Vertical Surface Finish
This test is used to determine how well each machine can create the walls of the print. Often these walls have other characteristics in them such as holes, text, or designs. A common problem with many machines is a resonance caused by these details in a print such as echoing, a repeat of a pattern beside a feature caused by resonance in the printer. A perfect score of a 5 is a clean print without echoing or or significant Z scarring.
Horizontal Surface Finish
Completing the top layers of a print is important for creating a finished-looking piece. Angles, flat surfaces, and curved or domed surfaces all pose different challenges for the printer to complete. If the machine is under-extruding, printing too fast, or has a bad fill or perimeter setting, it can cause holes in the top surface. A perfect score of 5 is given to machines without holes and with even top surfaces.
When you design and print a part, you want to ensure that the part you print is exactly the size you designed it. If the printer’s motor settings (e-steps) are not set correctly, or if it is over- or under-extruding, the print may not be the size it was intended as being. If the second layer of the tower is exactly 20.00mm x 20.00mm, a perfect score of 5 is given.
FDM 3D printers need a surface for the molten plastic to adhere to. When the print starts, this is the build platform, after that, it is the print itself. If layers are not stacked directly on top of each other but instead angle out, this is an overhang. This test determines how great of an angle the printer is capable of printing an overhang before the print is ruined. If all angles are printed cleanly, a score of 5 is given.
An overhang that jumps between two points creates a bridge. With proper temperature, speed, and cooling, a print can jump large gaps cleanly. This probe has 5 gaps, each longer than the next, that show how cleanly the machine is capable of spanning gaps. A 5 is given to a printer that can bridge the largest gap without excessive drooping of filament.
Negative Space Tolerance
When printing a part that you want to be able to move after it has finished, such as a wheel on an axle, it is important that the printer is capable of accurately printing negative spaces. A machine that is over-extruding or is not properly calibrated will need larger spaces between parts to make them moveable. This print consists of a block with 5 pegs. For each peg that can be removed after the print is complete, a point is given to the machine. All 5 pegs equals 5 points.
While this print might look like some kind of medieval torture device, it’s designed to torture your extruder. Each of the nine spikes causes the printer to print an ever-smaller detail, retract its filament and then move to the next spike. This constant repetition of retraction and extrusion can result in a stringy print or even a jammed extruder. If all the towers print cleanly, without strings or deformation, then the print is scored a 5.
Support material is used when a gap is too large to bridge or an overhang is too great to allow the print to be completed cleanly. For this test to pass, the support material must be able to be removed from the print with relative ease without destroying the print or leaving scarring behind. This is a pass/fail test, 2 points given for a pass, 0 for a fail.
This tall, thin box print can show us if there is a wobble in the Z-axis of the machine. This will show as a ripple up the side of the print. Scarring caused by layer shifts is acceptable but any repeated inconsistencies in the layers as they move up the print will result in a failed score. The second of our pass/fail tests, scored either 2 or 0.