stop it grabbing the pulley. I think If I did one I'd might be tempted to use this motor due to the quality.
http://mugul.com/wp-content/uploads/2017/02/DC-Motor_51x88_1.13.044.2XX.pdf (http://mugul.com/wp-content/uploads/2017/02/DC-Motor_51x88_1.13.044.2XX.pdf)
Thoughts?, you can get them on ebay salvaged from printers. I might do some more tests on it. :)
Search "buhler 3140-1081" on ebay
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Makky would you even use a concave machine for doing roughing?
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.
That looks like a decent motor, I have a couple of nice Siemens motors saved from old Teleprinter machines stowed away for this project.
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Rusted, I don't know mate, I've never even seen concave faceting done ;D Be tricky polishing a table on it so your probably right. After feeling the torque on that motor I'm thinking it would probably be enough. I just found another motor the same brand with an encoder on it with a worm drive, maybe I could use that for the oscillator.
Have you got your encoder going yet?, offer still stands send me the bits and I'll see if I can get something basic going for you to get you started. :) Did you ever get your Arduino board going?? it might be missing the boot loader as from memory you bought the cheap Chinese ones.
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Thanks Makky. No same with me, when I see concave faceting done it will be a first.
The arduino is fine,library for the display is the problem, but not really a problem I can just fall back to a very basic display and it will be a goer.
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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.
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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.
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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
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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
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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 (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.
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I quite like this machine, polymetric.
https://www.youtube.com/watch?v=Q1oBOCm0V-o
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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.
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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.
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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 (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)
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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.
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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
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@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.
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Would a windscreen wiper motor be overkill for your oscillator drive?
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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 (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.
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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
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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
Given the quality and play in some of the ball bearings I have purchased from China maybe. Generally in these little motors I think the ball bearings give a longer service life. Some of the smaller dc motors we have purchased with brass bearings have a very short service life, like 150hours from their datasheets. The front ball bearing in your 775 is good imo.
I suppose the next step up would be a motor like the printer motor I have where there is preload between the front and rear bearings and a service life of thousands of hours.
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Agree. Preloading should also help with runout.
If I had a lathe, I would set up the motor separately from the oscillating shaft and run it via a belt. This would allow the motor to be changed or upgraded easily. A similar concept to the VJ but without the flex drive and using a separate oscillator driver so it cant be oscillated too fast.
Basically 2 linear bearungs holding a tube bearing which osillates using a yoke that pushes and pulls a flange or tab on the tube. A keyed pulley mounted between guide bearings to keep it stationary with respect to the base and a shaft running through the pulley with flanges each side of the tube so the tube bearing pushes and pulls the central shaft.
Regards
Gordon
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In this clip you'll see the Polymetric Scintillator 88 mast/faceting head on the concave machine etc. (at roughly 28-33 seconds) What I would like to know is how have they setup the bearings for the horizontal pivot on the mast. Any ideas?? I want to use a pivot like that but it's hard to figure out which bearings especially the rubbish I recently got from china. I'm a bit lost for ideas that will be rock solid and precise. Maybe I'll have to use tapered roller/cone bearings.
https://www.youtube.com/watch?v=Q1oBOCm0V-o (https://www.youtube.com/watch?v=Q1oBOCm0V-o)
https://www.polymetricinc.com/home_htm_files/76.jpg (https://www.polymetricinc.com/home_htm_files/76.jpg)
CheersMB
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Why would you need to go with ball or roller bearings for that pivot? Brass or bronze or Delron would work and could be machined to whatever tolerance you want.
Delron is beautiful stuff to work with.
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Delron is nice I've used it a bit. It has to take all the side to side movement of the hand piece and I was thinking bearings would be smoother.
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Delron is nice I've used it a bit. It has to take all the side to side movement of the hand piece and I was thinking bearings would be smoother.
Solved, i'm going to recess a couple of thrust bearings.
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Milestone in the project! I have made up my mind about the motor! ;D
This is the lucky one:
https://www.omc-stepperonline.com/brushless-dc-motor/24v-3500rpm-023nm-84w-50a-%D1%8457x49mm-brushless-dc-motor-57blr50-24-01.html (https://www.omc-stepperonline.com/brushless-dc-motor/24v-3500rpm-023nm-84w-50a-%D1%8457x49mm-brushless-dc-motor-57blr50-24-01.html)
Its small, I think the torque is enough, if not I can always buy a stronger one from the same series.
