X "Walking" .3mm with each layer?

Re: X "Walking" .3mm with each layer?

IceMan — Tue, 05 Nov 2013 07:13:30 -0500

Hi all,

I have had some time to clear my head and the problem I have is NOT electronics or software.
It's my own stupidity. (Nophead... I think you're right...need a new... and a bigger house)
In regards to my two old machines I have had a good look at them (3hrs....I was not going to, but had no choice....) and they are not as bad as I thought after first run. They have a timber frame and needed some adjusting before they where back working ok again after being retired for a while. Just coincidental that they slanted on first try and I was just in too much of a hurry when I did my first test. (Could not see the trees for the forest)
Don't bother testing with the files I posted. They will turn out good.

Lesson learned? Well, don't rush when you try to test and solve a problem. (And use your head....:) )
I will come back later with information when I have resolved my problem.

Thanks again for your replies.

Regards
Jan

Re: X "Walking" .3mm with each layer?

leadinglights — Tue, 05 Nov 2013 04:02:53 -0500

Have you tried a different Arduino? Although rare, it is possible to get problems in the MCU such that a bit in one register is communicating with another bit. In this case it may be something like the counter for layer toggling the step output. That is, not a software or firmware problem but a hardware problem.

Mike

Re: X "Walking" .3mm with each layer?

IceMan — Tue, 05 Nov 2013 02:58:55 -0500

Quote
nophead

Quote

And why at around 117-118mm?

When it is independent of position, mechanical drive system, firmware, host and slicer the only explanation I can think of is a small discontinuity in the space time continuum in your house :S

Quite possible....I do seem to loose track of time when I "play" with these printers.....but my i3 is not the Einstein variant... :)

I will concentrate on my i3 to see if I can find the solution as it is easy to access in regards to electronics and drive train.
But this is what I have done so far on my i3
Tried 3 different firmware
Tried 3 different slicers
Tried 2 different hostware

All on same machine just to see if there was a difference. And I have changed any setting I can think of.

I am printing very nice parts on this machine and speed can be from slow to fast and no issues, as long as the part is less than 117mm in X or Y.
Layer height is 0.2mm.

Things I will try next:
1) Change layer height
2) Create the file I try to print using various CAD applications (maybe this is an excuse to learn OpenSCAD).
3) Rotate the file 45 deg.
4) Print a file with base less then 117mm but larger above (Like a vase)
5) Continue to google.....
6) ...
.
.
666) Call a priest..........

If anyone could try to print the files using a printer with Arduino 2560 and Ramps 1.4 and report back that would be great. And if anyone does experience the same then I would love to hear from someone that could print the files using a different board (Rambo, X3 or any other) and report back.
Thanks in advance.

The printing takes only a couple of minutes.

Regards
Jan

Re: X "Walking" .3mm with each layer?

nophead — Mon, 04 Nov 2013 16:39:09 -0500

Quote

And why at around 117-118mm?

When it is independent of position, mechanical drive system, firmware, host and slicer the only explanation I can think of is a small discontinuity in the space time continuum in your house :S

Re: X "Walking" .3mm with each layer?

IceMan — Mon, 04 Nov 2013 16:22:16 -0500

Quote
nophead
So you are saying you have the same problem with three types of mechanical drive, three different firmwares, two hosts and three slicers? And always 0.3mm per layer?

Wow that is so weird it is spooky.

Hi nophead,

Yes it is driving me crazy at the moment.
My layer height is 0.2mm as I use 0.3 nozzle right now, but the problem is very weird indeed. Will try different heights and report back.
As I said before I normally don't print over 100mm parts so the problem does not show up..
I will try to do some different layer heights and report back.
What really gets me is that I can run at snail pace, heat sinks and fan and cool drivers and all "looks and sounds ok" but as soon as the layer change happens it is skewered a smidgent (same every layer). I need to double check the 45 degrees rotation and see what happens.
And why at around 117-118mm?

When I get back from work I'll do some more investigation/ testing.

Thanks for your reply

Regards
Jan

Re: X "Walking" .3mm with each layer?

nophead — Sun, 03 Nov 2013 09:29:49 -0500

What layer height are you using? Does the angle of the slope change with different layer heights?

What happens if you rotate the object 45 degrees?

Re: X "Walking" .3mm with each layer?

nophead — Sun, 03 Nov 2013 09:21:43 -0500

So you are saying you have the same problem with three types of mechanical drive, three different firmwares, two hosts and three slicers? And always 0.3mm per layer?

Wow that is so weird it is spooky.

