Kentucky rookie

[J0nesy]

Finally got my plasma table making sparks after tinkering with it on and off for 5 years. This site is consistently in my search results when trying to figure out an issue, so I figured I would sign up so I could learn some more.

As most home built tables are, mine is a frankenstein machine. Pretty sure I need to redo some stuff but I'll get to that in a minute.
Specs:
48x66 cutting area
Gecko G540
Dual Y axis motors Nema 23 300 oz-in
Single X axis motor Nema 23 300 oz-in
CNC4Newbie z axis assembly with Nema 23 156 oz-in
Custom floating Z axis with touch off switch
#35 chain for drive
water table

Mach 3
Sheetcam

After running several test parts I've come to several conclusions. My Y axis motors are not big enough to handle the acceleration needed. And the chain drive was a poor choice and I will be upgrading to rack and pinion for both X and Y axis. Considering the Avid CNC components with the 2.73:1 gear reduction drive.

[adbuch]

That's an interesting looking setup. Nice job on your build! This is the first time I have seen the chain drive used for both carriage and gantry. I like the AvidCNC stuff. I have one of their Pro4848 tables (for wood routing/engraving) and I am very impressed with the Nema 34 motors and drives.
David

[acourtjester]

Welcome aboard, great to see more DIY types here. I would agree on the increase in stepper motor size. I have used chain drive for my X and all the tables I built and is also used on table built from my plans. I think you are using the convention of the X being the motor on the top of you table, I use that as Y. With that being said my X uses chain and has a Nema 34 motor with a cross table drive shaft driving both sides together. I also support the chain with a shelf under it the stops any flopping, it also make the chain like a rack drive. I agree with the rack for your X and more gear reduction for the drive assembly for both axises. The smallest motor I use is a 425 nema 23. I am not saying I am right but it has worked for me and others very well. Do some research and find solutions you can use and make changes as you see fit. you have a great start.

[J0nesy]

Welcome aboard, great to see more DIY types here. I would agree on the increase in stepper motor size. I have used chain drive for my X and all the tables I built and is also used on table built from my plans. I think you are using the convention of the X being the motor on the top of you table, I use that as Y. With that being said my X uses chain and has a Nema 34 motor with a cross table drive shaft driving both sides together. I also support the chain with a shelf under it the stops any flopping, it also make the chain like a rack drive. I agree with the rack for your X and more gear reduction for the drive assembly for both axises. The smallest motor I use is a 425 nema 23. I am not saying I am right but it has worked for me and others very well. Do some research and find solutions you can use and make changes as you see fit. you have a great start.

Thanks. I'll have to search through some of your posts to find some pictures of your chain drive. I'd like to make the chain work if possible, but a couple friends have me convinced that it is the main issue with my table. I'm for sure going to upgrade both motors on the gantry to the 420 nema 23's. Might start there, as well as try to trim some weight off the gantry.

[J0nesy]

That's an interesting looking setup. Nice job on your build! This is the first time I have seen the chain drive used for both carriage and gantry. I like the AvidCNC stuff. I have one of their Pro4848 tables (for wood routing/engraving) and I am very impressed with the Nema 34 motors and drives.
David

Chain drive idea originated several years ago before I knew the little I do know about linear motion. Also was picked since it was a cheaper route that the rack and pinion at the time. This is very much a budget build. The only things I spent good money on is the plasma (Hypertherm 45xp), Z axis unit and the Price THC kit. All the aluminum, linear guides, cable ways and several other components were scrounged out of the scrap bin at a previous job. Gecko, computer, and software were bought used off craigslist.

Besides the mounting, what else would I need to change to upgrade from 23's to 34's?

[acourtjester]

Here are a few images showing both the chain and rack drive I use, and I will send you a PM from here with other info.
Excuse the Pink the lady I built this table for wanted it, Those images show both sides of the chain drive. I also have adjuster on both ends of the chain drive for adjusting for square alignment of the table.

[N2 Welding]

Tom, I like the idea of chain drive gantry’s “ cost effective “ and see here that you incorporated a through shaft like I had inquired about previously to get away with using only one controller port, driver and one motor to drive both sides of the Y axes.

My concerns here with chain drive:

#1 Does the chain rust out and eventually lead to binding and or causing the gantry to become out of square or cause rubber banding issues from uneven kinked chain links that would show up in cut quality?

#2 Other concern is controlling end play or backlash. Do the chains stretch over time/usage and cause issues similar to concern #1 with out of square gantry or poor cut quality from too much slop in the chain? I see you have ability to adjust chains on both sides.

#3 sprocket teeth and chain wear. Do the sprockets and chains eventually wear out needing replacing. Estimated hours of use prior to needing replacing?

[Joe Jones]

I cannot imagine that the forces of a cnc machine would stretch the chain. Backlash? Well, that is a matter of a thumb wheel to tension the chains. Sprocket wear would not be a concern. The chains are made to take many hundreds of times of pressure that a cnc machine can produce.

Joe