Other components are also slowly coming in; brackets and linear shafts, linear scales (or whatever the name is) etc etc. Cleaned and mounted the bearings, running smooth and no play.
(http://i1226.photobucket.com/albums/ee403/cutter10/DSCN1637.jpg) (http://s1226.photobucket.com/user/cutter10/media/DSCN1637.jpg.html)
(http://i1226.photobucket.com/albums/ee403/cutter10/DSCN1636.jpg) (http://s1226.photobucket.com/user/cutter10/media/DSCN1636.jpg.html)
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8) what motor driver did you get? Did you go with theirs or a cheap one off ebay? You should be happy with that motor if it's the same quality as their steppers. And a massive 8mm shaft :)
Looking very flash with the digital readouts.
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I didnt order yet, but I will buy their driver with it. Big thanx for that link Makky!
Looking very flash with the digital readouts.
Hahaha, I thought they were pretty cheap, and after all I need to know where the spindle is, I liked that the readout is separate so I can build it in.
I am thinking about how to make the spindle head itself now;
I have one of these:https://www.ebay.nl/itm/50Collet-Chuck-Holder-CNC-Milling-Extension-Rod-Straight-Shank-C10-ER16A-150L/142057947085?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649 (https://www.ebay.nl/itm/50Collet-Chuck-Holder-CNC-Milling-Extension-Rod-Straight-Shank-C10-ER16A-150L/142057947085?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649)
And want to combine it with these:https://www.damencnc.com/nl/fk10-fixed-ballscrew-support-units-c3-quality/a1431 (https://www.damencnc.com/nl/fk10-fixed-ballscrew-support-units-c3-quality/a1431)
and one of these: https://www.damencnc.com/nl/60x60-servo-motor-bracket-mba10-d/a2109?c=314 (https://www.damencnc.com/nl/60x60-servo-motor-bracket-mba10-d/a2109?c=314)
and the motor inline with a shaft coupler. (thought this was more easy than explaining without the links.
Do you think one of those bearings is enough, or do I need two?
Anyways thanx for all the input!
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Yeah, nice idea. I'll been doing a similar thing to this on my new faceting machine to drive my index/quill. But on a smaller scale and making it myself. They are pretty expensive brackets though but look pretty accurate.
Have you seen these
https://www.aliexpress.com/item/57-stepper-motor-bracket-nema-23-fixed-seat-connecting-seat-support-seat/32821387669.html?spm=2114.10010108.1000014.1.152543128OUBnL&gps-id=pcDetailBottomMoreOtherSeller&scm=1007.13338.106568.000000000000000&scm_id=1007.13338.106568.000000000000000&scm-url=1007.13338.106568.000000000000000&pvid=18b8900f-acb4-4050-8e56-f30689f2cd71
https://www.aliexpress.com/item/CNC-NEMA-23-Stepper-Motor-Accessories-Mounts-Bracket-Support-Shelf-nema23-Stepping-Motor-For-57-Motor/32960143402.html?spm=2114.search0104.3.106.172b4bebxCxMT2&ws_ab_test=searchweb0_0,searchweb201602_10_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=e278efb4-2513-43ec-b0ab-08a9845ff413-16&algo_pvid=e278efb4-2513-43ec-b0ab-08a9845ff413&transAbTest=ae803_4 (https://www.aliexpress.com/item/CNC-NEMA-23-Stepper-Motor-Accessories-Mounts-Bracket-Support-Shelf-nema23-Stepping-Motor-For-57-Motor/32960143402.html?spm=2114.search0104.3.106.172b4bebxCxMT2&ws_ab_test=searchweb0_0,searchweb201602_10_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=e278efb4-2513-43ec-b0ab-08a9845ff413-16&algo_pvid=e278efb4-2513-43ec-b0ab-08a9845ff413&transAbTest=ae803_4)
Maybe you could make your own bearing holder with adjusters to line up perfectly.
I think one bearing but good quality.
