New Build! need some thoughts!

[papagolf]

This is my first build that I am creating from an old Helava photo negative scanner. it already had everything I needed for the X/Y axis' as far as rails and pillow blocks and a good foundation. The motor drives only had a movement of about 4 inches each direction. I fabricated a gantry from the aluminum plates they used to move the negative around with. I want to do a dual purpose machine for artwork so .001 tolerances are not really my concern. I will be using a rotozip or dremel for a routing spindle but my dad would like to do plasma. I have considered a belt type rack and pinion vs a dual acme lead screw for the X and the same for the Y but with a single acme. my travels are only in the 22" range so im not concerned about lead whip or anything just complexity of the design. Also in the case of a lead screw would you consider center drilling the lead screw and attaching directly to the motor? or would a bearing on each end with a motor coupler be in good design? and finally how would I determine the motor force required to move this thing?! thanks in advance!

[johnmac]

I'm not sure you need a dual lead screw for a 22" travel. I think it would be easier to build a sturdy table that doesn't "rack". If you can get good alignment, you could couple the screw directly, but the steppers are not designed for thrust loads.

John

[papagolf]

Originally Posted by johnmac I'm not sure you need a dual lead screw for a 22" travel. I think it would be easier to build a sturdy table that doesn't "rack". If you can get good alignment, you could couple the screw directly, but the steppers are not designed for thrust loads. John

The table is sturdy enough (60-70lbs of something - no flex at all)but the clearance in the linear bearings across the gantry will cause it to rack if driven from only one side. maybe tightening them up may help.... I thought dual lead screws may be over kill.... I was leaning toward mounting the X motor on the gantry and running a driven shaft across the gantry with a timing belt pulley on each end and doing it rack and pinion style. I'm just not sure if a 1/4"(its whats on hand) timing belt is up to the cutting forces of a small router if it hits a hard spot in the wood.

thanks for the thought on the steppers though... thats what I thought but I wasn't for sure!