Scaling and X-Y deviation

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rootboy
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Scaling and X-Y deviation

Postby rootboy » Fri Nov 03, 2017 3:53 am

Hi guys,

For the longest time I was having problems with the hotend jamming and the extruder stripping the filament. It turned out the scaling was off on my printer by just under 6%. I found this out when I printed a NEMA 17 to NEMA 23 adapter and it was too small. Up until that time I was printing knick-knacks, so I didn't even bother checking for accuracy.

When I discovered the error, it occurred to me that the volume of plastic would also have to be corrected. It turns out that about 91.5% of normal is just about right. Now I've got nice, clean prints, with zero jamming.

Since I knew that my scaling was off, I found a 100 mm x 100 mm "L" block on Thingiverse and printed it up. I got the scaling factor that I needed, but found that the X and Y lengths were off by about 1 mm (the X axis being the longer of the two). The "L" block is 10 mm wide (and 5 mm tall), and it's thicker nearer the angle, and tapers off towards the ends. It is also a little over on the X plane, while the Y plane is a bit under.

The printer has been leveled using a dial indicator and the new arm lengths were stored in the EEPROM. The printer prints out a very nice and flat circle at any diameter.

Are there any adjustments that can be made to correct for this?


Thanks!

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pouncingiguana
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Re: Scaling and X-Y deviation

Postby pouncingiguana » Fri Nov 03, 2017 7:14 am

Quite possibly. Can you post a dump of your Eeprom?

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rootboy
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Re: Scaling and X-Y deviation

Postby rootboy » Fri Nov 03, 2017 10:32 pm

Sure! here you go. Thanks!

Code: Select all

Baudrate|250000
Advanced User|1
Filament printed [m]|550.995
Printer active [s]|527478
Max. inactive time [ms,0=off]|900000
Stop stepper after inactivity [ms,0=off]|600000
Steps per mm|80.0000
Max. feedrate [mm/s]|250.000
Homing feedrate [mm/s]|80.000
Max. jerk [mm/s]|32.000
X home pos [mm]|0.000
Y home pos [mm]|0.000
Z home pos [mm]|0.000
X max length [mm]|250.000
Y max length [mm]|250.000
Z max length [mm]|387.300
Acceleration [mm/s^2]|1850.000
Travel acceleration [mm/s^2]|3000.000
Diagonal rod length [mm]|290.800
Horizontal rod radius at 0,0 [mm]|135.500
Max printable radius [mm]|145.000
Segments/s for travel|80
Segments/s for printing|200
Tower X endstop offset [steps]|0
Tower Y endstop offset [steps]|0
Tower Z endstop offset [steps]|0
Alpha A(210):|210.000
Alpha B(330):|330.000
Alpha C(90):|90.000
Delta Radius A(0):|0.000
Delta Radius B(0):|0.000
Delta Radius C(0):|0.000
Corr. diagonal A [mm]|0.000
Corr. diagonal B [mm]|0.000
Corr. diagonal C [mm]|0.000
Z-probe height [mm]|-0.100
Max. z-probe - bed dist. [mm]|20.000
Z-probe speed [mm/s]|60.000
Z-probe x-y-speed [mm/s]|50.000
Z-probe offset x [mm]|0.000
Z-probe offset y [mm]|0.000
Z-probe X1|-123.565
Z-probe Y1|-71.340
Z-probe X2|123.565
Z-probe Y2|-71.340
Z-probe X3|0.000
Z-probe Y3|142.680
Autolevel active (1/0)|0
Bed Heat Manager [0-3]|1
Bed PID drive max|255
Bed PID drive min|80
Bed PID P-gain|415.670
Bed PID I-gain|140.900
Bed PID D-gain|306.560
Bed PID max value [0-255]|255
Extr.1 steps per mm|88.000
Extr.1 max. feedrate [mm/s]|100.000
Extr.1 start feedrate [mm/s]|45.000
Extr.1 acceleration [mm/s^2]|6500.000
Extr.1 heat manager [0-3]|1
Extr.1 PID drive max|180
Extr.1 PID drive min|80
Extr.1 PID P-gain/dead-time|4.0900
Extr.1 PID I-gain|0.2000
Extr.1 PID D-gain|20.9300
Extr.1 PID max value [0-255]|235
Extr.1 X-offset [steps]|0
Extr.1 Y-offset [steps]|0
Extr.1 temp. stabilize time [s]|3
Extr.1 temp. for retraction when heating [C]|150
Extr.1 distance to retract when heating [mm]|0
Extr.1 extruder cooler speed [0-255]|200
Extr.1 advance L [0=off]|0.000

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geneb
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Re: Scaling and X-Y deviation

Postby geneb » Sat Nov 04, 2017 10:43 am

Steps per mm for the extruder look to be unusually low to me.

g.
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rootboy
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Re: Scaling and X-Y deviation

Postby rootboy » Sun Nov 05, 2017 8:04 pm

geneb wrote:Steps per mm for the extruder look to be unusually low to me.

g.


Good catch! They would be if it were the original extruder. :)

I replaced my ez-truder with a:

https://www.ebay.com/itm/Aluminum-Bowde ... 2749.l2649

and I'm driving it with a NEMA 23 stepper.

The extruder had to be modified for the larger shaft of the NEMA 23 motor by drilling out the filament drive gear to 1/4" and then cutting away the extruder frame where it got in the way of the drive gear set screw (Lewisburg isn't the place where you want to live if finding small machine parts on a weekend is a necessity). This was actually a bit of a rush job so I had to make do with the parts on hand.

The screw that holds in the roller was removed and inserted from the inside of the extruder (where the screw threads are). I now have a NEMA 17 stepper motor with a 5:1 gearhead on it, which would at least look nicer (no tiewrap to hold things together). But since it is working flawlessly (not taking into account its looks), I'll probably leave well enough alone.

So far it has stripped the filament just once. That was because the filament had a "Z" crimped into it from the factory that wouldn't go into the head. That's it. :)
Attachments
Modded Extruder.png

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geneb
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Re: Scaling and X-Y deviation

Postby geneb » Mon Nov 06, 2017 8:36 am

Using a Nema 23 for an extruder is like pulling a bike trailer with a bulldozer. Holy overkill, Batman! :D

g.
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rootboy
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Re: Scaling and X-Y deviation

Postby rootboy » Tue Nov 07, 2017 9:47 am

geneb wrote:Using a Nema 23 for an extruder is like pulling a bike trailer with a bulldozer. Holy overkill, Batman! :D

g.


Yup! Grin.

After replacing the hotend, the old extruder worked much better. But it would still stall out for no apparent reason (although I now suspect that my volume problem was the root cause). I got *really* tired of having to nudge the filament along from time to time as it went, and so I got medieval with it. :)


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