Steel frame cnc router design/build

[JAZZCNC]

No don't use 5mm pitch for X & Y you want 10mm so RM1610. Use Rm1605 on Z axis.

Either rails will work but your correct the 16mm are lower so very close without machining the plates to allow clearance for ballnut.

Dump the 24V ASAP.

[CraftyGeek]

That'll teach me for posting when i'm tired :-p
Brain said 1610, fingers typed 1605.

Ok - i'll go SB20 all round for simplicity sake.

24V will be upgraded - but it means upgrading the stepper driver boards as well...so it won't happen immediately, but as soon as its possible.

[CraftyGeek]

As i'm getting further into the design now & tweaking parts sizes to make leadscrew bearing housing line up etc i'm wondering about methods of assembly & tweaking the fit of parts.
This is a 2 pronged question..

Firstly - I see many mentions of shimming parts to get accurate spacings & alignment....what is normally used for shimming?

Secondly - some of the parts that i'll be constructing have a length of steel box with an end cap plate that needs to be welded on.
On the design, i'm drawing this as a neat, flush fit like this:


Given that i'll be completely new to welding (yes i'll be practicing first), the tutorial video that i've watched suggests fitting parts together like the next image so that the actual weld can fit between the box & plate.

That obviously makes getting accurate positioning very tricky & i'm guessing a bit of a nightmare.

So I was wondering if something like this would be a better approach...grind out some notches on the end of the box section - sit the plate flat on the end, then tack weld into the gaps that were created by the grinding...this should help keep alignment more straightforward & accurate?


If i'm missing something here please fill me in...or I could be missing something entirely

[Clive S]

Could you not just make the green bit a bigger so that you can weld it from the other side to get your fillet weld ..Clive

[CraftyGeek]

Some of the joints extend on 2 sides of the box already - I guess it might be easier to tweak the layout slightly so they all do that.

[mekanik]

If you practice on some scrap bits with no gap between & try increasing the Amps so you get better penetration, or try a weld prep on both parts(ie 45deg chamfer)

[Gytis]

So I was wondering if something like this would be a better approach...grind out some notches on the end of the box section - sit the plate flat on the end, then tack weld into the gaps that were created by the grinding...this should help keep alignment more straightforward & accurate?

what if you weld some wire on inside face and use them like a spacers?,
or just grind the end plate edges to get weld in

[CraftyGeek]

Thanks chaps - adding a chamfer to the edges could be an option. I'm off work on Friday - I think i'll take a trip to the steel yard & see if I can get some scrap, then have a play with a few different approaches.

[mekanik]

Just a pity you didn't have a TIG setup, all you do then is strike the arc wait to get your pool and advance the torch, it make a very clean weld.

[mekanik]

If i were you i would try just putting a prep on the box section, leave the end caps with square edge, then when you lay down your weld you won't(hopefully) melt the outer edge of the blank and it will look a lot better, i am fortunate as i have TIG so can just fuse the two together.
Regards
Mike