First build - leadscrew selection and opinions

[Andrebr]

This is my first build for a aluminum woodworking router. Its a good idea to use acme 1/2 .5 pitch hi-lead or its best to use 16mm diameter 8mm lead trapezoidal given its 60 kg of gantry? (I will install in a custom fixed-fixed bearing configuration).
I am using v-rollers on a 3/16 - 3/4'' angle, Gantry lateral is 3/4'' 6061 aluminium and extrusion is 160 - 80mm 6063 alu. (16kg). The motor I have bought are 435oz/in steppers.

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[ger21]

The acme should be faster.

[Andrebr]

As you can see, its a sort of Gatton inspired aluminum professional cnc.

[steve323]

I had better results with cheap rolled ballscrews. They run faster with less resistance. Backlash is lower than I have ever achieved with acme.

Is your gantry really 60kg? Your motors should be fine. The side rail motors share the load and the other motors have smaller loads.

Steve

[Andrebr]

My concern is about column strenth. Could a 1/2'' acme , bend with compression, because calculators in the internet, says its too slender?

[ger21]

How long are the screws?

I'm using 1/2" acme, and don't have any issues. As long as they aren't much longer than 1m, they'll be fine.

[wizard]

My concern is about column strenth. Could a 1/2'' acme , bend with compression, because calculators in the internet, says its too slender?

It depends upon the length of your axis. Your long axis, the X, is the one likely to have issues, You didn't mention length or I didn't see it but if the calculator you are using indicates a problem there may very well be a problem. Alternatively ou could have never estimated something.

[Andrebr]

Its 152cm between bearings.... I am more towards the 16mm diameter 8 pictch 2 start, because of good price, the acme 3/4 will be a huge price here... Don't know how a slower lead could penalty a workmachine.... My actual router is only 750w anyway.

[louieatienza]

Well you sacrifice some top end speed... but you may gain a bit more torque and acceleration. That may be negated by the additional inertia of the larger screw and increased friction.

As Steve mentioned, a set of import rolled ballscrews with the requisite bearing blocks may be the better option. You could even save some money and make your own bearing blocks and just go with radial BBs instead of AC bearings - your spindle will bog down long before you exceed the axial load limit of dual radial BBs. Then again with such a strong machine why make the spindle the limiting factor as far as performance?

[Andrebr]

Its a sort of jungle machine too.. Its all stainless and aluminum for use in salty, near sea region... so, all bearings, rails etc are stainless . And about the lead screw, I think is more rugged and easier to repair ( and ball screw is difficut to find all stainless). Maybe for a next upgrade, a powerfull router and a faster screw... The price for a speed gain is 2.5X , I could be wrong if it really takes off...