Big-ish router concept review

[Boyan Silyavski]

Rotating nuts are the correct choice for that size. 2020 screw is small for the long axis / according to me/ . I used on mine 2510 and rotating nuts. 400w servos are just the right choice in that case.

Bolts? Mehhh, for that size. It will be difficult enough to level everything and bolts will lead to the everlasting suspicion if sth has not moved. You can use bolts and pins, but anyway, my advice is weld it.

1.8 kw is small for that machine. 2.2kw as minimum, 3kw better.

Maybe read my second build log so you will get all the info there on 2600x1300x200 machine.

Again- for such a big machine to be precise, its not a small feat. Dont start the build before informing yourself. You will see that i have spend 3x 200 euro on epoxy before i learned 100% how to make it properly. its one thing to think that you have made it properly, its another thing to compare it against 2m straight edge and dial indicator.

There are only 700kg in my machine frame and it will stand on 2 or 3 legs without any distortion or twist / less than 0.05mm measured/ . Gantry weights 180 kg and flies 20m/min at 3000cm/s2 accelertation. Its not absolutely necessary to make the Z like mine overbuild, but gantry must be similar for perfect aluminum finish.

That frame you show is at the most for foam and wood. Not aluminum. Its incredible how shaky and bendy become things the longer they are. a piece of steel that 2 people can not bend at 1m at 3m you can bend with one finger.

[mbele]

Hi Boyan, thanks for the reply!

I'm still at the concept phase...

For the long axis, I figured that 3232 screw pre-stretched between 2 BK mounts with 20:48 reduction could maybe work, screw would turn 330 rpm to get to 10m/min (i think that's below critical speed), and 2048ppr encoder would then allow 0.001628mm/pulse.
It's just that I'm trying to get by with the low rpm/high torque motors I already have (I would also have to reduce moving weight). Rotating nut would be better but more complicated and probably more expensive solution. And I'll probably end up doing it "your" way after all, but I want to check all the options before investing.

I saw bolts and epoxy putty(eg. jb weld) leveling method in "principles of rapid machine design", so I assumed it worked fine.

1.8kW is what I already have, and I haven't ran into problems not having enough torque (it gets to max at 12kRPM).

I read your build threads, and I was amazed :) Thank you for sharing all the info, it's invaluable resource. Without the epoxy leveling solution you've adapted for your machine I wouldn't even think about making something this big.

Since the space is not a problem, and machine will not move, I'm thinking about pouring concrete foundation(frame) and ditch the steel frame completely, so there will be no overhangs and unsupported parts at the base.

I'm also considering aluminium gantry to reduce weight, same outer dimensions but with thicker walls and ribs, made of 250x10 plate screwed and glued together.

I will draw the complete machine with all the features, and when/if I'm sure and happy about all the details, I'll buy what's needed.

Thanks again for looking at it!

[Boyan Silyavski]

I think you are mistaken about the spindle. Ideal speeds with most of the most popular bits are 16k-24k.

[mbele]

I think you are mistaken about the spindle. Ideal speeds with most of the most popular bits are 16k-24k.

Again, I should have been more clear in what I'm writing... sorry. Spindle reaches max torque at 12kRPM, but it can spin up to 24kRPM:
https://www.damencnc.com/en/milling-...rospindle/1226
It works well with both alu and wood. With constant TEA paths and smaller TiAlN coated endmills it has enough torque for light work in steel (min. 6kRPM), but I don't do that often since the machine is not rigid enough.