Steel frame cnc router design/build

[JAZZCNC]

Jazz will now tell us how far out of square is acceptable and I will stand by to say "Told ya so!" when it all goes tits up

If you look again you'll see I mention 1-3mm.!!. . . Now let me ask you this Robin.! . . How many Steel framed routers have you built.?

I'll say it again just to be clear.!!. . So long has the welds are kept Short 1"-2" Max and Don't weld in one spot moving around the frame you'll be fine. Even just welding several short bursts and having a break to prevent heat form travelling if your unsure will help. . . . Remember it's DIY so there's no Rush it doesn't have to be done in same day.!

Is this a thick fast cure resin, medium/slow cure with additive/filler or some sort of putty that i've not come across before?

It's a 2 part putty paste called Milliput, see here Milliput - The epoxy putty with a thousand uses in modelling, DIY and industry
Comes in sausage shaped cellophane wrappers. Easy to use just mix equal parts in your fingers just like mixing Play-doh. Then spread on Clean dry surface and sets like concrete in about 6-8hrs, packet says 3-4 but I've found it's longer and leave over night. Leaves a super flat surface it can be tapped, filled and ground just like steel.


Here's Where and how I use it. It's also why steel or frame distorting slightly is no big deal.!!

Most of the frames I build are a mix of welded and bolted like these pics below. ( Frame only here no Bed, it's adjustable) At the joints and where top rail sits on plates is where it's used.
When I'm all finished and welding up then I bolt frame together to get an idea of how far off things are.? Most the time they are hardly off at all and just a quick grind or tweak of mounting plates brings it near enough to call Ok.!! . . . Some times shims may be needed.
Remember the rails being parallel and on same plane are the important areas and because the top rail is Bolted we have complete control and adjustment of this. It also doesn't get welded so NO distortion happens, just choose the straightest unbent piece you can find. (We have ways around bent rails has well but won't get into that now.)

Now in most cases after shimming or grinding true and square I could leave it at this but I don't. I go one further and disassemble again this time rebuilding with Epoxy putty at each joint with cellophane between to prevent sticking together.
This gives me about 1hr to set the frame square and true, Doesn't matter if the welded frame isn't quite square or plates not perfectly flat etc because the putty is going to take up any slack. . . . . So long has the shims from first assemble are used then All that matters is that frame is SET square and uprights vertical Now because Putty's going to fill any discrepancy and when it's set solid over night you have perfectly flat and true surfaces. The shims can be removed or set left into Epoxy.
Now where not talking 5 -10mm thick epoxy pads here, there often just wafer thin just filling voids etc.
Drilling and pinning the joints with dowel pins helps make sure everything goes back in same place and makes assembly easier.

Again the main frame being 100% perfectly square isn't overly important, it's the top rails that matter.!! . . Can't stress this enough.

Now what can be more of a pain to deal with is Twist of welded sections from distortion but again depending on design etc this can be got round. Often it's just a case of forcing the twist out by twisting in opposite direction, if twist is happening then you can often see it has your welding so stop and twist it back. This is also why spreading the welds around is important.
The bed is the main area you need to keep an eye on distortion and even then again Epoxy can be your friend if really bad and with a bit of Brute force and epoxy if need be then the Bed can easily be sorted to within a knats cock. When spoil board is surfaced then it will be Cock On.!!

Now here's what the scare mongers, who probably have never built a steel framed machine are not saying.? . . . If at first you don't succeed just grind the bastard apart and re-weld or re-set that's one of the beauty's of steel is it's flexibility for having another crack at it.