DIY/Building CNC Plasma questions

Share and learn with other DIY members who have built their own plasma tables and accessories.
Post Reply
gamble
4 Star Member
4 Star Member
Posts: 950
Joined: Thu Jan 02, 2014 6:33 pm

DIY/Building CNC Plasma questions

Post by gamble »

Playing with the idea of building my own table since nobody makes a decent 2x4 that I found

How do you calculate size motors for top speed, acceleration?
For a rack/pinion setup, is there any advantage to using a helical vs straight cut? And how do you figure out how many teeth are ideal on the gear?

Was thinking of a direct drive instead of a gear reduction due to cost and it seems to work well for lots of other companies like premier, wright, plasmacam, and a few others

Working on making my own brackets for the bearings. Have one made but not crazy about having slotted holes for bearings. They keep sliding around so may switch to a single hole
Any help is appreciated.
Torchmate 2x2 - Flashcut
Powermax 45 - Machine torch
Taig CNC Mill - Flashcut
Razorweld Distributor
User avatar
acourtjester
6 Star Elite Contributing Member
6 Star Elite Contributing Member
Posts: 7770
Joined: Sat Jun 02, 2012 6:04 pm
Location: Pensacola, Fla

Re: DIY/Building CNC Plasma questions

Post by acourtjester »

PM sent from here
DIY 4X4 Plasma/Router Table
Hypertherm PM65 Machine Torch
Drag Knife and Scribe
Miller Mig welder
13" metal lathe
Small Mill
Everlast PowerTig 255 EXT
Rodw
4 Star Member
4 Star Member
Posts: 780
Joined: Sun Aug 21, 2016 1:49 am
Location: Brisbane, Australia
Contact:

Re: DIY/Building CNC Plasma questions

Post by Rodw »

I wrote this Plasma CNC Primer document which is part of the main documents for Linuxcnc
was written with the new plasma table builders in mind and actually answers many of your questions.
http://linuxcnc.org/docs/devel/html/pla ... revolution

So in answer to your questions:
1. I settled on 269 Oz/In Nema 23's but upgraded to small Nema 34's for convenience as I found some cheap prebuilt 5:1 belt drive reductions for that frame size. One of the experienced builder on Linuxcnc reckons Nema 17's are the way to go.
2. I have both helical and straight gears on my machine. The helical gears are much smoother and nicer. I will never use straight gears again.
3. The ideal travel is about 15-25mm per revolution. Mine are about 30mm and work fine
3. I did a fair bit of experimenting to determine the maximum velocity and Accelleration for my machine and I built all the gantry to be lightweight.
4. Direct drive does not put stepper motors in their optimum operating parameters. You will find it is a mistake!

Reduction derives are not that hard to make if you have a lathe. ThIs thread I raised when I first started prompted me to build 3:1 reduction that bolts onto a Nema 23 mount to replace my original direct drive design.

https://forum.linuxcnc.org/30-cnc-machi ... ve?start=0

This is what I ended up with using a couple of normal ball screw bearings plus a shaft that follows the normal ball screw dimensions for bearing journals
reduction1.jpg
redction2.jpg
reduction3.jpg
reduction shaft.jpg
So basically the pinion shaft is assembled in the bearings as if its a ball screw.

You currently do not have access to download this file.
To gain download access for DXF, SVG & other files Click Here

robertspark
4.5 Star Elite Contributing Member
4.5 Star Elite Contributing Member
Posts: 1806
Joined: Mon Jun 12, 2017 6:43 pm

Re: DIY/Building CNC Plasma questions

Post by robertspark »

gamble
4 Star Member
4 Star Member
Posts: 950
Joined: Thu Jan 02, 2014 6:33 pm

Re: DIY/Building CNC Plasma questions

Post by gamble »

belt driven is not even a consideration for me
Torchmate 2x2 - Flashcut
Powermax 45 - Machine torch
Taig CNC Mill - Flashcut
Razorweld Distributor
Rodw
4 Star Member
4 Star Member
Posts: 780
Joined: Sun Aug 21, 2016 1:49 am
Location: Brisbane, Australia
Contact:

Re: DIY/Building CNC Plasma questions

Post by Rodw »

gamble wrote: Tue Aug 06, 2019 3:38 pm belt driven is not even a consideration for me
Thats what I thought. I could not see it would last long with a few sparks around
robertspark
4.5 Star Elite Contributing Member
4.5 Star Elite Contributing Member
Posts: 1806
Joined: Mon Jun 12, 2017 6:43 pm

Re: DIY/Building CNC Plasma questions

Post by robertspark »

think you're a bit wrong there, I've had no problems with belts (HTD 5mm, steel wire reinforced).

Its where you put them and how you plan your design.

What I run is very similar to this,
https://www.picclickimg.com/00/s/NTI1WD ... x2-_57.jpg

with belts in place of the rack on the outside of the machine, works fine + its cheap to replace anything on my table, not a worry. I think I'd be more reluctant using hwin rails with grinding dust

a 2x4 table is a tiny table,

each to their own YMMV
Post Reply

Return to “DIY Plasma Table & Accessory Discussion Forum”