The section we are concerned with, is the line that begins M92. This sets the number of steps which, in turn controls the print accuracy of a 3d printer.
To Calculate Accurate Steps
( Distance to Travel / Distance Traveled ) * Number of Configured Steps
For example, on the X axis (40 / 39.90) * 84.40.
This gives new steps of 84.612 ( we only need a few places of accuracy, the real calculation gives more).
Enter this with the command M92 X84.612 (Make sure the letters are capitalized)
Do the same for Y axis.
That takes care of X and Y.
On the Printrbot Simple, the Z is an ACME screw, it's number of steps will always be 2020.
For the extruder, we're going to measure the amount of filament, much the same as the amount of travel on X and Y. We mark the filament, with a piece of tape or post-it.
We measure the distance from the top of the extruder to the 'flag'.
We extrude some filament and then measure the new distance from the top of the extruder, to see how much filament was extruded.
Then we use the same formula (amount told to extrude/real amount extruded) X number of steps.
We add this value with M92 Exxx
Then we save all the settings with M500 and check the new settings were saved by invoking M501.
You should have an accurately configured the steps of your printer.
E Steps Fine Tuning
Fine tune e-steps using Triffid Hunter's calibration.
Now, with everything very close to ideal values, we can finally dial E steps in that final little bit!
- Find an object with flat tops on a number of levels, such as this cube stack test (scale this object by 250% after loading in Slic3r)
- Slice at 95% rectilinear infill. Use the lowest layer height you're comfortable with - the lower the layer height used for this test, the finer your resulting E steps calibration will be. I use 0.2mm for first run, and if I'm feeling ambitious I'll repeat this process at 0.1mm.
- Ignore the first 5-6 layers because they're too sensitive to the exact height of the first layer. If it's obviously over-filling or under-filling, alter E steps or Z=0 point and restart the print.
- Observe infill. If you can't see tiny little gaps between the lines, reduce E steps by 0.5% every 2 layers until you can see tiny gaps.
- Observe solid top layers. If you can see tiny gaps, increase E steps by 0.5% every 2 layers until there's no gaps in the top.
- Send the new E steps to your printer with M92 Ennn without even pausing the print - you will see the result in a couple of layers when the change is this small.
- Goto 5 until the infill has tiny gaps AND the solid top layers do not.
- Now, your E steps value is extremely fine-tuned! Save this value in your firmware's configuration and flash to make permanent.
Now print your favourite calibration piece (e.g., ultimate calibration) and see how it measures!