Shapeoko made Spindle

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danimal
Posts: 332
Joined: Wed Mar 13, 2013 5:53 pm
Location: Colorado

Shapeoko made Spindle

Post by danimal » Sat Nov 23, 2013 8:39 pm

My 660 has been on the way out since I bought it. It simply rotates at too high of an RPM for my machine. The problem is that at 30,000 RPM and a 1/8th end mill you should be cutting at about 900 mm/min according to most speed calculators and depending on your end mill number of flutes. On some of the plastics that I am cutting I still seem to get rubbing and I still have issues particularly during plunge operations at the beginning of a pocket and I get those wonderful little balls of plastic stuck to my mill that destroy everything. When moving at 900 mm/min the rubbing seems to stop, but I am forced to cut with shallower passes due to torque applied to the machine by the cutting surface. Also I wanted to get a 1/4 collet system so that I can use larger mills for faster removal of larger amounts of material.

With that said this is what I came up with so far. I am changing the design slightly from what I have below to give better plunge thrust capabilities. I am going to replace the upper bearing pre-load shaft collar with a plastic spacer and use the main drive pulley shaft locks for this function then I am going to use the upper shaft collar to against the upper tail angular contact bearing for an additional thrust load surface.

The Drive motor that I used was a Old Milwaukee angle grinder that I got for free that was shot. The motor was good, but the cord had been cut up. I don't really care about it's run-out in this case anyway and you cant beat free. I estimate the cost of materials to be about $80, and while that is not a huge savings over just buying another spindle, I learned a lot and I think that it has capabilities that spindles twice that price do not. The bearings were about 60% of the total cost for precision angular contact bearings, and that was bargain bin prices for clearance items. Most high end spindles have about $150 in bearings alone, I found out through hours of research.

In the photos there are some pieces and parts missing as I am in the middle of the change listed above. I ran it for a while last night and had a rubbing issue with the upper shaft collet. The lower one fits perfectly due to the thrust clearance left on the plate holding the lowest angular contact bearing. The seal rides just below the shaft lock screw. The upper collet sets about 1.5mm lower causing it to hit the set screw which I have to fix before any extended testing can be done. At full speed I am measuring a spindle rpm of 15100 RPM and I can get to 10,000 easily with a lot of power and torque from the motor using my speed adjust. This was impossible with my 660 because at 10,000 rpm it probably would stop on cold butter the torque was so low. I know that there are better ways to adjust rpm that maintain torque, but that still would not meet my needs from above and all solutions would have cost more than $80 as far as I could find.

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Shapeoko # 1458

RT0701C Spindle || dual y motor || x axis nema23 with custom carriage 1000mm length || z axis nema23 linear rail upgrade with 1/2-10 ACME

danimal
Posts: 332
Joined: Wed Mar 13, 2013 5:53 pm
Location: Colorado

Re: Shapeoko made Spindle

Post by danimal » Thu Nov 28, 2013 7:24 pm

So I am getting a little frustrated with this whole project, but before I scrap everything, I thought that I would ask around here and see if anyone has any ideas first. I have a friction problem somehow. I can not figure out a solution. When I have the oil seals on, the thing heats up so bad that it starts smoking in about 5 minutes. The shaft is too hot to touch for extended periods. When I have the seals off, there is significantly less friction, but the bearings really should be running on oil not grease for this RPM. I took the collars off and trued them, and polished the contact edge to a mirror shine. The seals seem to seal up well. I tried to make a plastic spacer as indicated above, but it immediately melted at the seal contact point. I greased the seals, oiled the seals filled the whole thing with oil and still it heats up way way too much.

I am surprised at how well it holds oil. There is only some slight seepage here and there that I planned on sealing with RTV gasket sealer when I got the final design up and running as a last step so that I did not have to fight it while troubleshooting these other issues. Any insight or thoughts would be greatly appreciated because I have been racking my brain trying to figure all this out.

The seal contact surface is at 3215 fpm with seal ratings of 5000 fpm. The bearings are rated for 20,000 rpm on oil, but only 14,000 on grease. It currently rotates at about 14,150 RPM. It is has awesome torque, the angle grinder motor is 5.5 amp and with the gear reduction I imagine it will tear through anything like butter if I can just get this overheating issue resolved.
Shapeoko # 1458

RT0701C Spindle || dual y motor || x axis nema23 with custom carriage 1000mm length || z axis nema23 linear rail upgrade with 1/2-10 ACME

Improbable Construct
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Re: Shapeoko made Spindle

Post by Improbable Construct » Thu Nov 28, 2013 8:31 pm

I wonder if the plastic is acting as an insulator causing the heat buildup.
Maybe if you made the whole thing out of aluminum it would help to dissapate the heat.
Another thing to try would be to reduce the belt tension so there is not a lot of side load.
Shapeoko #Classified some of the bolts may be original parts.
Shapeoko 1 # ???? Stainless plates, still in the box.
Shapeoko 2 # 3926 not stock
Shapeoko 3 # 0003
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PsyKo
Posts: 430
Joined: Thu Aug 30, 2012 8:42 pm
Location: France

Re: Shapeoko made Spindle

Post by PsyKo » Fri Nov 29, 2013 9:49 am

Hello,

I agree with Improbable Construct. I think the plastic is not a good choice here.
I had the same issue on my Kress 800. It was heating a lot with the temporary wood holder. As soon as I replaced it with aluminium holder, it went better.

I would also double check that the shaft is perfectly straight and that the 3 bearing are well aligned...
Shapeoko #736
Kress 800, Z Axis upgrade, dual Y, 600mm X&Y rails, metal spacers and V Wheels, home switches, 4th axis
Goko - Free CNC Control Software - http://www.shapeoko.com/forum/viewtopic ... 380#p44380

danimal
Posts: 332
Joined: Wed Mar 13, 2013 5:53 pm
Location: Colorado

Re: Shapeoko made Spindle

Post by danimal » Sat Dec 07, 2013 2:37 am

My final plan was to make the whole thing out of aluminum once I got all of the design kinks worked out. The bearings are in very close alignment, I used my split gap micrometer to adjust the separate plates until the bearing outer races were as close to equidistant as I could get them. I tried to limit the bearing pre-load and the belt tension, but neither seemed to do much for the heat. Maybe the heat sink action from using aluminum will fix the issues. I am thinking of scrapping the seals and going with grease while designing the upper and lower plates to tight tolerances around the shaft collars.

Thanks for the input, it motivated me to give it another shot this weekend.
Shapeoko # 1458

RT0701C Spindle || dual y motor || x axis nema23 with custom carriage 1000mm length || z axis nema23 linear rail upgrade with 1/2-10 ACME

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