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View Full Version : 1st CNC Router: Overwhelmed - Some advice please?



wallyblackburn
23-09-2017, 10:53 PM
I'd like to build a smallish machine that can cut shapes out of wood up to 3/4" (19mm) or so. Doesn't have to be in one pass. Accuracy only to "woodworking specs" - 50 thou would be awesome. That's it!

For this version, not really interested in cutting Al or the like. Not interested in 3D carving. I'd mostly like to be able to CAD up templates and cut out for use with a manual plasma cutter. And then make progressively more capable machines and learn, learn, learn.

I am learning Fusion 360 via YouTube vids now too.

I've looked at so many designs and build logs that I'm quite overwhelmed. I have some 2" square steel tube with 1/8" wall thickness that I thought I'd use. Since I am pretty flexible on size and such, I am considering the following guides and ballscrews, and then building around them:

http://www.ebay.com/itm/USA-Square-Linear-Rail-400-700-1000mm-Ballscrew-1605-400-700-1000-BK-BF12-HGH20/162674684089?_trkparms=aid%3D222007%26algo%3DSIM.M BE%26ao%3D1%26asc%3D47507%26meid%3De5f9957221ff44a 1a854a195f8457371%26pid%3D100011%26rk%3D4%26rkt%3D 12%26sd%3D272842580129&_trksid=p2047675.c100011.m1850


I'm fairly tooled up:
Bridgeport mill
14" South Bend lathe
MIG welder
Plasma cutter
Bandsaws, grinders, etc.
Woodworking equipment

I'm a decent hobby machinist. A beginner welder (but, hey, it's MIG). A decent woodworker. Comfortable with computers and electronics. I'm frugal but not cheap.

Thanks,
Wally

routercnc
24-09-2017, 09:52 AM
It is no problem to build a DIY machine to meet those needs. 2" square box is a fair start for frame but note that the 1/8" wall is a bit thin where you need to mount the rails. Usually you would add a 5-6 mm strip of metal on the inside to reinforce the mounting point and get a decent length of thread engagement. Also if the gantry is made from this it should really be multiple sections joined together (i.e. single 2" box is not large enough to create the beam).

That kit of linear motion parts you linked to is a good all round set of sizes for X, Y and Z, with 20mm rails etc, but the pitch of the ballscrews is only 5 mm. I have that pitch and it is ~OK, but starting again for wood working the advice is go for 10 mm. You could email them and see if they have 1610 instead of 1605 ballscrews. This gives you the speed you need for wood. You might think that you can add a pulley ratio and drive the ballscrews twice as fast but then you are in danger of the ballscrews whipping (the long ones anyway) due to the higher rotation speed.

For machine designs there is the fixed gantry style and moving table (which is very rigid but requires lots of space) and there is the moving gantry type which gives a much large working space for a given footprint.

The moving gantry type is generally use for wood working. This can be split a bit more into frame gantry where the gantry has sides dropping down to the bed:
22870
(c) Dean/Jazz

and beam gantry, where the bed is raised up to give more stiffness but can limit access for sheet feeding onto the machine:
22871
(c) Clive

On this forum we would usually recommend the beam gantry because of it's versatility (extra stiffness helps for aluminium cutting), but strictly for what you want to do the frame gantry would be fine.

If you post some sketches, even hand drawn and scanned in if F360 skills are not ready yet, then you will get more detailed advice from this forum.

Finally, here is a link to the finished machines gallery to get you going:
http://www.mycncuk.com/threads/10066-Finished-builds-picture-menu

wallyblackburn
24-09-2017, 02:28 PM
Thanks! I will check with seller for 1610 ballscrews. I think I'll also see about adding another long one because I can't really come with a design in my head that wouldn't need one on each side and still be stiff enough.

I'm starting to get the hang of Fusion 360, so I will try to get some initial sketches up this coming week.

Regards,
Wally

wallyblackburn
25-09-2017, 02:40 PM
1610s would have to come from China. Based on what I've been reading, if I need to have shipped from China, I'd likely go with BST Automation. I'm going to look over their stuff.

