Time for mk2 upgrade!

[routercnc]

Brief update on progress, with more photos ....

Ballscrews machined and fitted. Spindle bracket complete and fitted. Stepper mounts complete and fitted. Energy chain support rails still to do, plus end pieces of baseframe, limit switches, and base plate to fit. Also water cooling system to buy and install.

Jogged the axes around yesterday and all move well

May upgrade gantry sides to aluminium, but I'm mainly cutting balsa and lightply so we'll see how it goes.

Already thinking about version3 :exclaim:

[GeorgeD]

Do you get any gantry side shake with using a roller bearing slide like that?

I was told that the lower the gantry the less side movement and a more precise cut using the linear rail system.

[routercnc]

Hi George,

I've not finished it yet so not cut anything, but . . .

If you mean translating sideways, then none at all. What I've tried to photograph (but it's not eay to see) if that there are a pair of roller balls in plates on the side of the gantry legs, which run against the side wall of the aluminium extrusion. These are the types used to support big sheets of wood or steel and provide a friction free rolling surface, or they are used to push cargo boxes onto planes. On one side they are fixed rigidly to the leg, and one the other side they are pre-loaded by means of two bolts so that the base frame is hugged by the legs. Does this make sense?

If you mean flexing, then even though the sides are 2 x 18mm ply, I can flex them by pushing quite hard. But given that I'm cutting liteply and balsa, I think this will be OK. I've done some calculations to show that if you want to reduce the sideways flexing (due to gantry legs bending), without upgrading or changing anything else, you can significantly reduce it by simply lowering the ballscrew in Z. If you put it down at the same level as the cutting tool, there is no bending load on the gantry sides at all, only translation loads which are reacted by the side bearings. I've got it all on a spreadsheet which I may post when I'm happy with it.

As you can see on my current design, with the ballscrew right at the top, I worked this out after much of the construction was done! Next time though . . .

Lowering the gantry height would help, but I want the clearance to the workpiece if I want to do other jobs.

If you can afford it profile linear rail is about the best there is I believe. Next best is probably supported rail, and way down is running bearings onto the ali section. But it is a big step up from the unsupported 1200mm rail that I had before, so making progress.