2024-02-23

Last modified: 2024-02-23 22:31:06

Machine design

First I want to check that the new design still fits in the material I have, and then see if I can tell it that the spindle motor is made out of a different material to the rest of the frame. And potentially also the rails.

So I think the only changes were:

• rear gantry plate is cut in half
• uprights get 50mm shorter, 40mm deeper, and filled in at the back

Here's a solution if we chop the front off the bottoms of the uprights so that they tessellate better, and make the X carriage out of the middle of the lower base plate:

Need to FEA that to see how much worse it is.

The last result was:

• X: 0.21mm
• Y: 0.13mm
• Z+: 0.14mm

And with the front 100mm cut off the uprights, we have:

• X: 0.22mm (+0.01mm)
• Y: 0.14mm (+0.01mm)
• Z+: 0.15mm (+0.01mm)

So it's 0.01mm worse in every axis, but with the benefit that it actually fits in the material I have available.

And what if we then cut the X carriage out of the base plate?

• X: 0.23mm (+0.01mm)
• Y: 0.14mm (=)
• Z+: 0.16mm (+0.01mm)

So again slightly worse, but with the benefit that it can now be made. Here's the material layout:

Also, the values I'm noting down are the maximum displacement of any part of the machine - but that doesn't necessarily occur at the tool.

In this plot of max. displacement for instance:

The tip of the spindle is orange, but the rear of the spindle is red, which means the rear of the spindle has moved further than the tool has, so the numbers I'm noting down are slightly worse than reality.

But forget about that for now. I can't work out how to find out the displacement at the tool any more precisely than looking at the colour on the mesh.

Next I want to look at telling it that the spindle + clamp are made of aluminium.

Meh, can't figure out how to do it. It let me select a bunch of surfaces and associate them with a material, but it didn't make any difference to the result, even after a remesh. And even if I select the surfaces, I'm not sure how it would know which parts of the volume are in what material.

I'm going to update the main machine model to match the latest from FEA, and maybe I'll stop there.

There's not an enormous amount of clearance to the front and back of the laundry basket. I may have to remeasure that once the old machine is out just to check it will definitely fit.