Re: X "Walking" .3mm with each layer?

IceMan — Sat, 02 Nov 2013 20:52:45 -0400

Hi all,
Every now and then this issue pops up and I have not found a "definite answer" to the problem. Could be me so correct me if I am wrong and please point me to the answer.
Here is the story:
Slanting as in posts above but no mechanical problems..
Happens on several printers. One with nema23 and threaded rods as drive train. One with belts and 2 Prusa i3's with braid line.
BUT it only happens when the part is larger then 117mm (??)
I can print any parts that have an x or y smaller then 117mm perfectly on these printers.
I can print the parts on any part of the bed and at any speed I set the printer at without loosing steps.
As an example I print the large wades herringbone gear anywhere on my table and no problems at all.
I have made up some test files of a simple rectangle and printed slowly and fast.
I have changed everything I can think of in the firmware but no change.

The issue happens at layer change as in post above.
I tried to add the delay but no change. (Maybe I added it in the wrong place....been some long nights)

Firmware tried: Marlin (I normally use this)
Sprinter
Repetier

Host software: Pronterface and Repetier

Slicer tried: Kisslicer, Slic3r and Skeinforge

Hardware is Arduino with Ramps 1.4 and Pololu drivers

Checked vref on drivers.
Have active cooling on drivers with heatsinks

Most parts I print are way smaller then 117mm so it does not affect my prints BUT why does it slant above 117mm?

Have attached some test files for those who are willing to try and report back.
117mm file prints ok
118mm and above slants
150mm file slants

The critical point is somewhere between 117 and 118 both X and Y
Rotate part in slicer to test Y axis

Any help on this much appreciated.

Regards
Jan

Re: X "Walking" .3mm with each layer?

Chris the Carpenter — Tue, 12 Jun 2012 20:31:54 -0400

Hey guys, sorry for the delay.

I have been a bit swamped with orders --I gotta do stuff that feeds me before I get to go play with printers.

Okey dokey, the delay itself was added to the actual HIGH/LOW step command. This can be found under the "Marlin" tab in some versions and under the "stepper" tab in some other versions. In either case, you can usually find what you need by doing a "find" search for "HIGH". Eventually, you will find something that looks like this:

if (counter_x > 0) {
WRITE(X_STEP_PIN, HIGH);
counter_x -= current_block->step_event_count;
WRITE(X_STEP_PIN, LOW);
count_position[X_AXIS]+=count_direction[X_AXIS];
}

There will be similar routines for each axis. My delay-added version looks like this:

if (counter_x > 0) {
WRITE(X_STEP_PIN, HIGH); <-- this is the actual step
counter_x -= current_block->step_event_count; <-- this is the code "counting" steps
delayMicroseconds(2); <-- this is the added delay to make the step pulse longer
WRITE(X_STEP_PIN, LOW); <-- end of the step, back to low
count_position[X_AXIS]+=count_direction[X_AXIS]; <--more counting stuff
}

I should also add that this whole problem stems from the fact that I have a habit of reinventing the wheel. Reprap and all of its cousins, has been pretty much figured out. In hind sight, I would have been better served by simply replacing the "standard" reprap frame with my beefy welded-steel assembly and called it good. Instead, I felt the need to upgrade to really over-sized motors and thus, really big drivers. These drivers, unlike any "standard" reprap driver you could use, includes opto-isolators. These opto-isolators are basically a LED and a photo sensor (facing each other) inside of a little chip. These are handy in that the thing that is sending the signal and the driver itself are completely isolated from each other. There is no chance for noise to backfeed and no problems with any kind of "surge". The problem is that the LED's and sensor take a little bit to physically turn on. Sure, we are talking millionths of a second here, but still much longer than what marlin and the arduino are spitting out.

Although, adding this delay solved my problem, I have now found that when I print, there is a "sweet spot" in terms of the final printing speed. (I use a ultipanel and thus, can speed up or down while printing). Even with the "fix" in the code, the walking effect can return if I simply print too fast or even if I print really slowly. Put simply, although this does indeed "fix" the problem, a FAR better fix would be to use the proper drivers in the first place. And on those lines, I am doing just that. I am in the process now of converting to more "standard" drivers.

Re: X "Walking" .3mm with each layer?

mouritsen — Sat, 09 Jun 2012 23:40:07 -0400

I am having the same issue, (although I was printing fine and it just suddenly came up out of the blue), but I'd like to try adding a small delay too. +1 for finding out where in the code you added it.

