Trushape is a shell molding foundry in India casting parts from 5 to 60 kg (11 to 132 lb) in carbon, low-alloy and stainless steels, held to ISO 8062-3 DCTG 8 to 12 and heat-treated, machined and tested under one roof for buyers across North America and Europe.
Shell molding, also called the Croning process, shell mould casting or resin coated sand casting (Maskenformguss in German), is a casting process in which fine sand coated with a phenolic resin is cured on a heated metal pattern into a thin, rigid shell. Two shells are joined to form the mould and molten metal is poured into it. The result is a casting with a smoother surface, tighter tolerances and better repeatability than green sand casting, at production volumes.
Trushape Precision Castings is an ISO 9001, ISO 14001, ISO 45001 and ISO 13485 certified shell molding foundry in Bhavnagar, Gujarat, India. We cast parts from 5 to 60 kg (11 to 132 lb) in carbon, low-alloy, case hardening, stainless, duplex and tool steels, hold ISO 8062-3 DCTG 8 to 12, and heat-treat, CNC machine and test them under one roof for buyers across the United States, Canada, Mexico, the United Kingdom and the European Union.
Follow one valve body from heated pattern to finished part. Every stage happens under one roof in Bhavnagar, with records that trace each casting back to its heat.
A two-piece metal pattern, made to the part's shape plus the shrinkage allowance, is heated to 175 to 370°C (350 to 700°F) and sprayed with a release agent so the shell will not stick to it.
The hot pattern is clamped to a dump box of resin coated sand and inverted, so the sand falls onto it. Heat softens the resin next to the metal and bonds the grains into a shell that grows thicker the longer it rests.
Loose sand falls away, leaving a shell 10 to 20 mm (0.4 to 0.8 in) thick on the pattern. Pattern and shell then go into an oven at 300 to 400°C (570 to 750°F) to fully harden the phenolic resin.
Ejector pins push the cured shell half off the pattern. It is a rigid, exact negative of one side of the part, and the pattern goes straight back to make the next shell.
Cores for bores and internal passages are set in the drag half. The cope half is laid on top, and the two are glued or clamped along the parting line to form the complete cavity and gating.
The closed mould is set in a flask and backed with steel shot or sand. Metal melted in our induction furnaces at 1,400 to 1,700°C (2,550 to 3,090°F), depending on the alloy, fills the cavity. Each heat is checked by spectrometer.
As the casting cools, the heat burns off the resin binder, so the thin shell breaks away easily, with far less sand to clean off than a green sand mould. The cores crumble out of the bores.
Gates and runners are cut off and ground, then castings are shot blasted, heat-treated, CNC machined and inspected to your drawing, all in-house, so parts leave ready to assemble.
A shell mould is only a few parts: two resin sand shells, the cores that form the bores and the gating that feeds the metal. Scroll or use Explode view to take this one apart, and drag to turn it.
The upper shell half, cured on the cope pattern. It carries the pouring cup, the sprue and the top of the cavity.
The lower half, holding the rest of the cavity. Cores sit in it before the mould is closed.
Resin sand cores form the bore and the bonnet opening of the valve body, and crumble out at shake-out.
The channel the metal flows through. It is cut off after shake-out and the steel is remelted.
The valve body itself, near net shape and ready for heat treatment and machining.
Shell molding typically holds ISO 8062-3 grades DCTG 8 to 12, against DCTG 11 to 14 for our no-bake sand and lost foam lines. Slide to your nominal dimension and pick a grade to see the total tolerance it allows as-cast.
| Nominal size (mm) | Nominal size (in) | DCTG 8 | DCTG 9 | DCTG 10 | DCTG 11 | DCTG 12 |
|---|---|---|---|---|---|---|
| Up to 10 | Up to 0.39 | 1.0 | 1.5 | 2.0 | 2.8 | 4.2 |
| 10 to 16 | 0.39 to 0.63 | 1.1 | 1.6 | 2.2 | 3.0 | 4.4 |
| 16 to 25 | 0.63 to 0.98 | 1.2 | 1.7 | 2.4 | 3.2 | 4.6 |
| 25 to 40 | 0.98 to 1.57 | 1.3 | 1.8 | 2.6 | 3.6 | 5.0 |
| 40 to 63 | 1.57 to 2.48 | 1.4 | 2.0 | 2.8 | 4.0 | 5.6 |
| 63 to 100 | 2.48 to 3.94 | 1.6 | 2.2 | 3.2 | 4.4 | 6.0 |
| 100 to 160 | 3.94 to 6.30 | 1.8 | 2.5 | 3.6 | 5.0 | 7.0 |
| 160 to 250 | 6.30 to 9.84 | 2.0 | 2.8 | 4.0 | 5.6 | 8.0 |
| 250 to 400 | 9.84 to 15.75 | 2.2 | 3.2 | 4.4 | 6.2 | 9.0 |
| 400 to 630 | 15.75 to 24.80 | 2.6 | 3.6 | 5.0 | 7.0 | 10.0 |
Total casting tolerance in millimetres to ISO 8062-3. When the tolerance is symmetric, half of it applies either side of the nominal dimension, so DCTG 10 at 40 to 63 mm means ±1.4 mm. The grade for each part is agreed at drawing review, and tighter tolerances on critical features are reached by CNC machining.
