Re: Fingers crossed it'll cut ally
I'm just looking at spindle design and A/c bearings so I'm intrigued if you know of a cheap type.
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im not totaly convinced a double row A/C bearing will be tight enough for ally, the ones iv got dont feel like they have that much pre-load, i might end up stacking the two of them
Do you mean rigid enough for milling Ali? If so be careful adding addition preload to a factory set tandem one as I believe you just end up un loading one side!!! if its a double row then lock it to the sharp end and fit a floating bearing at the other end.
According to SKF the distance between the CL of the bearings should be 3 to 3.5 time the shaft dia, so 12mm shaft = 36 to 42mm so a 100mm shaft should be way long enough.
The optimum design seems to be to use 2 opposing A/C bearings with a spring loaded pre-tensioner.
Have you seen the "DIY spindle design" on here, or these?
http://www.cnczone.com/forums/showth...t=12184&page=6
http://www.cncathome.com/spindles.html
It seems this has been done many times and the problems are mounting the motor to the spindle, the first link post no. 64 and 65 shows a flexible mount and water cooling for the motor.
I also have an ER11 collet and a RC motor to power it but as its for machine No. 2 I haven't got around to doing anything with it yet. so I will be watching with interest.
Good luck
Re: Fingers crossed it'll cut ally
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Originally Posted by
blackburn mark
Ah, im with you on the speed issue, i think i get you with the large motor to,, im guessing you would be fitting a rotory encoder for position feedback if you use the large DC motor ? (im no expert with these)
Err I hadn't really thought about feedback. I was thinking something along the lines of using a stepper motor and the big brushless motor and switching between the two. For instance start by using the big motor for CNC lathe then switch to stepper motor to perform any milling on the part.
It would be good to switch back and forth between the big motor and the stepper but that of course requires the motors to engage at precisely the same point. Maybe get the brushless motor to stop at a set position (doable) and have another solenoid push a pin in the shaft to engage the stepper (tricky) ... the best would be to just use a servo but that's very very expensive to get anywhere near the power of this brushless motor.
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Originally Posted by
blackburn mark
for the brake i would be looking at a motorcyle cluch plate maybe, im not sure youll get the force with electric solenoids to lock it for milling though but thats my guesstimation... id be tempted to consider an actual disk brake and caliper... the caliper would have to be beautfully fitted and have oposing pistons
I'm not sure about the solenoids either, hence how I've milled spaces for several of them.
Clutch plate... that looks promising.
An actual brake disk and calliper would be very nice. Sounds expensive though. I don't know much about them - what would be required to actuate/use it? Are they available with small enough disks since the biggest disk I would want to use is realistically 6".
Re: Fingers crossed it'll cut ally
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I'm just looking at spindle design and A/c bearings so I'm intrigued if you know of a cheap type.
"5200 zz z 2z ball bearing 10mm A/C" ebay aprox £16 for two... they might be to good to be true
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just end up un loading one side!!!
och!! i hadnt thought of that... i hadnt decided if id just throw two in for good measure or pre-load them against each other
iv decided now!! cheers ross
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According to SKF the distance between the CL of the bearings should be 3 to 3.5 time the shaft dia, so 12mm shaft = 36 to 42mm so a 100mm shaft should be way long enough.
i think you misunderstand, jonathan has a motor that has a 100mm long body so with a 100mm shaft there is no room left to add an A/C bearing and housing
yea iv seen those thread, they make interesing reading, one of those guys has his own ballancing machine!! to posh for me:)
Re: Fingers crossed it'll cut ally
i thought a servo motor was just that "a motor with a rotary encoder" maybe somone can jump in and help us on that one
you could make your own disk easy enough... the calipers would take to much effort compared to going to a bike breakers
you need to look over some motorcycles and posh mountian bikes for inspiration :) im sure some of the mountain bike disk brakes are machanical,,, could be worth a look.. the hydraulic ones would need a cam and lots of torque to actuate
Re: Fingers crossed it'll cut ally
Penis in pocket when around cnc machines is is a very good safety tip, no one wants to miss a tip :-)
Re: Fingers crossed it'll cut ally
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Originally Posted by
routercnc
Quickly sketched this ...
Thanks for the explanation. It's good to have it presented so clearly.
3 Attachment(s)
Re: Fingers crossed it'll cut ally
iv got some 8mm id A/C bearings but they are open (as apposed to sealed) so for now ill stick with the skate bearings
it would be nice to seal the nose and have a nice light oil swishing around in there :)
Attachment 2570Attachment 2571Attachment 2572
still a bit of work to do on this but it will give those that are interested an idea of what we have been on about
2 Attachment(s)
Re: Fingers crossed it'll cut ally
My ER11 10mm shaft turned up,, nice tight fit.. i may loctite it when im happy
Attachment 2616
Iv decided on one double row A/C bearing for now... i left room in the housing for two just in case :)
i ran it no load for ten mins... the bearing gives off more heat than the motor but nothing to drastic, if i remember correctly up tp 110 degrees is passable... it was nowhere near that
Attachment 2617
I tried to keep the housings 43mm but it wasnt really pactical
i havnt fully decided on how to setup the small motor, iv considered inserting an engraving bit straight throgh the motor but im struggling to find engraving bits with enough length to allow for more bearings on the nose... i may modifiy a needle vise....
anyway the engraving motor is not overly inportant to me but Its killing time while i wait for parts for the main build
just got to hope they will work as well as they look :)
Re: Fingers crossed it'll cut ally
Re: Fingers crossed it'll cut ally
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Originally Posted by
z3t4
Yes please!
There was an article in MEW (Feb 2008 issue, No 135 ) about making outrunner motors but there wasn't much about how to power them. I'm guessing that the 'servo tester' provides a PWM pulsetrain and the speed controller (is this aka an 'ESC'?) sees the pulsetrain and uses electromagick to provide a 3-phase supply to the motor.
John
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Originally Posted by
routercnc
Quickly sketched this to show aircraft vs cnc application for those interested:
(You could probably delete the 4.8V supply if using a BEC ESC)
1/ Whats the PWM signal characteristics?
2/ 'Servo Tester' sounds an expensive beast
3/ Surely you'd want a 0-10v input so you could control spindle speed from MACH3?
