[elfen]

Hi everyone,
I’ve been looking around trying to find a good way to make a small cnc on the cheat and yet get good results. I pretty much like the KRMX02 design, and I thought maybe if it were made smaller (12”x12”cutting area), there could be a way to make something affordable and yet rigid enough for wood, plastics and small alu milling.
I’m droping this here because I want to get some input before I get too far with this winter time-killing project…!
Here is the basic of what I came up with:
Attachment 259114
Attachment 259116
You can see I would use 1515 extrusion for the cnc, 1010 extrusion at the bottom and ¼” cold rolled steel.
Here is a closer view at one of the linear carriage:
Attachment 259118
Cncrouterparts linear carriage are 35$ each and I wanted to keep the price down so I came down with this. What do you think? Yay or Nay?
So far that makes for 220$ of extrusion, something like 75$ of cold rolled steel and 81$ in T-slot joining plates (which sounds like more money than just using metal angles and plates, but I don’t know what thickness and size would be enough…).

So:
-Does it seems as a good idea or not?
-Will be rigid enough?
-See some design flaws?
-Ways to make it cheaper without too much effort?
-Feel like it’s worth throwing around 500$ in it?

[Eldon_Joh]

If you spend a lot of time with layout dye you can grind cold rolled steel to be flatter than those aluminum extrusions.

For 500$ you can buy a lincolin 225 or other cheap welder off craigslist and make a bigger machine from steel.
then pour a 1/8th inch thick layer of epoxy on top and scrape it flat, then bolt rails on it, or your hand scraped cold rolled steel plates.

alternatively you can cast the base from cement, then pour epoxy on top, it will level out.. then bolt the steel to the epoxy.

[elfen]

I'm a bit late for some answer Eldon, but let's just say I prefer bolt-on than the soldering learning curve for now.

Anyways, got back to the drawing board and came out with a better made/looking solution using 10 series extrusion. I'm just not sure if I should use 2020 or 2040 for the x axis, considering the x axis extrusion is 30" wide, with less that 20" unsupported. I'm seeking input from anyone having some experience and that might want to share it.

From the looks, I prefer 2020:
Attachment 272370

But 2040 might provide a more reliable solution (less prone to twisting?):
Attachment 272372

Feel free to comment/review.

I can provide more details if someones show interest.

[elfrench]

The rectangular blocks will be about as stiff as a wet noodle Consider adding flat plates on both sides to form a torsion box.

[elfen]

stole the idea from fineline automation and it seems to work just fine:
https://www.finelineautomation.com/p...x-4-cnc-router

I scaled it down to 3/16" x 2" x 3" steel tubes which i don't think would bend, but I could always go up to 1/4" thick steel.

[streetrodlover]

stole the idea from fineline automation and it seems to work just fine:
https://www.finelineautomation.com/p...x-4-cnc-router

I scaled it down to 3/16" x 2" x 3" steel tubes which i don't think would bend, but I could always go up to 1/4" thick steel.

Fineline's risers are turned a quarter turn every block to help with the flex and twist.

[elfen]

Well spotted I'll fix this!

[elfen]

Attachment 272874
How about this?

[elfen]

Decided to put 4 steel tubes on each sides, looks better this way. I think i pretty much figured everything on and, unless someone sees something wrong, I'll probably start buying parts this week.
Attachment 273338

[pierantoine]

Hi,
1 - you should lengthen the horizontal main gantry profile to be the exact length of the gantry this way you could add a plate at each end to limit twising instead or in addition to the little folded part you use.
2 - you may increase the section of the profile regarding the Z excursion you seems to have or using 2 aluminium profiles.

take a look at : Jazzcnc