[CNCDevil]

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

[solodex2151]

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

[CNCDevil]

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