Thread: Fingers crossed it'll cut ally
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05-08-2010 #41
I'm just looking at spindle design and A/c bearings so I'm intrigued if you know of a cheap type.
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
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
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05-08-2010 #42
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.
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".
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05-08-2010 #43I'm just looking at spindle design and A/c bearings so I'm intrigued if you know of a cheap type.
just end up un loading one side!!!
iv decided now!! cheers ross
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.
yea iv seen those thread, they make interesing reading, one of those guys has his own ballancing machine!! to posh for me:)
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05-08-2010 #44
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
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06-08-2010 #45
Penis in pocket when around cnc machines is is a very good safety tip, no one wants to miss a tip :-)
Sherline lathe, Chester DB11V lathe, Myford/ Rodney mill, CNC mill Isel/ home made, Sealy Hack Saw, Meddings Pillar drill.
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06-08-2010 #46
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06-08-2010 #47
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 :)
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
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12-08-2010 #48
My ER11 10mm shaft turned up,, nice tight fit.. i may loctite it when im happy
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
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 :)
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12-08-2010 #49
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12-08-2010 #50
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