Full ISO 8062-3 and VDG P690 tolerance tablesEvery route has a sweet spot. Pick a process to raise its profile in 3D and drag to turn the chart. The scores are relative and indicative; the right choice always depends on size, volume, alloy and tolerance.
A thin, rigid resin sand shell made on a heated metal pattern gives smoother, more accurate and more repeatable castings than green sand, with fast cycles that suit medium to high volumes.
Moulds of sand bonded with clay and water are cheap and quick to make and suit very large castings, but surfaces are rougher, tolerances looser and more machining follows. It is a common alternative we compare against, not a line we run.
Chemically bonded sand sets at room temperature around a pattern, so tooling is simple and cheap. It suits bigger, lower-volume castings, with looser tolerances than shell molding. We run no-bake sand from 3 to 40 kg.
A new ceramic mould around an expendable wax pattern gives the most design freedom of any casting process: thin walls, undercuts and fine detail, near net shape, in almost any alloy.
Metal is poured into a reusable steel die, which gives accurate, repeatable parts quickly, but die costs are higher and the process suits aluminium, zinc and copper alloys rather than steel. We run it from 0.1 to 3 kg.
| Criterion | Shell molding | Green sand | No-bake sand | Investment casting | Gravity die casting |
|---|---|---|---|---|---|
| Typical tolerance | ISO 8062-3 DCTG 8 to 12 | Looser than shell molding | DCTG 11 to 14 | CT5 to CT7 | DCTG 7 to 9 |
| Surface finish | Smooth, around Ra 6.3 to 12.5 µm on steel | Commonly Ra 12.5 µm or rougher | Moderate | Ra 3.2 to 6.3 µm | Smooth |
| Weight at Trushape | 5 to 60 kg | Not offered | 3 to 40 kg | 0.003 to 30 kg | 0.1 to 3 kg |
| Alloys | Carbon, low-alloy, stainless and tool steels | Most ferrous and non-ferrous | Most ferrous and non-ferrous | Almost any | Aluminium, zinc, copper |
| Tooling | Metal patterns, moderate cost | Low | Low | Moderate; none with 3D-printed patterns | High, steel dies |
| Best volumes | Medium to high | Low to very high | Low to medium | Prototypes to high volume | High |
Pick what your part needs most. The deck turns to the steel we would start with, with ASTM, EN and UNS equivalents, relative ratings and the parts it usually goes into.
Need: Economical strength
Typical parts: brackets, flanges, hubs and general engineering parts.
Economical and easy to machine, with good strength after normalising.
Need: High strength
Typical parts: levers, couplings, hydraulic and drive parts.
Through-hardening strength, quenched and tempered in-house to your specification.
Need: Toughness under load
Typical parts: heavy-duty levers, crank and drive parts, off-highway parts.
High strength with toughness in heavier sections, for parts that take shock loads.
Need: Hard wearing surface
Typical parts: gear blanks, cams, pins and wear parts.
A carburised, hard-wearing surface over a tough core after case hardening.
Need: General corrosion
Typical parts: pump casings, valve bodies, food and chemical parts.
The default choice for corrosion resistance and toughness.
Need: Hardness and corrosion
Typical parts: valve trim, pump wear parts and cutting parts.
Hardenable stainless for wear, with moderate corrosion resistance.
Need: Cavitation and erosion
Typical parts: pump casings, impellers, diffusers and turbine parts.
Tough and cavitation resistant, the classic grade for hydraulic machinery.
Need: Chlorides and seawater
Typical parts: seawater pump and valve parts, marine and chemical fittings.
