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How to Improve 3D-Printed Shape Accuracy? -Sharp Corner (XY Axis)

Shape accuracy is a critical criterion for accuracy and refers to the extent of how well the surface shape of the fabricated part matches the design. Common surface shapes include round, flat, column, conical, linear etc. This blog discusses how to improve the 3D printing shape accuracy of a sharp corner using ideaMaker.

Note: To be precise, this blog entry only discusses accuracy applied to a Cartesian FFF printer and ideaMaker.

A rectangular specimen printed for reference


Example of a Common Flaw: A Corner Bulge in the XY Direction

A sharp corner is formed by the encounter of two straight surfaces. A bulged angle is formed when the vertex where the surfaces meet bends towards the convergent point. The following comparison shows the difference between a bulged and a fine corner. The contour of a fine sharp corner is straight without visible bending. A bulged corner may cause a printed part to have poor assembly quality and an enlarged dimensional tolerance, resulting in printed parts not fitting correctly.

Bulged Corner (Left) vs. Fine Sharp Corner (Right)

Image Source: https://www.printedsolid.com/


Situation 1: A Bulged Corner at the Start and End Point

It is common practice for slicing software to define a corner vertex as a start or end point on each layer. A bulged corner forms when over-extrusion occurs at a start point or end point during printing. When there is too much pressure applied or too much material melted at these points, the amount of filament extruded at these points will be more than the ideal amount along the vertex.

Image from https://reprap.org/


How to Fix with ideaMaker:

1. Increase the Amount of Retraction Material (Advanced Settings>Extruder>Retraction Material Amount)

This setting can reduce existing material in the nozzle at the start/end point. But a value that is too high may result in under-extrusion and a gap in the corner.


2. Increase the Value of Gcode M572 (Advanced Setting>GCode>Start GCode)

Gcode M572 refers to the advance pressure feeding compensation rate based on speed. In case of normal printing, when printer printing speed increases, the printer feeding rate increases accordingly. When printing speed decreases, the feeding rate also decreases. Increasing the value of M572 heightens the feeding rate reduction when printing speed down at the end point of the printing loop before next layer.


Situation 2: Corners without Start and End Point

Sometimes a corner is irregular, and can also be known as ghosting, ringing, echoing or ripping, even if it is not defined as a start or end point. This is usually caused by machine vibrations during the printing of the corner area. When the extruder is moving fast along a certain direction and has a sudden speed change, it will generate lots of force, which has to be absorbed by the printer. A printer with more weight and a stiffer frame can absorb this force better, resulting in less vibration.

Image source: https://3dprinterly.com/


How to Fix with ideaMaker:

1. Lowering the Inner and Outer Shell Print Speed (Advanced Settings>Speed)

In ideaMaker, loops forming contours of each layer are defined as the outer shell and inner shell. Therefore, lowering print speed value for these two structures can reduce existing vibration when printing corners.


2. Lowering the Acceleration Speed ( Advanced Settings>Advanced)
Lowering the acceleration speed of the inner and outer shell can also reduce vibration when printing corners. Lower acceleration speed brings less shaking when the speed begins to change. Users need to enable the Acceleration option in ideaMaker first.


3. Reduce the Jerk Speed (Advanced Settings>Advanced)
Jerk speed refers to the instantaneous speed to start printing or the minimum speed required before printing stops or changes direction. When printing a sharp corner, the extruder movement direction will change significantly. The extruder has to suddenly drop its speed to zero along the original direction at the turning point. The jerk speed refers to the instantaneous speed along the original direction at that moment. A larger jerk speed means the printer absorbs more force when the extruders change direction. However, if this value is too low, the printing duration will be significantly extended and result in flaws in the final print.