couldnt find it anywhere !!

[v1r05]

hello everyone.

ok here it goes, what i want to do is a small cnc/plotter machine what got to be very light and fairly small to just draw i mean no drilling no milling pcbs no metalworking no nothing just drawing on a sheet of paper and has two axis and the z-axis will only controls the pen (up or down) on a table that has the size of an A3 paper.

i am searching for a CNC designs that fits my need but i couldnt find any so i guess i would have to do my own, i was thinking of stealing motors from old printers what i got is a black stepper motor that has 1.8/rev and looks powerful, the other is a sissy small M42SP-7 7.5/rev motor
am not looking for torque anyways so probably i will end up buying matching motors with 1.8/rev and what should be the torque ? or can i use two different motors for each axis probably not a good idea isn't it ?
and how can i calculate how much torque i roughly need ?

the M42SP-7 has this values what do they mean ?
Holding Torque 49.0mN·m
Pull-out Torque 23.5mN·m/200pps
Pull-in Torque 19.6mN·m/200pps


and am thinking of using a threaded screw for the linear motion.
i need an advise on what should be moved as the y-axis, the table or the whole x-axis assembly and why its better

also can someone name me an easy to use CAD program to glue all my plans together in a nice 2D & 3D way

thats all hope am not asking alot

thanks

[Al_The_Man]

In this part of the world HP Pen plotters are almost given away, I don't think I would bother re-inventing the wheel.
Al.

[vger]

Al is correct. I stop in at a computer recycler occasionally for parts and have seen pen plotters being tossed in the scrap heap. Many many years ago I built a pen plotter using steppers from old hard drives. It would do letter size paper and was pretty quick. It was all aluminum construction using small C channel stuff. Both motors were mounted to the base and controlled the pen position with steel fishing line. The fishing line was spring tensioned and wrappend several times around the motor shafts directly and suprisingly it stayed registered reasonably well. I made some tiny grooved rollers out of hobby brass and used screws through short pieces of brass tubing for bearings for the rollers. If I remember correctly it took just under 2 minutes to draw the Autocad demo file of the space shuttle.
If I were going to build a pen plotter today I would use servo motors, encoders, and different rigging.

Steve

[v1r05]

hi, vger

thanks for the info man yesterday ive stumbled across this website http://www.luberth.com/plotter/ditwasplotter.htm but luberth dosent explain everything in detail although this website is very helpful i researched about thread screws bearings motors and lots of other things but havent came up with a solid ready to be done plan yet.

iam also looking for an easy to use 2D/3D CAD program to put my plan together nice and neat so i can print everything and have all dimensions ready with all top view/side view.... etc, (gona do all the work on my university's workshop since i dont have no tools except for a damn mini drill for PCB)

so you can tell me what you use for drafting or what do you recommend


thanks

[Netjams]

Some times reinventing the wheel is a mission one has to take in life to feel full