On Tue, 2008-02-12 at 13:39 +0000, [EMAIL PROTECTED] wrote: > Just a quickie. > > Can anyone recommend a UK supplier of stepper motors and associated drive > electronics? > eg just add mill, and computer running EMC. > > Mill is a light / middleweight Pinnacle universal job, XYZ travels are 400, > 180, 150 mm with > quill head having separate raise / lower facility and rotation about X and Y > axes too. > > Buying a DRO today with GS500 series glass scales (5 micron) from > www.machine-dro.co.uk > so will hopefully be able to use output from linear scales as direct input > into EMC computer, > (phase 2 of the upgrade) max rapid speed of the scales is allegedly vastly in > excess of > anything I could need, so don't need 740 watt steppers... X table may weigh > 200 lbs and > perhaps another 150 for Y table, not trying to pull high G accelerations and > a rapid of 300 > mm per minute would be double what I'd be happy with. > > On a budget of course (aren't we all) but definitely prepared to pay a little > more for something > not prone to glitches such as interference on power rails etc causing missed > steps. > > Doing it this way appeals to me for two reasons. > > 1/ redundancy, can use linear scales with either EMC computer or standalone > DRO at will. > > 2/ eliminates backlash and screw mapping etc, linear scales will measure > actual position of > tables and quill. > > many thanks in advance.
With the experience I have gained so far, it leads me to believe that you are making choices that may make your quest more difficult. If you are trying to have a CNC machine to make parts and spend as little as appropriate for that end, then you should consider studying other machines that are already proven to perform and copy their success. If you want to explore different methods of machine control, be prepared to spend allot more time, money and run into dead-ends. You will also need to be able to develop your own software because these days, hardware won't do anything without software. Successful stepper systems tend to be very consistent in their design, which doesn't include scale (or any) position feedback. The appeal of steppers is to not have the complexity of feedback, so if you are a stepper idealist, you would be corrupting the design with feedback. If a stepper system malfunctions, it is due to a flaw in the original design, tuning, or, part or maintenance failure. My take on the stepper theme is to anticipate all performance parameters and accommodate the requirements before hand. I need to admit that I have not built any stepper systems, but my attempt at using scales with a DC servo system proved a waste of time. Unfortunately I couldn't grasp why, until I saw the mode of failure which indicated to me that scales indeed give you position feedback, but what is needed is motor motion feedback. Scales aren't good at motor motion feedback because of backlash and other dynamics that real machines have. If you can accurately model the backlash and dynamics between table position and axis motor motion then maybe scales could be used, but currently you would be completely on your own to achieve this. Current systems control motor position and motion to a high degree and then achieve the required machine positional accuracy by eliminating positional flaws due to backlash and flex. Bottom line, I believe making parts and charting new motion control territory are very different pursuits with different rewards. -- Kirk Wallace (California, USA http://www.wallacecompany.com/machine_shop/ Hardinge HNC lathe, Bridgeport mill conversion, doing XY now, Zubal lathe conversion pending) ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
