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General Mach Discussion / Re: Lead or Ball Screws (lathe Conversion)
« on: June 14, 2011, 10:52:07 AM »
IMHO, you are much better off with a really good quality lead screw than a cheap ball screw. In the hobby CNC world 'ball screws' have this magical aura about them and many think that you can't build a good machine without them, which is non-sense. It all depends on how you are using your machine and what you want out of it.
If you are using a machine in an industrial situation than the money spent on a good quality ball screw is money well spent. You are using your machine all day long and time spent tweaking things is money down the drain. As your machine size goes up then the additional efficiency offered by ball screws is also a big benefit. A more efficient drive train means small motors, smaller drivers, smaller power supplies, a smaller foot print, and less power used. The cost of energy to run machinery is huge factor on an industrial scale and should not be ignored. (Since Hood depends on his machines for a living then ball-screws are a great investment.)
For hobby use or small scale commercial use a ball-screw may not be as good an investment. Most hobbyist spend more time tweaking their machines than running them (as it is fun), so a few minutes spent every now and then to adjust the backlash nuts is not a big deal. Also as I mentioned before a good quality lead screw is much better choice than a cheap ball screw. A cheap, inaccurate ball screw is a waste of money.
Open loop backlash compensation, like Mach does, has limitations and it cannot make a sloppy machine work like a precise machine. Think of it like driving an old truck that has a lot of play in the steering wheel. Your brain is really good at trying to compensate for the slop in the steering but you'll still be darting around in your lane on the highway more. What happens when you hit a pot-hole though? The truck is pushed around by external forces that you have a much harder tiem trying to compensate for and you cna loose control. The more slop in the steering the worse the situation can be.
If you are using a machine in an industrial situation than the money spent on a good quality ball screw is money well spent. You are using your machine all day long and time spent tweaking things is money down the drain. As your machine size goes up then the additional efficiency offered by ball screws is also a big benefit. A more efficient drive train means small motors, smaller drivers, smaller power supplies, a smaller foot print, and less power used. The cost of energy to run machinery is huge factor on an industrial scale and should not be ignored. (Since Hood depends on his machines for a living then ball-screws are a great investment.)
For hobby use or small scale commercial use a ball-screw may not be as good an investment. Most hobbyist spend more time tweaking their machines than running them (as it is fun), so a few minutes spent every now and then to adjust the backlash nuts is not a big deal. Also as I mentioned before a good quality lead screw is much better choice than a cheap ball screw. A cheap, inaccurate ball screw is a waste of money.
Open loop backlash compensation, like Mach does, has limitations and it cannot make a sloppy machine work like a precise machine. Think of it like driving an old truck that has a lot of play in the steering wheel. Your brain is really good at trying to compensate for the slop in the steering but you'll still be darting around in your lane on the highway more. What happens when you hit a pot-hole though? The truck is pushed around by external forces that you have a much harder tiem trying to compensate for and you cna loose control. The more slop in the steering the worse the situation can be.
