Mounting Material Calculator
Calculate the amount of mounting material (resin) needed for compression or castable mounting based on your sample and mold dimensions. This helps reduce waste and ensures you have enough material.
Density of the selected resin is used to convert volume → grams.
Leave blank to assume the sample is ≈5% of mold volume. For cylindrical samples, enter Length = Width = diameter.
What mounting does
Mounting encapsulates a metallographic specimen in a polymer cylinder so it can be ground, polished, and handled in a repeatable way. A good mount protects the edge of the specimen, supports irregular shapes, and gives the operator (or an automated holder) a uniform surface to clamp.
The right mounting workflow depends on three things: specimen sensitivity to heat and pressure, edge-retention requirements, and throughput. The two families below cover almost every metallographic case.
Compression vs. castable mounting
Compression Hot mount
Resin pellets or powder are cured under pressure (≈30 MPa) at 150–180 °C in a mounting press. Cycle time is 5–10 minutes per mount.
- Best for: heat-tolerant alloys, routine throughput, edge-retention work.
- Avoid for: heat-sensitive (low-melt) alloys, electronics, polymer composites, large or hollow parts.
- Typical safety margin: ~10% for fill consistency and pellet/powder loss.
Castable Cold mount
Two-part liquid resin (resin + hardener) is poured into a cup at room temperature and cures over minutes to hours. No press required.
- Best for: heat-sensitive parts, large or irregular samples, porous infiltration, vacuum or pressure impregnation.
- Avoid for: high-throughput labs where cycle time matters more than versatility.
- Typical safety margin: ~15% for shrinkage on cure and mixing loss.
Resin reference table
Properties drive both polishability and how much material you need. Density determines the volume-to-mass conversion the calculator uses.
| Resin | Type | Density (g/cm³) | Hardness | Key trait | Best for |
|---|---|---|---|---|---|
| Phenolic (Bakelite) | Compression | 1.40 | Medium-hard | Workhorse, fast cure | Routine ferrous & non-ferrous QA. |
| Conductive Phenolic | Compression | 1.45 | Medium-hard | Cu/graphite filler | SEM/EDS, EBSD, electroplating prep. |
| Diallyl Phthalate (glass-filled) | Compression | 1.35 | Hard, low shrink | Excellent edge retention | Coatings, thin layers, plated parts. |
| Epoxy | Castable | 1.15 | Hard | Low shrinkage, vacuum-compatible | Porosity infiltration, PCBs, ceramics. |
| Acrylic | Castable | 1.18 | Medium | Fast cure (~10 min) | High-throughput cold mounts. |
| Polyester | Castable | 1.20 | Medium | Clear, low-cost | Display mounts, transparent inspection. |
Density values are typical vendor-published averages and vary by formulation; use the supplier datasheet for tight-tolerance work.
How the calculator works
For a cylindrical mold of diameter D and height H, the resin needed is the cavity volume minus the specimen volume, multiplied by a safety margin and the resin density:
- Mold volume = π · (D/2)² · H
- Specimen volume = L·W·H (rectangular) or π·(Ø/2)²·H (cylindrical)
- Resin volume = (Vmold − Vspecimen) × margin
- Resin mass = Vresin × ρresin
Standard PACE compression molds use a 0.75 in (19.05 mm) cavity height. For castable cups or non-standard cavities, choose "Custom Size" and enter the actual values.
Tips for clean, repeatable mounts
- Weigh, don't scoop. Compression resin is forgiving by volume but a gram balance gives reproducible fill levels and pressure profiles run-to-run.
- Orient the specimen first. Place the face you want to polish against the bottom of the cavity. The opposite face becomes the back of the mount.
- Use mold release. A thin film prevents the cured mount from sticking and extends mold life, especially for castable cups.
- Mind the cure profile. Compression mounts need cooling under pressure to prevent radial cracking. Castable epoxies generally prefer slow, low-temperature cures for low shrinkage.
- Match resin hardness to the specimen. Hard specimens in soft resin "round off" at the edge during polishing; soft specimens in glass-filled resin can suffer relief. Aim for hardness parity.
- Vacuum-infiltrate porous parts. Castable epoxy + a small vacuum chamber pulls resin into voids. Essential for castings, sintered powder, thermal-spray coatings, and concrete.
Frequently asked questions
How does mold size affect material usage?
Mounting material scales with cavity volume; volume goes as the diameter squared. A 2″ mold uses ~4× the resin of a 1″ mold for the same cavity height. The calculator handles this directly; pick the smallest mold that comfortably accommodates the specimen.
Why two different safety margins (10% vs 15%)?
Compression resins lose a few percent to pellet-to-pellet packing and minor flash; 10% covers it. Castable resins additionally shrink several percent during cure (especially polyester) and lose volume in mixing cups and meniscus, so 15% is more realistic.
I left the sample dimensions blank. What does the calculator assume?
It assumes the specimen displaces ≈5% of mold volume, which is conservative for most metallography samples (typical specimens occupy 2–10%). Entering actual dimensions gives a tighter estimate and avoids over-ordering resin for batch work.
Which resin gives the best edge retention?
Glass-filled diallyl phthalate (compression) and certain mineral-filled epoxies (castable) hold the specimen edge sharpest during polishing. That's critical for coating thickness measurements, case-depth work, and any plated layer. Standard phenolic and acrylic round off slightly under aggressive polishing pressure.
Do I need conductive resin for SEM?
Yes. For EDS/EBSD or any high-resolution SEM imaging, the mount needs to be conductive to prevent charging. Conductive phenolic (copper- or graphite-filled) is the simplest path; alternatives are carbon coating or silver-paint bridges from specimen to stub.
Can I re-use the same mold for compression and castable?
Compression molds are steel cavities designed for the press; castable cups are disposable silicone or plastic. They are not interchangeable. If your shop runs both methods, keep separate inventories.
Need more help?
Browse our mounting consumables, presses, and castable systems, or talk to a metallographer about a specific specimen.
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