Thanks,

Steve

Re: X "Walking" .3mm with each layer?

thejollygrimreaper — Sat, 09 Jun 2012 06:00:51 -0400

i would be tempted to say you timing pulley is slipping i would rough up the surface of the shaft and put the timing pulley back on and tighten it right up, also i'd get those belts nice and tight (springy), i'd also be tempted to print some abd timing pulleys anf press fit those on instead, how much current are you putting into those steppers?

Re: X "Walking" .3mm with each layer?

dzach — Sat, 09 Jun 2012 05:36:33 -0400

Could you please indicate where in the Marlin code you inserted the delayMicroseconds(2) ?
Thanks!

Re: X "Walking" .3mm with each layer? (Solved)

Karl_Williams — Sun, 20 May 2012 21:27:40 -0400

It would be nice if the pulse width time could be set in the configuration.h file. I have an extra CNC controller that I am thinking about using for a 3D printer I'm building right now. I had a similar problem with a board I bought on Ebay that came from China. The problem with that board was that the opto couplers were too slow and made the square wave look like a triangle wave so at faster speeds it lost a lot of steps.

http://www.kwartzlab.ca/2011/06/taig-milling-machine-stepper-motor-and-controller-upgrade/

Re: X "Walking" .3mm with each layer? (Solved)

Chris the Carpenter — Sat, 19 May 2012 22:49:47 -0400

Solved and solved. AND I GOT MY MARLIN BACK!

Once again, I can not tell you guys how much I appreciate your help on thinking this one through. It is a real blessing to be part of so many open source communities. Sharing and helping are good things.

Alrighty -- Yes, I was loosing steps. However, I was not loosing steps via the motors actually "slipping" or "skipping". Instead, it was a simple matter of the pulse width coming from the Arduino (and Marlin firmware). We had arrived at this earlier in this forum thread, but I can now confirm this with data. I finally got around to getting a scope/ logic analyzer on one of my drivers. I was able to monitor the pulse going into the driver (via the O-scope) and also the 4 outputs going to the stepper (via the logic analyzer). I could see each step being sent clearly, but I did not always see a corresponding change in the 4 bits that were showing me the state of the motor coils. Put simply, the pulses were just too quick for the drivers to catch.

You wanna know what I did? --I made them longer (and it could not be more KISS than this...)

delayMicroseconds(2);

That's it. I simply added a 2/1,000,000 second delay and all is right in the world. The walking is simply non-existent. I can see no noticable change what-so-ever in the function of the firmware with this tiny delay added. I have also repeated my original test (scope/logic probe) and, I can confirm the fix. Oh! It is SOOOO nice to have my LCD, encoder wheel and on-the-fly adjusting back.

On a side note, I should mention that I also got around to finishing my heated bed. I milled my own PCB(s) and (because God loves me) I got pretty darn close to the resistance I wanted. I now have (2) 6x9 PCB's for a total heater size of 9x12 (230x300). The machine is actually capable of 14x14x16 (350,350,400) but for now, I think 9x12 should do me just fine. The final specs for the heater come out to 1.8 ohm @ 24v = 13.5 A and 320 watts. Not too shabby.

Thanks again guys.

Re: X "Walking" .3mm with each layer?

Chris the Carpenter — Sun, 13 May 2012 22:29:48 -0400

Interesting indeed.

I will put a O-scope on the output for both Marlin and Sprinter and I will tell you my friend, exactly how long those gosh-darn pulses are. Well, I mean I will get to it... At this point, I simply have a working machine and I just want to use the darn thing! I have been doing a bunch of test prints and trying to get things dialed in, so far with fantastic success. To put it simply, I am currently distracted by a shiny thing --forget the problems of the past. :)

Here is your update, guys --Its a good one.

http://www.youtube.com/watch?v=UYBbkfThmOM&feature=youtu.be

Oh, and specs for the driver? Um, yeah --I think there is one, single, EE in Shenzhen who designed the board and thus knows the specs of these drivers. For the other 99.99999% of the world, we just shell out our 17 bucks to ebay and hope for the best. --Joking aside, I am sure I could unbolt the heat sink and find out what chip is in it but again... ...distracted by a shiny thing.

Re: X "Walking" .3mm with each layer?

Polygonhell — Sun, 13 May 2012 17:58:16 -0400

Interesting, the counter change in marlin is going to be of the order of 1-3 clocks, so you'd end up with pulses in the low 100s of ns range assuming WRITE_E_STEP is just writing to a memory mapped location, which is really short compared to what something like Mach3/EMC would put out for a mill.
I just looked and the drivers on my mill are specced with a minimum pulse width of 2.5us or 2500ns.

