Manual Support Definition & Generation

[dkightley]

Here's the results of a brief investigation I've done on the definition and generation of manual supports.

I set the test up with the following basic parameters:
Nozzle diameter = 0.2mm
Extrusion width (manual) = 0.2mm
Support Infill %age = 100% (initially)
Extra Inflation Distance = 0

I created an "L" shaped block 10mm wide and 20mm both high and deep..this shape then tipped on its nose to form an overhang.

I then added three single columns of manual support, 1mm, 2mm & 3mm left to right...as shown here (with z cross section to make things clearer) :

Observation: The simulated columns are shown smaller than the defined size! The grid on the bed is 0.1mm

Slice and the Preview view is:

Observation: So far so good. Support generated to cover the full cross section of all three columns...5 lines for the 1.0mm, 10 for the 2.0mm, and 15 lines for the 3.0mm.

I now lowered the Support Infill %age to 50% and resliced:

Observation: We now have half the number of strips....well almost. Rather than 2.5, 5 and 7.5 (which is not possible), we have 3, 5, and 7. Still looks sensible.

Continued in next post as only three attachments allowed per post.....

[dkightley]

I then reduced the Support Infill %age to 25% and resliced again:

Observation: Starting to look inconsistent. 1 strip for the 1.0mm column, two for the 2.0mm column and 4 for the 3.0mm column. What can be seen is that the extruded support material appears to be placed at multiples of a regular spacing...in this case, a spacing of 0.8mm...one in 4 extrusion widths...25%!

The final test....I reduced the Support Infill %age to 10% and resliced again:

Observation: Looking strange. A BUG! I hear you say!! But look closely....extrusions are every 1.0mm....or 10%!!!!

Conclusion: The support is firstly generated according to a single pattern determined by the Infill %age...1 strip then a gap 9 strips wide for 10%, 1 strip then a gap of 4 strips for 25%....and so on. The resultant pattern is compared with the area(s) for which support has be defined as being required....either automatically or manually....and a support extrusion is laid where they overlap.

This method of generating where support should be extruded...to me...seem totally logical, particularly when you start looking at generating support in both the X and Y directions. The only disadvantage is that where you have low infill %ages AND small sized support definitions, the resultant support is not evenly distributed according to the support definition.

Its a good job there are many ways of adjusting the position of manual support to give the desir3ed result....which can be previewed prior to printing.