Topics

1

General Mach Discussion / Dugong Tuning Problems, Positioning Error

« on: February 13, 2014, 09:15:12 AM »

 Good morning all,

I've got a rather frustrating problem with a pair of Dugong DG2S-0080 servo drives driving a pair of Kelling 34-170 brushed servos. The issue is that my positioning error is never centering on final position. This system is on a lathe. The Z axis has a 1000 count line driver quad encoder, and the X axis has a 2500 count line driver quad encoder. Both have been confirmed to be good (actually, the 2500 count encoder is brand new). There is no appreciable noise in the system which I've confirmed with a scope. I have tuned and tuned and re-tuned again these drives. The only way I can get the position error to stay somewhat close to 0 (+/- 10 counts) is to turn the Kp and Kd gains up to the point where things start getting "buzzy". The critical thing to note here is that NO MATTER WHAT THE Kp and Kd tuning, Ki inputs (integral, error correcting over time) does absolutely nothing to the curves. This doesn't seem possible to me since it should just be math driving the transistors in the drives, but if I didn't know better I'd say the integral term in my drives was broken. The configuration software for the Dugong drives allows inputs of Ki from 0 to 65500. The response graph at Ki=0 and Ki=65500 look nearly identical with neither of them eventually landing on 0. I have these same drives in my mill with some older DC servos but identical encoders and I have never had this problem.

Any thoughts would be very much appreciated.

SG

2

General Mach Discussion / Mach Turn Index Pulse and IPR question

« on: January 01, 2013, 09:07:20 PM »

 Good evening,

I've just finished a control retrofit on an old Crusader Anilam CNC lathe. It has turned out very nice and I'm almost finished working through the bugs. My experience with Mach Turn is very limited and it appears to be far more buggy than Mill has been in years. This evening I was doing a bit of testing with G95 and IPR feed rates. It seemed to be working fine (I have a spindle index pulse which seems to be working with good stability) and then my VFD cut out due to an unrelated issue. I would assume that as the spindle index slowed to a stop as a result of the faulted VFD, the feed rate would also go to 0. This isn't what happened. The feed rate continued along happy as usual, both through the completion of that particular move, and then right on through to the end of the program (I was cutting air, so I let it continue running with the spindle stopped). I find this rather disturbing. Is the IPR just based on the programmed "S1500" and not looking at the index pulse? I haven't messed around with CSS yet, but if this thing isn't reading the actual index pulse than I suspect it won't work as I had hoped. I'm interested to know whether this is a problem others have experiences or whether maybe I'm doing something wrong....?? I do have the "Use Spindle Feedback in Sync Modes" checked.

Thanks

SG

3

G-Code, CAD, and CAM discussions / FeatureCAM to Mach3 Turn Post Processor

« on: November 27, 2012, 07:11:52 PM »

 All,

I am just finishing my first CNC lathe conversion after completing a number of successful mill retrofits. I have been progrmaming with Featurecam V11 all along and now realize that some of the critical aspects of the post processor won't carry over between mill and turn. I know there is a post processor online for free download but it is created on a newer version and it won't load for me. Any assistance with this would be greatly appreciated.

SG

4

General Mach Discussion / Help For a Frozen Northerner...Mach3 Won't Talk

« on: November 15, 2006, 08:34:44 PM »

 I'm just finishing up (so I thought...) a bridgeport 3 axis mill conversion. I just soldered up the last of the connectors this morning and figured I'd be well on my way to making computerized metal chips. Or not.

 I have both the PC Motherboard Parallel port as well as a second PCI parallel port installed in a 1GHz Dell desktop. The only program loaded onto the machine is Mach 3. My controller consists of a power supply, (68 vdc), 3 Gecko G201's, and a cnc4pc.com parallel port breakout board. The motors are 8 wire steppers wired parallel. I have all my limit switches OP'd together on one input, and each home switch has its own pin. All switches used the method described in the Mach 3 mill book (5v, 470 ohm resistor, yada yada yada). I've tested my inputs (outputs from my mill to the computer) and they all trigger high (a tripped switch is sending a 4.75v signal). When I power up the controller, the steppers lock under power.

When I'm in the congif menus, I have tried both the motherboard parallel port, as well as the PCI board. Neither of them relay any signal back and forth. Messing around this evening, I got the PCI board to trip the "LED's" on the diagnostics screen which are in the form of the end of the DB25 connector. These leds are tripping when I trigger a limit switch or home switch. The LED's for the appropriate functions below the DB-25 LED cluster don't light up. I have noticed that with the machine and program sitting idle, a number of the LED's on the DB-25 cluster are lit up...without any inputs or outputs being requested (at least on purpose). I am admittedly way deep over my head on this one. I'm a mechanical engineer...this electrical stuff just makes me cranky:) I think I'm close, but there is obviously something in some setup menu that I have overlooked. There has been some discussion about the type of parallel ports which work with this system...I didn't know if that would have an effect on anything... Needless to say...the motors are not responding to any manual keyboard emulator jog inputs. Any help would be most appriciated.

Spencer Garrett
www.gpe-machine.com