New spindle idea for my machine - DC 1HP

I am now officially out of hibernation now the weather has got slightly better and I have been putting together something I have been thinking of doing for a while now, a new variable speed DC spindle drive.

Gathered together the following parts -

1HP DC Motor - Its bigger than i thought it was going to be and quite heavy but good quality DC motors all seem to of a similar size to this. Max RPM is 2000 which is slightly slower than I wanted but will gear it up to get more speed.

DC variable speed motor control board - This is 240V input and will drive a DC motor at 180V up to 8A which will be slightly more than I need for the motor I have got. This is a very good quality board which has a lot of features that I will probably never use but the ones I will be using are the ramp up and down speeds, forward and reverse, and it accepts 0-10V input for speed control so should be easy to interface with my controller so that I can get it working with Mach3.

AC Mains filter - Apparently the motor speed control board needs one of these to clean up the electricity going into it so I bought a 30A one. Bit overkill but the price was right!

Spindle 2 board - Got this from Roy at DIYCNC, I have used Roys boards for everything on my machine and do rate them. The spindle 2 should allow me to send the 0-10V signal to the motor controller. Not tried it yet but somehow I don't think it will be too difficult to setup.

Spindle cartridge - Found this in a box of stuff that came with my lathe, I have re-engineered it and replaced the original spindle which had some odd size taper in it for an ER16 collet version. Was a pretty straightforward mod and the original bearings are very nice quality German ones so should be perfect for what I want.

Toothed belt drive - Gone for a toothed belt drive because....well.... I wanted to and I got them for nothing! Spindle pulley is a 22 tooth which was the smallest that I could get to fit onto the spindle cartridge and the motor pulley is a 72 tooth. This gives me a 3.27:1 ratio which means I should be able to get the spindle running at about 6,500 RPM max. This should be perfect for what I want to use it for but not convinced that it will provide the torque at low RPM so may need to double up the sprockets later to give me an additional 1:1 option. Just have to wait and see! I will be making provision for quick mounting my original Kress spindle to the machine for when I need a high speed option, trying to cover all the bases.

Electronics enclosure - Once I have everything running then I will put together a nice enclosure for all the electronics, want to make sure that it works first!

Ordered some more aluminum plate today to make a couple of mounts for the spindle cartridge so hopefully next week I should be getting close to putting everything together.

I will update this thread as I go so if anyone fancy's building something similar then you will be able to learn from my mistakes!

Photo's below of the bits and pieces and also a quick screen grab from my CAD software of what I have got in mind.

Sweet. Looks similar to what I was planning, although I'll be using a 3 phase motor and vfd. Any reason for using DC? Where did you get the ER collet with the threaded end or have you made it?

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Originally Posted by Ross77

Sweet. Looks similar to what I was planning, although I'll be using a 3 phase motor and vfd. Any reason for using DC? Where did you get the ER collet with the threaded end or have you made it?

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Reason for DC was because you get a smoother torque curve through the speed range (apparently) which means it should still provide decent torque when running slowly, tell you next week...!

I got the ER collet chuck from Fleabay via China, it came with a straight shank and I machined the thread on etc, 19mm x 1mm pitch left hand! Why is nothing ever simple.....

Spent another few hours at my DC motor spindle upgrade tonight and I think another couple of hours should see it mounted on the machine and ready to go.

I removed my Z axis from my machine and mounted up the new spindle and motor to it, all went together pretty nicely and pretty much just as I drew it up.

Mounted the motor on a couple of old 15mm linear rails for belt tensioning which may seem a bit over the top but I had a couple of old ones lying around and on further inspection they would not be much good for anything else, certainly made life a bit easier.

Just need to make up a belt tensioning screw tomorrow, get it all back on the machine and wire it up. It looks like it should work so fingers crossed!

Photo's below - think that the bench may need a tidy up after I get it running....

Looking good Steve

We will have to meet up sometime seeing that we are not to far away from each other.

Andy

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Originally Posted by audioandy

Looking good Steve

We will have to meet up sometime seeing that we are not to far away from each other.