Since Sprinter appears to work I think your suggested change to Marlin would actually provide a longer pulse than sprinter so it's worth a shot.

I wonder what the spec for Chris' drivers is?

Re: X "Walking" .3mm with each layer?

nophead — Sun, 13 May 2012 06:30:04 -0400

Sprinter looks like this:

void do_step(int axis) {
  switch(axis){
  case 0:
    WRITE(X_STEP_PIN, HIGH);
    break;
  case 1:
    WRITE(Y_STEP_PIN, HIGH);
    break;
  case 2:
    WRITE(Z_STEP_PIN, HIGH);
    break;
  case 3:
    WRITE(E_STEP_PIN, HIGH);
    break;
  }
  steps_taken[axis]+=1;
  WRITE(X_STEP_PIN, LOW);
  WRITE(Y_STEP_PIN, LOW);
  WRITE(Z_STEP_PIN, LOW);
  WRITE(E_STEP_PIN, LOW);
}

So X gets a shorter pulse than the others.

Marlin looks like this:


      if (counter_x > 0) {
        WRITE(X_STEP_PIN, HIGH);
        counter_x -= current_block->step_event_count;
        WRITE(X_STEP_PIN, LOW);
        count_position[X_AXIS]+=count_direction[X_AXIS];   
      }

      counter_y += current_block->steps_y;
      if (counter_y > 0) {
        WRITE(Y_STEP_PIN, HIGH);
        counter_y -= current_block->step_event_count;
        WRITE(Y_STEP_PIN, LOW);
        count_position[Y_AXIS]+=count_direction[Y_AXIS];
      }

      counter_z += current_block->steps_z;
      if (counter_z > 0) {
        WRITE(Z_STEP_PIN, HIGH);
        counter_z -= current_block->step_event_count;
        WRITE(Z_STEP_PIN, LOW);
        count_position[Z_AXIS]+=count_direction[Z_AXIS];
      }

      #ifndef ADVANCE
        counter_e += current_block->steps_e;
        if (counter_e > 0) {
          WRITE_E_STEP(HIGH);
          counter_e -= current_block->step_event_count;
          WRITE_E_STEP(LOW);
          count_position[E_AXIS]+=count_direction[E_AXIS];
        }
      #endif //!ADVANCE

So all pulses are the same and a bit shorter than Sprinter. Simply moving the low write to after the update of count_position might be enough to make it the same as Sprinter.

Re: X "Walking" .3mm with each layer?

Polygonhell — Sun, 13 May 2012 05:05:04 -0400

Glad you've got it working.
Interesting info about Sprinter/Marlin and I assume the other derivatives, I wouldn't have guessed that and I've never put a scope of the signal pins because I've never had an issue.

Re: X "Walking" .3mm with each layer?

Chris the Carpenter — Sat, 12 May 2012 18:26:20 -0400

Do you think this would be as easy as just adding say, a 1 or 2 uS delay in the code after the high/low step? The Mach3 software I use for my mill has this "elongated pulse" option standard, I wonder if I can replicate this lengthened pulse by doing the above.

Don't get me wrong, I am very happy to be printing again, and I am stoked to start work on the proper build table and to start getting things dialed in for good prints --that said, I sure do want my LCD back.

Re: X "Walking" .3mm with each layer?

nophead — Sat, 12 May 2012 18:20:49 -0400

It probably is the pulse timing then. Sprinter gives shorter pulses on the X axis that it does for Y, which is shorter than Z and so on.. Marlin may well be shorter still.

Re: X "Walking" .3mm with each layer?

Chris the Carpenter — Sat, 12 May 2012 17:20:41 -0400

Fixed. I guess...

It was firmware. I am running Sprinter now and all seems right in the world. Of course, this means I have lost my fancy-schmancy LCD and encoder wheel, but I am getting prints going straight up now.

Now I have to figure out if I want to go back to Marlin and see if I can find the problem (I am thinking more now about float rounding problems) or if I want to just suck it up and stick with Sprinter. Ugg.

I cannot tell you guys how much I appreciate your help on this one.

Chris

Re: X "Walking" .3mm with each layer?

Chris the Carpenter — Sat, 12 May 2012 16:11:14 -0400

Thanks guys,

I had a moment of clarity last night when I noticed that we seem to be walking exactly the same distance as we are moving up on the Z. --Z is moving up .3mm (approx) each layer and what do you know, we are also walking about .3mm on each layer.

