Living-room project... CNC !

Jekul · Post by **Jekul** » Mon Dec 17, 2012 5:27 pm

Are they gearmotor steppers (motors with built-in gearboxes) or just steppe motors? If they latter, how much did you have to gear down?

ben_mtl · Post by **ben_mtl** » Tue Dec 18, 2012 4:20 am

Those are regular stepper motors.
For the X axis (Rack & pinion) I have a 2.73:1 reduction ratio thru this.
For Y (5-start ACME rod) and Z (single-start ACME rod) it's a direct drive.

Jekul · Post by **Jekul** » Wed Dec 19, 2012 12:14 pm

Did you do any torque calculations, or rely on the work done with the slightly smaler design? I'm not sure how to measure/estimate the lateral cutting forces.

ben_mtl · Post by **ben_mtl** » Wed Dec 19, 2012 3:38 pm

I've been lazy and just was satisfied with what I've seen on the smaller machine (my gantry is the same size as on the "smaller" machine...) only difference is I have the added weight of the steppers on the gantry as I went with rack&pinion instead of ACME screw...
Twizz is also using NEMA 23 on his steel machine.. and anyways I wanted to keep it "lowish" cost so NEMA it was !

twizzstyle · Post by **twizzstyle** » Wed Dec 19, 2012 4:35 pm

Yeah I've got 495 oz-in nema23's on my machine, they've been good so far! And my gantry is HEAVY!

Jekul · Post by **Jekul** » Thu Dec 20, 2012 6:37 am

I think rolling resistance and cutting resistance or probably more critical than gantry weight. I can see having some interial problems if you're doing high rates of accel or decel. But once the system is moving the inertia portions are quite small in the calculations.

Jekul · Post by **Jekul** » Tue Jan 01, 2013 10:39 am

Guys,

I found a guy selling a pre-fabbed Bosch RExroth Y-axis on craigslist. He wants $400 USD for the 1.7meter long axis with 6 additional pieces of T-slot aluminum and a box full of connectors. Is does NOT include a motor and drives but does have the drive mechanism integrated.

I think it's a decent price, but wanted to get another opinion or two before pulling the trigger.

Feedback is appreciated.

ben_mtl · Post by **ben_mtl** » Tue Jan 01, 2013 1:46 pm

I'm really not familiar with that.. sorry I can't help you on this one.

SHIF · Post by **SHIF** » Tue Jan 01, 2013 2:05 pm

Jekul wrote:Guys,

I found a guy selling a pre-fabbed Bosch RExroth Y-axis on craigslist. He wants $400 USD for the 1.7meter long axis with 6 additional pieces of T-slot aluminum and a box full of connectors. Is does NOT include a motor and drives but does have the drive mechanism integrated.

I think it's a decent price, but wanted to get another opinion or two before pulling the trigger.

Feedback is appreciated.

I use Bosch extrusions and linear bearing components in my professional life, they are top-notch products. This deal you found is an excellent price, jump on it.

-S

ben_mtl · Post by **ben_mtl** » Sun Jan 27, 2013 3:45 pm

Finally some progress on the machine !!!

I went and picked-up the new rails for X and Y, quality is second to none compared to the company that made the previous ones... It was worth the (super-long) wait !

I managed to spend a few hours in the shop over the week-end and I finished the basic assembly of the machine. Of course it will require a complete tune up to square and true all the axis but at least I have that big toy I can plug on the computer !

Here's the latest picture :

Next step (tomorrow) will be the real test with the machine controlled by the computer, then a preliminary tuning (squareness and that kind of stuff), then send all the steel parts for powder coating ! "Pimp my CNC" style !

Meanwhile the router mount will arrive (ordered it from CNC RouterParts) + a couple small items.

knightsofnii · Post by **knightsofnii** » Mon Jan 28, 2013 5:25 am

is this a 2x8? i think i'm gonna go 2x8 just because if i go 4x8 then the nema23's apparently get bogged down, plus i could use that extra 2x8 of square footage for my shop!!!

amidnightproject · Post by **amidnightproject** » Mon Jan 28, 2013 5:39 am

Man so jealous!!

ben_mtl · Post by **ben_mtl** » Mon Jan 28, 2013 5:59 am

The footprint is 3'x just under 8', theorical machining area is 2' x 7'. 6in travel on Z.

For now I have NEMA23 steppers.. if it's not enough it won't be a huge re-work to fit NEMA 34.

amidnightproject · Post by **amidnightproject** » Mon Jan 28, 2013 6:09 am

ben_mtl wrote:The footprint is 3'x just under 8', theorical machining area is 2' x 7'. 6in travel on Z.

For now I have NEMA23 steppers.. if it's not enough it won't be a huge re-work to fit NEMA 34.

I think that's a perfect size. I've been toying with the idea of building something similar. 4x8 is just too big for my space.

If you don't mind me asking, what's your total build cost so far? (you can PM if you want).

I'm trying to stash money away to build one for next season.

ben_mtl · Post by **ben_mtl** » Mon Jan 28, 2013 6:35 am

For now I'm a bit over $3000... but I had a few parts that I had made twice (some for my mistakes, some due to super-loose tolerances in the manufacturing). + a bunch of screws and smll items from McMaster that I bought but won't need...
I think I'll be at $3500 at the end (not incuding the computer and the software).

I'm pretty sure if I had to build a new one, from what I learned and what not to do I would get it for $2500 max.

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Living-room project... CNC !