Living-room project... CNC !

twizzstyle · Post by **twizzstyle** » Thu Dec 06, 2012 2:08 pm

The only reason I didn't make my machine a full 4x8 was because of shop space

3x7 was the biggest I could fit without blocking my door.

Jekul · Post by **Jekul** » Thu Dec 06, 2012 2:34 pm

Looks like we all agree on the next "must - have" toy in home ski building...I think 3x7 is optimal for ski building. I know I could fit a 4x8 in my garage, but then my wife get's to park outside (I already do).

twizzstyle · Post by **twizzstyle** » Thu Dec 06, 2012 3:49 pm

I set expectations before we bought our house, that my building was a "shop", not a "garage", and she will never be parking a car in there

3x7 has been enough, but of course I always wish I had just a few more inches. It can get tight clamping things down sometimes.

ben_mtl · Post by **ben_mtl** » Sat Dec 08, 2012 3:33 pm

I know what you mean Twizz, when we bought the house last year I had a few "to have", one of them was a nice "large" detached garage or a price that would allow me to build one... the 2nd case happened so I spent my fist summer there building my workshop, it was an nice experience !

On the CNC : I received all my 8020 extrusions and "all" the hardware ... some of the screws ended up not being the right length (my fault) so I have to order some new ones...
The laser-cut part should be done by next week-end ! can't wait !

knightsofnii · Post by **knightsofnii** » Thu Dec 13, 2012 2:58 pm

did u buy the extrusions as a kit, or from mcmaster or somewhere else?

ben_mtl · Post by **ben_mtl** » Fri Dec 14, 2012 3:57 pm

I bought the extrusions from a local dealer (faztek.ca), it's the same as 8020 extrusions but it's cheaper and I saved the shipping costs. I selected the extrusions in their catalog and ordered only the lengths I needed + t-nuts. If I had to order again I would ask them to tap the holes (at the ends of each extrusion)...

Just got all the lasercut parts today... looking for a few hours of fun : tapping tenth of holes and assembling everything !

Total cost for the custom metal parts : 1000 CAN$... $400 of that is for the aluminum parts only (4 pieces).
I catched a couple mistakes I made on the parts (a few holes are too small, didn't account enough for the metal distorting while bending, things like that... nothing major but stupid rookie mistakes I could have avoided if I haven't been so excited..)

Jekul · Post by **Jekul** » Fri Dec 14, 2012 5:13 pm

Exciting! And that seams very reasonable for all of the metal.

ben_mtl · Post by **ben_mtl** » Sun Dec 16, 2012 1:44 pm

Gantry being assembled :

That's the time you realize Quality Control is not done for every customer... I had and sill have a lot of tuning to do on the parts. For now it's assembled but is not perfectly square... the Y rails are not parallel ( I tried briefly and understood it's not gonna be that easy...).

Anyway it's progressing and it's a lot of fun !

Jekul · Post by **Jekul** » Sun Dec 16, 2012 2:32 pm

Did you put in any dowel pins or high-tolerance alignment edges to help with the squareness?

Looking further it appears you had some aluminum stanchions machined, and then added some bent sheet metal for additional rigidity?

ben_mtl · Post by **ben_mtl** » Sun Dec 16, 2012 3:10 pm

I tried to stay as low tech as possible to keep the cost down. Same thing for high-precision tolerances : it's way more expensive !
The rails are the critical point of my design, the 45 degree bend it the weak point in terms of tolerancing and precision. I'm gonna enlarge the holes used to fasten the rails to the 8020 extrusion so I can adjust everything a bit more.
If I don't manage to get something OK I'll have 2 options :
- Have another set of rails machined / bent, I would probably go with 1-piece rails (with the 2 bends on the same part) like for the Z axis, as opposed to the 2 rails you ca see for Y... I would set some pretty tight tolerances on those parts !
- Change the rails design and go with some other commercial option... that would require changing a lot of parts on the machine... that would suck !

You're right about the uprights : it some 3/8" aluminum + bent steel for rigidity. My problem here is that the big 8020 beam has not been cut 100% square... that also suck big time and I'm gonna have to make some kind of shims so the uprights are square to the beam... I contacted the seller to see if something can be done ( = new part) but I don't have high hopes for that...

knightsofnii · Post by **knightsofnii** » Sun Dec 16, 2012 7:11 pm

i think any machine requires some "dowels" or shimming/adjusting to get it true when you get it assembled... i did a lot of research and checking forums etc and every single machine has its quirks to get it cutting perfect,

just get the thing together and operational... then work on the squaring of it all... sometimes the software can compensate for if say your machine is out a pinch, you can run a check to see how far out the cut is, and the software will make adjustments to compensate. no? Are you gonna use mach3?

ben_mtl · Post by **ben_mtl** » Mon Dec 17, 2012 8:26 am

Yes I'm gonna be using Mach3... i didn't really investigate on software compensation for "non-true" axis but I believe some squareness problems can be fixed.

Regarding the 8020 beam I'm thinking about bringing the beam to a machine shop to have both ends surfaced on a mill... it would make it a bit shorter but it's easy to add a flat shim instead of a wedged one... plus I can just ask "OK make it "original length - 1/8" and put a piece of 1/8" sheetmetal as a shim... that would be easy :p

I'll keep on assembling and keep a list of what need to be addressed before I commit to any solution.

knightsofnii · Post by **knightsofnii** » Mon Dec 17, 2012 12:18 pm

how wide is that gantry? and what motors did you go with, nema23 or 34?

twizzstyle · Post by **twizzstyle** » Mon Dec 17, 2012 12:29 pm

Mach3 has backlash compensation, but I don't think there is any compensation for things not being square - I could be wrong though. I've never really measured the backlash on my machine.

ben_mtl · Post by **ben_mtl** » Mon Dec 17, 2012 1:43 pm

knightsofnii wrote:how wide is that gantry? and what motors did you go with, nema23 or 34?

the gantry is 32in wide for a 24in travel on the Y axis. I went with NEMA 23 steppers \ G540 controller for now as it was easier/cheaper and that's what was used on the machine I took as a reference. If I see the steppers are not strong enough, switching to NEMA 34 won't be a huge modification.

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Living-room project... CNC !