A telecom enclosure that needs RF shielding, weather resistance and repeatable dimensional accuracy is most often produced on a zinc die casting machine sized to the largest single part plus a 25-30% pad, with Zamak 3 or Zamak 5 alloy and a hot-chamber or cold-chamber cell matched to shot weight.
For telecom-grade parts, the practical envelope sits between 80-160 ton clamping force, 0.5-2.5 kg shot weight, and 0.5-1.5 mm wall thickness, with surface finish held to 1.6-3.2 µm Ra for direct cosmetic surfaces [S2].
Why zinc, why telecom enclosures
Zamak alloys cast at 410-430 °C, roughly 120-150 °C below the 660 °C liquidus of aluminum, which means longer die life and tighter as-cast tolerances on small, thin-wall enclosures [S2]. Zinc's EMI shielding effectiveness at 30-1000 MHz typically falls in the 60-100 dB range for 1-3 mm wall sections, and that is the same band where 4G/5G base-station radios, small-cell housings and remote radio heads (RRH) live. Compared with an aluminum die casting machine running A380, a zinc cell can hold ±0.03 mm on critical datum features without a secondary trim press, which matters when an enclosure has to mate with a gasket groove and an RF gasket without rework.
For an indoor splitter or fiber distribution box under 300 g, a hot-chamber cell with a 1.0-2.0 kg shot pot is the standard pick. For an outdoor macro-cell radio housing between 1-3 kg with thicker ribs, the call shifts to a cold-chamber machine because the shot volume starts to exceed what a hot-chamber plunger can deliver cleanly without entraining oxide [S2].
Alloy choice: Zamak 3, Zamak 5, ZA-8, when each fits
Zamak 3 (Zn-4Al) is the default for telecom enclosures needing plating or chromate conversion: it has the lowest Fe pickup, the cleanest as-cast surface, and a tensile strength around 280 MPa. Zamak 5 (Zn-4Al-1Cu) adds about 10% more tensile and harder creep, which is why many outdoor pole-mount and roadside cabinets are specced in Zamak 5 to handle bracket loads and wind vibration [S2].
ZA-8 (Zn-8Al-1Cu) jumps to roughly 380 MPa tensile and keeps more ductility than Zamak 5, but its wider freezing range (about 380-410 °C) means more die soldering risk on long production runs, so it is reserved for structural bracket-style castings that do not need an A-class finish. For RF-tight covers that also get a decorative chrome or powder-coat finish, the engineering call is almost always Zamak 3 over ZA-8: less Cu means less intergranular corrosion under the coating, a documented failure mode in coastal telecom sites.
Clamping force, shot weight, platen size: the three sizing levers
Clamping force is set by projected area, not weight. A typical wall-mount telecom enclosure with a 200 × 250 mm projected area and a 1.2 mm wall needs roughly 0.6-0.8 MPa of specific pressure to keep flash under 0.15 mm, which lands the spec at 120-160 ton for a single-cavity die and 200-280 ton for a 2-cavity family die [S2].
Shot weight is sized to part weight plus 25-30% pad, never less. The pad is the safety margin that keeps the plunger pushing molten metal into the cavity until the gate freezes; a 1.0 kg part on a thin-wall die wants a 1.25-1.30 kg shot. On a hot-chamber machine, that means a shot pot of 1.5-2.0 kg, and on a cold-chamber machine a horizontal cold chamber with a 2.0-2.5 kg shot sleeve. A common miss is specifying a small cold-chamber machine on a part that should have run hot-chamber, and the symptom is oxide streaks in the casting plus plunger tip erosion after 20,000-30,000 shots.
Platen size is set by the die footprint plus tie-bar clearance. A standard 160 ton horizontal zinc machine typically ships with 560 × 560 mm tie-bar spacing, which fits a 450 × 450 mm die block, which in turn fits a single telecom cover up to about 350 × 350 mm before you have to step to the next platen class. For larger outdoor cabinets that exceed this, the spec moves to a vacuum die casting machine cell, where vacuum-assisted cavity evacuation removes the trapped air that causes porosity in thick rib intersections.
