[bullethead67]

Ok im racking my brains on this I have read posts where people are promoting belts then more where some have changed their machine from belts to chain and wre happier with it being stiffer. I am ready to buy parts but i dont know for sure what to buy. I have a light (50-75#) 8020 type gantry and i think i will use kellings 495oz steppers 3/8 shaft to a gearhead with sprocket attached. I intend to drive one side of the gantry with the stepper mounted on the table not the gantry

I have also read a lot on gearing and reduction. I am still struggling with it. I am trying for 360 to 400 ipm. So far I think I should use #40 ansi chain as it is common bicycle chain with sprockets. I am still not sure on witch sprocket to get or what gear head to put on the motor.

I intend to use this for both X and Y

Also the tensioner. I have found on Mcmasters a manually adjustable tensioner that i was going to get. It holds the idler sprocket that would be mounted to the other end of the bed. Seemed good at first but there is no spring tension, its just a bolt that pulls the sprocket in a slot then gets tightened up. Would this work loose or would stretch in the chain keep me constantly adjusting it? I also found a spring tensioner that would keep it tight its similar. it moves on 2 little linear guides and also has a sprocket wheel.

is this chain appropriate or should i be looking for something smaller to keep the mass down?

[Bowman]

ask the woman which she prefers. LMAO :devious: j/k I couldn't resist.

[samakthachai]

Hi All,
I am thinking to built my plasma table. I am puzzled if I use timingbelt or ballscrew to drive of each axis. Which type does it have accuracy and precision better? Who can advise me?

Cheers,
Samak

[bullethead67]

I was thinking a 12.5:1 or 15:1 gearbox not sure though. im still trying to find out what sprocket. I seem to be having trouble findinga idler that matches the drive.

Also the gearbox what is GN and GK. how do i know if it will bolt up to my stepper. I have been looking at plccenter dot com

[bullethead67]

samakthachai dont use ballscrews. plasma dust will either ruin them or keep you cleaning constantly.

[jcc3inc]

Sir,

I'm maybe a bit biased, but rack and pinion would be my definite choice! You can buy rack from www.stdsteel.com/gear.htm The cost of (2) pcs of 1/2 x 1/2 x 6 ft is about $23.20 per piece. This should be 20 DP, 20 degree pressure angle since this is stock. Get pinions of at least 18 teeth, to match the rack. Setup a pivoting arrangement on your motor/gearbox to hold the pinion into the rack. Have the pivot line set so that it falls on the pitch line of the rack. Choose a spring to load the pinion into the rack; the force required for 20 degree PA is 0.364 x the max drive force you will need. Thus if you want 50# max force, the spring must provide 50 x .364 = 18.2#.

If you're serious about making a machine, contact me and maybe I can send you some dwgs of some of this stuff.

jccinc-at-owc-dot-net

Regards,
Jack C.

[bullethead67]

I have decided to go with belts on this plasma table. I bought the table off ebay and its kinda an oddball design. Thats why i diddnt go for rack. Ill be doing that for my next table. The pulley dia is .875 and i will try 2:1 reduction. is it possible to get a double pulley design to use 2 belts to drive the x axis?