How much Torque is needed?

[Tjippy]

Gday folks!

I'm planning to build my own CNC routertable right now. Because I'm a real woodworker and not een electronerd it's quite hard to understand all the things about the electrics!
But still going strong, this forum helps a lot. Allready read a lot of interesting things and seen some amazing pics!

My specs:
Table size: app. 70x60 cm. Due to the size I want the table to be static
I'm thinking about the HobbyCNC plan or something like that.
Material: Wood, Acrylic glass, MDF. I want to use standard 6mm bits or smaller to cut 18mm thick material or thinner
Router: I'm planning to use my Metabo router (710Watt 6mm shaft) and/or a standard Dremel. But I guess for the bigger parts the dremel is to light.
Software: want to use software which is easy and makes it possible to translate Coreldraw pics to.
Motors: haven't got a clue
Hardware: dito
Gliders: dito
money: <500$

In all I think it must be pretty heavy duty.

I'm watching Ebay for parts and read a lot of sites and forumannouncements allready but I can't find good advise about the amount of torgue (Ncm / Oz/in) needed to make the machine work.
Can someone give me some good advise and/or share his experience building a machine like mine?

NB.
I'm planning to come to the US in april 05 (SF.area CA.) Thanks to Bush the Dollas is incredibly cheap at the moment. Being Dutch I want to order my motors and hardware in the US and pick them up by then..

[rackbox]

I got good answers to similar questions on http://www.cnczone.com/forums/showthread.php?t=7146

[ViperTX]

Tjippy....so if you have servos or steppers that develop 400 to 600 oz-in of torque you should be set...you can adjust the gearing to gain more torque. If you like to experiment then take your router or dremel...put in the bit that you most likely will use...and use the material that you will most likely be routing/milling...measure the amount of force that you use to push the router through your selected material...use various depths of cuts and various bits...translate that force back to the motor driving the x or y axis...remember Torque = Force X Distance....so simply with 1 to 1 gearing or pulleys of the same diameter....and the motor 1 foot away from the lead screw and 1 pound of force you would have 1lb-ft or torque applied to the leadscrew...depending on type of leadscrew you would have some loss of torque due to the leadscrew...anyway...that's off the top of my head...hopefully I didn't err too much.

[Tjippy]

Two helpful replies!

I'm going to find three steppers with at least 1.6Nm for the job. Because the driver and the steppers are the biggest investment I have to direct my plan in such a way my budget isn't running away the wrong way :-)
crappy sentence.......

What a lot of variables to consider building a machine!
Maybe thinking about building a machine is even more fun then having one!!

[michaelvw]

Hello,

I`am from the Netherlands too and also beginning to collect parts for my project. If you want cheap parts in the Netherlands place a wanted ( gevraagd ) on www.marktplaats.nl with the parts you would like to have, you get lots of responds.

Regards,

Michael

[Tjippy]

MichealVW,

I'm allready looking for Steppermotors on Marktplaats but haven't seen them yet.
The Gecko driverboard is OK but I want to focus on the mechanical parts first.
I still haven't found cheap parts for constructing the XYZ axels except for an old Epson printer who's containing a nice iron glider with two brass rings (prob. good for the Z axle if I find one more!)

Is it an Idea to jion forces together?
I'm planning to go to the US in April so if necesarry I can bring parts back home...