Lighting-fixture die selection in 2026 is a two-axis problem, alloy family and projected area, with steel grade, hardness, and shot count resolving tie-breakers; the dominant pairings are ADC12/A380 aluminum in cold-chamber LKM C50 + P20 dies fitted with H13 or Dievar inserts hardened above HRC45, paired with shot weights of 1-8 kg per cycle in the 160-630 t clamping band [S1][S3].
Zinc and brass trim, including pendant bodies, ceiling-rose covers, conduit hubs, and switch housings, runs on hot-chamber machines between 50 t and 400 t clamping force, with Zamak 3 (ASTM B240, UNS Z33521) as the default alloy and shot weights between 0.1 kg and 4 kg per cycle [S2]. For comparison, the same die-casting die architecture used for premium aluminum heat sinks carries 50,000-120,000 shots on H13 inserts before refurbishment, while a 160-200 t cold-chamber cell covers 1-3 kg of aluminum and lands a typical 300×300 mm high-bay housing in the 200-300 t tonnage band [S1][S3].
Alloy-to-Die Pairing: ADC12, A380, A360, and AlSi9Cu3
ADC12 and A380 aluminum are the workhorse alloys for die-cast LED housings, with thermal conductivity of 96-100 W/m·K, density near 2.7 g/cm³, and die-cast flow behavior that fills 1.5-3.0 mm wall sections and fins as thin as 1.2 mm at aspect ratios up to 8:1 with proper draft [S1][S4]. AlSi9Cu3, the European near-equivalent of ADC12, is specified for outdoor IP-rated luminaires where anodizing and powder-coat adhesion are critical, while A360 sits between them for thinner-wall heat-sink housings because its lower iron content improves ductility [S1]. A side-by-side conductivity comparison from a Wuxi LED-housing producer lists AlSi12Fe at roughly 120 W/m·K, AlSi9Cu3 near 110 W/m·K, A380 at 100 W/m·K, and ADC12 at 96 W/m·K, with castability and corrosion resistance traded against each other per alloy [S4].
Steel Stack-Up: LKM C50 + P20 Base, H13 / Dievar / 8407 Inserts
Standard die-casting tooling for LED panel, downlight, track-light, and street-light enclosures pairs an LKM C50 + P20 mold base with cavity inserts in H13 (the most common choice, 50,000-120,000 shot life on lighting tooling), Dievar for higher thermal-fatigue loading, or 8407 / 1.2344 for hot-work endurance at hardness above HRC45 [S1]. H13 chemistry per GB/T 1299-2000 runs 0.32-0.45% C, 4.75-5.50% Cr, and 1.10-1.75% Mo, with a working hardness of 205-245 HB on one verified lighting-housing tool [S1]. T1 sample lead times run 3-10 weeks and production runs ship in 2-5 weeks for the same die architecture, a window that fits most 2026 fixture launch calendars [S1].
Process Boundary: When Die Cast Wins, When Resin Sand Wins
Aluminum die casting is specified when wall thickness sits in the 2.5-4 mm band, annual volume per part exceeds roughly 5,000-10,000 pieces, and the housing must double as a heat sink for the LED engine [S1]. Resin-bonded sand molding on flasks from 600×500 mm up to 1,200×1,000 mm with 30-60 s cycles fits the other half of the program: pole bases, decorative brackets, and large reflector bodies exceeding 500 mm in any dimension, where surface class is allowed to be Ra 12.5 or coarser and pattern variety per SKU is high with annual volumes per pattern in the 500-5,000-piece band [S1]. The boundary case is the high-bay and street-light housing, where one OEM may run a 1,200×1,000 mm flask on a resin sand line for the pole-base casting while sourcing the same fixture's heat-sink housing from a die-casting die, a useful reminder that the die-casting die decision is per-SKU, not per-program. The same boundary logic drives buyers to a gravity die casting machine for indoor decorative parts where cosmetic finish matters more than thermal performance, because gravity cells can hit surface finish on a different curve than vacuum HPDC [S5].
Tonnage Sizing by Projected Area and Shot Weight
Tonnage scaling follows projected area: a 300×300 mm high-bay heat-sink housing lands in the 200-300 t cold-chamber range, while a 600×600 mm roadway luminaire body climbs to 400-500 t [S3]. Vacuum die casting widens the band, with 200-400 t units handling under 3 kg shot for MR16 and GU10 form factors, 400-800 t presses handling 1-6 kg of aluminum for mid-size ceiling and track-light housings, and 800-1600 t cells covering 6-12 kg shot for streetlight and high-bay fixtures [S5]. For zinc trim, tier-1 buyers run 0.3-1.5 kg Zamak 3 pendant bodies on 88-160 t hot-chamber cells with 2-cavity dies and 35-45 s cycles, while thicker structural components such as downlight canisters and track-light adaptor bodies step up to 250-400 t machines with 3-cavity dies at a 2026 cost-per-shot of 0.08-0.15 USD [S2].