Resists chloride pitting and stress corrosion, with about twice the yield strength of 316L.
Need: Strength and corrosion
Typical parts: levers, brackets, valve and pump parts under load.
Strength close to low-alloy steel with stainless corrosion resistance, set by age hardening in-house.
Need: Tooling and abrasion
Typical parts: forming tools, wear plates and abrasion parts.
High-carbon, high-chromium tool steel for extreme wear resistance after hardening.
A starting point for engineers comparing cast grades across North American and European specifications. Final selection always follows your drawing, service conditions and governing standard.
| Steel family | Common grades | Equivalents | Why it is chosen | Typical parts |
|---|---|---|---|---|
| Carbon steel | EN8, C45 | AISI 1040, 1045; 1.0503 | Economical strength, easy machining | Brackets, flanges, hubs, general engineering parts |
| Chromium-molybdenum steel | 4140, 42CrMo4, EN19 | 1.7225, UNS G41400 | Through-hardening strength after quench and temper | Levers, couplings, hydraulic and drive parts |
| Nickel-chromium-molybdenum steel | 4340, EN24, 34CrNiMo6 | 1.6582, 817M40 | Strength with toughness in heavy sections | Crank and drive parts, off-highway parts |
| Case hardening steel | 8620, 16MnCr5, 20MnCr5 | 1.7131, 1.7147 | Hard-wearing surface over a tough core | Gear blanks, cams, pins, wear parts |
| Austenitic stainless | 304, 316, 316L (CF8, CF8M, CF3M) | 1.4308, 1.4408, 1.4409 | Corrosion resistance and toughness | Pump casings, valve bodies, food and chemical parts |
| Martensitic stainless | 410, 420 (CA15, CA40), CA6NM | 1.4011, 1.4027, 1.4317 | Hardness, wear and cavitation resistance | Valve trim, pump parts, impellers, diffusers |
| Duplex stainless | F51, CD3MN | 1.4470, UNS J92205 | Chloride resistance with high strength | Seawater pump and valve parts |
| Precipitation-hardening stainless | 17-4PH (CB7Cu-1) | 1.4525, UNS J92180 | High strength after age hardening | Levers, brackets, loaded valve and pump parts |
| Tool steel | D2 | 1.2379, UNS T30402 | Extreme wear resistance after hardening | Forming tools, wear plates, abrasion parts |
Equivalents are the closest common matches, shown for comparison. We cast to the ASTM, EN, ISO or customer specification on your drawing and verify the chemistry of every heat by spectrometer.
See all 50+ alloy gradesIn 1943, Johannes Croning found that sand and resin on a hot pattern make a mould as thin as a shell and as true as the pattern. We still cast the same way. Only now the shells hold DCTG 8 to 12, the parts weigh up to 60 kg, and the steel is any of more than fifty grades.
Move the lens across the two surfaces. Fine resin coated sand, bonded into a rigid shell, gives shell castings a smoother, more even skin than green sand, which prints its coarser grains into the metal, so less grinding and machining follow.
Fine sand bonded by resin holds the pattern's shape and leaves a tight, even skin on the metal.
Every heat checked on Spectromaxx and Bruker spectrometers against your grade.
Mechanical properties tested to your material specification.
Internal soundness of critical sections, to the acceptance level you specify.
Internal flaws and wall thickness in heavier sections.
Surface and near-surface flaws on carbon and low-alloy steels.
Surface-breaking cracks and porosity on stainless and other non-magnetic grades.
Dimensional reports on profiles, bores and datums against your drawing.
Leak and pressure checks on valve bodies and pump casings where your plan requires them.
One record from melt to dispatch, ready for your incoming inspection and your customers' audits. Material certificates are issued to EN 10204 3.1 as standard, and to 3.2 when your order calls for independent inspection.
Good castings start on the drawing board. These are the guidelines our engineers use when they review a new shell molding part. Hover or tap a card to turn it over.
Draft. Shells are lifted off a metal pattern, so walls square to the parting line need a small draft angle. We set the value per feature at design review.
Parting line. Keep the parting line on one flat plane where you can. It simplifies the pattern, the two shell halves and the finishing of the casting.
Walls. Uniform walls fill and solidify evenly. Blend thick to thin gradually so heavy sections can feed without shrinkage.
Corners. Generous fillets help metal flow, remove hot spots and lower stress. Sharp internal corners concentrate stress and invite cracks.
Cores. Bores, ports and internal passages are formed by resin sand cores set in the mould. Give each core firm prints so it stays put while the metal flows.
