[catalin_cluj]

Hello,

I've been lurking around for quite a while, not knowing much about CNC and machining in general, but liking the idea nevertheless, at least for routing my own PCBs.

Today I bought this "Compound Sliding Table": http://www.houseoftools.com/product.htm?pid=187674

and I'm having doubts already: maybe it's too big for my needs (I think mainly routing PCBs, but maybe small aluminum /plastic hobby robot parts), it weighs about 25Kg (50 pounds?).

-It has "backlash" (is that when I can rotate the screw a little back and forth without the table moving?). I hear that can be compensated for in software, but if true, why does everyone want zero-backlash ball-screws? Maybe I can use some springs, but then I'll need stronger motors... I think.

The biggest stepper I have is an old IBM one, 4.5V, 1.4A and I don't know other specs; I'm not sure if it's strong enough (IBM PN 1476996, STEP SYN 103-820-6) to move the bottom axis.

I'm thinking maybe I should think lighter and continue the wood (imitation) and aluminum with drawer slides I started a little while ago... it won't mill metals, but it might be easier to route PCBs with it...

Any thoughts/recommendations, please?

Thanks,

Cat

[ViperTX]

Cat,

You would be better off if you removed the backlash....but before you spend much time, make a few measurements....move the table to the far edge....find a way to create a reference point then move the handle x number of turns...now measure the distance from the reference point to the edge of the table....continue the process over the length of the table and only turn the crank in one direction.

Do the same for all 3 axis. This will give you some idea as to the accuracy of the lead screw (without backlash).

[catalin_cluj]

Within the limits of my measurement system (a ruler) it seems quite precise, at 10 turns/inch.
In fact I can't imagine a screw ... not being accurate...

[ViperTX]

Well when you CNC the table that 30 or 50 thousands variation in the screw is going to make a difference. Different types of screws have different accuracies as do the nuts that fit them.