Controls Discussion

This page is currently just a compilation of the discussions for the Lathe Bed, spell checked and with extraneous content removed. Thanks Bruce!

How should this page be organized? I'm not sure yet, as this area has had a lot less discussion. Feel free to reorganize, and once you've done so, snip out this first person commentary, or add your own.

Control System

Alan: 04/27/08

David, encoding options are something we do have to think about if the individual wishes to go with a linear encoder. (i.e.; extra space is needed). Servo’s by nature can run stand-alone and obtain positional info via contour EMF (or back EMF). Disc encoders are so inexpensive (less than $40) and take no space in the bed design. If going with steppers, the individual has the option at any time of adding feed back at any time, or not. I’ve priced out linear encoders in the past and nearly had a heart attack over the price.

Then on to the DRO. I do like the notion of having a DRO if the lathe is manual. But many want to go CNC where the DRO is automatically built right into the computer screen (like on Mach3, EMC2, WinCNC, FlashCutCNC, etc, etc). I also plan on buying a touch screen (5” by 8”) and have the same Mach3 DRO info on a small display right in front of me. I guess it doesn’t matter if the screen (computer, touch or just a DRO) are used, they can be easily table mounted somewhere near the lathe. Take a look at these guys:

Something that may or may not interest the users may be if they also want to run a CNC mill (or another CNC lathe) next to their lathe. Personally I will be converting my LatheMaster mill to a 4 axis (3+1) along side my CNC lathe and drive both the lathe and mill with the same CNC controller and windows computer and touch screen (just not simultaneously of course). There are also very low cost hand-held pendants available that you can easily program and run either the lathe or mill away from the computer if you want to keep it away from the flying’ chips. And of course Mach also takes care of limit switches, homing routines, tool touch-off for zeroing against the material, fine threading (imperial and metric) capability (not just course), cnc driving a tool post grinder, an ATC (automatic tool changer) with a dozen or so lathe tools, an auto-feed for stock through the headstock spindle, etc. It will take me some time to get this all going, but all of it is very doable. I know this is my vision of what I want out of my lathe and the reasoning why I will go with CNC (so I can build upon it).

David G. LeVine: 04/27/08

Finally, is it desirable to plan for a DRO even if none is used most of the time? Having the mounting pads (which is all we are discussing here) may be incrementally cheap, especially if they are not machined
unless the DRO is planned for installation, and a purpose-built grinder would make short work of a surface parallel to the way. Servomotors running with a DRO, rather than a rotary encoder, get VERY accurate, in the 1970s we were getting 0.00025" (yes, a quarter of a thousandth) over a 24" x 24" X-Y table driven by steppers which corrected based on linear encoders.

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