Thread: DIY 400mm CNC mill
I've been working on my chassis/platform.
So far any comments? Any glaring issues (bear in mind its not complete)
I am getting confused over the ball screws ends and fixtures. Any suggestions to what goes where?
OK, So Irving suggested i move my thread form a question that spawned out :)
With regards to ballscrew ends. Whats the difference between floating or fixed ends? (looking at Zappa website). I think i will go for one either end to support the ballscrew better but i am not sure the differences and wha ti would need.
I have access to machinery for the next week!
What machined on them? Just down in diameter to fit what looks like a 15mm end?
This is to fit the the BK and BF mounting blocks.
The table needs to be supported on 4 bearings arranged at least 65% of the table width & length apart (some simple bending stress analysis will show the best location with regard to workpice size and weight)
You may need some more bracing on the gantry sides in the X direction, depends on the size and rigidity of those green angle blocks.
I don't know what rail or table you are planning but I can tell you that a 19mm 500 x 500 sheet of MDF supported as mentioned above supported on 500mm long, 16mm dia, rails deflects .05mm in the centre under 4.5kg of load. Depending on the working load, and accuracy you require, 16 or 20mm rails may suffice - you might need a central fore-aft strut to remove a tendency for the end extrusion to rotate inwards under load (due to the twisting moment of the linear rails in their supports). The X-pattern extrusion has a high area moment of inertia in bending but is surprisingly much worse tortionally.
Looks good so far!
Ok, new question...
I am looking at getting my motors and dont know how to spec them.
i have been offered a couple of free mclennan M500 servo motors (without gearboxes) http://www.mclennan.co.uk/datasheets...reddcmotor.pdf
They need repair (positional optics parts) but are free
are they suitable?
what spec do i need for medium duty >400mm travel?
Thanks for the replies guys.
I think 0.15Nm isnt enough and they are pretty big without gearing.
Now i am thinking to repair these and gear them will be more costly than buying say 3Nm Nema 23 steppers?
Although accuracy is good i doubt very much i will need much below 0.25mm (and thats being REALLY tight for hobby use).
I may pass on the servos and just get the steppers.
Don't wait too long mate, prices seem to be rising alarmingly.
The stepper kit I bought from Zapp only a few months ago has gone from £206 to £289!Nothing is foolproof......to a sufficiently talented fool!
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