[kosmo]

Hoping to get feedback on what people have had success with in Mach3 motor tuning with Bridgeport steppers.
I am running with a 72 volt power supply, gecko's 203V at 7amps. Bridgeport Sigma stepper motors 1 to 1 pulley ratio. My mach motor tuning settings are Steps 10,000, Velocity 60, Acceleration 1, Step Pulse 1, Dir Pulse 1. 35,000 kernel speed.

What I'm finding is that when I rapid in any axis at full speed the motors start to sound like their grinding and loosing steps (shop temperature was in the 50's). It's not always been like this. When I first finished the retrofit they sounded good and smooth. That was in the summertime when temps were in the 80's plus. If temperature has anything to do with it I don't know, just giving all the information. (mid-band resonance issues perhaps)

I also set a low feed rate of 2 inch per min and adjusted the gecko 203V to try and smooth them out. Even towards the end of the adjustment range I still get table vibration. I will eventually upgrade to newer steppers but have to settle for the old ones for now.
My question is what are your settings and how smooth are your motors? Thanks

[kosmo]

91 views and nobody has feed back on what they have their bridgeport steppers tuned to in mach3. Come on don't be shy !:wave:

[BOSS5]

Sounds like your ways are dirty, gibs are tight or the oil very thick due to low temperature, but in any case your speeds and acelerations are indeed very low. I've been building up my series 1 boss 5 conversion and am using older industrial slo-syn d6 drivers (used on ebay - for less than the price of a gecko) on the original steppers and pulleys. These drives run an internal 180 volt bus (rectified line voltage) and output 6 amps. At this bus voltage the high winding inductance of the size 42 steppers is largly overcome. I'm running at 10 microsteps, so 10000 steps per inch in mach3. With the default 25Khz kernal speed, I have it set to max at 150 ipm, and acceleration at 4 in/s/s. There are no issues. Can run the roadrunner test file at full rapid speed. The limit is about 6 in/s/s when it starts skipping. I've also had the speeds above 200 in/sec, did not see the need to run this fast so slowed it down for reliability. At one point while testing x table movement I even had the mill visibly rocking on its base due to the inertial forces!. I did also try the geckos at 82 volts in earlier tests using a function generator instead of mach3, and was able to get into the 120 ipm range, but acceleration was not well controlled, so back to back comparisons are not valid. I expect that with half the DC bus voltage you should see about half my maximum speeds, thus around 100 ipm. I'm presuming you have the windings tied in series. The motors are not at all smooth during low speed, and make quite a bit of noise especially at at 2 ipm, but it does not really affect their torque performance in a noticeable way, as there is way more torque output than needed or useable at that speed. 10 microsteps helps alot, but certainly they run much smoother when going fast. I hear most people are are able to get near the original rapid speeds with Geckos, and per the manual that is 120 ipm. Hope you find your problem.

[scottly]

With a 50V supply, 6 amp drivers (AHHA for X and Z, Gecko 201X for Y), Sigma motors wired in parallel, my machine would rapid at about 180 IPM during testing. I slowed it down to 120 for actual use. BTW, the temp in my shop is also in the 50s for most of the winter.

[BOSS5]

As an experiment, I hooked up the X axis on my Boss series 1 machine to a gecko 203V running 7 amps (windings in series). The power supply was at 76.5 volts. Reliable rapid moves were 90 ipm, with the fastests at ~ 100 ipm Any higher would inevitably initiate stalling... say 105 ipm.. Bumping the voltage up to 82.5 had the system past 110 ipm, with no issues at all running 100 ipm. Temperature was in the mid 60's F. Did not try with the windings in parallel.
I then re-installed the slo-syn D6 (6 amps, 180 volt DC bus) and was reliably running to 160 ipm under the same conditions. The axis could do 180 ipm, but not consistantly over the full table travel range. I've had it hit 200 ipm freshly lubed & warmer in the past.
One thing I did notice is that when you are close to the speed limit, the response to the acceleration setting is counter-intuative. Accelerating quite slowly, say at 0.5 or 1 in/s^2, it stalls the system at a somewhat lower max speed than when you bump it up to a higher rate, say 3 in/s^2. My system seems happiest in the 3 -5 in/s^2 range, but it can go up to 7. Present axis settings are 150 ipm., and 4 in/s^2, and it can run that without worries.

