marker pen driven over an 8x4 sheet help.

[wiatroda]

Totally agree with JAZZ .
If that's going to be pen only there is no point to mess with ballnuts and screws. Belt is defenetly a way to go. I wouldn't drive it directly but made some reduction, but of course direct drive will work as well.
eg belt 3M pitch belt driven with 15 tooth pulley gives you 45 mm of axis movement per revolution of driving pulley. Reducing it further 5x gives you 9mm/rev. Driving it with stepper (after reduction) @1/2 step (400 steps/rev) gives you 0.0225mm resolution. I think its enough for your boat drawing or even for cutting
Driving it directly with 15 tooth pulley @1/2 step will give you 0.1125mm resolution
Just some example calculation -hope it helps

[NB70]

Here's a simple and cheap large format plotter:



Build instructions are here:

http://makezine.com/makeitlast/

http://blog.makezine.com/archive/201...r-drawbot.html

[blackburn mark]

ive read some of the other posts and the talk is very technical is this kit above simple enough for a novice like myself, i have rebuilt engines but electrical jargon is scary to me ,but i can follow instructions well, should i bow out gracefully i wonder.

hi Danny, the reason i bought this kit was because its cheap and like you im not to handy with the electrickery
i just followed the instuctions thay came with it and i was up and running, im not saying its simple but with those instructions and this forum you will get through it if your willing to stick at it and push on to the end

using timing belts is a winner of an idea to keep the price down
i get mine from here
http://www.beltingonline.com/polyure...5toch08jpn8j62

( can i just import dxfs and this software will control the pen as well as work out the tool paths?)

not quite... you will import your dxf and use this sofware to create a file (g-code) that will have your tool paths feed rates etc and insruct your machine via mach3 sofware

im gessing you will be able to twist somones arm where you work and get them to help you with g-code ????

if your willing to use AutoCad to do your drawings it may be worth reading robins thread and trying his RCAD
http://www.mycncuk.com/forums/showth...5432#post25432

it may offer a simple alternative to G-code and is driven through a usb and might just be an absolute winner for avoiding the complexaties of CAD to CAM to Mach3

[JAZZCNC]

eg belt 3M pitch belt driven with 15 tooth pulley gives you 45 mm of axis movement per revolution of driving pulley.

My experience is 15T is too small for a machine this size.! Problem being the number of teeth in mesh is on the lower safe limit. It will work ok but the belt wears prematurely.
Obviously a plotter has very little work to do so the load is light meaning it won't be so much a problem but if it was to be used for cutting wood etc the force's will eventually tell there toll.
IMO for the sake of few more quid, and it literally will be £1 or £2 per pulley, and seen as gearing is required either way then it's just not worth not doing.!