Hot box core shooters for lighting-fixture castings typically deliver 3–25 kg per shot with 6–14 kW installed heating power, matching the small-to-medium core sizes used in lamp housings, brackets, and decorative iron fixtures [S3][S5].
The hot-box process blows resin-coated sand into a heated core box at 200–260 °C, then cures the binder thermally in 25–60 s; for lighting-fixture cores weighing 0.5–5 kg, the dwell window is closer to 25–35 s on a 6–8 kW heater, which is why Selva Lakshmi's SLI 3C hot-box variant ships with a 6–8 kW heater pack and a 3 kg rated shot [S3][S5].
Core-Box Temperature and Cure Window
The controlled hot-box cure window sits at 200–260 °C, held by zoned electric cartridge heaters or gas burners, with cure times of 25–60 s per shot [S5][S10]. Thinner-wall lighting cores (under 15 mm wall) reach full cure near 25 s, while bracket and base cores with 20–30 mm walls need 40–60 s to drive the exothermic reaction to the core centre, per the 2026 buying-guide spec gates [S5]. Selva Lakshmi publishes a 50 s cycle time across all four hot-box models, indicating a conservative dwell chosen to handle their maximum 25 kg shot class [S3].
Spec Comparison: Hot-Box vs Cold-Box vs Shell
Three core-making process families compete for the same lighting-fixture foundry budget, and the decision turns on energy input, cycle time, binder emissions, and tooling cost [S5].
Energy input per cycle is highest for hot-box because the 200–260 °C box must be maintained continuously; cold-box runs near ambient with energy spent on amine vaporisation and scrubber fans; shell core shooters use 220–300 °C investment-cure ovens over a smaller heated area [S5]. Cycle time favours cold-box at 10–20 s versus hot-box 25–60 s and shell at 90–180 s, but hot-box tooling (cast iron or aluminium with embedded heaters) sits in the mid-cost band, above cold-box wood or plastic boxes but below the fine-pattern tooling premium of shell core boxes [S5]. For lighting fixtures where pattern detail is moderate and run rates are measured in hundreds of cores per shift, hot-box typically wins on the balance of cycle time, surface finish, and tooling amortisation [S5].
Selection Criteria: Shot Weight, Heating Power, Sand Tank, Clamping
Four hard spec gates determine machine class for a 2026 hot-box buy: shot weight in kg per cycle, heating power in kW, sand tank capacity in litres, and clamping force in kN [S5]. Selva Lakshmi's vertical-parting hot-box line covers 3, 5, 10, and 25 kg shot classes, with core-box sizes from 300x150x250 mm up to 650x400x500 mm and hydraulic clamping throughout [S3]. Lighting-fixture cores for lamp housings, downlight bodies, and decorative castings generally fall in the 3–5 kg shot class, putting the SLI 3C (1.5x1.5x1.5 m footprint, 2.5 t machine weight, 40 CFM air per core) at the right size for jobbing foundries [S3].
Heater sizing scales with the shot class: 6–8 kW on the 3 kg unit, 8–10 kW on the 5 kg, 10–12 kW on the 10 kg, and 12–14 kW on the 25 kg [S3]. Buyers running two-shift operations on a 5 kg class should compare this 8–10 kW draw against the 1–2 kW heater on the equivalent cold-box SLI 5C, since the cold-box machine trades thermal energy for amine-gas handling infrastructure [S3]. Air consumption runs 40–60 CFM per core across the hot-box line, roughly 10 CFM higher than the cold-box equivalent because of the faster shoot-and-pack cycle [S3].
Resin Binder and Emissions
Hot-box uses furan or phenolic resin cured at 200–260 °C, which generates formaldehyde and phenol fumes that demand local exhaust ventilation at the core box and shot station [S5]. The cold box core shooter vs resin sand molding line uses phenolic-urethane (PUCB) cured with amine gas at room temperature, which pushes amine and VOC load to a scrubber system rather than a thermal oxidiser, but the binder itself is more expensive per kilogram of sand [S5]. For lighting-fixture foundries running indoor cells, the amine-cured cold-box line typically requires a larger ventilation capex line, while the hot-box line carries a smaller scrubber but a steady thermal-energy bill [S5].
Tooling and Pattern Cost
Hot-box core boxes are typically cast iron or aluminium with embedded electric cartridge heaters, which puts tooling cost in the moderate band, higher than the wood or plastic boxes used in cold-box but lower than the fine-pattern investment tooling on a shell core shooter [S5]. For lighting-fixture patterns with moderate detail, lettering, and small draft features, hot-box aluminium boxes deliver acceptable surface and reasonable pattern life, generally several thousand shots before heater or vent maintenance [S5][S10]. The 2026 buying guide flags that buyers should treat the heater element as a consumable, with replacement intervals of 1,000–3,000 shots depending on duty cycle and box temperature setpoint [S5].
Clamping and Cycle Mechanics
Hydraulic clamping is standard across the hot-box models, with horizontal clamping strokes of 300–600 mm single-side and a 50 mm vertical stroke fixed across all four sizes [S3]. Cycle time, excluding gassing, shoot, and exhaust, starts at 25 s on the single-station flagship, while the published per-core cycle is 50 s with curing included [S3]. For a lighting-fixture cell running the SLI 3C at a 50 s cycle, the theoretical output is 72 cores per hour per machine, with practical throughput around 50–60 cores per hour once sand feeding and box cleaning are factored in [S3]. A dual-machine cell with auto sand feeding covers most lighting-fixture jobbing demand under 10,000 cores per week.
Standards, Sourcing, and Spec Discipline
There is no single IEC or ISO standard that fixes hot-box cure temperature; buyers should specify 200–260 °C box temperature, 25–60 s cure, and 5–50 kg shot class on the enquiry, then cross-check the manufacturer's electrical detail table against the foundry's 3-phase 415 V, 50 Hz supply [S3][S5]. Mainland China manufacturers, including Quanzhou Sanjia Machinery, list hot-box units alongside automatic double-head core shooting units on their Made-in-China showrooms, giving 2026 buyers a wider sourcing pool than the India-dominant Selva Lakshmi range [S1][S5]. For an overview of the broader hot-box machine category, the hot box core machine reference covers zoned heating, sand tank sizing, and the 180–250 °C controlled-window operating range that buyers should compare against the actual process spec sheet [S10].
Cross-process buyers evaluating a switch to room-temperature cure should weigh the cold box core machine cycle-time advantage against the amine scrubber capex, since cold-box drops to 10–20 s per shot but pushes ventilation and binder cost upward [S5]. For higher-volume lighting-fixture lines, an auto core shooter or double-head configuration from the broader core machine family can double the per-hour output without doubling the floor space [S1].
See also our earlier report, Concrete mixer truck selection for agriculture: 2026 spec map.