sreisig1
Posts: 30
Joined: Fri Sep 02, 2016 4:57 pm

How To: Calibration Boxes

I tried printing a case for a raspberry pi, its a little off and the pi barely fits. I'm sure the file is fine and I just need to calibrate/tune for each material/manufacturer I'm using correct? I have the FlashForge Creator Pro and have files for a 20mm cube and also the "calibration cat". There are tons of calibration files out there which are easily found, but can' find anywhere that talks you through what to do once you've printed the thing. Can anyone help talk me through what to do and what settings to change, and by how much, etc.
CompoundCarl
Posts: 2005
Joined: Wed Aug 05, 2015 7:23 am

Re: How To: Calibration Boxes

I like to print a cube that is maybe 20mm wide with a 10mm square hole in the middle. Then you can measure the outside and inside and adjust extrusion amounts as needed
Rob65
Posts: 8
Joined: Mon Dec 16, 2013 8:11 am

Re: How To: Calibration Boxes

The printer needs to extrude the right amount of material at the right place.
If the case you printer is a bit too small, this can be either due to a wrong steps/mm value, the X-Y axes not being under 90° or too much material is being extruder.

Assuming that the printer is in good order, it is important to check the amount of material being extruder.
There are multiple ways to do this, I'll just describe how I check this.

I start with a 10x10 mm cube (Perimeter shells - 2, infill = 100%). If too much material is being extruded you will see bulging in the layers and blobs on the top. As soon as that cube looks nice and square with a flat top layer I do this once more for a 20x20 cube. Adjust the extrusion multiplier until you are satisfied and have a 10x10mm cube.

You can do this with 20x20 cubes, but 10x10 cubes print 8 times faster and use less material.

After this I change the extrusion with to manual and set this at the same size as my nozzle (0.4mm), then I print the 20x20 cube with 1 perimeter shell and 0% infill. With calipers I measure the wall thickness, most of the times this is a little bit bigger than the nozzle size (for me around 0.43mm). Now I start playing with the extrusion size a bit and check that 0.45 / 0.5 and 0.6mm results in the same wall thickness.

And that's about it. Set the extrusion width of your profile to auto or to a value that is not smaller than a bit bigger than the value measured at the nozzle size. I found that 0.45mm works OK for me (nozzle = 0.4mm, wall thickness = 0.43mm) but 0.5mm results in parts that are a bit tougher (at 0.45mm it is easier to break the part than at 0.5mm)

You can also print one of those "hole calibration" parts that have different sizes of round, square and hexagon holes. This is not for calibrating your printer but for calibrating your files. Small holes (1-5mm) always end up a bit smaller than designed so if you do not want to post process and ream the hole with a drill bit you may have to draw the hole a bit bigger than it should actually be.

One last thing to take into account is that higher speeds result in higher pressure in the nozzle. Depending on the material used this may result in expansion of the extruded material that varies with the speed used. With ABS and PLA I hardly see this effect but PETG and ColorFabb XT show this more.
This is clearly visible in the 20x20 cube: printed with a normal (20-30%) infill I see bulging of material at the corners when printing at 6000 mm/min. At 4800 mm/min this is almost not visible.

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