DIY CNC Milling Machine From Scratch

[totts]

Hmmm yeh true i will add a back the column now, but im not sure on the ribs as if i weld these it may upset my ground face, i may add a couple bars inside to act like rebar. I will get some info on the z axis as im not sure weather to make them out of steel or ally for acceleration.
Ballscrews are 1605 on all axis.

Toroidal transformer is the way i am going for now, just need to do some research.

[Jonathan]

Hmmm yeh true i will add a back the column now, but im not sure on the ribs as if i weld these it may upset my ground face, i may add a couple bars inside to act like rebar.

I don't think adding more than the plate to the back of the column will make much difference, as it's the least stiff parts of the machine you need to target if trying to make it stronger. Intuitively I'd say that's a different part, but hard to say without modelling it, which takes a long time...

I will get some info on the z axis as im not sure weather to make them out of steel or ally for acceleration.

Yes please do. The difference in torque required from using aluminium vs steel is unlikely to be significant, plus steel has better damping properties so I'd prefer steel. Although as Lee has pointed out, there are other ways to solve the damping problem.

[totts]

I don't think adding more than the plate to the back of the column will make much difference, as it's the least stiff parts of the machine you need to target if trying to make it stronger. Intuitively I'd say that's a different part, but hard to say without modelling it, which takes a long time...

Not quite sure what you mean there? Would it be a good idea to add a plate to the back of the column and fill it with resin, or concrete?


Steel it is then! Cheaper too! Does anyone know the realistic weight of a 2.2kw spindle?

I will hopefully be goin to have a bt30 cartridge and motor, but i suppose it wont be too difficult to change the stepper motor of needed in the future.

[Lee Roberts]

Not quite sure what you mean there? Would it be a good idea to add a plate to the back of the column and fill it with resin, or concrete?

Steel it is then! Cheaper too! Does anyone know the realistic weight of a 2.2kw spindle?

I will hopefully be goin to have a bt30 cartridge and motor, but i suppose it wont be too difficult to change the stepper motor of needed in the future.

He’s talking in terms of adding strength to the machine and he’s right but I was really referring to eliminating resonance more than anything, I can’t see that adding ribs/reinforcing plates wouldn’t add extra strength to the column, I think they would help towards stopping any twist in the column at the very least.

I think the problem with concrete is that it’s relatively brittle (though I note your suggestion of using rebar), cracks could form in the concrete and over time it may break down inside the column, I don’t know enough but I’m guessing that it doesn’t really have the same dampening properties as other materials, epoxy resin is a favourite but so is kiln dried sand and the sand is cheaper in comparison.

I think what I will do with mine is to, reinforce the column on the inside, use a mix of aggregate (different sizes, type 2, pea shingle and so on) to then fill the column, then backfill the lot with epoxy resin (filling up the leftover voids) all the way to the top, hopefully creating one solid mass. The idea being the aggregate is just away to use less resin (cost vs. cost) but also brings back the properties of using sand.

.Me

[charlieuk]

I would be very carfull filling anything like that with that much epoxy and when it cures it can produce a huge amount of heat and contained in a metal tube you could have a small disaster on your hands. If you do want to do this make sure it is extremely slow curing and if anything put some bags of ice around it to keep the heat down and only do a little at a time.

He’s talking in terms of adding strength to the machine and he’s right but I was really referring to eliminating resonance more than anything, I can’t see that adding ribs/reinforcing plates wouldn’t add extra strength to the column, I think they would help towards stopping any twist in the column at the very least.

I think the problem with concrete is that it’s relatively brittle (though I note your suggestion of using rebar), cracks could form in the concrete and over time it may break down inside the column, I don’t know enough but I’m guessing that it doesn’t really have the same dampening properties as other materials, epoxy resin is a favourite but so is kiln dried sand and the sand is cheaper in comparison.

I think what I will do with mine is to, reinforce the column on the inside, use a mix of aggregate (different sizes, type 2, pea shingle and so on) to then fill the column, then backfill the lot with epoxy resin (filling up the leftover voids) all the way to the top, hopefully creating one solid mass. The idea being the aggregate is just away to use less resin (cost vs. cost) but also brings back the properties of using sand.

.Me

[Lee Roberts]

I would be very carfull filling anything like that with that much epoxy and when it cures it can produce a huge amount of heat and contained in a metal tube you could have a small disaster on your hands. If you do want to do this make sure it is extremely slow curing and if anything put some bags of ice around it to keep the heat down and only do a little at a time.

Thanks for the heads up Charlie, is it really that bad?

.Me

[charlieuk]

Thanks for the heads up Charlie, is it really that bad?

.Me

depends exactly on the epoxy but yes especially in warm temps, if you left a cup of epoxy to cure on its own you would be surprised how much smoke it can make! its a exothermic reaction so when if heat starts to build its a chain reaction and just gets hotter and hotter and will quickly turn into a smoking and bubbling mess. Ive never had flames but have heard of it. It all so doesn't make any different if you have some sort of filler mixed in with the epoxy so less actual resin to fill the space it will still have the same effect. As i said small quantities a bit at a time in a cold temp is your safest bet.