[kosmo]

Please check out the video on my other thread "Bridgeport stepper motor trouble VIDEO" . First hand on what its doing and sounds like. What puzzles me most is that last summer it was fine but now after sitting most of the winter it behaves like this. Which leads me to think the temperature has something to do with it, I wont know for sure until the temp stays above 60 at night.

[scottly]

Thanks for conducting the experiment and posting the results, BOSS5. To sum it up, with half again higher voltage and one amp more current, the series configuration gave 1/2 the speed of the parallel.
kosmo, re-wire your motors to parallel. Do the X axis first, as it's the easiest.

[BOSS5]

Kosmo, the first thing I'd do is put a voltmeter to your power supply while it is under load and see if it holds steady. I've seen the video before my first reply, just classic stalling of the steppers. What struck me is that it appears to happen equally on all the axis, thus I would suspect the supply giving out under load if nothing else changed. I expect you must have initially experimented with the motor tuning when you set it up, and then rolled it back a good margin to ensure reliability. Somehow I doubt that the temperature would make that much of a difference unless you put some type of lube that just gells up in the 50's, or some type of grease that dried out. It has to be an oil.

[kosmo]

I have my Sigma motors wired in parallel as follows: terminals 4+8, 2+7, 3+6, 1+5 are connected. I am using the automatic oiler filled with a light weight oil that seems to flow pretty good. I have a nice drip coming from the spindle as well as the ways when the machine is on.
That is correct BOSS5 I tuned it down to not push it too much and possibly miss steps. I read somewhere that if the table had a heavy load on it and the speeds were excessive then sometimes you could get a "back voltage" off the motors when slowing down. This could harm the Geckos. Don't know for sure but didn't want to chance it.
When able I will check the power supply under load with a voltmeter and post the results.
Would Series be wired as follows ? Terminals 7+8, 5+6 are both jumped. Terminals 8+2, 7+4, 1+6, 3+5 are connected. Thank you

[BOSS5]

Kosmo, you have parallel wiring right now. In series 7+8 and 5+6 are jumpered. Leads 1 and 3 would go on A and "not A", leads 2 and 4 on B and "not B" respectively. An ohm meter would read about 1.1 ohm across 1/3 and 2/4. Series winding gives higher low speed torque, but your high speed torque becomes very limited unless the drives have a very high DC bus voltage like my Slo-Syn. The motors are designed to take 6 amps per winding without overheating. In parallel you would need to drive them with 12 amps, as this value gets split between them. With the 7 amp Gecko's driving parallel windings, the windings are seeing 3.5 amps each, so the torque at low speed is approx 58% of the motor's rating, although you would be able to carry such torque to a higher speed. Basically you need a 12 amp Gecko, but such an animal does not exist.
Glad to see you have the oiling side well handled. Like I said, probe things with a multimeter before you tear into it. Unlikely there is anything wrong with the software or Gecko's given that all axis exhibit the same problem, and it appeared sudenly. Check the power supply.
I've read in other post's that people have had success running Gecko's in half winding mode, as this closely mimick's the unipolar set-up of the original Boss5. (You would only connect half the windings) In Unipolar the machine winding current was set to 8.2 amps, with a dynamically variable voltage supply. I believe the supply voltage rose to about 80 volts DC at high pulse rates. 8.2 amps times root 2 gives ~6 amps. Root 2 is the conversion factor for RMS power dissipation between a modern bipolar drive like the Gecko, and the single ended current sinking power transistor unipolar setup as used in the original stepper motor drivers.
I've never seen excess back voltage while decelerating with the Gecko's. My DC power conditioning board for the Gecko has an LED that lights should this be the case, and I believe the Gecko itself has an LED indicator for this condition too. You risk killing it however by unplugging one of the windings when it is powered up. The 203V has a 5 amp circuit board level fuse and ought be pretty good against abuse. BTW, the RMS amperage of the Gecko is 5, 7 amps represents a peak winding current.