Mitsubishi FGF Recycled CARBON-P PET-G pellets are introduced directly into the heated hopper of a large-format fused granular fabrication cell, where a single-screw extruder with an L/D ratio of 24:1 or greater and a hardened steel barrel maintains the melt temperature between 240 °C and 260 °C for initial qualification. The carbon fibre filler raises melt viscosity relative to unfilled PET-G; therefore, nozzle diameters below 0.6 mm are avoided, and extruder drive current is monitored as an indirect measure of nozzle pressure. Pellet feed is dried in a desiccant dryer to a residual moisture level below 0.02% before extrusion, usually at 65 °C for 4 h, with drying time extended when ambient relative humidity exceeds 60%. Build chamber temperature is held at 45 °C to 60 °C on gantry systems equipped with active heating; without this, flat tool faces wider than 500 mm exhibit corner lift and interlayer separation. Because published data for this specific recycled carbon-filled grade is limited, initial qualification on each FGF cell includes printed tensile coupons tested according to ISO 527-2 and heat deflection temperature specimens tested according to ISO 75-2, with results compared against the certificate of analysis before production acceptance.

For low-temperature thermoforming tool faces, the printed shell is machined on a 3-axis CNC router to bring the working surface to within ±0.2 mm of the CAD reference, then sealed with a two-part epoxy surface coat mixed at a 100:55 resin-to-hardener ratio by mass. The epoxy is applied in two coats to close the open bead surface and prevent vacuum leakage through the printed wall. Because the heat deflection temperature of carbon-filled PET-G restricts continuous tool surface exposure to 65 °C or below, the tool is limited to thin-gauge vacuum forming of polystyrene, ABS, and low-temperature PET-G sheet with chilled water circulation through printed internal channels. A water-soluble release agent diluted at 2 wt% in deionised water is sprayed on the sealed tool face before each forming cycle to prevent sheet adhesion. The terminal product is a short-run vacuum forming tool; published data for this specific configuration is limited, so tool face condition is inspected after every forming batch and the epoxy seal coat is touched up when visible bead texture appears. Regulatory compliance for this industrial tooling application falls under REACH 1907/2006 and RoHS 2011/65/EU; no food-contact claim is made because the recycled carbon-filled feedstock is not validated under FDA 21 CFR 177.

The process window for reliable layer fusion is narrower for carbon-filled recycled PET-G than for unfilled PET-G. A reduction of 5 °C in melt temperature below the lower end of the established barrel profile reduces interlayer adhesion to the point where a sectioned test bead can be split between layers with hand pressure. An increase of 10 °C above the upper end produces visible surface discolouration and a sharp acrid odour associated with partial thermal degradation of the copolyester matrix. Consequently, barrel zone temperatures are controlled within ±5 °C, and extrusion speed is reduced in the first and last 100 mm of each tool perimeter to prevent start/stop bead width variation. Build chamber temperature is verified with at least three thermocouples placed at the corners and centre of the printed part, and any reading difference greater than 5 °C is corrected before the deposition of the next layer. These controls reduce the batch-to-batch variance observed when recycled carbon fibre content shifts by more than 2 wt%, which alters melt viscosity and changes the acceptable extrusion speed range for the same nozzle diameter.

Can Carbon-Filled Recycled PET-G Replace Machined Nylon in Robotic End-of-Arm Tooling?

Robotic end-of-arm tooling and assembly fixtures are produced by printing carbon-filled recycled PET-G sections, then assembling them with mechanical fasteners and a methyl methacrylate structural adhesive mixed at a 1:1 ratio by volume. The adhesive is applied in a continuous bead to internal ribs, and the sections are clamped for 30 min at 20 °C to 25 °C before any load is applied. Because the carbon-filled material is stiffer than unfilled PET-G but less impact resistant than unfilled copolyester, gripper fingers incorporate corner radii of at least 5 mm and load-bearing wall thickness not less than 6 mm. Locating surfaces are machined flat to ±0.1 mm after printing, and reamed holes are produced to an H7 tolerance for hardened steel dowel insertion. Structural acceptance of the gripper bodies follows ISO 527-2 tensile testing on printed coupons cut from the same production batch, while the integration risk assessment follows ISO 10218-1:2011 and the Machinery Directive 2006/42/EC.