Process parameters: injection, die temperature, cycle time
Fast fill is the rule for thin-wall zinc: fill times of 10-30 ms for 1.0-1.5 mm walls, with injection pressures in the 30-60 MPa range, are what get you an as-cast surface that can go straight to plating or powder coat without polishing [S2]. Slow fill on a thin wall is the most common cause of cold shuts and cold laps on telecom covers, and operators see them as spider-web lines near the gate.
Die temperature should be held at 150-200 °C on the cavity side, with the shot sleeve 30-50 °C hotter to prevent premature skin formation. Cycle time for a typical telecom enclosure (gating, filling, cooling, ejection, trim) runs 20-45 seconds depending on wall stock; thinner walls cool faster but the cooling channels have to be tighter, often 8-10 mm diameter spaced one channel-diameter off the cavity surface.
Vacuum-assist becomes worth the capital premium on telecom parts with blind cavities, threaded inserts, or any internal feature that traps air. A standard die casting machine running at atmospheric pressure will tolerate 0.5-1.0% porosity in thick sections, and that porosity is what leaks RF on a shielding-critical cover. Vacuum pulls porosity down to under 0.2%, which is the typical OEM acceptance line for outdoor telecom enclosures.
Surface finish, plating, and gasketing integration
As-cast zinc from a properly polished H13 or 8407 die lands at 0.8-1.6 µm Ra, which is good enough for most indoor telecom enclosures. Outdoor parts that get powder coat or wet paint usually need a fine bead-blast or light vibratory finish first, not because the cast surface is rough, but because the oxide skin left from die release agents can cause paint adhesion failures [S2].
For EMI gasket grooves, the casting has to hold ±0.05 mm on groove width and ±0.07 mm on groove depth, otherwise the conductive elastomer gasket either over-compresses (loses shielding) or under-compresses (leaks RF). That tolerance is well within hot-chamber zinc capability on a well-maintained machine, but it is at the edge of what a standard gravity die casting machine can hold on a long run, which is one reason gravity casting is rare in telecom enclosure volume production and is mostly used for prototype batches under 500 pieces.
When zinc is the wrong choice
Zamak does not belong on a telecom enclosure if the part sees sustained skin temperatures above 100 °C, because the alloy creeps. It also does not belong if the part is larger than about 5 kg or has a projected area above roughly 600 × 600 mm, because the shot volume and platen size push you into aluminum territory, where a magnesium or aluminum cell becomes more economic [S2].
For very large outdoor cabinets (typically 8-25 kg), the engineering call moves to a magnesium die casting machine running AZ91D, or to a stamped-and-welded aluminum sheet enclosure. Both lose some of zinc's net-shape advantage, but they gain thermal headroom for power electronics and easier recycling at end of life. The [conference track on zinc die casting alloys and process technologies run by the International Zinc Association in Koblenz, Germany](https://www.zinc.org/2020-zinc-die-casting-conference-europe/) has historically been the main venue where these alloy-versus-application trade-offs are updated by the IZA and Initiative Zink community [S1].
Selection checklist for a telecom enclosure RFQ
Run a 60-second triage: confirm the part weight band (under 0.5 kg indoor, 0.5-3 kg outdoor small-cell, 3-25 kg outdoor macro-cell), confirm the projected area and wall stock, confirm the surface spec (raw, plated, painted, powder coated), confirm the RF shielding requirement in dB and frequency band, and confirm any temperature or corrosion exposure. From those five answers you can pick hot-chamber vs cold-chamber, choose Zamak 3 vs 5, and size the clamping force within one machine class, which is roughly the same triage [die casters apply to automotive connector housings](http://die-casting-china.com/) where similar volume and tolerance dynamics apply [S2].
Track these signals going into late 2026: IZA and Initiative Zink event updates on zinc alloy and process developments from the [International Zinc Association conference circuit](https://www.zinc.org/2020-zinc-die-casting-conference-europe/) [S1], and any new datasheets from [zinc die casting service providers](https://www.zincdiecast.com/) publishing revised shot-weight and porosity data for outdoor telecom enclosures [S3]. Also watch the zinc.org Spanish-language engineering portal's case-study updates on enclosure design freedom and dimensional accuracy [S4], which are the most consistent public source of new telecom-enclosure application data outside OEM direct releases.
See also our earlier report, Air Impact Wrench Selection for Road Maintenance Crews.