Z height on touch screen doubled when printing multiple parts.

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mb300sd
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Z height on touch screen doubled when printing multiple parts.

Postby mb300sd » Wed Apr 25, 2018 7:42 pm

I've noticed that the displayed part height is doubled when printing multiple copies of the same part. It shows that the height increases by 1 layer after the first part, but the Z screw does not move. This only happens between part 1 and part 2, not between 3, 4, 5... It also seems to print the skirt again after the first part.

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Vicky@Raise3D
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Re: Z height on touch screen doubled when printing multiple parts.

Postby Vicky@Raise3D » Thu Apr 26, 2018 1:31 am

Is it possible to ask your gocde and data files to have a look?

mb300sd
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Re: Z height on touch screen doubled when printing multiple parts.

Postby mb300sd » Thu Apr 26, 2018 3:31 am

Vicky@Raise3D wrote:Is it possible to ask your gocde and data files to have a look?


http://mb300sd.net/Stop_Block.zip

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Vicky@Raise3D
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Re: Z height on touch screen doubled when printing multiple parts.

Postby Vicky@Raise3D » Fri Apr 27, 2018 1:31 am

Does the problem happen at some specific height or each layer? We tried from layer 0 to layer 1 yesterday after work, the results seems fine.

mb300sd
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Re: Z height on touch screen doubled when printing multiple parts.

Postby mb300sd » Fri Apr 27, 2018 2:32 am

Vicky@Raise3D wrote:Does the problem happen at some specific height or each layer? We tried from layer 0 to layer 1 yesterday after work, the results seems fine.


The print comes out perfectly fine, its just a display error. I looked at the gcode myself, and it does print the skirt twice, but other than that, no extra layers are printed. Notice with the gcode I posted, it prints a skirt, the first layer of the first part, the layer height on the screen changes, but the Z screw doesn't move, goes over the skirt again, then the first layer of parts 2-4. Then the Z screw actually moves, and the height displayed on the screen changes, it prints the second layer of part 1, the height on the screen changes without the Z screw moving, and it prints the second layer of parts 2-4. Repeat for every layer. It's a display issue only except for the fact that it extrudes the skirt twice at the same height.

The issue seems to exist any time I add more than 1 part in ideamaker.

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Vicky@Raise3D
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Re: Z height on touch screen doubled when printing multiple parts.

Postby Vicky@Raise3D » Sat Apr 28, 2018 3:33 am

We will test more and feedback to your later.

Alex M.
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Re: Z height on touch screen doubled when printing multiple parts.

Postby Alex M. » Sat Apr 28, 2018 4:15 pm

We seem to be having this problem too. It seems the touchscreen reading for the Z axis in the utilities menu is not reset when a print starts. So every time we lower the deck to get a print off the Z number gets larger. We are now at 700mm and the deck is only about a quarter of the way down.

mb300sd
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Re: Z height on touch screen doubled when printing multiple parts.

Postby mb300sd » Sun Apr 29, 2018 7:02 pm

Alex M. wrote:We seem to be having this problem too. It seems the touchscreen reading for the Z axis in the utilities menu is not reset when a print starts. So every time we lower the deck to get a print off the Z number gets larger. We are now at 700mm and the deck is only about a quarter of the way down.


Try hitting the Z home button, I think that resets it.

Alex M.
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Re: Z height on touch screen doubled when printing multiple parts.

Postby Alex M. » Mon Apr 30, 2018 6:38 am

mb300sd wrote:Try hitting the Z home button, I think that resets it.


Thanks, been meaning to try that but can’t until the print is off and somehow always forget once we have removed it. I just expected the software to reset once we start a new print and the printer homes, but it doesn’t seem to do it. ☹️

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Vicky@Raise3D
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Re: Z height on touch screen doubled when printing multiple parts.

Postby Vicky@Raise3D » Wed May 02, 2018 7:04 am

Alex M. wrote:
Thanks, been meaning to try that but can’t until the print is off and somehow always forget once we have removed it. I just expected the software to reset once we start a new print and the printer homes, but it doesn’t seem to do it. ☹️


Added into developing list.

Jetguy
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Re: Z height on touch screen doubled when printing multiple parts.

