Epoxy granite and polymer concrete
Epoxy Granite Machine Bases (Mineral Casting)
Graded mineral aggregate in epoxy resin, cast cold into a mould with steel inserts in place. The highest damping of any machine base construction, and the most expensive to change. We tell you honestly whether your design justifies a mould and which route is realistic.
We are a sourcing service, not a foundry or a fabrication shop. You pay the fabricator you choose, nothing to us. Reply within 24 business hours.
What it is
Mineral casting, also sold as epoxy granite or polymer concrete, is a mix of graded aggregate and epoxy resin poured into a mould that carries the steel inserts at exact coordinates. After cure the cast surface is not machined; only the insert faces are. It has the highest damping of the common constructions, typically several times cast iron for the same section, and low thermal conductivity and high thermal capacity, so it drifts slowly. Density is around a third of iron, near aluminium.
The tradeoff is that the mould is the design. A late change is the most expensive of any construction here, the first unit waits for the mould and a long cure, and the material is weak in tension, so loads go through cast-in inserts. There is also no widely adopted grading standard for mineral cast, unlike iron or steel: the mix is the supplier's own formulation, so you ask for its cured properties directly instead of assuming a grade.
Where it fits
- Metrology frames and coordinate measuring machines
- Laser, optical and fine finishing machine bases where vibration and thermal drift decide accuracy
- A design that is frozen and a volume that repays a mould
- Machines where mass has to stay low because of density, not where weight has to be high
Where it does not
- Prototypes and designs still changing
- Low volume that cannot repay a mould
- Heavy tensile or point loads without cast-in inserts to carry them
- Anything needing site repair, since mineral cast is effectively not repairable
Process
How it is made
- Mould built, usually in steel or GFRP, to the finished part geometry
- Steel inserts and levelling elements positioned in the mould at exact coordinates
- Graded mineral aggregate mixed with epoxy resin and cast cold into the mould
- Cured, typically over several days, then demoulded
- Only the insert faces receive machining; the cast surface itself is not cut
Standards
What governs it
ISO 1101, ISO 2768, EN 10204 (inserts).
Each is explained in the standards index, including the one that is most often cited where a different one was meant. Themanufacturing technologies page shows the stages side by side with the other constructions.
Before you ask for a quote
What to put in the RFQ
Typical ranges for this construction, and what to state so two quotes can be compared. Ranges are not promises: they depend on the shop and the part.
| Item | Typical | Say in the RFQ |
|---|---|---|
| Mould and volume | The mould is tooling and the largest cost. Cost per unit falls with volume. | Annual quantity, how long the design stays frozen, and who owns the mould. |
| Insert layout | Steel inserts and levelling elements cast in place at stated coordinates. Loads go through them. | A drawing of every insert, thread and load point, with the datum scheme. |
| Mix and cured properties | Supplier's own formulation. No common grading standard. | Ask for the cured density, compressive strength, damping and thermal data you rely on, in writing. |
| Cure and lead time | Mould build plus a long cure before machining. Slow first unit. | The expected cure time and the date you need the first unit. |
| Finish of insert faces | Only the insert faces are machined. Flatness is held there, not on the cast surface. | Flatness, parallelism and squareness of the insert faces and the datum scheme. |
| Handling and weight | Lighter than iron per unit volume, but section is larger to compensate for lower stiffness. | Final weight, lifting points and the crate requirement. |
The full checklist is in the RFQ checklist guide, and the seven things that move the price are on the home page.
Questions
Is epoxy granite the same as polymer concrete?
They are close relatives and the names are used loosely: aggregate bound with a polymer resin. The specific resin, aggregate grading and filler change the properties, so compare cured data from the supplier rather than the name.
Can mineral cast replace cast iron?
For damping and thermal behaviour, often. For stiffness per unit volume and tensile loads, no: the section has to grow and loads have to go through inserts. The polymer concrete vs cast iron guide compares them property by property.
Can you source it from Vietnam?
Availability depends on the part. Send the drawing and the volume and we tell you plainly whether a route exists and whether another construction fits the job better, including a filled weldment.
Can it be machined or repaired later?
Only the cast-in insert faces are machined. The cast body is effectively not repairable, so a damaged part is replaced, not fixed.