Wobblycogs CNC Mk2

[Wobblycogs]

Thanks for the suggestions Jazz most are drawn up already. Anyway, here are some shots of the project so far.



I've added in a triangle brace for the gantry side plate but I rather like the one here so I might switch it for that. Depends on how much of an improvement it would make though.

As suggested the spindle mounts have been redesigned so that they fix from the front and the z-axis back plate now has a waist to reduce weight.

I initially had the z-axis stepper using stand-off legs like the x and y steppers but I felt this would weaken the top plate too much so it got a proper frame. The benefit of this is I can lock the z-axis back plate into the stepper support for additional rigidity. The stepper and pulleys will also be enclosed in a bent metal box.

The y-axis stepper has been mounted on an extension of the right hand gantry plate. Again this will be enclosed in a bent metal box to stop chips getting in. I've split the front chip guard in two so that the left section can be removed for accessing the belt and pulley for the y-axis without taking the machine completely apart (more cunning than a fox)!

I've had a think about where cables will run (very good suggestion). I think a cable drag on the right hand side and across the back should work fairly well. I've not even considered drawing it yet but I don't see anything obvious in the way to stop that idea.

I've not upgraded the bed to 45x90 yet because I wasn't sure if it should have the 90 edge vertical or horizontal. I assume vertical to provide resistance to twisting.

Now for the problems...

I've been reading loads of threads and I'm getting concerned that 45x60 profile in the gantry isn't strong enough and that I should probably go with 60x90. It's a damn sight more expensive and I don't want to upgrade if it won't help but I'd rather have a machine that was a bit over built than a bit under built.

The plan currently has SBR16 rail all over but I (and and a lot of other people it seems) have noticed there's not a lot of clearance (e.g. none) on the z-axis ballnut. The million dollar question is do I switch to SBR20 rail or try and rout out a pocket for the ballnut on the z-axis if needed?

And the big one... At the moment the rail is mounted straight onto the profile. Ooops, school boy error. I think I'd get away with it on the x-axis as there's a good 6mm of aluminium to bolt into. On the y-axis though it's clearly not enough as drawn. Presumably a 10mm plate bolted to the profile will fix this? Does it need to be toolplate?

Some other, probably stupid, ideas have come to mind though, would this machine be capable of engraving and or cutting brass? I've cut a couple of small bits of brass with a hacksaw and it seemed similar to aluminium in hardness. I've also considered making the x-axis significantly longer, say 1000mm of cutting length, I'm trying to resist that though as I still want to build my Mk1 machine which will be designed to handle large pieces.

EDIT: As well as considering using SBR20 rails what about moving to profiled rails instead? They would be a budget buster but I believe I could mount 15mm rails straight onto the extrusion and from what I've read they would lead to a better machine over all. A couple of lucky buys from the far east might make it possible.