PCCF — properties and libdrone use
Summary¶
PCCF (polycarbonate carbon fibre composite — Prusa PC-CF in libdrone's BOM) is the stiffest printable material in the libdrone stack. It is used exclusively for the three structural X body layers where dimensional stability matters most. It requires a hardened steel nozzle, high print temperature, an enclosed printer, and a glue stick on the bed. It is abrasive, brittle under impact, and must never be used in crash-contact zones.
Concept¶
Why stiffness matters in the structural core¶
The X body sandwich carries the rod channels and T-slot pockets that define the drone's geometry. Rod channels must hold their diameter under the compressive preload of the pre-tensioned CF rods. T-slot pocket walls must maintain their geometry under the lateral loads of tab engagement. Any dimensional change in these features changes the rod preload, the structural assembly alignment, or the tab engagement — all of which degrade structural performance.
PCCF's extremely high stiffness and low thermal expansion coefficient (the carbon fibre reinforcement constrains thermal movement) keep these dimensions stable across the operating temperature range. Under sustained load it does not creep. Under temperature variation it does not expand or contract enough to change critical fits.
Why brittleness is acceptable in the structural core¶
PCCF fractures rather than deforms under impact. This is acceptable — even desirable — in the structural core because the core is not designed to absorb crash energy. It is designed to survive while the designated fuse elements (arm shafts, tabs) absorb energy in front of it. If the failure hierarchy works correctly, crash energy is consumed before it reaches the PCCF layers.
If the PCCF layers do fracture, they fracture cleanly — which means the failure is visible and the replacement decision is unambiguous. A PETG layer might deform invisibly and continue to carry load at reduced capacity; PCCF either survives intact or breaks clearly.
Carbon fibre abrasion¶
The carbon fibre in PCCF is chopped short-strand, distributed throughout the matrix. It is highly abrasive to brass nozzles — a standard brass 0.4 mm nozzle will wear significantly within a single print. A 0.6 mm hardened steel nozzle is mandatory. Keep a spare — PCCF and PETG-CF together will exhaust a nozzle faster than PETG alone.
Reference¶
Material properties¶
| Property | Value | Notes |
|---|---|---|
| Print temperature (nozzle) | 290–300°C | Higher than standard PC; verify with spool datasheet |
| Bed temperature | 110°C | PEI sheet; glue stick mandatory |
| Enclosure | Required — door closed, >40°C ambient | Without enclosure: layer delamination and warping |
| Cooling | 0% | No part cooling — maintains inter-layer adhesion |
| Nozzle | 0.6 mm hardened steel — mandatory | Brass nozzles wear within one print |
| Moisture sensitivity | High | Dry at 80°C for 6 hours if any doubt; PCCF is hygroscopic |
Key print settings (X body PCCF layers)¶
| Setting | Value |
|---|---|
| Layer height | 0.20 mm |
| Perimeters | 4 |
| Infill | 40% Grid or Gyroid |
| Solid layers | 5 top / 5 bottom |
| Orientation | Flat — all three identical layers |
| Glue stick | Mandatory on PEI |
X body PCCF layer specification¶
| Parameter | Value |
|---|---|
| Quantity | 3 identical layers (layers 2, 3, 4 of sandwich) |
| Thickness | 3 mm each |
| Mass target | 9.0 g each / 27.0 g total |
| Rod channel diameter | 2.2 mm (sliding fit — not interference) |
| Coupon required | Coupon 8 (T-lock fit) — must pass before full production |
What PCCF must not touch¶
- Interference fit rod channels — use 2.2 mm, not 2.1 mm; brittle matrix cannot tolerate radial compression stress
- Post-processing with Dremel — PCCF chips and cracks; any reaming operation risks micro-fractures
- Heat-set inserts — PCCF is too stiff and too brittle; heat-set inserts go in PETG top layer only
- Crash-contact zones — arm shafts, tabs, bottom layer must be PETG
Procedure¶
Drying PCCF¶
- Dry at 80°C for 6 hours minimum before any print.
- Print immediately — PCCF re-absorbs moisture quickly in humid conditions.
- Signs of wet PCCF: surface bubbling, voids in perimeters, poor layer fusion.
- Never print PCCF with a spool that has been open for more than 48 hours without re-drying.
Bed preparation¶
- Clean PEI sheet with IPA — 99% isopropyl alcohol, lint-free cloth.
- Apply thin even layer of glue stick to the full print area.
- Heat bed to 110°C before starting print.
- Do not remove part until bed has cooled to below 50°C — PCCF contracts on cooling and releases cleanly if allowed to cool fully.
Rationale¶
Why Prusa PC-CF specifically¶
Prusa PC-CF is validated at the print settings documented here on a Prusa CoreOne+ printer. Generic PCCF filaments vary in carbon fibre loading, matrix viscosity, and moisture sensitivity. Using an unvalidated PCCF risks print failure on the most difficult parts of the build. Once a reliable alternative is validated with documented settings, it may be added to the approved materials list.
Why 0.6 mm nozzle rather than 0.4 mm¶
A 0.4 mm nozzle limits the minimum feature size but increases the number of perimeter passes required for a given wall thickness. For PCCF, which must not be reprocessed, a failed print from nozzle clogging mid-layer wastes expensive material. The 0.6 mm nozzle provides larger melt throughput, lower pressure build-up, and longer service life against abrasion. The slight reduction in maximum feature resolution is irrelevant at the X body's minimum feature sizes (smallest feature: 2.2 mm rod channel wall).
Connections¶
requires: - material-selection-philosophy related: - petg - sandwich-structure - cf-rod-architecture - coupon-validation - print-profiles leads_to: - asa