Odd Bed Shape - ski ramp at the front.

lawson.brian · Friday at 6:52 PM

Hi,

I have a new built LDO 2.4 350mm Rev C (with Rev D updates - Leviathon and Nighthawk) that I am finishing off. Currently not enclosed while I get a couple of print hours on it to shake it down. Bed has 1 tight, 2 snug and one loose bolts.

I am running PCB Klicky and when I run a bed mesh (currently 5x5) it turns up relatively flat bed except for the front (see the bottom of the raw data below). In preparation I run homing, QGL and then homing again prior to the mesh. I am used to seeing nice taco's with my bed slingers but not one that is flat with a ramp across the front and am wondering if there is possibly a different issue in play then the bed that i should be looking for. This is my first flying gantry and first corexy so a lot of new stuff for me - I come from Switchwire and Ender 3's. Running 70% heater duty.

Any ideas?

probe at 310.000,285.000 is z=5.682500

probe at 310.000,285.000 is z=5.681250

probe at 242.500,285.000 is z=5.672500

probe at 242.500,285.000 is z=5.673750

probe at 242.500,285.000 is z=5.671250

probe at 175.000,285.000 is z=5.672500

probe at 175.000,285.000 is z=5.673750

probe at 175.000,285.000 is z=5.672500

probe at 107.500,285.000 is z=5.677500

probe at 107.500,285.000 is z=5.678750

probe at 40.000,285.000 is z=5.686250

probe at 40.000,217.500 is z=5.687500

probe at 40.000,217.500 is z=5.686250

probe at 107.500,217.500 is z=5.677500

probe at 107.500,217.500 is z=5.676250

probe at 175.000,217.500 is z=5.665000

probe at 175.000,217.500 is z=5.663750

probe at 242.500,217.500 is z=5.660000

probe at 310.000,217.500 is z=5.661250

probe at 310.000,217.500 is z=5.660000

probe at 310.000,217.500 is z=5.658750

probe at 310.000,150.000 is z=5.606250

probe at 310.000,150.000 is z=5.607500

probe at 242.500,150.000 is z=5.621250

probe at 175.000,150.000 is z=5.647500

probe at 175.000,150.000 is z=5.646250

probe at 107.500,150.000 is z=5.665000

probe at 107.500,150.000 is z=5.663750

probe at 40.000,150.000 is z=5.642500

probe at 40.000,82.500 is z=5.628750

probe at 107.500,82.500 is z=5.665000

probe at 107.500,82.500 is z=5.663750

probe at 175.000,82.500 is z=5.658750

probe at 242.500,82.500 is z=5.612500

probe at 310.000,82.500 is z=5.592500

probe at 310.000,82.500 is z=5.591250

probe at 310.000,15.000 is z=5.685000

probe at 242.500,15.000 is z=5.708750

probe at 175.000,15.000 is z=5.741250

probe at 107.500,15.000 is z=5.730000

probe at 40.000,15.000 is z=5.691250

probe at 40.000,15.000 is z=5.690000

shiftingtech · Friday at 8:15 PM

Range.0.150.

Meh. Pretty decent bed. Are you seeing anything in actual prints to make you think the mesh isn't accurate?

If there is something, one thing that comes up occasionally is cables/reverse bowden being pulled too tight, so it torques the toolhead at the very front

3dCase · Saturday at 5:19 AM

I agree with @shiftingtech, pretty good looking bed.
One thing they do with this visualisation of the numbers is they exagerate them so it looks like you have something to look at. You need pretty good eyesight to spot a few thousands in difference really, so their picture is exponential and looks enormously warped.
I stopped looking at them and just print. If you have a decent first layer just go with it and don't worry too much about this picture.

lawson.brian · Saturday at 3:22 PM

Thanks for the replies. First layer (without using the bed mesh) is pretty good after the QGL but you can measure the first layer difference depending on the part of the bed (0.3 layer height gave around 0.1mm difference from min to max that I could measure) but it did all stick ok. Mesh should cure this - I guess I am being a bit too critical

The only other issue i noted is the bed temp at the top is around 8 deg C lower then the bed thermostat indicates (at 60 deg C) when using an IR gun where as my Switchwire is bang on measured vs indicated (several checks during a 2h print). Not a biggie but will need to keep this in mind when setting bed temps but is a bit of a surprise to see such a deviation.

Thanks for all the help

!

