I don't think you'll find many people advocating use of the std leadscrews. You simply can't make them accurately enough to give acceptable backlash whilst still being able to assemble the nut to the leadscrew. Even if they seem OK when brand new, they will soon bed in and you will have measurable backlash. The friction is also pretty high relative to ballscrews.

Ballscrews are readily available from AliExpress and ebay for starters. It's one of the first things people usually buy when embarking on a conversion.

Makes you wonder what else they have cut corners on? Check out the hundreds / thousands of conversions done on similar machines. I assume the generic design used by Warco is available under any number of other brand names.

Murray

As well as cutting backlash ball screws reduce the torque required from the motors which gives the choices of smaller motors or higher traverse speed. Also kits mean someone else is making a profit at your expense, it may be worth costing up doing everything yourself. It's not too hard and there are plenty with experience on this forum. The CNC cookbook website also has a lot of useful information for someone starting out in CNC.

Martin C

IMO overpriced and likely more power than required for the machine.(8.7Nm)

Emgee

Any problems with back-driving of the ballscrews on these conversions?

MYCNCUK have a few threads on converting this type of mill, which may be of assistance..

John

I assume the 4th axis would use a rotary table or similar to achieve a reduction ratio, in which case 8.7Nm must be wonderfully OTT. Calculate what torque would be available at the work and ask what you could possibly need that for. You could destroy significant parts of the machine with that. Even 4Nm for the main axes must have a pretty large safety factor.

One thing to understand about steppers is that their torque falls off rapidly with speed. When I plotted a variety of stepper motor characteristics (torque vs speed), I noted that they display a characteristic that is very close to constant power. What that means in practice is that you might as well drive the ballscrews directly rather than gear the motor down through a reduction stage. That's the most common arrangement for steppers but you do see some with a reduction stage. With the latter you simply reduce the all-important(?) "rapids" whilst doing nothing to increase the torque / force available at a given speed of movement. For a willy waver, the stall torque at the ballscrew might be legendary but if you ever tried to develop it, something would break….

If you spend more money and go for a proper servo motor rather than a stepper, you will find that the stall torque is less than he headline figure for a similar size stepper but generally that torque will be achievable over most of the speed range. So you would probably need a reduction (typically 2 – 2.5 is achievable) but it will achieve much better performance over the whole speed range.

Murray

I did the same on my (BusyBee) version based on your recommendation and I agree. The difference is astounding. I wouldn't mind kitting it out with the Benchtop-Precision 3-ph motor adapter + VFD if I could find a suitable motor locally whose price didn't assume gold-plated windings.

I hope King are better to deal with than BusyBee. When I was looking at fitting ball-screws, I tried to order a spare table and cross-slide from BB (to make it easy and allow me to use the same mill to do the mods) – which they said they were OK with but would have to order from the Far East. They (supposedly) went ahead but in two years I could never pin them down and then they went away completely.