Extruder steps calibration. What am I missing?

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JamesD
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Extruder steps calibration. What am I missing?

Post by JamesD » Thu Feb 02, 2017 4:12 pm

Been trying to dial in the first layer with a Dual Extruder head.

At default Cura settings of 125% initial line width and 100%flow rate it has been over extruding. I dialed the first layer width down to 100% and backed the flow rate down to 95-96% and tweaking at layer 5 down to 94% to actually get a decent first layer pattern and overal print pattern. So to me it sounds like the extruders' steps/mm are off slightly. NOTE: I said slightly.

I marked the filament and clicked extrude 10x expecting 100mm of travel. It only pushes through 80mm. Ok possibly mis-counted. manually Sent a g1 with 100mm extrusion and got the same result.

My first thought is maybe the hobbed bolts are a different size than the single extruder because the dual extruders' steps/mm were a lot different than the single head. 808 on the dual vs. 851 on the single. To me it wouldn't make sense to have different sizes between the two, but I didn't design it.

Anyone have any thoughts?

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DougZ
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Re: Extruder steps calibration. What am I missing?

Post by DougZ » Thu Feb 02, 2017 6:58 pm

Doesn't the dual extruder have the e-steps values written on stickers on the backside of the toolhead? If you have the e-steps set to the value on the toolhead and request 100mm you should get close to that, not 80mm.
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JamesD
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Re: Extruder steps calibration. What am I missing?

Post by JamesD » Thu Feb 02, 2017 9:17 pm

It's on there. That's where my 808 number came from. I'm definitely getting 80mm but the prints are almost perfect. That's why I'm so confused. I'm just trying to tweak settings to get the first couple of layers a bit nicer. I'm definitely not getting a stringy under-extruded mess which is what I would expect if the numbers were actually that far off.

MikeO
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Re: Extruder steps calibration. What am I missing?

Post by MikeO » Thu Feb 02, 2017 10:27 pm

You might try cutting your extrude speed by 50% or more when doing that test, if you can do that in Cura (I don't use Cura).

If the manual extrusion is trying to push too much plastic out of the nozzle either the filament drive is slipping or the drive stepper motor is losing steps, in either case due to the back pressure.

I've had that problem, and cutting the extrude speed down by 50% or more gave me the numbers I expected.

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DougZ
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Re: Extruder steps calibration. What am I missing?

Post by DougZ » Fri Feb 03, 2017 6:37 am

Good point. I use these commands (even in Cura's control panel) and it works just fine. The "F50" slows the feed rate down to more realistic printing speeds:

eSteps Calibration
Heat Nozzle
Mark filament
G1 E100 F50
Measure
M92 E0 (to reset then go back up to the "mark filament" step and repeat until dialed in)
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JamesD
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Re: Extruder steps calibration. What am I missing?

Post by JamesD » Fri Feb 03, 2017 5:01 pm

MikeO wrote:You might try cutting your extrude speed by 50% or more when doing that test, if you can do that in Cura (I don't use Cura).

If the manual extrusion is trying to push too much plastic out of the nozzle either the filament drive is slipping or the drive stepper motor is losing steps, in either case due to the back pressure.

I've had that problem, and cutting the extrude speed down by 50% or more gave me the numbers I expected.
I thought maybe it was that too. But I opened a gcode file of an actual print and it was about 500-900. I'm extruding at 100-150.

Today I did several tests and lowered the e-steps by 8 every time and upped the flow rate by 1% and it stayed consistent. At 776 steps/mm I got the normal flow rate up to 100% but had to up the first line width to 125% which I'm fine with because that's the defaults. I'm still having to tweak the flow rate down to 94% after five layers to get a good top layer.

To add even more confusion, I re-measured the extruded amount after all the tweaking and now it's only extruding 76mm when I do a "G1 E100 F100". But I'm getting really good prints so maybe I should just leave it alone and not worry about the numbres not making sense.

Edit: I guess it's not that confusing since I was trying to reduce the extrusion amount.

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