On Mon, 5 Aug 2013 19:42:48 +0100, you wrote: >On 5 August 2013 18:34, Sven Wesley <[email protected]> wrote: >> As you might know (according to recent mail activity) I'm going to build a >> new machine. My plan is to use a mesa card setup and the machine will >> support 5 axis, but I will start with three... ...I think. This is where my >> need of decision support comes in. I have always used servo's even on >> smallest machines. But when I look at the stepper setups, they are like >> half price even if I go with beefy motors. > >My experience with steppers is limited, but the small NEMA 23s are >quite nice, however the bigger NEMA23s became noticeably more >"sluggish" which rather counted against the increased torque as far as >performance was concerned. >I can imagine that the big stepper motors continue this trend, and get >stronger but more ponderous.
Bigger motors generally are more coggy and at low rpm they want to bump from step to step rather than rotating smoothly, but not all bigger motors are "sluggish" - many will do 2000 rpm or more. Most poor performing stepper systems seem to be low voltage machines running crappy Xylotex or similar drives at 24-30V. If you run the same steppers at 60-80V with decent drives the difference can be amazing. The new DM range Leadshine drives are very good with software tuning and a lot of programmable parameters. Have a look at the manual for the DM856 http://www.zappautomation.co.uk/en/attachment.php?id_attachment=144 I'm not a fan of Gecko drives. They all seem to suffer from DIR problems, including the latest G320X servo drives! >Having built a stepper machine initially I decided on a servo machine >for the second build, and have so far not regretted it. Just the >repeatability of index-homing is a big plus to me. There are closed loop stepper systems too :) I saw a large closed loop stepper driven router/vinyl cutter recently that was being made for a sign company, it's performance was outstanding. I honestly thought it was a servo system when I saw it under test. It had two heads, they could be vinyl knives or high speed spindles and took about a minute to change. Price wise - steppers are cheaper than servos, and if chosen carefully they can perform well. My router is stepper driven, direct drive to 4mm pitch ballscrews, it will run at 5m/min+ if required. I normally run it in the 3 to 4m/min range and I can honestly say I've never suffered from lost steps or lack of torque and it's right on the performance range I designed it for. Steve Blackmore -- ------------------------------------------------------------------------------ Get your SQL database under version control now! Version control is standard for application code, but databases havent caught up. So what steps can you take to put your SQL databases under version control? Why should you start doing it? Read more to find out. http://pubads.g.doubleclick.net/gampad/clk?id=48897031&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
