[CROSSHATCH]

Hello everyone,

It seemed like it was going to be a promising week starting Monday when I finally started after months of preparation cutting my prototype product. I cannot say what the product is as of now, only the problems I am experiencing.

Let me start off by saying here are my specs:


Gecko 540
Keling 7.3 Amp;48 volt PS
Keling KL23H276-30-8B- Bipolar (Parallel) which is 4.2 Amps Per Phase
I have a 3.2K Set risistor on ea' axis.


***NOTE***Ok before I go on, to clarify I can push against my table as hard as I can and I can't get the motors to stall when jogging at 24 IPM Per axi. Seems like there is way to much power****nOTE*****


So my table has mounted a 7x5x.75 block of aluminum and using CUT 3D as my CAM for this 3d object. Work began all day monday. Monday was my first cut which consisted of a rough cut at:

.1875 endmill
15 IPm cutting
7 IPM plunge
1.5 mm doc
24 IPM Rapids all axis.

The rough cuts uses a Z-axis Rasta cut and then profiles the part for smoothness. The rough cut at first glance on Monday looked perfect! Until yesterday, I seemed to noticed that it had seemed to lose steps in the why because the part start a little head each time it x-axis down. (However, this is very minimal and with a total depth cut from 0mm-9mm it has progressed about 2mm which is not good but not the biggest problems here). So thats that.

I would like to note, that during this rough cut, the Z-axis retracts probably over two dozen times to cut different areas of my product. Make note.


So the rough cut was ok, now came what I thought would be the last of it; the Finishing Pass.

Specs:

.1875 Ball nose
20 Ipm
16 plunge Ipm
.40 mm DOC
24 IPm all rapids.

On the finishing pass, the z-axis only picks up about 5 times and moves to another area. It does not do the part in one pass because because I do not have it on a RASTA where it would try to cut the entire stock which would be a waste of time! My initial finish cut was done at a 45 degree angle. Everything at first looked great! Until I came back over and hour later and found the machine in the z-axis cutting just ABOVE THE STOCK. The x and Y axis seemed to be in the right area both on machine and screen. But the z-axis was above the stock not touching the metal, in fact it was over the stock about 3 to 4 mm moving but never touching the material. This resulted in my prototype not being properly finished and cut oddly. The basic shape was there, but the finish pass left smooth curves and stock rough cut to be untouched.



So after this, I ran numerous tests! I ran the finish pass again and again and again with a 135 degree angle, back to 45, then to a 90 and every time, in certain areas. The cutter was above the surface!!!!!! Some areas cut and then no areas cut and some areas from normal surface height to higher and higher to stock height of the material.

Then I said ok, maybe it's the speed. So I dropped the velocity on all axis on rapids, I dropped all cutting speeds. In fact! I even went so far to drop the Cutting IPM AT 6 INCHES A MINUTE! <------This turned out the worst!!!! I came back to see the cutter was about .50-.75 inches above the cutter in certain areas. The same areas that did not get cut over the past 5 times I ran the finish pass.




So again, I said WTF to myself! I ripped off my aluminum, I ripped off my jig and I slapped on some wood! I wasn't going to flip the wood after the cut because it was only a test to see if it would work; so no alignment jig needed with dowel pins! I redid some programming, figure I was in wood and could up the speed since 6 IPM on the finish pass showed no gooood! So I now ran the BOTTOM portion of the part which is identical to the top (Hence why I use a jig, so when it's flipped, it's right on 0,0). Anyway, I decided to do the rough cut on the bottom and proceeded with:

.1875 endmill
18 IPM
9 IPM plunge
24 IPM all rapids.
1.5 mm DOC

First layer all good, so I left. Came back. Y axis was out of wack, the part looked like steps. It started here, the here, then here, then here. So the part was useless.


Ran the file again on a new piece of wood! This time I dropped the program file from 100% down to 95% of speed. Left and came back and knew there was trouble. I saw my endmill was broken! Z-axis seemed to get stuck in wood and the table decided to move and snapped the tool! That just shows how much torque I must have. for that to happen! This part did the same thing; started here, then here, then here, then here. The x-axis every rough cut seemed fine, the y axis was off much more in WOOD then in Aluminum.






I have lost sleep over this, i thought after all the months of prepping the machine, new electronics, software upgrades, tweaking, jig making, that Monday the protype of my part was going to be made! (nuts)(nuts)(nuts)(nuts)(nuts)(nuts) I can keep going now.....(nuts)(nuts)(nuts)


I thought that this was at first software problem with Vectric cut3d, but changing the value of the Rapids seemed to mess everything up. So i assume this is machine/electronics error.



Here is why i posted this in the Gecko forum. My steppers are rated for 4.2 amps, the way they are wired. When I do a rough cut, there is less movement with all three axis. The z-axis sets it's depth in a plunge and then the the x and y do the work.

