A sufficiently strong machine

[george uk]

Hi

you could not have timed this better for me, am just about to start a build. I want quite a heave duty machine for milling stone/ally

Question. Would there be a benefit from using larger motors Nema 34s or 42s or might it be a problem

[Jonathan]

I want quite a heave duty machine for milling stone/ally

Question. Would there be a benefit from using larger motors Nema 34s or 42s or might it be a problem

For the machine in this thread, there would be no benefit - in fact it would probably make the machine worse. Larger stepper motors tend to not spin as fast, but output more torque. If the smaller motor can output sufficient torque to obtain the required aceleration and speed, there is therefore no point using a larger motor as it will just cost more and sometimes not go as fast.
You would have to be building a huge machine for Nema 42 motors to be the correct choice. See this thread for a more detailed explanation.

[george uk]

thanks, am reading that now. Brilliant stuff.

I have another 2 questions or request for your opinion.

1. To stiffen up Z and Y ( when in action together ), i was thinking off adding rails to the inside edge of the X top support. ( i may want to add an impact head to it in the future ). Any opinions ?

2. any idea when the files will be available, am eager to have a crack at this.

[Jonathan]

1. To stiffen up Z and Y ( when in action together ), i was thinking off adding rails to the inside edge of the X top support. ( i may want to add an impact head to it in the future ). Any opinions ?

It's hard enough to align 2 rails let alone four. If you really need the higher load ratings, it's easier to just use bigger rails.

2. any idea when the files will be available, am eager to have a crack at this.

Soon. Sasha's still sorting them out but he's more interested in making the enclosure for the machine at the moment!

- 2 x 100x100 steel box for the gantry

Could do, but clearly that makes getting an accurate surface to mount the rails on more difficult. An early design for this machine did use 60*60 box section, but we decided not to use it as aluminium is much easier to machine.

-The bearing blocks and rails on the gantry to be at the upper side/or at the lower side/ so i can use epoxy and level them easy

Definately lower side as you want to keep them as close to the bed as you can to minimize the overhang.

-2x ballscrews at the gantry near the rails

I presume you're referring to the Y-axis? If so then yes it will make a noticeable difference to the stiffness of the Y-axis, but bear in mind it's already exceptionally strong so it's by no means mandatory. You could achieve the same by increasing the spacing of the Y-axis bearing blocks quite significantly.

What worries me most is the Z, making the z box and adjusting rails and fitting everything in place there. maybe using some ready box section and fit the spindle inside and fix the bearing blocks to the sides of it.

We used separate plates as they can be adjusted to get the rails parallel. Also it means you can machine features inside the Z-axis and you're not restricted to limited standard sizes.

[JAZZCNC]

It's hard enough to align 2 rails let alone four. If you really need the higher load ratings, it's easier to just use bigger rails.

I mentioned something similar to you in an email Jon and feel the machine would benefit from 1 more rail on both Y & Z axis. One Higher up on Y axis and on 3 sides of box on Z axis but more to help with resonance and vibration in all cutting directions rather than increase load ratings.?

Would also add another ballscrew to Y axis rather than increase bearing plates has the action of 2 screws pushing/pulling together would be smoother than widening the plates.?

Like you say it's very strong already but feel these changes would make it the close to ULTIMATE strong machine.!

[george uk]

Hi

Thanks for your reply Jonathan. To add a second rail, i was going to set it up and level it following your excellent instructions, then use the level surface prepared for the first rail, to mark the second. I was thinking of adding the second rail 90deg relative to the first ( on the side ) for the reasons stated in JAZZCNC above.

In fact, if i get the first rail level, and use it to mark the second, it would be quite hard to make it to far out ( as long as am carfull ). The main reasons i require stiffnes to the gantry is so i can add a B/C head or plate if needed. Am also adding a turret/lathe to the bed.

[Boyan Silyavski]

A couple of questions as i am designing my own build, using your ideas:

-so you believe 3kw spindle would be better than 2.2kw?
-how you did the oiling system? did you use the original nipples and modify them? why not grease? how much oil is used under operational condition? What oil?
-where did you get that spring shims that make the preload? what are the specifications? how did you calculate the distance between the 2 nuts , so that they would be mirroring each other exactly and the shims to fit in?