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| Can we talk about lead screws? http://www-.luthiersforum.com/forum/viewtopic.php?f=10102&t=6603 |
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| Author: | Marty M. [ Tue May 09, 2006 7:56 am ] |
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Hello, If I were to buy a lead screw for my homemade CNC router what should I really be looking for? I like the torque of 1/4-20 allthread but would like higher rapid speeds. Can anyone point me to something in stock somewhere that could fit the bill for a 36" long machine? I go to CNC lead screw sites and they are bombarded with too many choices. I've heard that plain ol' acme screws would work fine for an application like mine. I'd like to keep the cost down and they will be driven by medium sized steppers so that kind of limits things. This seems to be an area that isn't discussed enough in my opinion. Any help or discussion would be helpful. Thanks! Marty |
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| Author: | John Watkins [ Tue May 09, 2006 8:06 am ] |
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Marty, how do you have an anti-backlash plan? Spring-loaded nuts? That's going to be your biggest source of position error. Second will be screw torque. If you use too small a screw, it will actually twist under the inertia of your gantry. My last machine had this problem and it took me forever to diagnose it because squares would come out square and circles would come out oval. This is because over the length of the side of a square the inertia has time to fade. Lead/ball screws can be had for cheap with pre-loaded nuts already on them if you hunt around enough. What size are the steppers? What kind of couplers and end supports do you plan to use? |
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| Author: | Marty M. [ Wed May 10, 2006 8:35 pm ] |
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John, My steppers are about 200 lb/in. They are nema 23. I am using tapped delrin for nuts. My accuracy is excellent,so that isn't a problem area. I see all sorts of lead screws that provide more efficiency and speed on the commercially-made small machines, so I just thought I'd investigate them. Marty |
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