Andy

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Keep away Andy, the bastard borrows everything that's not bolted down and you never get it back.

.

Looking good Steve

can't wait to see some videos, will be doing the same thing but my motor is 4000 rpm, will still gear it 3.1 ratio.

Michael

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Originally Posted by John S

Keep away Andy, the bastard borrows everything that's not bolted down and you never get it back.

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Thanks for the heads up :lol:

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Originally Posted by John S

Keep away Andy, the bastard borrows everything that's not bolted down and you never get it back.

.

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I can't help it if you keep giving me stuff everytime I come round, i've given you a colour (knackered) laser printer and a packet of hobnobs so I thought we were even....:rolleyes:

Got the Z axis back on the machine tonight and spun it up, I'd like to say it worked perfect first time but afraid not, lifes never that easy but thats what makes it interesting!

Noticed some vibration around 500rpm on the motor which after some investigation I found that after running the spindle for 5 mins the bottom half of the spindle head was getting a bit too warm. Disconnected the drive belt and turned everything by hand to find that my smooth as silk running spindle head was now feeling a bit tight and lumpy, BASTARD!

Stripped it down and looks like the bottom 2 bearings are either knackered or the inner race has been slipping on the spindle shaft or a combination of the 2. Flushed out the bearings, re-greased them and fitted them back on to the spindle with some bearing fit loctite.

Now all feels smooth again but not 100% convinced that it has solved the problem, will leave it over night and give it a run again in the morning. Got a feeling I will be off to the bearing shop next week!

Other problem is the weight, when the steppers are powered off the z axis now slowly falls down. Thought this may happen and will be ordering a couple of 150mm stroke variable pressure gas springs tomorrow. The stepper drives it up and down fine but not comfortable with it having to shift that much weight.

But.... it does look nice...!

Nice Job Steve :clap:

Steve,

Steve get one of these Constant Force springs .

http://www.ondrives.com/springs-cons...-65n-load.html

Like a gas strut but can't leak and always adjustable both ways if you cock up. Compact as well.

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Originally Posted by John S

Steve,

Steve get one of these Constant Force springs .

http://www.ondrives.com/springs-cons...-65n-load.html



Like a gas strut but can't leak and always adjustable both ways if you cock up. Compact as well.

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I think I need more force than 9.55kg which looks like the biggest one they do, not weighed it but took some lifting when fitting back on the machine and I nearly broke into a sweat so it must be at least 20-25kg.

Thats why I thought gas spring, the ones I am thinking of usually go up to 40kg with a little valve in the end to release the pressure. If you are dead against this idea then fair enough I will come up with something else, got any more idea's?? !

Just ran the spindle again and still not happy with it.....

The problem bearings at the moment are 2 x 16004's - dimensions OD 42mm x ID 30mm x width 8mm

Decided to change them for some 6004's - dimensions OD 42mm x ID 20mm x width 12mm

Will need to do a bit of a mod to the housing and make up a new spacer for the spindle but think its worth it as they have a higher load rating than the originals.

Just rang my bearing man up and he has them in stock, apparantly they are used quite a lot for motorbike wheel bearings and he has plenty on the shelf. Price - £3.50 each for NSK's!

Where's me van keys.........

Isn't that motor just a tadge excessive? :eek:

How on earth are you going to channel 1hp through such a tiny tool without blowing it to shards? :eek:

If I was going to put in a 1hp layshaft I wouldn't go below 3/4" :eek:

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Originally Posted by Robin Hewitt

Isn't that motor just a tadge excessive? :eek:

How on earth are you going to channel 1hp through such a tiny tool without blowing it to shards? :eek:

If I was going to put in a 1hp layshaft I wouldn't go below 3/4" :eek:

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Robin,

When I got the motor i too thought it was a bit excessive but based on my simple calculations I ended up looking for a 1HP DC motor and was very suprised at the size when I collected it.

