started printing & looking for advice

ok …so i really like this MPCNC concept & i can see me making multiple of them. a CNC, a Plasma cutter & a larger 3d printer. not sure about a plasma build but hey ill give it a try. will probably melt the PLA. but maybe i could cast the 3d parts in alu?
i already own a cnc or a few lol :wink:
its the ebay 6040Z… a shenhui G350 laser. 7x14 mini lathe & well a couple 3D printers. so a CNC is nothing new to me & ive modded all mine a fair bit,
ive been planning on building a larger CNC for a while & i came across alteds design & been in love with it on the Price front for a few weeks!
your a top man alted & making it open source is just awesome! do you have a paypal for donations :slight_smile:

now about the design!

I want to build a larger bed CNC using this design with some modifications of course. I want to do a 1.5m x 0.75m build & its actually just for 5mm acrylic sheet.
the few things im thinking of doing are basically adding a mid brace to the outer tubes along the 1.5m long sections.

so im basically thinking of this for modifications overall

1’’ solid steel bar for the conduits.
larger pulleys & belts like T10’s with idler’s etc instead of clamping or zip tying.
mid braces along the 1.5m long length (welded) to Metal base frame & bar?
Nema 23’s with a 6 axis bob… will only use 3 of them & maybe add a fourth later… i want to use mach 3 & my tradititional solidworks & well i just know my around these to well & dont want to change.

the bob
pulleys & belts
I will also be remaking the Z mount for an acme ballscrew & will be using a 1.5kw spindle with a VFD.

this is just a basic idea & ive started to print the basic parts & will go from there. got the 4 corners done with clamps. 2 middle ends. 2 middle Z’s & printing the rest will be a few days.

any thoughts anyone on what else could improve it anymore?

Thank you for the compliments. if you are so inclined.

I need to make a FAQ now as this comes up a lot.

Acrylic is easy to cut, other than maybe bracing the 1.5m outer tubes I doubt you need any modifications.

1" is the wrong size, you would need to redesign the entire machine to fit. Every single piece.

Solid bar is only slightly stronger than tubular in a supported cantilever setup (, and negates its benefits with its added mass. Not to mention price.

23’s are over kill. If you are worried use larger 17’s. this uses 2 per axis one on each side overcoming most machines weakness of 1 sided pushing (try using a broom with one hand vs. 2).

You can use mach 3 if you prefer.

You don’t really need the BOB with this it is very easy to move by hand. Other machines are tedious to move hence the bob.

Acme z axis major benefit would be plunge speed, precision doesn’t seem to be an issue. downside, cost, redesign.

1.5kw spindle is overkill for acrylic, you could easily use a cheap dremel.

6mm gt2 belt has a working strength of 6.5lbs and a breaking strength of 125 lbs and there are 2 so double those numbers, why go larger? You would also need to ensure it fits or modify the drive train to accommodate a large belt.

Boils down to please try the machine as is before you modify anything I would wager that you will be more than satisfied.

thanks for that.

for 1’’ tube i meant 25mm. although alu & steel tube is in inches from my supplier. so its 25.4mm OD?
i was thinking of 303 stainless rods. thats all i can find at 25mm. a little pricey but should reduce wear.

I know the rest is probably a bit overkill & well ive decided to just try it with nema17’s… 86oz versions & the Gt2’s at first.
but i will still use the bob & spindle/vfd setup. thats just my own preference really.
I will probably end up beefing it up though with 23’s & better pulleys just to see if it can run faster :wink:

ive ordered the bob/steppers/bearings/bolts etc.

just need to buy tube or rods now & sort out the spindle setup.

do you have any idea on what the max feedrates you are running for acrylic? like whats the max DOC & stepover etc.
i want this to be as fast as possible so just forward thinking.

I’ve been working with industrial CNC plasma cutters since for a ridiculously long time (circa 1993). Sure, you can easily generate temperatures in the range of 50,000 Kelvin but be aware the process is a total EMI nightmare and it only works on conductive materials. To get a predictable result you also need an adaptive height control that continuously senses the arc voltage and adjusts the Z axis accordingly.

If you do decide to go down that road please be extremely careful because even hundred or so mA of DC current is lethal.

@ MrMach3: You started an interesting posting 6 months ago on some system improvements you were going to make to a your cnc. Just wondering how that went, and if you had any componant/design recommendation you might be willing to share. I’m especially interested in hearing about your results with the linear bearing/rods.