Vacuum, Porosity, and IP-Rated Housings
Vacuum die casting machines running chamber pressures of 5-50 mbar suppress gas porosity in thin-wall sections below 3 mm, with dry-cycle times under 12 seconds once the die is heated and vacuum is established [S5]. Air entrapment in conventional HPDC produces internal porosity above 2% by volume, which causes thermal-resistance spikes in LED heat-sink fins and visual defects in polished reflector bowls; pulling chamber vacuum below 50 mbar before injection reduces dissolved-gas content and lets the alloy fill 1.5-2.5 mm webs and fins taller than 80 mm while keeping surface Ra under 3.2 µm [S5]. A 50-200 m³/h two-stage rotary-vane or dry-pump set sized to the press holds 5-30 mbar through the slow-shot phase, and water-based die lubricants with low silicone content are specified to keep post-casting surfaces clean for downstream vacuum metalizing of reflector bowls at 80-120 nm aluminum coating thickness [S5]. For programs targeting IP65 or IP66 ingress ratings, the practical acceptance window for plated lighting hardware is no surface pore larger than 0.3 mm and no cluster of more than 2 pores within any 25 mm × 25 mm patch, a spec gate that pushes most premium programs to vacuum-assisted HPDC [S2][S5].
Alloy-and-Process Map for Common Lighting Part Families
Pendant bodies, ceiling-rose covers, and switch housings almost always spec Zamak 3 because the alloy casts cleanly at 0.8 mm wall and accepts bright chrome or PVD brass plating without blistering [S2]. Heat-sink-adjacent bezels that sit within 10 mm of an LED junction run Zamak 5 (UNS Z35531) for its roughly 10% higher yield strength at 95-120 °C, which prevents creep-induced sag over a 50,000-hour service life, while decorative finials and chain links use Zamak 7 (UNS Z33522) where the slightly higher copper delivers a smoother as-cast surface that skips a grinding pass before polishing [S2]. Aluminum die castings cover the higher-power end: high-bay and street-light bodies in ADC12/A380 land in the 160-630 t cold-chamber band, magnesium-alloy housings for portable or vehicle-mounted fixtures cut weight by roughly one-third versus aluminum at comparable stiffness but require SF6/cover-gas melt protection that only justifies itself in weight-critical programs [S3]. Across the three zinc alloys, die temperature is held at 150-200 °C and the shot sleeve is preheated to 180-220 °C; straying outside that band is the dominant cause of cold-shut defects in thin-wall lighting castings [S2].
Where Die Cast Is the Wrong Tool
Aluminum die casting loses to resin sand molding when the lighting casting exceeds 500 mm in any dimension, when surface class is allowed to be Ra 12.5 or coarser, and when pattern variety per SKU is high with annual volumes per pattern in the 500-5,000-piece band [S1]. The same HPDC line loses to LPDC on parts that benefit from 0.3-1.5 bar fill pressure into a heated steel die held at 110-120 °C, where molten aluminum near 950 °C is lifted through a graphite-coated riser tube and lighting components such as heat-sink housings, street-light pole bases, down-light bodies, and chandelier arms fit under 0.75 kg per shot [S7]. A separate aerospace-grade die program, mapped in aerospace die casting die selection: alloy, shot life, gating, and CT-grade gates, uses the same H13/Dievar insert family but tightens CT-grade inspection gates that most lighting programs do not need, a useful contrast when a lighting OEM is tempted to over-spec a CT-X-ray requirement that belongs on aerospace structural castings, not on commodity LED heat sinks.
Decision Criteria, Compared
The four most common 2026 lighting die-casting die pairings line up on three selection criteria: projected-area tonnage, alloy thermal conductivity, and minimum wall/fin geometry, and the table below consolidates the numbers cited in the source set so a fixture engineer can map a part to a die in one pass. [S1]
Aluminum cold-chamber HPDC (ADC12/A380) handles 1-8 kg shots in the 160-630 t band, delivers 90-110 W/m·K thermal conductivity, and fills walls down to 1.5 mm with fins at 8:1 aspect ratio, the dominant choice for LED heat sinks and street-light bodies [S3][S4]. Vacuum-assisted HPDC widens the band to 200-1600 t and 0.5-12 kg shot, cuts porosity under 0.5% (versus above 2% in conventional HPDC), and is the right pick for IP65/IP66 housings and thin-wall reflectors below 3 mm [S5]. Hot-chamber zinc HPDC (Zamak 3/5/7) runs 0.1-4 kg shots in the 50-400 t band at 20-90 s cycles, casts cleanly at 0.8 mm wall, and wins on decorative trim, ceiling-rose covers, and switch housings where chrome or PVD plating is specified [S2]. LPDC on aluminum caps at 0.75 kg per shot under 0.3-1.5 bar fill pressure into a 110-120 °C die, fits street-light pole bases, chandelier arms, and down-light bodies, and is the lower-porosity alternative where the part geometry suits a riser-fed fill [S7].
Trackable signals for the next planning cycle: whether 2026 vacuum-cell retrofits on hot-chamber zinc machines become the default on export programs serving the Guzhen cluster, and whether LED high-bay tonnage demand continues to skew cold-chamber aluminum into the 200-500 t band that Long Hua, Tao Jin, and Warom all currently catalog [S2][S3]. A useful cross-reference for buyers sizing lighting enclosures alongside other facility equipment is skylight selection for prefab halls: base steel, glazing, and leak-test gates, which sits one tier up the building envelope and faces the same IP/leak-test gate logic that an IP65 LED housing must clear.
Detailed specification references: die casting, and die casting die.