Current Kress 240v AC spindle - 1050W = 1.408073 HP

New big 180V DC motor - 750W = 1.01HP

Then throw into the equation that I have geared the spindle up to increase speed from the 2000rpm motor max which will in turn reduce the torque, so in theory I will have less power than the Kress but I will have slower spindle speeds which is what I am after.

I can't find a torque/speed curve for the Kress spindle but I imagine that when running at its slowest speed (10,000rpm) that it is not developing 1HP, hopefully when my spindle is running I should get decent torque at 3,000-6,000 rpm but time will tell....

Swapped the bearings in the spindle last night which made an improvement but still got a vibration/resonance problem which looks like is coming from the toothed belt, tried different belt tensions which altered when the vibration came in. After a couple of phone calls I think it could be to do with the small amount of 'wrap' i have on the smaller pulley, will be making up an idler pulley to run against the back of the belt to push the belt further round the small pulley.

Note to self - when feeling round for vibration on machine do not put hand on bare motor connections as it makes you jump and shout BASTARD really loud...!

Maths isn't exactly my strong point, but...

For sake of argument, consider a 6mm tool at 6000rpm

6mm*pi*100rps=1885mm/s=6.18ft/s at the cutting edge

1hp=550ft.lbf/second

550/6.18=89 lbf=Whoops!

Irving will now tell me where I went wrong :naughty:

Best

Robin

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Originally Posted by HiltonSteve

Robin,


Swapped the bearings in the spindle last night which made an improvement but still got a vibration/resonance problem which looks like is coming from the toothed belt, tried different belt tensions which altered when the vibration came in. After a couple of phone calls I think it could be to do with the small amount of 'wrap' i have on the smaller pulley, will be making up an idler pulley to run against the back of the belt to push the belt further round the small pulley.

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Should have used a Polyvee belt

Nar nar nar nar nar

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Originally Posted by John S

Should have used a Polyvee belt

Nar nar nar nar nar

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I know your right and you know you are right.....

Still got the tool to make them and the 2 sample pulleys that I borrowed from you! Where did you say to get the belts from?...... smart arse.

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Originally Posted by HiltonSteve

Still got the tool to make them and the 2 sample pulleys that I borrowed from you! Where did you say to get the belts from?...... smart arse.

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See what I mean, BORROWED - huh, fat chance of even seeing those again.

Belts ? try the belt company..............

Let me get this straight John he needs belts for what reason? (keep his trousers up from the weight of the stuff he is pilthering in his pockets). And the 2 pulleys are his accomplices i take it that keep watch?
LOL!

Right then, looks like I better get the van loaded up and head round to johns with a couple of packets of hobnobs before it's too late.

Probably find a couple of polyvee belts lying around whilst I am there.:whistling:

Been playing with the Spindle2 board today and have interfaced it with my controller, got it all working but I have got a little bit of discrepancy with the volts coming out of it and the programmed spindle speed.

Configured my spare A axis to output to the Spindle2 board and ended up with my spindle motor tuning set at 1000 steps per unit and velocity at 130, tried tweaking above and below these but these settings seemed to give me the best output voltages from the Spindle2.

Set the max speed in mach (pulley selection) to 6500.

I now get 10.00V exactly from the Spindle2 board when I program the speed in mach to S6500, but when I set it to half (S3250) I get 5.7V. Tried lots of different values in the motor tuning settings which do change what voltages you get but 5.7V is the lowest I can get it to when the speed is programmed at 3250, I would like to see it closer to 5V but can not see any other settings which influence it. Have i missed something??

Sounds like your pulse rate -> voltage conversion is not linear. According to the spindle2 manual its intended to be used at 2000 steps/min for 10v and tweaked using the adjustment on the board to get this spot on. I suspect your starting point of 1000 is too low and at 500ppm the board is having difficulty adjusting to it...

To adjust these correctly you need a special screwdriver shaped like Roy Harding.

Thanks for that Irving, seems like you were on the right track.

Seems that the steps/unit and velocity were linked (which makes sense), if I increased the steps to 2000 then I had to decrease the velocity to 65 to give me 10V at full speed which releated to my original 1000steps/130 velocity. This still did not give me 5V at half speed, still the same 5.7 as before.