On the finish pass all three axis move together when making contours on edges etc. Lots of movement, maybe much more amps being drawn! I thought that maybe because I only have the 3.2 K resistor on ea' axis instead of a 3.5 K resistor, the steppers are not at efficient as they can be.


This all confuses me because everything seems to contradict itself. Cutting in aluminum at the initial test was bad, but not the worst. Figuring lowering the speeds would help, the z-axis ended up higher then originally thought. Cutting in would at the normal speed of the rough cut end up WAY worse then cutting in the aluminum.(nuts)




I am so exhausted from this week, frustrated and sad! I have prepped so long, was so excited and am dealing with such crap.





I have no idea what to do at this point. So maybe it's my resistors or maybe not enough amps for ea' axis to consume from only a 7.3 amp PS. ?????


Please for the love of god, help me members! Help!



-Jason

[zenbot]

sounds like possibly resonance or electromagnetic interference. Are the motor cables routed next to power cables? Did you properly set the mid-band resonance on the driver? The thing you will learn about cnc is that it requires a lot of patience. You will encounter the strangest electrical phenomena with seemingly no explanation. I've had problems pop up out of the blue and drive me crazy, only to go away on their own. Good luck, I'm sure you'll get to see your shiny new prototype soon enough

[P.Passuello]

What sort of PC are you using. Have you used it on a previous machine and know it to be good?
What controller software are you using? Mach3, EMC, Turbocnc etc.
I had a similar problem with Turbocnc and found that if I ran the file from disk without loading it to the editor everytime the PC accessed the file it lost track of what it was doing on the parallel port. The results was the same as you are getting here and slowing the whole thing down did not help and seemed to make things worse. So it is possible that the problem may not be the G540. I am tempted to think that the axis motors are not losing steps because of a mechanical failure because if the Z axis was going the fail because of binding it would more than likely fail when raising which would cause the cutter to go deeper not higher. I have also heard of lost steps caused by power problems and to test it an extension cord was run from the house to the garage and that is what the PC was run from while the router was run on the garage mains.
Just a couple of thoughts, I hope they help.

Cheers
Peter

[jalessi]

Speed,

Taking a simple approach might be less frustrating.

I am guessing you are running Mach3 now since you mentioned Vectric Cut3D.

One:

Make a simple part that takes only 5 to 10 minutes so you can watch your machine instead of leaving it unattended.

Two:

For testing use a larger cheap end mill so you don't break expensive cutters.

Three:
Don't cry, your parts might rust.

Four:
The testing needs to be logical.
Changing two or more settings each time you run a test wont do any good because you wont know what is causing which problem.

Question:

Do you have the Sherline Mode enabled in Mach3?

Remember all the drama Fixittt had until he made that adjustment.

Don't worry about the resistors on the steppers 99.9999% they are fine.

Slow down, your machine will be working flawless in the next few days.

Jeff...

[CarveOne]

Isn't 4.2 amps/phase too much for the G540/G251 boards, which are rated for a maximum of 3.5 amps/phase? Are the optional heatsinks installed? Are the boards overheating?

CarveOne

[CROSSHATCH]

zenbot- Right now the electronics are sitting in a steel cabinet which is unfinished and on my desk. Right next to the the 540 and PS is the switch for my Spindle. And right next the the 540 and PS is my flat screen/computer and power strip which has about 3 cords running from it, one powering the 540, one powering the computer and screen. I have not touched anything that has to do with the mid-band resonance.

P.Passuello- I actually bought a new PC in the summer because I thought it was going to fix problems running a Xylotex 3 axis system. To say the least it did not. But it has been running the 540 flawlessly! It's called E-Machines, and it's been converted to Linux because i'm using EMC2. Also that was my thought to, originally I thought if I lost steps going up, then it would cut into my part....but it's not.

jalessi- I design everything in my room on my very fast PC. the garage computer is the E-Machines strictly running EMC2, no internet, nothing else but milling. I also have been making simple parts and they turn out great, there pretty small but are very good when done! They take a few minutes to cut.

I was just wondering if should have changed the resistors to 3.5k so that they would be the most efficient.

CarveOne- The 540 will only output 3.5 amps anyway, so my motors at most are only getting 3.5 amps, or in my case. 3.2 amps because of my resistor, even though they are rated for 4.2 amps they way they are wired.



Also, the 540, power supply is sitting on the desk in that large steel cabinet which is next to the power strip less then two feet away and next to the computer and next my giant milling enclosure.



Thanks for the input guys, keep them coming



-Jason

[CROSSHATCH]

I would also like to mention, that from what I have seen over the past few days and I hope this isn't my internal suffering trying to cover up anything. But when I ran the finish pass, and over the files I ran, I changed some things. Stepover from 6% back up to 10%, the 6% stepover rate creates a large file. I have noticed that in the end process of the file, the computer is very laggy, especially when in EMC2. It's not smooth.....Just throwing that out there.


