filament extruding comes up short. January 18, 2015 08:53PM |
Registered: 9 years ago Posts: 133 |
Re: filament extruding comes up short. January 18, 2015 11:17PM |
Registered: 9 years ago Posts: 465 |
#define DEFAULT_AXIS_STEPS_PER_UNIT {80.0,80.0,4000.0,128.5}
Re: filament extruding comes up short. January 20, 2015 09:49AM |
Registered: 9 years ago Posts: 133 |
Quote
SupraGuy
At least for Marlin...
Look in the Configuration.h file for a line like the following:
#define DEFAULT_AXIS_STEPS_PER_UNIT {80.0,80.0,4000.0,128.5}
It shoud be about 2/3 of the way down the file. This is the list of values is for the various axes of the printer. 80.0 steps per mm for X, 80.0 steps per mm for Y, 4000.0 steps per mm for Z, and 128.5 steps per mm for the extruder.
Re: filament extruding comes up short. January 20, 2015 10:35AM |
Registered: 9 years ago Posts: 1,011 |
Re: filament extruding comes up short. January 20, 2015 11:01AM |
Registered: 9 years ago Posts: 133 |
Quote
Zavashier
Just a question, where from comes 78.7402 ? Don't you have regular GT pulleys ? It looks like you modified these values to get a cube of desired dimensions. You should not, because these values compensate only for THAT cube, any larger or smaller part will be unlikely distorted. I dunno why that stupid adjusting process is still in use today ! Somebody please write calibration for dummies !
Calibrating your extruder
Re: filament extruding comes up short. January 20, 2015 11:16AM |
Registered: 9 years ago Posts: 1,011 |
Re: filament extruding comes up short. January 20, 2015 11:51AM |
Registered: 9 years ago Posts: 1,159 |
Quote
Zavashier
Ok, let's make it easy : steps_per_mm = (motor_steps_per_rev * driver_microstep) / (belt_pitch * pulley_number_of_teeth)
For example : (200 steps*16 microsteps)/(GT 2mm * 20 tooth) = 80
As simple as that You can't have good prints without a printer proper setup or you're the luckiest man on earth.
Re: filament extruding comes up short. January 20, 2015 12:03PM |
Registered: 9 years ago Posts: 133 |
Quote
Zavashier
Ok, let's make it easy : steps_per_mm = (motor_steps_per_rev * driver_microstep) / (belt_pitch * pulley_number_of_teeth)
For example : (200 steps*16 microsteps)/(GT 2mm * 20 tooth) = 80
As simple as that You can't have good prints without a printer proper setup or you're the luckiest man on earth.
Re: filament extruding comes up short. January 20, 2015 12:49PM |
Registered: 9 years ago Posts: 1,159 |
Quote
rich1812
Quote
Zavashier
Ok, let's make it easy : steps_per_mm = (motor_steps_per_rev * driver_microstep) / (belt_pitch * pulley_number_of_teeth)
For example : (200 steps*16 microsteps)/(GT 2mm * 20 tooth) = 80
As simple as that You can't have good prints without a printer proper setup or you're the luckiest man on earth.
That's the thing, I have not looked into these: motor_steps_per_rev, driver_microstep, belt_pitch and pulley_number_of_teeth yet.
I know the pulley_number_of_teeth is 20
in GT2 the 2 means 2mm pitch, if there is a GT4 the pitch is 4mm is that correct? Not to sure that is correct but the idea is correct you can look up the specs of different belts to find your pitch count 10 teeth and measure the distance between them (use either the leading ed ge or trailing but be consistent and then divide that by number of teeth (the more teeth you measure the more accurate you will be
Is motor_steps_per_rev for NEMA 17 always 200 ? No it depends on the degrees per step the common is 1.8 but there are 0.9's out there and they would be 400 steps/rev
How about microsteps where do you find this number? this is a function of the Stepper driver pololus ar upto 16 8825 can be upto 32 and some others can be upto 128
Also before, my extruder always came out short of 1-1.5cm over a 10cm extrusion. So I pretty much trail and error found that 75.0 extrusion seem to work the closed. the way to do this is to remove the hot end mark the filament going in measure 100mm and mark extrude 100 mm and measure the mark in relation to the start point and the calculate what you need to change
Thanks.
Re: filament extruding comes up short. January 20, 2015 01:29PM |
Registered: 9 years ago Posts: 465 |
Re: filament extruding comes up short. January 20, 2015 02:00PM |
Registered: 9 years ago Posts: 1,011 |
GT2 belts can have 2,3 and 5mm pitch. Usualy repraps use 2mm belt&pulleys because it's the less expensive one, and it fits the needs. Measure from top, tooth to tooth, and if you get 2mm something, that's it.Quote
rich1812
in GT2 the 2 means 2mm pitch, if there is a GT4 the pitch is 4mm is that correct?