Tolerances. Shell molding holds ISO 8062-3 DCTG 8 to 12. Mark functional features and datums, and we machine the few that need more.
Machining. Add allowance only on faces, bores and threads that must be machined. Everything else can stay as-cast.
Volume. Metal patterns pay back over longer runs. For prototypes or low volumes we may suggest investment casting with 3D-printed patterns or no-bake sand instead.
We work to the steel casting, tolerance and inspection standards common on North American and European drawings, and to your own specification and inspection plan.
Trushape holds ISO 9001, ISO 14001, ISO 45001 and ISO 13485. We do not hold IATF 16949, PED or ASME approvals, so automotive, pressure-equipment and code parts are cast to your drawing, specification and inspection plan, and product approvals stay with you. We support them with samples, test data and full records.
Download our certificatesAn export-focused foundry with a dedicated export desk, already shipping castings to Germany, the UK, Belgium, Denmark, Spain and Italy. Pick a region to trace the lane from Bhavnagar.
Vehicle, off-highway, pump, valve and hydraulics makers across Michigan, Illinois, Ohio and Wisconsin.
Vehicle, rail, mining and machinery builders around Toronto, Windsor and Montreal.
Nearshore automotive and industrial assemblers in Nuevo León, Coahuila, Querétaro and Guanajuato that need certified castings on schedule.
Engineering, pump and off-highway equipment makers across the Midlands and the North.
Automotive and machinery suppliers in Baden-Württemberg, and heavy engineering around Dortmund.
Valve, pump and machinery makers in France, Belgium and the Netherlands.
Automotive and machinery suppliers in Lombardy, and vehicle and equipment makers in Sweden.
Series parts travel by sea freight in export packing, and urgent samples by air. Delivery terms and documentation are agreed with our export desk for each order, and every shipment carries English certificates and reports.
Drag the ring or let it turn. Each part family lists the steels we typically use, for castings from 5 to 60 kg (11 to 132 lb).
AlloysCF8M, 316, carbon steel
IndustryFlow control
Seats, bores and flanges machined in-house.
AlloysCF8M, CA6NM, carbon steel
IndustryPumps and water
Smooth hydraulic passages, pressure tested on request.
AlloysEN8, 42CrMo4
IndustryMachinery and vehicles
Bearing bores and faces machined to drawing.
Alloys4140, 4340
IndustryEngines and compressors
Quenched and tempered in-house for strength.
Alloys8620, 16MnCr5
IndustryPower transmission
Case hardened for a wear-resistant surface.
AlloysEN8, C45
IndustryMachinery
Repeatable geometry for series machining.
Alloys4140, 8620
IndustryHydraulics
Cored passages and sound, pressure-tight walls.
AlloysEN8, 42CrMo4, 17-4PH
IndustryGeneral engineering
Strong parts cast close to final shape.
AlloysEN8, 42CrMo4
IndustryAgriculture
Tough parts for hard-working equipment.
Alloys4340, 42CrMo4
IndustryRail and off-highway
Shock-loaded parts with full test records.
AlloysD2, 420 stainless
IndustryMining and processing
Hardened for abrasion and wear.
AlloysDuplex F51, CF8M
IndustryMarine
Pump and valve parts for chlorides and seawater.
Buyers in North America and Europe move shell molding work to us for the same six reasons.
Pattern, shell, melt, heat treatment, CNC machining, finishing and testing in one 100,000 sq ft facility, which cuts lead times by 30 to 40%.
IntegratedShell molding, investment casting, lost foam, no-bake sand and gravity die casting under one roof, so every part gets the route that suits its size and volume.
6 processesCarbon, low-alloy, case hardening, stainless, duplex and tool steels, melted in induction furnaces and verified by spectrometer every heat.
50+ gradesISO 8062-3 DCTG 8 to 12 as-cast, critical features machined, and every critical dimension verified on a Zeiss CMM.
DCTG 8 to 12ISO 9001, 14001, 45001 and 13485 systems, in-house NDT and an EN 10204 3.1 certificate with every batch.
Audit readyA dedicated export desk, English documentation and export packing for sea or air freight, plus a proven China-plus-one option.
NA and EuropeFrom a wartime discovery in Hamburg to a global standard for accurate castings at volume.
In Hamburg, Johannes Croning found that fine sand and phenolic resin on a heated pattern formed a thin, rigid shell that could serve as a precision mould.