Production-scale printing for this application is performed on a Cartesian gantry with a build envelope of at least 2 m in the longest axis, using a 1.0 mm hardened steel nozzle and a 0.6 mm layer height. Straight-run deposition speed is set between 40 mm/s and 60 mm/s for initial trials, reduced to 25 mm/s on radii below 20 mm to maintain acceptable carbon fibre orientation and bead width. The terminal product is a gripper or fixture body used for locating roof panels, bumper fascias, and bracketry during adhesive bonding and resistance spot welding. The printed body does not create the metallic debris associated with machined aluminium tooling, but it is not suitable for direct contact with hot steel surfaces above 70 °C. Field observation on an automotive assembly line showed that fixture finger wear was concentrated at the steel panel contact edge; a replaceable polyurethane wear strip of Shore A 90 was added to extend the printed body life. Published data for this specific configuration is limited, so wear life must be verified on the target assembly line rather than extrapolated from laboratory abrasion tests.

Foundry Master Patterns for Air-Set Sand Moulding Require a Sealed Print Surface

In foundry patternmaking, carbon-filled recycled PET-G is used for master patterns and split core boxes for air-set sand systems that do not require baking above 80 °C. The printed pattern shell is backfilled with a two-component polyurethane casting resin mixed at a 100:35 resin-to-hardener ratio by weight to a minimum thickness of 25 mm behind all working surfaces. After a 24 h cure at 23 °C, the pattern is machined to the required casting dimensions with a patternmaker’s shrinkage allowance applied in accordance with ISO 8062 or the foundry’s internal dimensional control plan. The carbon fibre filler lowers the coefficient of linear thermal expansion relative to unfilled PET-G and improves edge resistance to sand abrasion, but the working surface is still sealed with a two-pack polyurethane foundry varnish mixed at a 3:1 ratio by volume, then sanded to P320 grit before release wax is applied.

The split line is printed as a separate machined face, and brass locating pins are inserted into reamed H8 holes to maintain registration during repeated mould closing operations. Air-set sand compaction loads can produce localised flexure in unsupported pattern sections; therefore, rib spacing is designed to limit the unsupported span to 300 mm for a 20 mm thick working wall. The terminal product is a short-run foundry pattern; published data for this specific configuration is limited, so the pattern service life must be established in the target foundry, and the varnish layer is refurbished when release wax breakdown or sand abrasion exposes the printed substrate. The recycled carbon-filled grade is not appropriate for high-pressure moulding lines where clamping forces exceed 20 t on the pattern plate, and it is not recommended for flaskless moulding machines that apply simultaneous squeeze and jolt compaction because the printed pattern wall may crack at the bead fusion lines. Environmental compliance for the foundry pattern is evaluated under REACH 1907/2006 for the varnish and release wax system rather than for the printed polymer itself.

On aircraft maintenance production lines, carbon-filled recycled PET-G is printed into drill jigs and trim templates for composite panel rework under ambient-temperature curing conditions. The pellet feedstock is kept in a dry storage cabinet at 40 °C and 10% relative humidity, then fed directly into a mobile FGF printer positioned near the aircraft, avoiding the logistics and curing time associated with wet-layup epoxy tooling boards. These drill jigs are not used in autoclaves or ovens, because the material loses dimensional stability above 65 °C under sustained clamp load. Drill bushing bores are machined to H7 after printing, and sacrificial steel drill bushings with an outer diameter of 12.7 mm are inserted to prevent the carbon-filled polymer from contacting the drill bit directly. The carbon fibre filler reduces burr formation during post-print machining, but it accelerates cutter wear; therefore, solid carbide tooling and a feed rate reduction of 30% are used during finish passes. Compliance for aerospace tooling requires documentation under AS9100 or an equivalent production organisation approval, although the printed tool is not classified as a flying part and no flammability test to 14 CFR 25.853 is required for ground support tooling unless the fixture is used inside a fuel tank cell.

