DIY welded frame fixed gantry router build log

[ollied1981]

I thought I'd share my progress on a project that I've been working on for the last few months. I decided that I wanted to build a CNC machine capable of working aluminium. I have an RF45 type mill, but for me, the low spindle speed and limited Y travel make this not ideal for a conversion. I know you can replace the head with a high speed spindle, but I'd rather keep this machine as it is with the gearbox, still suitable for steel and manual work like using big diameter drills in steel.

It was pretty clear that I'd want a fixed gantry design because stiffness was more valuable to me than a very large working envelope. I thought for a while about using an old surface plate as the base, but given I wanted an X and Y of around 500 and 400mm, this would have needed a surface plate rather larger than the 24" square ones that usually turn up on eBay.

So I decided to go with a welded steel construction. I'm fortunate to have access to Solidworks through my day job so I used this to do the design work. Unfortunately I didn't take pictures of the various iterations but the current state of the CAD is like this:




My concept was to fabricate the machine in sections that could be welded, machined where necessary, and then bolted together in ways that would give enough adjustment to allow for the distortion from welding.

For the linear motion parts I went with cheap Chinese HGR20 rails and bearing blocks, and RM1605 rolled ball screws. I figured if these don't work well enough or last long enough I can replace them with Hiwin parts at a later stage.

The motors are all NEMA 24 hybrid closed loop steppers from stepperonline, driving the ballscrews via 15mm wide HTD toothed belts. The X and Y are 1:1 and the Z is 1.5:1 to help with the expected weight of the spindle.

The gantry itself is a 160x80x5 steel tube with a 60x60x5 tube welded to the back to make it into an L shape, and the rest of the frame is mostly 60x60x5 tube with some 30x30x3 for cross bracing.

A lot of the aluminium came from a large enclosure that came from the company I work for. The enclosures are meant to contain an internal explosion so they're very thick. It was a lot of work to cut the enclosure up and turn it into usable pieces, but I probably saved quite a few quid in metal. Also, the base of the enclosure happened to have a cast in pattern of ribs that I was able to fit between the bearing blocks, so hopefully this will make for a pretty stiff table.

So as to avoid making a super long post I've attached a few pictures of the progress so far and I'll attach more pictures in a subsequent post.

Starting with the Z axis:


Then the gantry:



Bringing the Z axis and the X axis together:



Hopefully this is all interesting to someone!

Oliver