Build thread for my CNC Plasma Table

I am pretty sure there are overload protections built into the stepper drives, but I would want to put some carefully sized fuses in there anyway.

Looks great so far. Take your time and be thorough. It's easier to do it right the first time than take a shortcut and be unhappy later and rebuild it.
 
Charley! Dude. your'e getting there! Those lokk as though they'll carry the torch for ya.
Bob
 
Rack & pinion or chain drive?

Ordered my steel today and called to order the gear racks for my gantry tavel and Z axis but thought it was a bit pricey $216.00 shipped. What do you guys think about using chain?
 
I have no experiance with gantrys or cnc tables in general, buy the chain seems like it would be sloppy to me. I would not "cheap out" this early in the build, a specially with something that is the heart of the machine like this.
 
Although there are ways to spring load two thinned sprockets to minimize play, I don't think I would use chain. Perhaps there are precision motion chain that I don't know about. Try the gurus at the power transmission products distributors for an idea. I've used chain for a few things for motion, but never for any real precision. In fact, in the back of my mind, I'm cooking an idea to power feed my small manual SG. Air cylinders and chain + sprockets. Different topic though.
 
Charley Davidson said:
These machines use chain & are well built/accurate machines http://www.trucutcnc.com/
Click to expand...

Your resolution will be better with a rack...pitch on a sprocket will be .25 if you use a #25 sprocket.. If you use a 20deg. rack it will be like .157.


I think by the size of your table a chain drive will hinder your performance over time... Yes it can be done and chain drive will work, but I think you would be more satisfied with a rack & pinion setup, plus a rack would be more versatile and gear changes would be cheaper.

I looked at chain drive extensively before deciding to go with the rack & pinion.

Do some figuring of your resolution using chain and rack & pinion...
heres a great video..
http://youtu.be/6vY26CIrVwg

heres a good blog for calculations.. http://www.joshuaglenn.com/jgblog/index.php/2008/08/08/how-to-calculate-cnc-step-resolution/
 
I welded up the 2 long sides of the table today, almost got them completely finished and ran out of wire so I called it quits for the day. I did go get more and can finish tomorrow. I also picked up some short pieces of gear rack yesterday at the scrap yard to use on my Z axis. Hopefully I'll be ready to mount the linear bearing tracks on Monday. Pictures tomorrow.
 
Got the main part of the table all welded up now I need to mount adjustable casters & and design the internal part of the frame that holds the material being cut.

Plasma table (2).JPG Plasma Table (3).JPG Plasma Table.JPG
 
Charley, that's a very nice looking job, certainly something to be proud of.
Bob
 
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