Hi all, I need some oppinions.

I'm building a gantry-style router with a working area of 1x1 mtr. (40x40in) It's made out of a composition of steel and aluminium and I'm going to cut wood signs with it. I think I will call it Beaver-Overdrive :)

The gantry weights around 70 lbs. I want to drive it from each side with two 305oz steppers from HobbyCNC. Will I have better overall performance with a two-start screw over a single-start? The single-start is a trapezoidal 16x4 (~6TPI) and the two-start then have 8mm pitch (~3TPI).

I know that the precision is reduced by choosing a two-start, but speed is more preferred. I'm just a little concerned about the acceleration?

Please give me some inputs on what speed/acc. I can expect by choosing the one or the other? What would you choose?


Brian

I would personally go with 1/2"-10 5 start over either of those 2 options. The HobbyCNC motors have 200 steps per rev. The 5 start there is 2 turns per inch. That is 400 steps per inch or 2.5 mils per step while FULL STEPPING. Wood expands and contracts by 1/32" all the time. You will be fine with any of them as far as accuracy goes. Get the 5 start though as it'll be 2.5 times faster than the 2 start. Also, go with acme lead screws.

What is your machine made out of? The rigidity in your machine will play an important role in how fast you can push your machine.

Nate

I'm from Denmark and it´s much easier to get hands on trapezoidal screws over ACME, at a preferable price, so that's why I choose them. I don't know where to get 5 starts ACME here in Europe, but if anybody knows, then please leave a comment.

The Gantry is made of "6082" 150x10mm aliminium bar, 1300mm long and is reinforced by the top and bottom of each side with 40x40x5mm aluminium angle bar ( like an I-shape). I've made a stress analysis in Inventor with twice the applied forces and it seemed to be deformed by 0,04mm at max., so I think it will do. I sure post som pictures later on.

Do you think it will get a reasonable acc. with a 5 start ACME? It just seems pretty coarse, but my experience is limited and therefore I have to ask.

Brian