Small Mill very early design stage

[Ross77]

Well good luck, since its for hobby use then you will probably find that you are continually tweaking and changing things anyway

If you are worried about thermal effects then you will definitely need the consider dynamics as well, beam/column frequency and moving masses etc. just adding more mass can lead to resonance not to mention problems with accel/decel.

As with the thermal effects I suspect that the small size wont be to much of an issue but might be some thing to look at on your pursuit of perfection.....

Have you ordered the C1 precision ground ball screws yet?

[Robin Hewitt]

If you are worried about thermal effects then you will definitely need the consider dynamics as well, beam/column frequency and moving masses etc.

I see the big problem is that the spindle connects to a slide that connects to a slide that connects to a slide that holds the workpiece. All this with a total slop of < 0.001" so there is something left to allow for flex in the system.

I just don't think it's possible using commercial bearings, there simply isn't enough contact area to take the load.

Robin

[leadinglights]

...
If you are worried about thermal effects then you will definitely need the consider dynamics as well, beam/column frequency and moving masses etc. just adding more mass can lead to resonance not to mention problems with accel/decel....

Hi Ross,
It was the mass/rigidity that convinced me that thermal probles should be addressed. The same mass of aluminium should be more rigid than steel, but has about twice the thermal expansion and also has much better thermal conductivity - hence easier to control the temp of the whole device.
Hidden agendas are, aluminium is also much easier to work with with the equipment that I have and my workshop temperature varies from freezing (4C) to bloody'ot (33C)

on the C1 ballscrews, I keep looking on ebay.
Mike

[irving2008]

.... The same mass of aluminium should be more rigid than steel...

about 3 times more rigid... but also 1.7x linear length, i.e a beam 5cm x 5cm steel will need to be 8.5cm x 8.5cm in aluminium for the same mass, or 6.5cm x 6.5cm for the same rigidity, but because it is less dense it will more easily transmit vibrations from motor to workpiece partly destroying the benefits...

[leadinglights]

about 3 times more rigid... but also 1.7x linear length, i.e a beam 5cm x 5cm steel will need to be 8.5cm x 8.5cm in aluminium for the same mass, or 6.5cm x 6.5cm for the same rigidity, but because it is less dense it will more easily transmit vibrations from motor to workpiece partly destroying the benefits...

Hopefully easier to address than many of the other potential problems. Modern motors, whether stepper, servo or BLDC tend to be smooth and powerful and compliance for damping in the mountings of less consequence than in ballscrews, guides etc.

Mike