But you could still go the simplest option and just adapt straight to the motor shaft. It is 8mm and there are a good few replacement motors in the cost of the bracket/bearing.https://www.aliexpress.com/item/ER11-ER16-ER20-C16-C20-C25-Motor-Shaft-Extension-Rod-Spindle-Collet-Lathe-Tools-Holder-Inner/32968409344.html?spm=2114.search0104.3.1.68cf6b7d2uLnSe&ws_ab_test=searchweb0_0,searchweb201602_10_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=3745efe0-ef3f-4ed1-ac3f-c836df7e5e3d-0&algo_pvid=3745efe0-ef3f-4ed1-ac3f-c836df7e5e3d&transAbTest=ae803_4 (https://www.aliexpress.com/item/ER11-ER16-ER20-C16-C20-C25-Motor-Shaft-Extension-Rod-Spindle-Collet-Lathe-Tools-Holder-Inner/32968409344.html?spm=2114.search0104.3.1.68cf6b7d2uLnSe&ws_ab_test=searchweb0_0,searchweb201602_10_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=3745efe0-ef3f-4ed1-ac3f-c836df7e5e3d-0&algo_pvid=3745efe0-ef3f-4ed1-ac3f-c836df7e5e3d&transAbTest=ae803_4)
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Just been thinking, oscilation might be nicer on a feed screw. Using endstops for safely and homing and an arduino+motor driver to reverse direction and control the speed and thus do nice slow down transition as it changes direction. And I just happen to have another motor from the printer with an encoder on it.
And I just purchase one other those collet holders for my little printer motor. ::) , no I'm not going to build one. :-\ maybe.........
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I just ordered the motor.
I will also have a look at those brackets, maybe it's a good option, I thought about making the bracket, or better maybe; let someone make it, since I dont have a cnc machine. A bracket with 2 good bearings! (better safe than sorry!)
There is a big community of "makers" in my town with 3d printers, cnc machines etc. so I will find someone that can make it.
The machine project is slow now, as I am busy with work, the garden and other things, but I will post it on the forum if I make some progress.
I did however buy a very small lathe this week on a dutch second hand site, I have always wanted a small lathe so I just could not help myself.
Seller said it needs some love, paid 100 euro for it. I think it is a small jewellers lathe or a watchmakers lathe, it has about 20 cm between centers.
(http://i1226.photobucket.com/albums/ee403/cutter10/_86.jpg) (http://s1226.photobucket.com/user/cutter10/media/_86.jpg.html)
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Hi Giel,
I'm envious of the mini lathe, although I don't know how precise it is. I recommend getting a dial indicator on an arm with magnet base so you can check your work, etc.
There are some great YouTube videos by Joe Pieczynski that talk about machining in terms dummies like me can understand. In one, he shows you how to accurately center your job even if the chuck is off center. He made something like a collett for the chuck.
Makky, I had discounted the extension tools for the ER11 etc as creating too much length. BUT I hadn't thought of mounting the shaft in a sintered bronze bearing with oil hole and driving the shaft. This would certainly get rid of the runout resulting from mounting a collet holder on the motor shaft. But it would require a close fit with the bearings.
Mounting the motor behind the shaft with a flexible coupling would add length, it may be better to drive the shaft with a belt like the Polymetric concave facetor does.
regards
Gordon
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Flash, I'll let you know how much run out I get from my cheap $7 ER11 adapter when it arrives. :)
Giel, Nice little lathe, bit of a bargain for the $$.
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Flash or anyone, how many mm of oscillation do I need ?
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I'm thinking I'll use a T8 1mm pitch feed screw to oscillate. Figure I'd roughly need to attach a 4000rpm motor with encoder to it or a stepper with a 2mm pitch screw. 1 osication (forward/back) per second at maximum speed. 35mm stroke max, 70mm return =70*60 = 4200rpm.
https://www.ebay.com.au/itm/T8-Pitch-1mm-2mm-Lead-1-2-4-8mm-Rod-Stainless-Lead-Screw-brass-color-nut/132381744971?hash=item1ed2911f4b:m:mDCgJZqzleCbGDJjXKZpunA:rk:1:pf:0
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Hi Makky,
The length of your cutting mandrels determines the distance between the max fsd and max backward stroke on the oscillator. I have 3 settings, 30, 40 and 50mm achieved using threaded holes on my oscillator arm at 15, 20 and 25mm from the centre of rotation.
My darkside mandrel made by gearloose is 42mm long so I'll provably have to use the 30mm setting so the dop stays under the entire facet. But if cutting a long facet, say 15mm long, I would need to make another arm with throws of say 15 and 25mm.
