Support material is the part of FDM that no one talks about until it becomes a problem. A part designed without thinking about supports may print fine, but the underside surfaces will be rough, the support removal will scar the geometry, and the post-processing time may exceed the print time.
Treating support strategy as a design decision rather than a slicing afterthought produces dramatically better parts. The framework below is what our shop uses, and what we coach customers to specify on their drawings.
Step one: design supports out
Supports are easiest to deal with when there are none. Work through the following checklist before you send a file to the slicer.
Reorient the part so the most critical surfaces face the build plate or the side, never directly downward.
Limit overhangs to forty-five degrees from vertical wherever you control the geometry.
Chamfer the entry to horizontal holes so the upper arc self-supports as the print progresses.
Break long horizontal spans with a sacrificial rib that prints cleanly and is removed later.
Split the part along a natural seam and bond the halves if no single orientation works.
Run a final preview in the slicer to confirm the support volume is what you expected.
Where supports are unavoidable
Some geometries genuinely require supports. Internal channels, complex undercuts, large unsupported overhangs and downward-facing surface features all force the issue. The question becomes which support strategy to specify, since the choice has real consequences for cost, finish and feature integrity.
The shortlist below covers the options our FDM service supports. The engineering filaments behind each choice are catalogued, with datasheets, through our partner brand OzFDM.
A note on support contact density
Modern slicers expose support contact density and Z-distance as independent parameters. Tightening the contact density gives a better surface but harder removal; loosening it reverses the trade-off. A short conversation with your supplier about the contact settings is often more useful than another design revision.
Same-material supports: cheapest, hardest to remove cleanly
Soluble supports: cleanest removal, requires a dual-extruder machine
Breakaway supports: designed weak interfaces for fast manual removal
Tree supports: minimal contact, well handled by modern slicers
No supports at all: redesign to avoid where the geometry permits
Specifying support strategy on drawings
For critical surfaces, specify support requirements on the drawing rather than leaving them to the slicer operator. Notes such as Surface A: no supports permitted or Surface B: soluble support required are valid specifications that a competent supplier can plan around.
Where supports are unavoidable on a critical surface, specify the post-processing required to bring it to the needed finish. Sanding to a defined grit, machining the affected face on our CNC service, or accepting the as-removed surface are all valid choices as long as the drawing says so.
The cost of bad support strategy
Supports can account for twenty to forty per cent of print time on a complex part. They account for similar fractions of post-processing time. A part designed with support strategy in mind from sketch one is often thirty to fifty per cent cheaper to produce than the same part designed without it.