But....

I have increased the pulse width from my original setting of 1 up to 10 and now it is giving me a much better linear relationship. Now have 10.00V at full speed and 5.01V at half speed.

Increasing the pulse width to 10 effects all the motor settings, what effect will it have on the steppers if any at all?? Everything seems to be running fine still.

Thanks again:smile:

shouldnt affect the others at all... at the default 25khz kernal speed the nomiinal cycle time is 40uS so a pulse width of 10uS isnt going to be an issue. Most stepper drivers need a pulse width of not less than 1 or 2uS but as they are edge triggered the larger width isn't an issue.

I thought that the pulse width might be the issue at that lower frequency. I am surprised though, I would have thought Roy would have put pulse-width conditioning if he was doing frequency to voltage rather then pulse-width to voltage conversion, I would have, but then I'm not designing for commercial supply (since he knew that pulse width can be adjusted in MACH3 maybe thats a cost he didnt need to bear).

I have left the direction pulse width at 1, shall I increase that to something similar to the step width to keep the 2 the same?

John, you are right about the screwdriver, had to modify the smallest one I had to tweak the pot!

shouldnt be necessary, as long as its all working OK... direction isn't a pulse as such, its a level - hi is forward, low is reverse (generally)... I can't think why you'd actually ever specify a pulse width for the direction signals...

Just got the tacho on my spindle to see how close it was running to the programmed speed and after a couple of tweaks to the max pulley speed in mach3 it worked out pretty good!

Turns out that my calculated max speed of 6500rpm was a little bit out, the motor must be running faster than the 2000rpm printed on the legend plate which is a bonus.

Just a few RPM out which is plenty close enough for me!

http://www.youtube.com/watch?v=OT-mm...eature=channel

Hi Steve

How did you get on with the normal bearings? I was looking at the 61908 (45x68x12) or the 61809 (45x58x7) as I was hoping the balls where smaller, which is better for high speed apparently......I have been looking all over the place and every one seems to recomed A/C bearings but there are a few that have had good results with Deep groove, but all seem to report overheating and short life. have you had any problems and what speeds are you getting?

sorry for so many questions but I dont want to fork out for A/C bearings if I just need to change £10 worth of bearings every 6 months or so......:o)

Well the bearings are still ok but not given it too much stick yet, they do get a little warm when running at full speed but it does not seem to be causing any issues. If they do need changing then it won't cost much and will only take 10mins.

What price have you been quoted?

Thanks Steve, its good to get advice from some one who has used them.

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What price have you been quoted?

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Ive not looked at the super scary high precision ones yet but standard A/C are about £15each and then the matched Pairs are about £40 each, where as I can get 5 of the deep groove ones for £35,

Did you notice if the balls in the smaller external dia. are smaller? Reduced mass seems to be one of the critical points for High speed so would be a bonus for the deep groove ones, as I could use 4 or 5 to regain the strengh

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they do get a little warm when running at full speed but it does not seem to be causing any issues

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out of interest are the push fit or a tight interference?

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Originally Posted by Ross77

Did you notice if the balls in the smaller external dia. are smaller? Reduced mass seems to be one of the critical points for High speed so would be a bonus for the deep groove ones, as I could use 4 or 5 to regain the strengh

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Have you considered bearings with ceramic balls? There's quite a few around on eBay. Apparently they're good for 30% faster than steel.

I wonder if buying normal bearings and replacing the balls with ceramic yourself is an option - probably not.

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Have you considered bearings with ceramic balls? There's quite a few around on eBay. Apparently they're good for 30% faster than steel.

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Thanks Johnathan, Yes I have but its the cost. The ones on ebay are small for skate boards etc... I'm after 45mm int. dia. so the price gets quite high. mind I'm not brilliant at searching the net so if youve seen any cheapies then pls point me the direction. :smile:

Not sure if they would be any use ... IGUS do some weird bearing setups