hi guys, i emailed rodney last night about a problem with one of my steppers last night, but woke up this morning and was able to get it back operational so i never called. i ran more parts today and left to run an errand while it was running, and returned to a finished part, and went to raise the head so i could pull the part, and it would not raise. said external e stop requested. tried all the simple stuff and nothing. i smelled an electrical smell, and started looking around. i found the x axis homing switch harness melted at the connection to the switch. this is my second harness in less then a year, and i continually have problems with this harness and it seems to wipe out the break out board with it. last time it just would not home x even with new harness, so a new board fixed it. this time, most of the leds are un lit on the board, and i cant get rid of the external e stop requested. now it is too late to contact rodney, and i have jobs stacking up! is it normal for a failed homing switch to wipe out the break out board and e stop the system?(kinda dumb question) how can this constant problem be solved? i went the extra mile and tried to better seal this last harness as the last one was all corroded up inside the clear plastic end, so i triple heat shrinked it and siliconed it and then wrapped electrical tape around to try to keep it all sealed as it is right out in the open for coolant. in less then a year i have had to replace one stepper, one break out board, one harness, pc power supply, and now all of what is now damaged. this machine doesnt seem to hold up in the semi professional atmosphere, and deffinately not great for flood cooling since nothing is sealed. i am not affraid of updating or improving the machine and love it otherwise, but it seems to fail rather frequently for me anyway. any help would be great. thanks
so deffinately fried the break out board! melted ic chips with severe burn marks etc. so i swaped the old board back in(just wont home x, but the x harness is fried anyway) and got it all back and running. interesting to note a few strange things from when i switched to the new board and now back to the old. first, whenever you e stop the system, it makes a soft "bonk" noise from the steppers, but with the new board it was a hard "bonk" now with the old board back to the soft. also, when i installed the new board, i had to recalibrate the spindle motor setting in motor tuning to get accurate speeds. now with the old back in, i had to recalibrate it back. that all seems kind of strange, why would they be different? any way the problem it had last night was the x axis motor started making wierd noises and stalling etc. this happened to the y axis a while back and it was full of coolant and all corroded up, so rodney sent me a new one. put it in and problem solved. so i pulled the x stepper last night and it looked great. so this morning i started inspecting the wiring. i took the main harness apart at he controler and plugged it in without the metal cover on it, and walla the stepper was working perfect. so i thought there must have been a short all though it all looked great. so i put it all back together, and ran a part. left and came back to a fried limit switch and break out board. did all the above and got it back and running, tried to start on the next part, and all was well for a minute, and then it started doing the wierd noises and stalling x again. checked all the wiring and tried all the tricks from before, and still having this problem. very frusterating!!!!!!!
I'm not sure about the older version but the current NM-200s2 uses a cnc4pc.com BOB (model C11G). They're usually pretty highly rated. They have had a number of revisions, though, so that may explain some of the differences you found when switching. They have some decent info for wiring/manuals on their website so you might want to check that our.
If yours is like mine it uses an optical proximity switch for axis 0ing. The manual for the BOB shows how it should be wired. It sounds like either you got a short somewhere (the wiring harness, or a faulty switch) or a bad resistor hooked to thr BOB, allowing free flow of current (and consequently melting things). Note that the manual specifies one of the causes of unsmooth travels to be a power drain. I assume the switch was replaced with the harness, as it's pretty cheap?
what happens when the X and Y proximity circuits are completely disconnected/disabled?
FYI The board is partially rebuildable if not overly damaged. They sell replacement chips on their page.
i did replace the limit switch along with the harness and break out last time. that fixed everything but it now had the little qwerks like the steppers making that loud noise when you estop the system like when doing a tool change. i think the short comes from the harness when things corrode up there at the plug. if you do not know where i am talking, the clear cover has a little board with red and green leds. that gets all white and cloudy and the green led burns out then the red and i lose homing/limit. i have done several things over the last day, and it keeps failing agin., i finally tracked it down to the harness on the gecko for the x axis. one of the black wires had arced out and kinda melted the copper tang that completes the connection when you tighten the little screw on the wire. it was tight, but that copper had melted back like a blown fuse. when i would wiggle the wire, it would arc and spark, and wiggle it just right and the stepper would work smooth, move it back and it craps out again. so i stole parts from the 4th axis gecko and all is well, accept now i lost the y axis homing switch. the led lights on both the harness and the break out board when it gets to the steel tang, but it passes right over it. i am using comprimised parts right now, so no real big surprise. if i had to guess, the limit switch harnesses were getting all corroded up and eventually started frying stuff causing a chain of events. first the stepper problem, then the break out board, then the geck harness, all from the short from the sensor. it is a c11g board, but this one is kinda fried. the one i have now maybe repairable, but i would rather a new one. i think i have it fixed now, just need the new break out, and new harnesses and limit switch. i managed to whip out 2 parts today, so hopefully i have found all the problems in the chain!
What are you using for coolant? It sounds almost like it's corrosive or highly conductive. Or mayve your water has a high salt content? Getting a bit of coolant on the limit switches shouldn't normally cause problems like this, but if it's eating it or shorting it than obviously all bets are off. if your parts will allow you could try a plexi containment shield built around the spindle nose - just a 4 sided "box" that bolts to the head with a hole drilled to insert the coolant nozzle. Make it come down to about where your tool holding device (toolholder/collet/chuck) ends so the cutter will stick out beyond it. It might "contain" the coolant enough to prevent this problem. Or, alternatively, maybe a containment system that goes around the table. It wouldn't have to be high, just high enough to direct the coolant down the drain. Obviously this would only be any good if your problem is coming from coolant flowing over the table.
There are also alternative designs for the proximity switches. Check out mouser and digikey, they have some. Maybe a different design would work better? Also, from the looks of it the sensor is actually inductive, not optical, which makes sense. I had assumed optical because of the leds.
Also, if you do change coolant/water due to high conductivity or corrosiveness don't use RO water as it's corrosive enough to cause electrical system problems (experience from other projects). Deionized water is usually safe.