Clarry Trevena makes dops up to 60mm long so the 50mm setting would be fine for facets under say 8mm long.
Stop press, I made the arm from 10x10 mild steel rod with the end cut to 5mm thick to accomodate a lock nut on the retaining bolt for the agm that pushes and pulls the assembly back and forwards. The 5mm tapped holes are 5mm apart but drilled in a zig zag patten. If I add a tab to the other side of the motor shaft I can add 3 more adjustments at 1/2 distances giving 6 settings at 5mm increments starting at 15mm throws.
Oscillation speed control is an advantage. Really slow settings give you time to position the mandrel for checking allignment, etc.
Regards
Gordon
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Thanks Flash I'll design for 50mm max oscillation, then I can have variable oscillation distance and speed control. I think for bearings I might just use holes in some Acetal brackets. I was playing with some linear bearings today and they were getting a bit grippy oscillating the same amount constantly. So I might just cut holes in plastic as bearings.
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Hi Makky,
Do you mean that you were using linear bearings on the oscillator threaded rod? I didn't think they would work very well with a rotating shaft in them.
The 6mm pitch threaded rod assembly I bought as a kit from Banggood has pillow block bearings at each end. The bearings are mounted in a ball like housing allowing the bearing to be off up to 5 to 10 degrees perpendicular to the mountings.
The 2nd one I mounted wasn't true, but it was just a case of putting the rod into the bearing and twisting the bearing housing until it was properly aligned with the direction of the rod.
Regards
Flash
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Hi Flash,
No I was going to use holes through plastic to act as bearings to slide on the smooth round linear rails. You can buy brass or plastic inserts, I may use those not sure yet.
To drive the oscillation I'm most likely going to use a stepper motor and 2mm pitch feed screw. I'll use small endstops for zeroing and an arduino to control stroke length and speed and smooth direction transitions. I'll also have a screen and control pad.
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I like the idea of a stepper to drive the oscillation, figure they are more quit than a geared motor, but Im not familiar with the arduino or other ways of controlling the action of a stepper. That's why I bought a geared motor.
The way I am making it now it has a max oscillation of 55 mm. I think in "concave mode" using round mandrels, that is more than enough. But it also depends on how big your stones are.
I have two slide tables, the middle point of the cutting mandrel is the point where the two slide tables can rotate up to 90 degrees.
I want to make it so you can disengage the oscillation of both slide tables and also use them as a "microadjustable cross slide" (dunno what else to call it)
So in zero position you use concave mode, one table for oscillation, the other for moving the mandrel sideways. for cutting parallel facets on a tourmaline for example. (thats why I bought the digital sliders)
In 90 degree position you can use both directions of oscillation. One way for a round cutting mandrel and the other way for a V-wheel.
No matter what you are doing you always have measurement of where your mandrel is relative to your stone.
Ah, I also found some info on the lathe, http://www.lathes.co.uk/boleyF1/ (http://www.lathes.co.uk/boleyF1/)
There is no brand tag on mine but it has the exact same cross slide as the one in the link. (photo under the machine with the bright red belt)
Its an old machine, does not have bearings for the shaft, but it does feel very tight, no play in the parts.
I am taking it appart, cleaning it of all kinds of gunk, lubricating and putting it back together.
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Giel, If your every wanting to do any arduino projects I don't mind helping. I'm also going to use the same processor that controls the stepper/oscillation to control the speed of the main rotating motor aswell.
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Giel, If your every wanting to do any arduino projects I don't mind helping. I'm also going to use the same processor that controls the stepper/oscillation to control the speed of the main rotating motor aswell.
That's very nice, someday I want to make some stuff with an arduino, but I will save that for later.
Thanx!!! beers
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Hi Geil,
Sounds good. I used a cross slide coupled to a thread so I can manually adjust the position of the cutting mandrel so it is centred on the axis running up the centre of the quill.
I think this is what you are talking about in relation to the cross table allowing parrallel concave facets.
55mm maximum oscillation would require rather long cutting mandrels and runout could be a problem.
If you can adjust the length if the oscillation, that would be good.
The length of oscillation should be a couple of mm shorter than the length of your cutting mandrel minus the maximum length of the facet you will be cutting, otherwise the edge of the mandrel may run on the face of the stone and mar it.
