Quick answer. Car seat foam is the polyurethane cushioning inside an automotive seat — the layer that determines comfort, support, and how the seat holds up over years of use. Miku Foam manufactures automotive car seat foam using both molded cold-cure HR (high-resilience) foam and cut/contoured slabstock foam, for OEM-replacement, automotive aftermarket, and Tier 2 seating programs. What we make, the specifications that matter, and how to choose between molded and cut for your program.
What we manufacture
Miku Foam produces polyurethane car seat foam for:
- OEM-replacement seat cushions and bolsters
- Automotive aftermarket (AM) and repair/replacement programs
- Tier 2 seating component supply for seat assemblers
- Off-road, heavy equipment, and specialty seating
- Prototype and low-volume cut foam for programs still finalizing a design
Both molded HR foam (poured into an aluminum tool for a fixed, repeating design) and cut/contoured slabstock foam (CNC-profiled from a cured foam bun, no tooling required) are produced, depending on your volume, shape complexity, and timeline. For the engineering and cost reasoning behind which process fits which program, see our guide: Molded vs Cut Car Seat Foam: Which Is Right for Your Program?.
Specifications
| Property | Typical range | Test / standard |
|---|---|---|
| Density (molded HR) | 45-60 kg/m3 | ISO 845 |
| Density (budget slabstock) | 25-30 kg/m3 | ISO 845 |
| 25% IFD (firmness) | 200-350 N | ASTM D3574 Test B1 |
| Support factor | 2.6-3.0 | 65% / 25% IFD ratio |
| Compression set | under approx. 10% | ASTM D3574 Test D (50%, 70 C) |
| Wet-aged compression set | per program | ISO 13362 / humid aging |
| Flammability | 102 mm/min max burn rate | FMVSS 302 / ISO 3795 |
Full methodology and the reasoning behind each number is in the molded vs cut comparison guide.
Density: the number that decides durability
Two cushions can measure identically on day one and diverge completely after two years of daily use. The difference is density. A primary cushion below roughly 40 kg/m3 is where sag, compression set, and a "dead seat" feel typically begin, regardless of whether the foam is molded or cut. For a durable OEM-grade cushion, HR foam in the 45-60 kg/m3 range balances comfort and service life; specify the density for your required service life first, then choose the process.
Choosing molded vs cut
- Mold it if you are producing the same seat design in real, repeating volume with a complex, contoured shape — the tooling cost is amortized across parts and you get fit and consistency cutting cannot reach.
- Cut it if you need parts fast, are doing aftermarket or repair work, or the design is still moving — there is no tooling lead time, and CNC profiling can reproduce an existing cushion from a sample.
A common path is to prototype in cut foam to lock the shape and comfort target, then move to a mold once volume is confirmed. The full decision framework, cost-crossover logic, and a side-by-side comparison table are in our molded vs cut car seat foam guide.
Testing and quality
Every automotive seating program should confirm, before comfort is even discussed:
- Flammability — FMVSS 302 (US) or the equivalent ISO 3795 horizontal burn test, at no more than 102 mm/min. This is a pass/fail gate for any interior cushion.
- Compression set — per ASTM D3574 Test D, confirming the foam holds its shape under sustained load and heat.
- Fatigue (roller-shear) resistance — catches foam that passes a static compression-set test but softens under real, repeated in-and-out use.
- Wet (humid-aged) compression set — relevant if your seats ship to a hot-humid market; foam that passes dry can still soften after humid aging.
OEM input checklist
Provide these items in one RFQ package so process selection, sampling, and production are evaluated against the same target:
- Vehicle/platform, seat position, intended market, and whether the program is OEM, Tier 2, aftermarket, off-road, or specialty seating
- 2D drawing and 3D CAD where available, datum scheme, finished dimensions, tolerances, and an original cushion or reference sample if reverse engineering is required
- Cushion, backrest, bolster, and insert scope; frame, trim-cover, sensor, heater, vent, wire, and attachment interfaces
- Density, 25% IFD/firmness, support factor, compression set, fatigue, and humid-aging targets with test methods
- Flammability requirement and target market, plus the evidence or production documentation required
- Prototype quantity, annual volume, order quantity by part number, program timing, delivery location, and forecast pattern
- Surface/marking, part identification, packaging, inspection, PPAP or other approval-document requirements
Unknown values can be marked “supplier recommendation requested.” A drawing or physical sample alone defines shape, not comfort or durability, so include performance targets wherever possible.
MOQ and sample questions to confirm
MOQ depends on whether the part is cut or molded, whether tooling already exists, material and flammability requirements, and the number of part variants. Ask the team to confirm:
- Is the quoted minimum per part number, tool, density/firmness grade, or delivery lot?
- Can CNC-cut prototypes be used before committing to molded tooling?
- Will the sample be cut foam, a soft-tool trial, or a production-tool part?
- How many samples are needed for fit, comfort, flammability, fatigue, and trim-cover validation?
- Which tooling, test, and sample charges are separate from unit pricing?
- What drawing revision and approved sample will control production?
Send your seat foam RFQ package
FAQ
Q: What is car seat foam made of? Automotive car seat foam is polyurethane, produced either as molded cold-cure HR (high-resilience) foam poured into a shaped tool, or as cut/contoured slabstock foam profiled from a cured foam bun.
Q: What density should automotive seat foam be? For a primary cushion, HR foam around 45-60 kg/m3 balances comfort and durability. Below about 40 kg/m3 is typically where sag and compression set begin.
Q: Do you produce both molded and cut car seat foam? Yes. Which one fits your program depends on volume, shape complexity, and timeline — see our molded vs cut comparison for the full decision framework.
Q: Does car seat foam have to pass a flammability test? Yes. Interior foam must meet FMVSS 302 (US) or the equivalent ISO 3795 burn-rate test at no more than 102 mm/min before any other specification is discussed.
Q: Can you reproduce an existing seat cushion from a sample? Yes. Cut foam can be CNC-profiled from a sample or drawing; a matching mold can be built for molded foam. Provide density and IFD targets along with the shape so the replacement performs like the original, not just looks like it.
Q: What information is needed for a car seat foam RFQ? Include the vehicle and seat position, drawings/CAD or a reference cushion, dimensions and interfaces, density and IFD targets, flammability and validation requirements, quantity by part number, timing, and delivery location.
Q: What is the MOQ for custom car seat foam? MOQ varies by cut versus molded process, tooling status, material and flammability requirements, and part variants. Confirm whether the minimum is per part number, tool, foam grade, or delivery lot, and separate prototype, tooling, and test costs.
Sourcing this line
Choosing between an OEM program and an aftermarket buy? See how to vet an OEM car seat foam manufacturer for a supplier vetting checklist, and how to read a car seat foam spec sheet for what density, IFD, and support factor actually mean on a datasheet.
Get specs, samples, or a quote
For density selection, process recommendation (molded vs cut), or test data for your seating program, contact our team. We pour and mold our own polyurethane foam and can work from your drawing, sample, or performance spec.
*Miku Foam manufactures automotive car seat foam — molded and cut — for OEM, Tier 2, and aftermarket seating. Related: Molded vs Cut Car Seat Foam · How to Vet a Manufacturer · Reading a Spec Sheet.*