Polymaker PolyCast – Investment Casting Patterns Without Tooling

What this material is for

PolyCast is not a material for parts but for patterns. The printed piece is never delivered – it is invested, burned out of the mould with minimal residue and leaves behind the cavity the metal flows into. What the customer ends up holding is a casting in bronze, silver, stainless steel or aluminium.

That is exactly where the economics sit: in conventional investment casting the wax pattern comes out of a wax injection mould whose tooling cost is incurred regardless of quantity. For a one-off, a spare part or a run of 20 pieces, that tooling is out of all proportion to the job. PolyCast skips the step entirely – the pattern comes straight from the CAD data.

The process

Step	What happens
1. Print	Master pattern in PolyCast, 190–220 °C nozzle, open build chamber
2. Smooth	Isopropyl alcohol softens the surface – layer lines disappear, sprues can be bonded on
3. Invest	Pattern is invested in ceramic or investment plaster (at the customer / foundry)
4. Burnout	Kiln at 1,100–1,200 °C for 40–60 min – shell sinters, pattern burns out
5. Pour	Metal is poured into the resulting cavity, then the shell is rinsed

What we supply is step 1 and optionally step 2. Investing, burnout and pouring happen at your site or your foundry – we do not operate a foundry.

Ash residue: what the number means

The manufacturer states < 0.003% ash residue (Polymaker Ash-Free™). This is the decisive figure for a burnout pattern: any residue left in the cavity becomes an inclusion in the casting.

Two qualifications matter:

First, Polymaker gives no measurement temperature and no test standard for this figure. For the actual process the manufacturer specifies 1,100–1,200 °C over 40–60 minutes, because the ceramic shell sinters at that temperature.

Second, the figure is a manufacturer statement under laboratory conditions, not a test certificate for your kiln. Burnout schedule, hold time and ramp rate depend on your investment material, pattern wall thickness and kiln type. Polymaker explicitly notes that each foundry has to determine its own schedule. We therefore recommend a sample part on the first run to dial in the schedule before a whole batch is invested.

After cooling, the shell should be rinsed with water to flush out any remaining ash.

Documented properties

Mechanical and thermal values from the Polymaker datasheet V5.4. The ash residue is stated in Polymaker’s product information (Ash-Free™) and is not part of the datasheet:

Property	Value	Standard
Density	1.10 g/cm³ (at 21.5 °C)	ISO 1183
Tensile strength X-Y	53.2 ± 1.1 MPa	ISO 527
Tensile strength Z	26.3 ± 2.1 MPa	ISO 527
Young’s modulus X-Y	2,215 ± 42 MPa	ISO 527
Elongation at break X-Y	5.7 ± 0.5 %	ISO 527
Flexural strength X-Y	78.0 ± 2.3 MPa	ISO 178
Charpy notched X-Y	2.9 ± 0.3 kJ/m²	ISO 179
Glass transition temperature	70 °C	DSC
Decomposition temperature	260 °C	TGA
Vicat softening	67 °C	ISO 306
Heat deflection temperature (1.8 MPa)	53 °C	ISO 75
Heat deflection temperature (0.45 MPa)	67 °C	ISO 75
Equilibrium moisture	2.09 % (70% RH, 23 °C)	–

Two points that matter in practice

Moisture. At 2.09% equilibrium moisture PolyCast absorbs considerably more water than PLA or PETG. A spool left out in the open is saturated within days, which causes bubbling and surface defects – and every surface defect on the pattern shows up as a defect in the casting. We therefore store and print the material dry; the manufacturer specifies 12 hours at 50 °C for re-drying.

Dimensional stability under heat. At ~53 °C heat deflection temperature a pattern will already distort in a hot car or a sunlit storeroom. Investment casting patterns are precision parts – any distortion transfers one-to-one into the casting. Patterns should therefore be invested promptly and kept cool until then.

Economic comparison

	Wax injection mould	PolyCast pattern
Tooling cost	high, independent of quantity	none
Lead time to first pattern	weeks	hours
Geometry change	new tooling	new CAD file
Cost per pattern at high volume	very low	constant (material cost)
Economical from	several thousand units	one-off to medium batch

Above a certain batch size the wax injection mould remains superior – unit cost there falls with every piece, whereas it stays constant for a printed pattern. PolyCast is the process for everything below that: one-offs, spare parts, prototypes and small batches.