Regards Gordon
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I think this is what you are talking about in relation to the cross table allowing parrallel concave facets.
Yes, that is what I mean, Sometimes it's difficult for me to explain technical stuff in english.
You also want to be abe to cut parrallel "V-groove" facets.
55mm maximum oscillation would require rather long cutting mandrels and runout could be a problem.
If you can adjust the length if the oscillation, that would be good.
Yes oscillation length will be adjustable up to 35-40mm. The 55 mm is for when it is not in oscillation mode, so I can cut parrallel facets on a stone up to 55 mm. (hope that makes sense and explains what I mean)
I used a cross slide coupled to a thread so I can manually adjust the position of the cutting mandrel so it is centred on the axis running up the centre of the quill.
Yes I am making something similar, "one mode for oscillation and one mode for manually adjusting the position" both tables can be used in both "modes"
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It sounds like you are on the right track.
I have just ordered a dial indicator on a magnetic base like you would use on a lathe to centre the job. It is so I can use it for trouble shooting and for checking the run out on my cutting mandrels.
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Hi All,
I had a Zircon on the dop that had a crack in the crown. I gave up trying to recut the crown and instead opted to concave cut the side facets on the Crown to cut away the fracture. The stone was an Old Mine cushion cut with facets at 95, 1, 23,25, etc.
It's the first run of my concave cutter. I found the following.
Allignment of the cutter to the centre of the mast was critical. Next time I'll opt for micrometer screw gages for mast alignment and mast stop alignment.
I am still learning how to accurately allign my cutter. It seems that with close indexes, imperceptable changes (less than 0.25mm) makes a big difference to the position of the facets. My laser level is just too course for that job.
regards
Gordon
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Allignment of the cutter to the centre of the mast was critical. Next time I'll opt for micrometer screw gages for mast allignment and mast stop alignment.
What do you mean with "mast stop allignment?
I think the ultratech fantasy machine also has a cross table under the mast for alligning it with the mandrel.
Maybe I will try something with precision dowels (is that the correct term?) so I can always find "zero" on the cross table.
And so I can only put the mast on the machine the correct way. (holes in the mast base and dowels on the fantasy cutter.)
Its good for me that you allready finished your machine. your post makes me rethink "potential problems" and how to avoid them. ;)
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Hi Giel,
All machines have a mechanism that alligned the dop with the centre of the cutter so you can allign the direction of the cut to the stone and lift and inspect the work then return it to the same allignment as cutting progresses. The VJ has a micrometer screw guage that clamps onto the swivell for the quadrant mast. Thes system wont work for a mast machine like a Facetron.
The Polymetric uses a quill stop to achieve allignment. Ive used something similar.
I tried to concave the mains on an SRB on a machine where the mast base was 3mm out if allignment with the cutter but the stone was centred on the cutter, the meets didn't line up.
If the cutter gets off centre to the stone, it is the same as rotating the stone on the dop.
This is why I set out to adjust the front/back positioning of the cutter. But you also need a stop to ensure that the Quill stays in the same side to side plane as the cutter, albeit above the cutter.
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Check this out, my cheap chinese collet/holder arrived. I stupidly tapped it on to the shaft of the printer motor I have. It was a tight fit will need a puller to remove. I should have perhaps cut a bit off the shaft first. Anyway it's on there. It's a 6mm shaft. So I put a bit of brass in the collet and measured the runout it was that good I even uploaded a vid. Run out is probably about 0.010-0.013mm, cheap chinese gauge is not that good. ;D Highly recommend the cheap chinese collet holder I got. The masking tape was to mark the side.
https://youtu.be/4T1Jas-lETk (https://youtu.be/4T1Jas-lETk)
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Hi Makky, impressive. How does it perform 50m. Down the brass from the collett?.
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It's still pretty good I was spinning a dop and couldn't see any run out by eye. The run out on the gauge may have even partially been the brass out of round slightly. I'll measure at 50mm for you.
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I think it should be pretty good. Jim Piezchulski (I think that's how you spell his bame) has a few you tube videos on machining, including one on centering the job that is worth a watch.
He also has one that shows you how to make a centering device for precision machining such as cutting mandrels. It us essentially a collet that is machined in the chuck jaws.
