Eyeballs and comments sought for noob build

[danilius]

Loads of luvverly advice, thanks!

Hi
In general this is easy to build design but I would change it slightly:

1. Put rails on spindle plate and blocks on Z plate (this will give zero torque at top spindle position, your design create torque on spindle plate regardless of the spindle position)

Great idea. I don't remember seeing this anywhere, or probably I did, but simply didn't notice it!

2. Y blocks I would install on top rather on the bottom (it easy to make guard if you want to protect blocks against dust) - too big arm from bottom blocks to top of the gantry - think about forces

I was wondering about the pros and cons, so that's very helpful. Will have to look around for ideas to protect the rails from dust, or at least mitigate the issue.

3. Direct drive is transfer vibration to the motor better to use gear and belt.

Is the direct drive on the z axis such an issue? Should I make that belt drive as well?

4. I would use one motor for Y drive driven by pulley

Is there a disadvantage of using two Y motors? Sure, they can get out of sync, but surely two homing switches/sensors should take care of that between jobs?

5. Gantry should be connected on the bottom - not open. This make it stiffer and side plate a bit thin

I was not sure about that. My thinking was that by using two Y motors, I could save some weight, and the two motors and lead screws would compensate for the added stiffness the connecting plate would provide. Is this incorrect?

[Tom J]

Loads of luvverly advice, thanks!

Is the direct drive on the z axis such an issue? Should I make that belt drive as well?

Is there a disadvantage of using two Y motors? Sure, they can get out of sync, but surely two homing switches/sensors should take care of that between jobs?

I was not sure about that. My thinking was that by using two Y motors, I could save some weight, and the two motors and lead screws would compensate for the added stiffness the connecting plate would provide. Is this incorrect?

belt transmission gives you extra flexibility, you can adjust gear ratio means=feed, easier do deal with resonance if any occurs, allows to mount motor in two position (up side down and shaft up).
Z axis takes most vibration as is driving spindle up and down, so those shaky shaky gets to the motor and disturb in high speed. My first machine was driven by coupling - cheap Chinese, than with plastic insert, odiham finally end up with 1:1 pulley.

Y drive, if your power supply can handle biggest nema 23 3Nm motor without extra voltage than one motor should be ok and will wait only few hundreds grams more than 1.9Nm. Advantage of having one motor and two ballscrew is lack of need for squaring the gantry (one motor less, 2 sensor less)
Motor have to be powerful enough so they do not loos steps, if you loose steps you loose your job, material, time.

Gantry - more braces make it stiffer - joining them under bed will increase the weight but benefit you gaining by stiffer, more accurate machine are far more important.
I hope somebody else will give you some inside, I only build 3 machines and even on last one I would make something different, now I designed another one will post it soon.

Good luck with the build

[danilius]

Thanks for that. I'm a little concerned that a belt that long will introduce other issues, so will see what to do about that. Will attempt to alter the z axis for a belt drive. I don't suppose it should be too difficult.

belt transmission gives you extra flexibility, you can adjust gear ratio means=feed, easier do deal with resonance if any occurs, allows to mount motor in two position (up side down and shaft up).
Z axis takes most vibration as is driving spindle up and down, so those shaky shaky gets to the motor and disturb in high speed. My first machine was driven by coupling - cheap Chinese, than with plastic insert, odiham finally end up with 1:1 pulley.

Y drive, if your power supply can handle biggest nema 23 3Nm motor without extra voltage than one motor should be ok and will wait only few hundreds grams more than 1.9Nm. Advantage of having one motor and two ballscrew is lack of need for squaring the gantry (one motor less, 2 sensor less)
Motor have to be powerful enough so they do not loos steps, if you loose steps you loose your job, material, time.

Gantry - more braces make it stiffer - joining them under bed will increase the weight but benefit you gaining by stiffer, more accurate machine are far more important.
I hope somebody else will give you some inside, I only build 3 machines and even on last one I would make something different, now I designed another one will post it soon.

Good luck with the build

[Tom J]

Thanks for that. I'm a little concerned that a belt that long will introduce other issues, so will see what to do about that. Will attempt to alter the z axis for a belt drive. I don't suppose it should be too difficult.

use good quality gates HDT 15mm braided one - there will be flex which shouldn't give you error bigger than 0.02mm (I referring here to my steel machine which was 115kg)

[danilius]

Food for thought. Thanks! Time to get back to drawing :-)

use good quality gates HDT 15mm braided one - there will be flex which shouldn't give you error bigger than 0.02mm (I referring here to my steel machine which was 115kg)

[paulus.v]

Hi,

Connecting the gantry at the bottom will give little benefits but, by moving the legs far apart, the base will be a lot weaker.

Why would you put the X rails "hanging"? Only for dust/swarf protection? The side plates extension for guide blocks will deflect a lot and put pressure on the rails/blocks trying to twist them. I don't think it's worth it.

The gantry side plates are beefy but only when looking from one direction. If you cut out one third longitudinally and bolt it perpendicular you will have more rigidity in the Y direction without any loss or weight gain. And you can connect to your t-slot profile overhang.

[danilius]

OK, I think I have understood all this correctly. So, I'll move the rails up top, and stiffen up the gantry walls.