Workshop case · three iterations
Three versions of one FDM part: improvements and remaining limits
This part initially showed sagging in a horizontal hole and an uneven surface. Layer height, speeds, cooling and the top surface were adjusted across three versions. The photographs show visible changes and remaining FDM marks. They do not establish measured fit, load capacity or final customer acceptance.
Not every part needs three prints. Simple or previously validated geometries can go straight to production. Layered FDM surfaces also remain different from polished glass or injection-moulded finishes.
A horizontal hole, an unsupported bridge or a critical top face can justify staged trials. This case follows real iterations of an anonymised black PLA+ part from our Groningen workshop.
Part and environment
A black PLA+ component for a folding stand
The customer supplied a model of a long U-shaped component with a horizontal hole near its rounded end.
During intake, the customer described indoor use, no regular direct sunlight and a mounted device that does not become noticeably warm.
Black SUNLU PLA+ was a defensible starting point within that reported environment. It is not a general material guarantee; prolonged sunlight, heat, moisture or different loading require reassessment.
Recorded trial settings
Settings used for this particular geometry
These starting and test values were adjusted for this job with a 0.4 mm nozzle. They are not universal recipes or guarantees for other models.
- Filament and colour
- Black SUNLU PLA+
- Selected for the reported moderate indoor environment without a heat source
- Nozzle diameter
- 0.4 mm
- Balance between detail and production speed
- Layer height
- 0.12 mm
- Finer steps around the horizontal hole
- Wall count
- 4 walls
- More material around the hole and a stiffer wall structure as a starting point
- Solid top layers
- 4–5 top layers
- Cover the infill without sagging lines
- Top surface speed
- Approximately 30–40 mm/s
- Controlled deposition for a more even surface
- Overhang speed
- Approximately 20–30 mm/s
- Limit curling at angled edges
- Bridge speed
- Approximately 20–25 mm/s
- Control the unsupported span above the hole
- Ironing trial
- 20 mm/s, 12% flow, 0.10 mm spacing
- Tune the top surface rather than treating ironing as an on/off setting
Identify the risks in the first output
Sagging above the horizontal hole and rough outer contours
Observations and analysis
The initial trial with standard settings showed sagging at the transition between the overhang and bridge above the horizontal fixing hole.
Without support, the upper circular layers had to span open space. Outer edges and the surface also showed uneven and ragged areas.
Even if the part might have been usable, the sagging hole and uneven finish were reasons to investigate before proceeding.
Actions taken
- Reduce layer height to improve the stepped approximation of the circular hole.
- Assess bridge and overhang speeds to address unsupported sagging.
- Prepare cooling and bed adhesion for the finer layer structure.
Finer layers, corner lift and several possible causes
A rounder-looking hole with remaining bridge strands and a line at hole height
Observations and analysis
Version 2 used 0.12 mm layers and showed a rounder-looking hole. Several settings changed, so the photographs do not isolate the contribution of layer height alone.
Inspection also revealed slight corner lift and horizontal lines near the bottom and top of the hole. Bed adhesion, cooling and thermal shrinkage needed further attention.
Possible causes of the line included different layer times through the hole, flow transitions between walls and bridges, and local shrinkage at changes in cross-section. The photographs alone do not establish one proven cause.
Actions taken
- Rebalance bed temperature, adhesion and cooling to limit corner lift.
- Coordinate overhang speeds around 20–30 mm/s and bridge speeds around 20–25 mm/s with the wall settings.
- Inspect the untreated diagonal top lines before calibrating ironing.
A more even top surface and a less prominent seam
Ironing calibration and seam placement on the underside and inside
Observations and analysis
This version was recorded as an inspection candidate. The photographs are not evidence of customer acceptance or a formal dimensional tolerance.
Ironing was tested at 20 mm/s, 12% flow and 0.10 mm spacing. The surface became more even while retaining FDM texture. Enabling ironing alone can still leave ridges or too much or too little material.
Seam painting moved perimeter start and stop points towards the less visible underside and inside of the U shape. The seam remains physically present; close-ups show a local mark.
The hole looks rounder and the visible surface more even than earlier trials. Layer lines and local marks remain around and inside the hole, which is why inspection from several angles matters.
Actions taken
- Test ironing at 20 mm/s, 12% flow and 0.10 mm spacing over 4–5 top layers.
- Move the seam towards the underside and inside using seam painting.
- Inspect the hole, flatness, edge finish and remaining marks from several angles.
Discuss the critical features in your file
Send the model, drawing or part and identify important fits, spans and visible faces. We assess whether a test piece or targeted slicer adjustment is appropriate.