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For my first mandrel, as I only have about 0.01mm run out on my lathe 3 jaw chuck so I'm just going drill a 1/4inch hole through some aluminum round bar and loctite it to a bit 1/4" brass rod. Then hold the brass rod in a er11 collet holder held in the lathe and machine the mandrel to size. Should get it pretty good. But I have a heap of other stuff to do before I do that ::) . Too many things to do. I have a heap of parts that have arrived, T8 feedscrew looks really nice considering how cheap they are. I have also collected quite a bit of 12mm alloy plate offcuts I intend to put to good use.
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Hi Makky,
From what I hear 0.01mm runout on a 3 jaw chuck is exceptionally good, is it new?
Wouldn't it be better to drill a hole the same diameter as the brass rod in a piece of stock mounted in the chuck, then mark the position of each jaw numbering them, then cut 3 cuts in the stock to form a collett for the chuck. This will allow you to mount your cutting mandrels directly in your 3 jaw chuck without the need for packing to prevent the chuck jaws marking the job.
regards
Gordon.
This would eliminate any error introduced by the ER11 collett chuck when machining the cuters.
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Yes the lathe is new and I was pleasantly surprised the 3 jaw is as good as it is, I haven't used my independent 4 jaw chuck yet. You can see it in the youtube clip. I have fitted steppers to it and can use manually or cnc. I have a quick change tool post I have to fit to it which is on the to do list aswell.
One cut might even do, that is how I was machining dops. But I was thinking I might just try drilling the stock, turn to size, loctite in the brass then part off the mandrel.
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Sounds good.
A lathe is on my wish list as is the space to have one. Have been turning cutting mandrels on a friends lathe, he is a a retired machinist/engineer.
You may need to approach the cutting face size in small increments to reduce sub surface damage, and produce a nice finish on the job and get all of the concave cutters within +/- 0.01mm of each other.
Ian had 6mm stainless rod from a printer, which we used as a mandrel, then sleaved it with brass from a tap spindle, turned that to size then pressed a piece of copper pipe with locktite over the brass and machined to size.
Kept one brass full cutter size as an experiment, it works well.
Regards
Gordon
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What diameter are you using for your mandrels? I have 6mm stainless from printers aswell, that may be better to use as most of the brass rod I have is very slightly bent. Brass should be nice for a prepolish/polish.
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Hi Makky
I purchased a couple of 13mm Darkside mandrels from Aussie Sapphire, old stock. They also had a 13mm BATT mandrel which I was going to use for cutting and prepolish, but it had a 3/8 inch shaft that was too big for the ER11 collet chuck.
If I was starting again I would use ER16 colletts so I could use the mandrels sold by Polymetric.
The 13mm Darkside mandrels are 12.31 and 12.34mm respectively. So we made 12.31 mm mandrels as I should wear the 12.34mm Darkside to 12.31.
These worked a treat for the 2019 AFG comp concave cut. I've posted a video of it on the Faceting groups on facebook. I had trouble putting it in the gallery of this forum, and gave up. I had a bit of chipping on the edge of the rolled girdle with this stone so finished it with a 100K polish so it sparkled and Mrs Flash has claimed it.
The stone is 11.7mm in diameter and I think using mandrels about the size of your stone works well.
I also have 8mm printer rod which fits snugly inside 3/8" copper tubing and will make mandrels about 9.5mm in diameter. we just need to turn the end to fit in the collett down to 6 mm, glue on the tube and size the mandrels so I have a set of 3 matched mandrels.
By the way, Polymetric sells mandrels in 4 sizes starting at 13mm.
regards
Gordon
Anyway
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How much horizontal adjustment have you on your machine Flash ? How much do you reckon you need?
CheersMB
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Hi Makky,
Anoit 2.5cm each side of the centre of the mast. It lets me cut parrallel facets on big step cut stones.
However, I found that you need to have the splash pan wide enough to accommodate the movement.
Am also looking to add splash protectors to my oscillation bearings. When I use water as a coolant, it splashes onto the rods the bearings run on.
Regards
Gordon
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Thanks Flash, I wouldn't worry about the oscillation bearings too much just keep a bit of light grease on your rails. I'm going to use plastic ones as they will run a lot smoother. My brother has them on his 3d printers and they are really nice.Easy to swap into the housings you have if you decided to.