Calibration With Prints

Material: PLA (Romscraj.com)
Heater: 180C
Bed: 60C

Characteristic: 
Nozzle: 0.5mm
Layer height: 0.4mm
Width over Height (W/H): 1.25
Feed Rate: 30.0
Flow Rate: 30.0
Skeinforge settings: more settings..

Software Requirements:

• OpenScad 

Bed Leveling
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Filename: bedleveling.scad
Built Size (Width-X, Length-Y, Height-Z): 
Objective: Level the print bed so that your objects will adhere to the surface.

Instructions: Use Pronterface to Home all the axises (X, Y and Z). Turn off the printer power and disconnect the printer USB cable from the computer. Make sure the thickness(distance) between the nozzle and the bed is like a piece of paper . Adjust the four screws at your printer bed by move your nozzle (X and Y carriages) with the direction from the bottom left to bottom right, to top right corner, to top left corner and back to bottom left corner. Make sure the bed center is level.

Print the file and ensure that each square is even, smooth and consistent. Download the original scad file so that you can change the dimensions to match your print bed.

Note: Remember to deactivate Skirt (Crave > Crave > Skirt)

Wall Thickness Calibration
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Filename: thin-wall-0.5mm-20x20x10mm.stl
Built Size (Width-X, Length-Y, Height-Z): 70mm x 74mm x 4mm(0.8 + 3.2)

Test for certain wall thicknesses:
0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2

Generate a new STL file with OpenSCAD for the below setting:

• BaseThickness=0.8;  //~2 layers
  2 layers with skeinforge layer height is 0.4mm (2 x 0.4mm)
• FeatureHeight=3.2;
  8 layers with skeinforge layer height is 0.4mm (8 x 0.4mm)

Layer Height Calibration
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Built Size (Width-X, Length-Y, Height-Z): 20mm x 20mm x 10mm
Objective: to correct the layer height settings to reflect your printers actual layer height.
Calibration Object: 0.5mm-thin-wall.stl
Instructions: Print the 0.5mm thin wall cube and make sure that the layers adhere well but the nozzle does NOT drag through while printing. Adjust skeinforge layer height in 0.01 increments until you get a nice print.

Infill Calibration
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Built Size (Width-X, Length-Y, Height-Z): 20mm x 20mm x 10mm
Objective: to correct the infill setting.
Calibration Object: 20mm-box.stl
Instructions: Set Skeinforge infill solidity to 1.0 for this test.Print the cube and analyze the top. If there is NOT ENOUGH plastic (a convex top), reduce the Infill Width over Thickness by 0.05 increments. If there is TOO MUCH plastic (convex top), turn that parameter up by 0.05 increments.
Once you're feeling close, start bumping it around in smaller increments.

You may also need to adjust your feed rate. Adjust the feed rate by increments of 2 or so until you feel close. If it looks really disgusting and blobby, go by increments of 0.5mm. Then go by smaller and smaller increments until you've nailed it. Although you probably just want to decrease Infill Width over Thickness instead of decreasing Feedrate because lowering feedrate will degrade the resolution.

Temperature Calibration
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Built Size (Width-X, Length-Y, Height-Z): 10mm x 10mm x 50mm
Objective: to set the hot end temperature correct for your preferred plastic.
Calibration Object: 50mm-tower.stl
Instructions:  As the tower has quite a small 'top' surface area you may need to cool this object as you print. If your printer doesn't have a built in fan you can use any room fan as a substitute. Set the 'Infill solidity' to 1.0. Start by using the Skeinforge default temperature to print. Reduce the temperature in 5 degree increments until the extruder starts skipping when you do a manual extrude. Turn the extruder up 5 degrees and note this as your minimum extruder temperature.

Print this block.If it looks like a blob, turn down all the temps by 5 degrees until you get something good. Chances are you won't need to do this more than 5 degrees.
Note:

1. Be careful as going too low can result in the plastic setting making it hard for the motors to drive the plastic, possibly causing wear or damage.
2. Different types of plastic and its color compound added have vastly different temperatures for both your hot-end and your bed. 

Perimeter Width Calibration
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Built Size (Width-X, Length-Y, Height-Z):  
Objective: correct the perimeter width over thickness
Calibration Object: perimeter-wt.stl
Instructions: This test prints two objects which are designed to fit together.
Try to insert the smaller block into the larger block. Try inserting it differently a few times, and check your belt tensions.Need notes on calibration of belt tensions

If you can get it in a few mm, good. If you can get it in all the way, awesome. The fit should be snug. If it is loose and can jitter around inside, decrease the perimeter width over thickness. If you CANNOT get it in AT ALL, and you are sure there are no whiskers blocking it, INCREASE perimeter width over thickness. The latter is more likely.

Bridge Calibration
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Built Size (Width-X, Length-Y, Height-Z):
Objective: to maximize your printers ability to bridge gaps (i.e. print in thin air).
Calibration Object: 20mm-hollow-box.stl (Object may not work)
Instructions: Print the calibration object and if the top droops in, increase the BRIDGE FEEDRATE MULTIPLIER in Speed by increments of 0.1 until the top stops drooping.

Note:

• Falling off can due to backlash in one or both of your belts. Make sure you are using the right pulley with your belt type.
• To get good bridges you want your deposited plastic cross-sectional area to be smaller than your nozzle. That way you are more or less stretching the filament. I am able to do bridges in PLA of over 20mm with virtually no droop.

Print Precision Calibration
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Built Size (Width-X, Length-Y, Height-Z):  
Objective: improve print precision
Calibration Object: precision-block.stl

Instructions: Then there is the precision block. No real huge calibration parameter here. Just play with this and see how well it does on the overhangs and shapes.

Overhang Calibration
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Built Size (Width-X, Length-Y, Height-Z):  
Objective: fix overhang problems.
Calibration Object: overhang-test.stl
Instructions: Print and observe the overhangs. This is up to you to figure how to improve the overhangs.

Oozebane Calibration
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Built Size (Width-X, Length-Y, Height-Z):  
Objective: stop material oozing out of the noozle during 'non-printing' moves.

Many extruders will emit (ooze) plastic even when the extruder motor is not turning. To overcome this your slicing software needs to 'retract' the print medium during head movement when not printing. The retraction creates negative pressure within the hot end heating chamber which effectively sucks the print medium back up through the nozzle, stopping it from oozing.
Calibration Object: oozebane-test.stl

The calibration object prints two towers about 30 mm apart. The head must move between each of the towers at each layer. If your printer is not set correctly then you will see many fine filaments (or strings) between the two towers. You can eliminate these filaments by eliminating ooze.
Symptoms


Instructions: This is to try to control ooze and calibrate it to be useful.Start by setting the Early Shutdown distance to 0 and Slowdown Startup Steps to 1.Print the piece and measure the length of stringers where the extruder shut off and the line is thick before becoming a thin whisker. Take that length and put it into early shutdown distance.Play with Early Startup Distance Constant until the place where the extruder arrives at the other tower is nice and smooth, so that there isn't any empty space where plastic should be, but there isn't excess plastic extruded.


Overhangs  Calibration
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Objective: eliminate droop from overhangs.
Calibration Object: BridgeTestPart.stl

Instructions: If the calibration object droops, you likely need to decrease "Bridge Flowrate over Operating Flowrate." Or increase "Bridge Feedrate over Operating Feedrate."


Resource

• RepRap Calibration by Wiki
• The Essential Calibration Set - Thingiverse
• Wall Thickness Calibration Test Piece - Thingiverse