Off-highway machines operate in some of the toughest conditions on the planet, from dusty fields to salt-sprayed building sites, and from mud and chemicals to long hours of heavy use. Sheet Moulding Compound (SMC) is a proven material choice for these environments because it combines durability, design freedom, and economical production, while also delivering excellent surface quality when required. Mitras designs and delivers SMC and DCPD components, including Class A painted finishes, for off-highway, truck, rail and industrial markets, so we see these benefits in real projects every day.

Core advantages of SMC for off-highway use

Durability and resistance to corrosion, moisture and chemicals
SMC is inherently resistant to corrosion, moisture and many chemicals, which makes it ideal for exterior bodywork, access panels and housings that face weather, road salts and site chemicals. That resistance helps parts last longer and reduces maintenance cycles.

High strength to weight, and fuel or energy saving potential
Compared with comparable metal panels, SMC can deliver significant weight savings, without sacrificing structural performance. Lighter bodywork translates into lower fuel use or lower energy consumption, which is important for utility, construction and agricultural fleets.

Design freedom, integrated features, and fewer assemblies
SMC is compression-moulded as a net or near-net shape, so you can create complex geometries, incorporate bosses, ribs and mounting points, and reduce the number of separate components in an assembly. That reduces assembly time at the OEM, and improves part reliability.

Impact performance and long service life
SMC formulations, fibre content and reinforcement length can be tuned to give excellent energy absorption and impact resistance, beneficial for fenders, hoods and protective covers that take knocks in the field. Formulation choices let you balance stiffness, toughness and repairability.

Class A finishes and on-site appearance
If appearance matters, modern SMC formulations and finishing workflows can achieve Class A, high-gloss painted surfaces comparable to metal. That makes SMC suitable for branded equipment cabs, operator panels and visible exterior parts. Mitras’ painting capability supports high quality finishes across SMC and DCPD components.

Thermal, electrical and fire performance where needed
SMC offers good thermal stability, electrical insulation and can be formulated for flame retardancy where regulations or safety needs demand it, for example near electrical cabinets or exhausts.

Typical off-highway parts that suit SMC

• Hoods, front end modules, and fenders for tractors, loaders and trucks.
• Operator cabs, roof panels, and access doors, including parts requiring integrated mounting bosses.
• Instrument housings, electrical enclosures, and air intake covers, where electrical insulation and corrosion resistance are important.

Spec choices, glass content, and practical trade offs

Glass fibre content, fibre length and resin chemistry are the levers that change part behaviour. Typical glass content for SMC can range widely, from low double digits up to 60% by weight, depending on the required stiffness, strength and cost. Higher glass fractions increase stiffness and tensile strength, while changes in glass volume and fibre length also affect impact behaviour and surface finish. A 22% glass content is a moderate specification, often chosen to balance surface appearance and mechanical performance, but for heavy structural panels you might select higher glass content.

Design for SMC, practical tips for engineers

• Aim for consistent wall thickness, to avoid sink and warpage.
• Use generous radii and avoid sharp corners, to improve material flow and reduce stress concentrations.
• Integrate features where possible, such as bosses and ribs, to reduce assembly operations and improve repeatability.
• Consider draft angles for ejection and plan tooling access for trimming and painting.

Cost, production and lead factors

SMC is efficient for medium to large parts and for production volumes where compression moulding tooling cost is amortised. There are strong cost advantages compared to multi-piece metal assemblies, because SMC reduces the number of welded or fastened joints, and can shorten assembly times. Finishing, such as Class A painting, is an added step, but modern in-house paint facilities allow control of quality and lead time, which Mitras provides.

Why work with Mitras for off-highway SMC parts

Mitras offers compression and reaction injection moulding, Class A painting, and full system design and assembly, backed by experience supplying the global leaders in automotive, off-highway and rail sectors. We can support material selection, tooling, prototyping, finishing and assembly, so you get parts that meet performance, aesthetic and cost targets. If you want an SMC part that replaces metal, reduces weight, or combines multiple functions into one moulding, Mitras can help take a concept to production.

Next steps, contact and collaboration

If you have a specific part in mind, a drawing, or a product brief, we can:

• Review the design for SMC suitability, including glass content and resin choices
• Offer a prototype or pilot run, so you can validate fit, finish and impact performance
• Provide cost and lead time estimates for production volumes, and advise on finish options including Class A painting

Email our team at new.enquiries@mitras.co.uk to start a technical review, or tell us the best time to call and we will arrange it.