Is motor_steps_per_rev for NEMA 17 always 200 ?
How about microsteps where do you find this number?
Also before, my extruder always came out short of 1-1.5cm over a 10cm extrusion. So I pretty much trail and error found that 75.0 extrusion seem to work the closed.
Thanks.
Re: filament extruding comes up short. January 21, 2015 02:00PM |
Registered: 9 years ago Posts: 133 |
Quote
Zavashier
Ok, let's make it easy : steps_per_mm = (motor_steps_per_rev * driver_microstep) / (belt_pitch * pulley_number_of_teeth)
For example : (200 steps*16 microsteps)/(GT 2mm * 20 tooth) = 80
As simple as that You can't have good prints without a printer proper setup or you're the luckiest man on earth.
Re: filament extruding comes up short. January 21, 2015 03:35PM |
Registered: 9 years ago Posts: 465 |
Re: filament extruding comes up short. January 21, 2015 04:00PM |
Registered: 9 years ago Posts: 1,011 |
Re: filament extruding comes up short. January 22, 2015 01:32PM |
Registered: 9 years ago Posts: 133 |
Quote
Zavashier
You're welcome. I bought Folger's and did not manage to print anything properly with that extruder. I'm printing ABS only so it's high temperature and Folger's extruder is not at his best with me. Some people have acceptable print quality with Folger's, so I hope you'll manage to print properly.
For the Z axis, the formula is : steps_per_mm = (motor_steps_per_rev * driver_microstep) / thread_pitch
As far we own the same printer, the good value is 4000 = (200*16)/0.8mm
For extruders, the formula is :
direct drive (your type) : e_steps_per_mm = (motor_steps_per_rev * driver_microstep) / (hob_effective_diameter * pi)
wade (geared extruder) : e_steps_per_mm = (motor_steps_per_rev * driver_microstep) * (big_gear_teeth / small_gear_teeth) / (hob_effective_diameter * pi)
BUT, for extruders, that's not that simple. Because the tooth of the hob comes inside the filament and that modify the hob effective diameter. So you need to calibrate manualy your extruder after a setup with the formula :
- Find your actual extruder step per millimeter settings, write the value
- Mark accurately the filament 150mm above the extruder
- Ask the printer to extrude 100mm of filament (repetier or so)
- Whait the extruder to stop
- Now measure the distance from the top of the extruder to the mark
- Calculate the real amount of filament extruded (150-the last measurement), write the result
- Calculate (last steps per millimeter*100)/the real amount of filament extruded
- You've got your new steps per millimeter value
- Open your configuration.h and make the correction
- Upload the updated firmware to your arduino
- Mark again at 150mm and ask again to extrude 100mm of filament
- Measure if the result is ok within 2%, if not calculate the new steps per millimeter
- When it's ok; your extruder extrude now the good length of filament
- The first step of extrusion calibration is done. Congratulations
It's good, but it's not done. We now need to measure accurately the filament itself. Some filaments diameter is not the same all along the filament. You need a digital caliper, and you want to make several measurements to find an average value. When it's done, set your slicer parameters with that value. Remember you want to set this up with each new spool of filament, event with the same colour from the same brand. Now our system is able to extrude 100mm of filament, and we know as precisely as possible the filament diameter. So the software side is able to deliver the right amount of plastic. Good.
BUT, we will melt the plastic, that means we will transform it. That means that the volume of cold (unextruded) plastic possibly differs with the volume of plastic out of the extruder... So we need to check this out.
- You need a STL file of a one wall cube, that wall of the same thickness of your nozzle diameter. For example you've got a 0.5mm nozzle, you need 0.5mm walls. Design it or get one at Thingiverse or so.
- Print it with slow settings, and verity all repetier (or so) settings are standard or 100%
- When it's done measure the thickness of the walls of your printed object, but at the top because the bottom of the part may be thicker.
- Calculate (your print wall thickness/nozzle diameter)*100 = your new feedrate
- Modify your slicer parameter with the new feed rate
- Print another test thin wall cube and verify the thickness of the walls
- If you're within 10% of the asked value, it's ok. Remember our repraps are not high precision machines.
- If not, Calculate again a new feed rate, BUT calculation is this time different !
- last feed rate * (nozzle diameter/measured wall thickness)
- when you get an acceptable print, your calibration is done ! Congratulations !
Now you can print benchmark parts, you're as precise as your printer can be. It's good to keep in mind the best your machine can do. You don't need anything else to be calibrated. If the accuracy does not matches your needs, you need probably to upgrade your printer's components do get better prints.
Good luck !
Re: filament extruding comes up short. January 23, 2015 04:11AM |
Registered: 9 years ago Posts: 1,011 |