Would a pre-fab z-axis like this from BST be usable for wood machine?

https://www.aliexpress.com/item/SFU1610-Ball-screw-Driven-Linear-Module-System-300mm-Stroke-Linear-Stage-Table-for-CNC-X-Y/32823716914.html?spm=2114.12010108.1000013.4.13efc 3dbkshav7&traffic_analysisId=recommend_2088_2_89359_shotall&scm=1007.13339.89359.0&pvid=dfd235b1-6689-45d0-981d-54201f1ec0bd&tpp=1

Would sure save some time, and the price is great.

Thanks,
Wally

Clive S
25-09-2017, 03:58 PM
Would a pre-fab z-axis like this from BST be usable for wood machine?

In a word no. But if you only want to cut to within about 2-3 mm it might do it. Don't forget you need to mount a spindle on it.

wallyblackburn
27-09-2017, 04:40 PM
OK, ditching any thoughts of pre-fab Z-axis for now - thanks Clive.
Been slogging through learning F360...whew! Finally got a first shot at the X-Axis base:

22882

I said it was a 1st shot... Anyway, here is my thinking:
I can cut the cross braces on bandsaw and then use mill to true ends up and make them square and same length. Then, I have a really nice Strong Hand jig to clamp them at right angles to side beams. I was then thinking of mounting linear profile guide rail on sides.

How much of a shot do you think I have of getting the 2 side beams parallel and coplanar enough that I won't have binding? (If I am even explaining this well enough to begin with) I could mount one side rail carefully, and then rig up a temp gantry to use to get the other placed - then pin it and tack weld.

Also, I jumped the gun and ordered a set of these:
http://www.automation-overstock.com/proddetail.asp?prod=SH350756GLC2W01P63&cat=146

with plans on using them for this axis. Dumb question: is this X or Y?

Thanks,
Wallace

Nr1madman
27-09-2017, 05:35 PM
Hello Wallace!

How do you plan to join the parts? Weld?
Welding can distort the frame alot..

If you want it to work without binding then you can use epoxy selflevelling or shim the rails. Shimming might be a big job with much trial and error :)

Skickat från min SM-N910C via Tapatalk

wallyblackburn
27-09-2017, 07:22 PM
Yes, welding. My hope is that between the clamp and going slow I can avoid too much distortion. We'll see.

Yes, I've been looking at the epoxy options. I guess I'd move the rail to the top of the beams for that.

Thanks,
Wallace

wallyblackburn
28-09-2017, 08:42 PM
After carefully milling end to be square and make pieces equal length, I can tell when clamping them up that, distortion or not, there's no way these will be flat and square enough. Sure many out there could've already told me, but steel like this just isn't clean enough as is.

There's a shop close that has huge Blanchard grinder and would grind for reasonable price. But, I think if you start grinding on this stuff it's going to spring all over the place as stresses get relieved.

Time to start reading up on epoxy!

Regards,
Wallace

wallyblackburn
01-10-2017, 04:17 PM
Welded up the base and added legs.

Milling ends to be square and even:
2289822899

My Strong Hand jig. Very handy for getting things square:
22900

So, here's where I'm at now:
22901

Got these for X (Y?) axis. They are 35mm NSK and 756mm long:
22902

These things are beasts! Weigh about 25lbs. each.

So, here are my next decisions. Any advice appreciated:

- Putting another 2" square tube on top of existing ones for added stiffness. I can either mount rails on top (using epoxy to level), or mount rails to sides and use bolts for tubing to provide adjustment for parallelism. Leaning towards welding tube on and using epoxy...

- Using only one of the trucks per rail. Given the size of these, would that work?

All for now. Thanks!
Wallace

Going to add leveling feet today.

m.i.k.e
01-10-2017, 06:29 PM
Hi wallace,
Are the linear rails and bearings new or s/h ?

mike

wallyblackburn
01-10-2017, 11:02 PM
New. Automation Overstock has some NSK stuff they bought as surplus and it is priced low:

http://www.automation-overstock.com/products.asp?cat=146

I got both rails and 4 trucks for $199US.

Regards,
Wallace