Croning patented the process, known as the C-Verfahren. After the war it was declassified and spread to foundries worldwide as the Croning process.
Foundries adopted shell molding to mass-produce cylinder heads, crankshafts and gearbox housings that demanded repeatability at volume.
Automated shell machines raised throughput, and ISO 8062 gave engineers a common way to specify casting tolerances.
Computer-controlled machines and advanced resins meet in-line inspection. Trushape shell molds steel parts from 5 to 60 kg for customers worldwide.
Shell molding, also called the Croning process or resin coated sand casting, is a casting process in which fine sand coated with phenolic resin is cured on a heated metal pattern into a thin, rigid shell. Two shells are joined to form the mould and filled with molten metal. Trushape casts parts from 5 to 60 kg (11 to 132 lb) this way in carbon, low-alloy and stainless steels.
A metal pattern is heated to 175 to 370°C (350 to 700°F) and covered with resin coated sand, which bonds into a shell 10 to 20 mm (0.4 to 0.8 in) thick. The shell is cured in an oven at 300 to 400°C (570 to 750°F), ejected and joined to its matching half with any cores. The mould is backed with steel shot or sand and poured, and the shell breaks away as the resin burns off.
Shell molding typically holds ISO 8062-3 grades DCTG 8 to 12, depending on size, geometry and alloy. For a 40 to 63 mm (1.6 to 2.5 in) dimension that is a total tolerance of 1.4 to 5.6 mm, or ±0.7 to ±2.8 mm, tighter and more repeatable than green sand casting. Critical features are held tighter by CNC machining.
Our shell molding line casts parts from 5 to 60 kg (11 to 132 lb). Smaller, more intricate parts from 0.003 kg move to investment casting, and heavier parts up to 90 kg (198 lb) to lost foam casting, so one supplier covers the whole range.
Shell molding suits carbon steels such as EN8 and C45, low-alloy steels such as 4140, 4340, 8620, 42CrMo4 and EN24, case hardening steels such as 16MnCr5 and 20MnCr5, stainless steels such as 304, 316, CF8M, 410 and 420, duplex, martensitic and precipitation-hardening grades such as F51, CA6NM and 17-4PH, and tool steels such as D2.
Green sand moulds use sand bonded with clay and water, which is cheap and suits large, simple castings but gives rougher surfaces and looser tolerances. Shell molding cures fine resin coated sand on a heated metal pattern into a thin, rigid shell, so castings come out smoother, more accurate and more repeatable, with less machining.
Shell molding forms a resin sand mould on a reusable metal pattern and suits accurate parts from 5 to 60 kg (11 to 132 lb) at medium to high volumes. Investment casting builds a ceramic shell around an expendable wax pattern and suits smaller, more intricate parts from 0.003 to 30 kg (0.1 oz to 66 lb) held to CT5 to CT7. We run both and recommend the better route for your part.
Fine resin coated sand gives shell castings a smooth, even skin, typically around Ra 6.3 to 12.5 µm (250 to 500 µin) as-cast on steel, against Ra 12.5 µm (500 µin) or rougher for green sand. Many non-critical faces can stay as-cast, and shot blasting or machining finishes the rest.
Metal patterns cost more than the wood or plastic patterns used for green sand, but they last for long runs, cycles are fast and repeatable, and smoother, more accurate castings need less machining. That usually makes shell molding the economical choice for medium to high volumes of accurate parts.
Yes. Heat treatment, CNC machining on 8 machines, shot blasting and inspection all happen in-house. Every heat is checked by spectrometer, dimensions are verified on a Zeiss CMM, and radiographic, ultrasonic, dye penetrant and magnetic particle testing are available, with EN 10204 3.1 certificates as standard and 3.2 on request.
Yes. Trushape exports castings to Germany, the UK, Belgium, Denmark, Spain and Italy and serves buyers across North America and Europe, including the United States, Canada and Mexico. Parts ship by sea or air freight with English documentation, and delivery terms are agreed per order.
German engineer Johannes Croning invented shell molding in Hamburg in 1943, which is why it is still called the Croning process. In German it is Maskenformguss or the Croning-Verfahren, in French moulage en carapace and in Swedish skalformsgjutning, and it remains one of the key foundry innovations of the 20th century.
More than eighty years after Johannes Croning's hot pattern, shell molding is still one of the surest ways to cast accurate steel parts at volume. Trushape casts, heat-treats, machines and verifies them under one roof for manufacturers across North America and Europe.