Postby Jetguy » Wed May 02, 2018 11:02 am

I think the bigger problem here is once again, users lack of understanding of the hardware system they actually own in front of them. This is topic is old, it's been brought up more times than I can count.
#1 This is an open loop stepper control system, so there is no positional feedback. The only time you can even assume safely you know the current position relies on 2 conditions to be true first being you have homed an axis and second being since homing you have not ever disabled that stepper driver. If either of those conditions is false, then the machine (the motion control board running the marlin firmware) has no idea where it actually is.
#2 The front panel LCD does NOT directly control the printer. It is simply a GUI interface to send gcode commands to the actual motion controller system and firmware. And this concept alone is the crux of the issue here. Users in this very topic are expecting this front LCD to tell them exactly where the printer is. That's nearly impossible in most cases, just based on the standard gcode and interaction between marlin as it exists today. Second is, the display is showing RELATIVE values based on manual commands SENT by the user using buttons on the LCD interface. Again, all it's showing is what you sent over time. It again, has NO IDEA where the axis actually is, because that's not what it is displaying (a query of the current axis coordinate). This is why you are complaining the display shows 700mm and you are nearly homed but not homed. You have manually sent cumulative moves that add up to 700mm since the last boot.
#3 There are limits to what is reasonable here given the architecture and given limits of standard gcode. If you stray from standards, now it's proprietary and opens a whole new can of worms. Example here is, even if possible, sending periodic queries of current axis position can, does and will impact operation of actual printing. Remember, it's printer first, features such as nice to have. When you start ramping up more and more serial communications, we already know there is a limit, we've proven that in small segment prints, adding more nice to have stuff just lowers that limit further.

Again, folks, fine to request whatever for a feature improvement, but rather than placate you and tell you it might be implemented, you should be told the limits of the system because you might be living with them for some time. It's BY DESIGN.
This printer is not that different from an off the shelf LCD less printer that only prints over USB and then you add a tablet running Octoprint gcode streaming server and GUI on the tablet. That same system would have all these nearly identical limitations.

Jetguy
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Re: Z height on touch screen doubled when printing multiple parts.

Postby Jetguy » Wed May 02, 2018 11:33 am

Again, what I am trying to explain to the new users to the group and new owners, you cannot get blood from a turnip.
This has been a limitation of the system since the Kickstarter back in January 2016 when these shipped.
Again, completely fair to ask for a change, but given it's been asked before and they just released the new Pro2 model that likely has the exact same limitation- just trying to be open and share an expectation level with you since this is a limit based on architecture of a 2 board control system based on standard gcode as a communications and command protocol, not to mention the entire concept of open loop stepper control.

Jetguy
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Re: Z height on touch screen doubled when printing multiple parts.

Postby Jetguy » Wed May 02, 2018 12:14 pm

Again, for all the same reasons listed here https://discourse.octoprint.org/t/why-d ... ywhere/232

Because there's no way to get it from the printer without constantly querying it. It can be queried from the printer's firmware using M114, however in order for that information to be actually useful (e.g. in order to use it to trigger timelapse snapshots or do other nifty stuff) that command would have to be issued after any command sent to the printer and also in certain time intervals (since the printer might have moved the head due to being instructed to do that via an LCD menu or because it's printing from SD). The connection between OctoPrint and printer is limited to serial speeds, so 250000 baud at max. This transmission speed can already be maxed out now by just streaming gcode with a lot of short moves (e.g. curve segments). Imagine what would happen if OctoPrint added another command just to query the current head position from the printer after every command sent to the printer in such a scenario. The transmission rate would half, leading to blobby ugly prints, and all that just for some fancy display of where the head is right now or the possibility to trigger timelapse pictures always at the same position. That's just not worth the loss in quality.

Also be aware that OctoPrint can't track that information on it's own either by just adding up any moves sent via it - what about moves not triggered by itself but the printer (see above as to how)?

If you desperately need to have the printhead position displayed somewhere, take a look at a custom feedback command 6 instead. But unless firmware starts to send this information with every acknowledgement of a received command, this won't get added to OctoPrint's core code due to a wrong cost/usefulness ratio.

Jetguy
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Re: Z height on touch screen doubled when printing multiple parts.

Postby Jetguy » Wed May 02, 2018 12:20 pm

Again, something you might not even be aware of now- just updating the temperatures of the 3 heaters (extruder 1, extruder 2, and the bed) takes time and resources away from the microcontroller actually running the printer. This is why that just like some complain position is not updated, well during the heating cycle, you may notice sudden jumps in temp or the bed not showing a temp rise and then a few seconds later in the sequence a jump. This is all due to the Marlin firmware and it's rate of controlling the actual printer hardware and then reporting info back to the LCD system.
Here is a recent topic showing that viewtopic.php?f=2&t=7014&p=27946&hilit=bed+not+heating#p27937

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Vicky@Raise3D
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Re: Z height on touch screen doubled when printing multiple parts.

Postby Vicky@Raise3D » Thu May 03, 2018 2:29 am

As Jetguy said, the real position is hard to get, but resetting the value after each homing is achievable.

mb300sd
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Re: Z height on touch screen doubled when printing multiple parts.

Postby mb300sd » Fri May 04, 2018 6:36 am

I believe we are having 2 different issues. There's the displayed height on the Utilities tab, and the displayed height on the Home tab which I was mentioning. The issue still exists in the latest ideaMaker, and I am still getting double extrusion of the skirt, which is definitely a G-code/IM issue.

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Vicky@Raise3D
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Re: Z height on touch screen doubled when printing multiple parts.

Postby Vicky@Raise3D » Fri May 04, 2018 10:04 am

We tried your gcode on our machine two more times, still didn't see the skirt and wrong height display problems.
Is it possible that you take a video to record these two problems on your printer?


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