-Jason

[jemmyell]

Hi,

Did you do the EMC2 latency test and set up the software stepping config?

Have a look here. Not all computers run EMC2 well.

http://wiki.linuxcnc.org/cgi-bin/emc...StepGeneration

-James

[ger21]

If you're computer is slowing down noticeably, I'd ten to look there. But I don't know anything about EMC.

[Mariss Freimanis]

It's all on the PC side of your parallel port cable, not on the G540 end.

The G540 will not put out more than 3.5A per axis; period. Put a 7A motor on and you still get 3.5A. There can be no resonance issues with the G540; the motor simply cannot resonate. The G540 is extremely stupid. It's history begins and ends every 4 full steps. It cannot possible know it is in a certain part of your program where it should screw things up.

Mariss

[CROSSHATCH]

The computer seems to run small files just fine. The finishing pass with a 6% step over rate creates a file that is about 1.11 MB. When thats loaded in the computer in the shop, it's smooth at first. When the file is nearly complete after mayb 1-1/2 hours of running time, the computer is laggy.

The only thing at this moment that I can think of, is if I create a code with stepover rate at maybe 20% Or even higher. If I do this, the file will be small and not use so much processing.

The finish will be poor, but this may prove my theory and see if this is do to computer lag.


I have done the latency test, I will re-do it again. But i am going to try my idea.

Usually, the files I cut are 15 kb, ....Not 1.11 MB


But again, this confuses me as to why the Rough cut in wood turned out way worse then it did in Aluminum. Minus that fact that I added a few IPM for the wood cut in plunge and in feed.



-Jason

[123CNC]

If it were me, I would double the BASE PERIOD and give the large file a go again in wood (or any sacrificial piece). If results improve, I would follow the EMC wiki to a tee on determining your system's minimum base period.

Do you have the g540 specs for step and direction timing?

[CROSSHATCH]

Do I change the base period in my Hal file? I'm not sure exactly where to look. I have never changed really anything in my Hal.


I also never changed anything for the 540 except putting the right timing in for Stepconf.


-Jason

[CROSSHATCH]

Ok, i'm going to look at the base period: But for example.

What should the timings of the 540 be? For emc2 this what they have as an example.

For example, the Gecko G202 manual says this:

Step Frequency: 0 to 200 kHz
Step Pulse “0” Time: 0.5 uS min (Step on falling edge)
Step Pulse “1” Time: 4.5 uS min
Direction Setup: 1 uS min (20 uS min hold time after Step edge)

The Gecko G203V specifications are:

Step Frequency: 0 to 333 kHz
Step Pulse "0" Time: 2.0 uS min (Step on rising edge)
Step Pulse "1" Time: 1.0 uS min
Direction Setup: 200 nS (0.2uS) before step pulse rising edge
200 nS (0.2uS) hold after step pulse rising edge




Lets start there.


-Jason

[CoAMarcus]

Jason,

The minimum time on and off for the G540 is 1uS for logic 1 and 4uS for logic 0. Set the step pulse width to at least 2uS and the direction pulse width to the same. The maximum step pulse frequency allowed is 350kHz which should not be a problem, as that would be over 10,000RPM on a step motor.

Marcus

[CROSSHATCH]

So something like this:

Step Frequency: 0 to 350 kHz
Step Pulse “0” Time: 4 uS min (Step on falling edge)
Step Pulse “1” Time: 1 uS min
Direction Setup: 2uS


Or did I mess that up ? (nuts)


-Jason

[CoAMarcus]

Jason,

That looks correct. Is that how you have EMC2 set up?

Marcus

[CROSSHATCH]

I don't think so, I will have to go check it out. I think I used EMC2 Gecko category which may have given me the 202 version.


Should I just try and run the file with those new settings or should I go into the Hal and change the base period and all that good stuff?? Maybe I should run it and take it step by step...or "pulse by pulse" get it?....ahahah, ok not funny


-Jason

[CoAMarcus]

Try running it with just these settings changed and see if that changes anything at all.

On a side note, my Spanish book in school was called "Paso a Paso" or step by step. This also happens to be what you call a stepper motor in Spanish, so I have always thought that would be the equivalent of calling and English book "Stepper". Okay, my lame humor is done now. :-)

Marcus

[CROSSHATCH]

Marcus- One last thing: Here is what I had in EMC2 for Gecko540 use:

Step time 4000ns = 4 uS
Step Space 500 ns= .5uS
Dir Hold 20000ns=20 uS
Dir setup 1000ns=1 uS

These numbers are totally off correct?

Can you replace those numbers with what they should be for the 540? I'm confusing myself with the names.



Let me know, so see your humor is accepted


-Jason