[RomanLini]

Hey everyone,

I've put together a CAD model of my desktop router which I think is sturdy and now I’m hoping that the community can point out any design flaws I might have overlooked.

In short, I want it to be built like a rock (by desktop router standards).

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Thanks for any input!

Nice CAD work! To critique this design I'd have to echo other people's comments because they are right of course.

In that size machine you will get huge rigidity gains from going to fixed gantry and moving table. I'll give my input having built almost exactly the machine you described (by specs) but done as a moving table build.

My design uses a "L shaped gantry plate" bolted directly to the base plate but at 90'. The L shape plate cannot flex at all trapezoidally giving massive rigidity from one cheap part. I see you are in Australia, you can ring one of the big aluminium suppliers to order the 2 main plates, they will even cut to size and cut the L shape for you on their table saw.

Once you have the gantry and base plate rock solid that can't move relative to each other, it's pretty easy to make the 3 axes pretty solid as you have flat rigid plates to bolt the X and Y directly to, and Z is the only axis mounted on another axis so you just need to keep the geometry good so you don't amplify slop.

I used plastic linear bearings as they are "snug" and it's more like a milling machine bedways; the precision of no slop but best at slower speeds. On a 400x300mm machine speed is not a problem!

You can see my little machine here; http://www.cnczone.com/forums/cnc_wo...ll_router.html and you are welcome to copy any ideas ie the "L shaped fixed gantry plate".

[JeremyFisher]

I've read on this forum time and time again that unsupported rod will deflect, so I did an experiment with the 20mm rods I bought.
I hung 12.25kg (27lb) off one of them in a simply supported setup and using a dial gauge, I found it deflected 0.1mm (0.004") at the centre. I didn't account for deflection due to their own weight, but at 400mm I think it would be negligible. I concluded that fully fixing each end, and having three of them would yield a rigid enough structure.

Also don't use a clamping end support on those Y ends... use a setscrew on the Y ends that are M shaped. this will make your Y much more rigid.
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Also that blue block, ... how will you attached the open end to your X bearings? and how will you cut it perfectly square?
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you really should make use of the wide bearing spacing by either using a wider blue tube or adding an angled support to the blue tube.

Why do you suggest that using a setscrew would make it stiffer? I was thinking that clamping around the rods with the entire housing would make for a more rigid structure. That's how the commercially available support blocks are designed.

The blue RHS was to be machined on all of its functional surfaces, thus making for a perfectly square end.
That aside though, the three bolt holes to which the m-shaped plates are attached would be over sized to accommodate for adjusting alignment of the gantry and compensating for any deformation due to welding. Would that be a sensible idea?

I agree about the angled supports. I might add some webbing there if I stick to that design.

Nice CAD work!
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In that size machine you will get huge rigidity gains from going to fixed gantry and moving table.
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My design uses a "L shaped gantry plate" bolted directly to the base plate but at 90'. The L shape plate cannot flex at all trapezoidally giving massive rigidity from one cheap part.

Thanks, I figured I might as well plan as best I can by having a good model and iron out any quirks on screen rather than in the workshop. I've seen your machine and good work on that. I was in fact planning on making a copy of your tool height setter as one of my first projects for its ease and usefulness.

When you say 'L shaped gantry plate', do you mean forming an L shape by bolting together flat sheet yes? Your gantry is a bit complicated looking (sorry) but from what I can tell, it's a plate going across the y-axis to which the y-axis rails are bolted, and that plate is attached to the table surface by bolting it to another perpendicular sheet?

The reason I have avoided the moving-table design was for it's large footprint. I didn't want to end up with a large machine with a comparatively tiny work area. The current design is already inefficient with space, so I didn't consider the fixed gantry as an option.

But if 4 out of 4 people suggest fixed gantry, I guess it's back to the drawing board for me. I'm still not sure though on whether I will use rods or supported rails on the gantry though.

Thanks everyone.