For a typical composite trim fixture, the printed shell is assembled from four segments joined with an epoxy adhesive mixed at a 100:45 resin-to-hardener ratio by mass and mechanically fastened with M8 zinc-plated bolts. The lower vacuum plenum is sealed with a two-part polyurethane coating applied at 200 g/m² dry film thickness. Vacuum is applied at −0.7 bar gauge to hold the composite panel during routing, and the fixture is inspected against the master panel after every 50 operations using a coordinate measuring machine verified to ISO 10360-2. Although the carbon-filled material has a lower coefficient of linear thermal expansion than unfilled PET-G, it is still higher than aluminium; the fixture is therefore maintained in an assembly hall at 22 °C ± 2 °C and is not exposed to direct sunlight before use. This temperature constraint is a documented operational boundary and must be included in the work instruction for the maintenance cell.

When Carbon-Filled PET-G Is Used for Concrete Formwork Panels in Architectural Precast

Concrete formwork panels printed from carbon-filled recycled PET-G are produced as negative mould surfaces for architectural precast elements with limited cast cycles and relatively low compaction energy. The printed face is coated with a solvent-free polyurethane formwork sealer applied in two coats at a total wet film thickness of 250 µm, followed by a vegetable ester oil release agent diluted 1:8 in water. Because the formwork surface is subjected to abrasive aggregate and alkaline pore water, the sealer must be reapplied after each pour, and any damage from formwork vibrators must be repaired before the next cycle. The carbon fibre filler improves scratch resistance relative to unfilled PET-G, but it does not provide the abrasion resistance of steel formwork; the printed panels are therefore limited to architectural finishes where minor surface texture variation is acceptable or where a post-cast acid etch hides the formwork grain.

The panels are designed with a printed wall thickness of 18 mm and backed by a rectangular steel tube frame on 300 mm centres to limit deflection to less than 1/400 of the span under fresh concrete pressure. In practice, fresh concrete is poured in lifts not exceeding 600 mm per hour to keep lateral pressure within the capacity of the printed face and its backing frame. The terminal product is a reusable formwork panel for a limited series of casts; published data for this specific configuration is limited, so the number of casts per panel must be validated on the first production pour, and the panel is withdrawn from service when the sealer no longer prevents surface water absorption. Load assumptions for the supporting frame follow EN 12812:2008 for temporary works, with the printed face treated as a sacrificial wearing surface rather than a structural member. Environmental compliance is evaluated under REACH 1907/2006 for the sealer and release agent; the recycled content claim is valid only when the batch certificate confirms the post-industrial or post-consumer recycled fraction.

Composite Layup Tooling and Vacuum Bag Support Shells for Room-Temperature Cure

Carbon-filled recycled PET-G can be used for composite layup tooling only when the cure cycle is conducted at ambient temperature, typically 18 °C to 28 °C, and the resin exotherm is measured to remain below 60 °C on the tool face. The tool surface is printed as a near-net shell, then sealed with a low-viscosity epoxy tooling gel coat mixed at a 100:30 resin-to-hardener ratio by weight and wet sanded to P600 grit. A semi-permanent release polymer is applied in three layers at 15 min intervals. The printed support shell is backfilled with a syntactic epoxy core to reduce deflection under vacuum bag pressure, and a vacuum groove network is machined into the perimeter flange. The tool is tested for vacuum integrity at −0.85 bar before first use; any leak is sealed with a thixotropic epoxy putty and the test repeated.

This material is not suitable for autoclave cycles above 65 °C, because the heat deflection temperature of the carbon-filled PET-G matrix is exceeded and the tool face can creep under autoclave pressure. It is also incompatible with solvent-based cleaning agents containing ketones or chlorinated solvents, which attack the PET-G surface and cause environmental stress cracking at the bead fusion lines. The terminal product is a room-temperature vacuum bag support shell used for low-volume composite repair panels, with dimensional inspection performed in accordance with ISO 1101 for geometrical tolerancing. Because carbon fibre orientation in the printed shells is anisotropic, tensile coupons cut from representative sections are tested in both longitudinal and transverse directions according to ISO 527-2 before the tool is released to production.