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Extruder digging into object

Posted by printer_man58 
Extruder digging into object
December 05, 2013 03:31PM
Whenever i start printing for the first few layers it prints properly, but then after t gets about a little ways up(30 min) the extruder starts to dig into the plastic. I believe it is still extruding, but it starts to embed itself. I think it could be that the extruder is to hot (200) degrees. Could anyone tell me what I am doing wrong?
Re: Extruder digging into object
December 05, 2013 03:43PM
200 deg is hotter than normal for PLA. Try 185

However, its more likely your Z calibration is incorrect. Have you measured that if you tell the Z to go up 100mm it actually goes up by 100mm

Also check for loose grub screws etc in your Z drivetrain
Re: Extruder digging into object
December 05, 2013 04:14PM
I try 185 but whenever i set that as the temperature it won't print until it gets up to 200 degrees
Re: Extruder digging into object
December 05, 2013 06:59PM
One way or another your are extruding to much filament. This is impacted by:

1) The flow rate multiplier(s) in your slicing program
2) The steps / mm in your firmware for the extruder
3) The *real* diameter of your filament (it's rarely 3.0, more likely 2.84 or 2.96 or 3.06)
4) The dryness of your filament

There are many other contributors, but those are the most likely ones.
Re: Extruder digging into object
December 06, 2013 02:43PM
printer_man58: you need to change the Print temperature to 185 deg C in slicers and then you have to convert to gcode so it would be changed


Enjoy life smiling smiley
Re: Extruder digging into object
December 06, 2013 06:03PM
Thanks toe everyone, but what do I change the steps/mm , but what do i change the numbers to?
Re: Extruder digging into object
December 06, 2013 07:13PM
I suggest you follow the reprap calibration guide. It has just about everything you need to get your machine calibrated.
Re: Extruder digging into object
December 06, 2013 10:37PM
Your entire printer is mated with the firmware in your control board. If all the settings are not properly done for your printer, things aren't going to work properly. Setting up the firmware is part of building the printer....
Re: Extruder digging into object
December 09, 2013 01:31AM
Hey, I had this same issue. Posted a question on forum somewhere but not sure I ever got an answer. Hopefully what I ended up doing can help...

After a bit of screwing around I found that my z-axis was missing steps so when the z axis should have been 30mm, say, it was physically at 25mm or so. I fixed this by lowering the speed of my z-axis in the config file - cant remember how but it worked. I also got some dinkey alu heat sinks off ebay and stuck them on my drivers so alleviate overheating.

It did not entirely fix the issue though. I had meticulously measured and checked the extruder feedrate and ended up with a number of 7-hundred and something in my config file. Nevertheless, too much material seemed to come out of hot end causing it to dig into my print. I found that changing my feed rate using 'M92 e300' in pronterface when about to start printing sorted it. I play around with the 300 number if I think things are going wry during the print.

Its not perfect but I get useful object at the end of it.

I would love to know why my extruder rate is so out (50% or so) but if you still have a problem this might be a temp fix until someone-who-knows can fill me (us!) in about extruder rate eh?
Re: Extruder digging into object
December 09, 2013 03:32AM
Hi Aegis1980 you have the calibration error in Extruder:
To calibrate the Extruder
1. Take the Extruder out of the Nozzle
2. Feed the ABS or PLA
3. Extrude 50 mm or 100 mm
4. Measure the Length Extruded
5. Note down the Expected length and extruded length readings
6. Change the Extruder Steps per MM in config.h in firmware by calculating Expected steps per MM in E

Here we go
x is the desired steps per mm need to be calculated (unknown)
y is the present steps per mm in config.h firmware

x = y * Expected length / Extruded Length

7. Update it in firmware and upload the new modified firmware
8. Do the above steps more than 1 time with lengthy extrusions
9. Update the repeated or average values in Extruder steps per mm

(There are some options with out changing the firmware it can be done by applying gcode directly to printer by changing EEPROM settings but I find difficult sometimes, so I don't use it)

if your firmware is Marlin you can find the steps per mm of E in the following line in configuration.h (around line no 360)
#define DEFAULT_AXIS_STEPS_PER_UNIT {126,127,5120,1800} // default steps

here
126 is X axis steps per mm
127 is Y axis steps per mm
5120 is Z axis steps per mm
1800 is E axis steps per mm

Change the last one reduce by half and try it hope it will work

"After a bit of screwing around I found that my z-axis was missing steps so when the z axis should have been 30mm, say, it was physically at 25mm or so. I fixed this by lowering the speed of my z-axis in the config file - cant remember how but it worked. I also got some dinkey alu heat sinks off ebay and stuck them on my drivers so alleviate overheating"
It is because your Z motors are built for lesser speed, when the speed goes up, motor's torque goes down so there will be struck between the rotation, good for slow printing


Enjoy life smiling smiley
Re: Extruder digging into object
December 09, 2013 06:12PM
well, backing up for a different issue tagged onto an unrelated thread ...

First thing to check is the current ratings on your motors. Those should be available from the people who sold you the motors.

Second thing is to grab a DVM and check the Vref voltages on all your stepper controllers.

For X and Y, a good starting point is to give the motors 1/2 the current they are rated for. On the Z axis, start at about the current they are rated for (each motor gets 1/2 the current).

If that works out to more than about 1.2A, you will need to compromise on a setting. The normal drivers aren't very happy much over an amp.
Re: Extruder digging into object
December 09, 2013 07:29PM
How are you able to extrude the filament. Whenever i hit the extrude button in pronterface it extrudes, but it ends up curling and i'm not able to get an accurate measurement.
Re: Extruder digging into object
December 09, 2013 09:22PM
When you calibrate the extruder, remove the hot end from the printer. Only have the extruder handling the filament. Do not run the filament through the heat up and melt process. That's the easy way. Start at step 4 below and don't worry about the speed (run at 20 or 30 mm/min) in step 5 if you do.

---------------

The not so easy way:

1) Leave the hot end on the machine
2) Heat it up
3) Make absolutely sure the filament is not extruding so fast the hobbed bolt is slipping
4)Mark a point on the filament 120 mm above the top of the extruder
5) Tell the extruder to do 50 mm of extrusion at 5 mm / min (come back in 10 minutes)
6) Measure the distance to the mark above the extruder
7) Take the difference between the two measurements

Ideally you would get a difference of 50 mm (first measure 120, second measure 70). You probably will get something else. Adjust the steps/mm settings in your configuration.h for the E motor.
Re: Extruder digging into object
December 09, 2013 11:24PM
> Whenever i hit the extrude button in pronterface it extrudes, but it ends up curling and i'm not able to get an accurate measurement.

You do realize you're supposed to measure filament going in to the extruder, not coming out of it, right?
Re: Extruder digging into object
December 10, 2013 05:43PM
Oh wow, I'm stupid. Thanks to everyone
Re: Extruder digging into object
December 10, 2013 06:10PM
..... it's a *very* common mistake....
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