3dCase · Sunday at 1:22 AM

lawson.brian said:
Thanks for the replies. First layer (without using the bed mesh) is pretty good after the QGL but you can measure the first layer difference depending on the part of the bed (0.3 layer height gave around 0.1mm difference from min to max that I could measure) but it did all stick ok. Mesh should cure this - I guess I am being a bit too critical

The only other issue i noted is the bed temp at the top is around 8 deg C lower then the bed thermostat indicates (at 60 deg C) when using an IR gun where as my Switchwire is bang on measured vs indicated (several checks during a 2h print). Not a biggie but will need to keep this in mind when setting bed temps but is a bit of a surprise to see such a deviation.

Thanks for all the help !

What do you mean with the bed at the top? You say you have a V2.4, bed should always be at the bottom

. If you mean at the back, or the front, mine is the same. The kit came with a keenovo pad which is way smaller then the bed itself. I thought that strange and I have actually converted another machine with a mains powerd keenovo but I took the pad that was just 10mm smaller all around. That bed never showed any variation anywhere more then 2 degrees from center to edge.

lawson.brian · Sunday at 6:42 PM

3dCase said:
What do you mean with the bed at the top? You say you have a V2.4, bed should always be at the bottom . If you mean at the back, or the front, mine is the same. The kit came with a keenovo pad which is way smaller then the bed itself. I thought that strange and I have actually converted another machine with a mains powerd keenovo but I took the pad that was just 10mm smaller all around. That bed never showed any variation anywhere more then 2 degrees from center to edge.

Hi,
By the top I mean on the PEI print bed. I took a few temperature checks during an early test print and it was consistently out at both 60 deg C and 70 Deg C by around 8 deg. I am using the LDO rev D printer.cfg file but the bed looks to be the same across the C and D when looking at both of the files. I have built the rev c kit (usually comes with the Octopus) with the Leviathan & Nighthawk boards.
From the LDO github they have the preconfigured klipper config files to make the Klipper config a bit easier.
leviathan-printer-rev-d.cfg
octopus-printer-rev-c.cfg

Bed thermistor should be the ATC Semitec 104NT-4-R025H42G but I will check when I next lift the bed but is the same across both files.

Pictures show the issue with 70 deg reported in klipper for the bed but 62deg on the IR tool. When taking the same measurement on the Switchwire (Prusa bed) from the PEI build surface it is +/- 1 deg on the IR tool.

Bed was under heat for a good hour for this test print. I will run it up to 100 deg c tomorrow and take some more readings. Even cold there is a 3 degree difference between the hotend and bed so some issue there

3dCase · Sunday at 11:08 PM

lawson.brian said:
Hi,
By the top I mean on the PEI print bed. I took a few temperature checks during an early test print and it was consistently out at both 60 deg C and 70 Deg C by around 8 deg. I am using the LDO rev D printer.cfg file but the bed looks to be the same across the C and D when looking at both of the files. I have built the rev c kit (usually comes with the Octopus) with the Leviathan & Nighthawk boards.
From the LDO github they have the preconfigured klipper config files to make the Klipper config a bit easier.
leviathan-printer-rev-d.cfg
octopus-printer-rev-c.cfg

Bed thermistor should be the ATC Semitec 104NT-4-R025H42G but I will check when I next lift the bed but is the same across both files.

Pictures show the issue with 70 deg reported in klipper for the bed but 62deg on the IR tool. When taking the same measurement on the Switchwire (Prusa bed) from the PEI build surface it is +/- 1 deg on the IR tool.

Bed was under heat for a good hour for this test print. I will run it up to 100 deg c tomorrow and take some more readings. Even cold there is a 3 degree difference between the hotend and bed so some issue there

Aha, ok you mean this way. First of all I have never seen just 3 degrees difference from a thermistor being wrongly defined. I have seen -60 or 20something degrees difference but that is no guarantee of course.
Secondly those Ir guns, unless of high industrial quality and calibrated, are always having their own standard deviation.
Secondly the surface colour of the measured object can also affect its reading, darker objects are more accurate for instance.
Even after a heat soak, if the room is at normal temperature and the printer is not enclosed fully, you will get a difference from where the thermistor sits and the top of the bed.
I would not waste too much time with being so specific, the components are not guaranteed to fall within a certain range of accuracy even, so from one to the other there will also be a difference. Just verify the correct thermistor and if the cfg is the same I would simply live with it.
With regards to you IR gun, you can check with a pan of boiling water and look up your altitude and check the boiling temperature of water at your elevation. Then do the test with a dark pan and a shiny aluminium pan. Chances are that if you bought a consumer temperature ir gun it will show some differences.

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Odd Bed Shape - ski ramp at the front.

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