Seems to me that I have some Z "bleeding" into my X. I mean, the math would be there for that theory.

Ok, for today, I am going to do the "print twice as big" thing, going to try swapping pins on the Arduino and finally, I will probably re-wire the X axis.

I think we might be running out of things "it could be".

Re: X "Walking" .3mm with each layer?

nophead — Sat, 12 May 2012 15:23:51 -0400

If you are using normal CNC drivers it is quite likely the step pulse width is too small or the setup and hold time of the direction signal is too short.

I got a similar effect when I had my step signal the wrong polarity so it changed too close to setting the dir signal.

Reprap firmware is designed to drive stepper motor chips directly. Often CNC drives have opto couplers which slow everything down.

Re: X "Walking" .3mm with each layer?

Polygonhell — Sat, 12 May 2012 12:28:52 -0400

Other thoughts.
You could try changing the I/O pins on the arduino that you're using to drive the bad axis.
Personally I'd re run the wiring for that axis as well.

Re: X "Walking" .3mm with each layer?

Nudel — Sat, 12 May 2012 04:45:35 -0400

Try printing the part twice the size. If it displaces twice the amount on each layer, the error accumulates as it's printing the layer. Bigger layer = more errors. Then it's likely a noise issue. You could also try out the default sprinter firmware to weed out that issue.

If the walking errors are the same and each of the layers come out fine, the issue appears as you move from one layer to the next. This implies noise from when the z motors activate. Are they always on, even when idle? How's the z acceleration? Either way, I'd double check every connection and soldering point on the offending stepper controller. You could try beefing up the grounding cables, but it's a shot in the dark.

You can also try to switch the z stepper controller for the x. I don't know the drivers you're using, but a faulty driver is not uncommon.

Good luck!

Re: X "Walking" .3mm with each layer?

Chris the Carpenter — Fri, 11 May 2012 22:28:55 -0400

Yup, I was afraid of that...

I remember fighting through different firmwares when I was printing with my CNC. Ugg

At any rate, I appreciate everyone's help on thinking this one through, I think I just have some good ol' fashoned tinkering time ahead of me.

Thanks, guys.

Re: X "Walking" .3mm with each layer?

Polygonhell — Fri, 11 May 2012 22:10:40 -0400

Ok then I misunderstood the description and it's likely not mechanical.
I assume you've tried slicing/printing something else?
Assuming you swapped the wiring bewtween the microcontroller and the drivers to swap the axis, it could still be a noise problem or an electrical problem before the drivers.
Without a scope or replacement hardware that's hard to test.

It's probably easier to try a different firmware and rule that out.

Re: X "Walking" .3mm with each layer?

Chris the Carpenter — Fri, 11 May 2012 21:58:28 -0400

I would agree, it would be amazing if this were an issue with slicer, pronter or marlin. However, in terms of mechanical...

The issue started on the X axis (gantry axis) and slowly stepped to the "-" side each layer. When I swapped out the driver, the issue was identical (thus, not the driver). When I tried to print on a different portion of table (thus, different part of the rods and belt) the issue was identical. Then, when I swapped the axis, and made the table into X and the gantry into Y, the issue was identical, but now slanting allong the axis of the sliding table. If this were a mechanical issue, then that mechanical issue exists on both the mechanics of the gantry and the mechanics of the table. I should mention that the issue is IDENTICAL whether using the table as my X or the gantry as my X --Thus, unless the mechanical problem exists (in exactly the same way) on both systems of glides. That would be a pretty big co-inky-dink.

Re: X "Walking" .3mm with each layer?

Polygonhell — Fri, 11 May 2012 21:37:07 -0400

I think unless you're using something really esoteric I really doubt if the issue is in the firmware/slicer/host software.
If you use something like repetier host you can preview the sliced file, and rule that out.

If the error didn't change directions when you swapped drivers etc, I would say the one thing you haven't ruled out is it being mechanical, or am I misunderstanding your description?

Re: X "Walking" .3mm with each layer?

Chris the Carpenter — Fri, 11 May 2012 21:08:08 -0400

And still some more...

I just swapped my X and Y axis and I can cause exactly the same problem using the mechanics of the Y axis. It is identical whether I use the sliding table as my X or if I use the gantry as my X. So far, I have swapped/tested each driver, each stepper and mechanics of each axis.

Looks like it is not mechanical. It also seems like the problem is not wiring either (a loose connection etc. would not be this consistant)

I suppose it has to be in the firmware, host software and or slicer.

Again, I am open to any thoughts