About 107 t to 179 t. That is the clamp a 170 × 130 mm enclosure in a general PC grade needs on one cavity with a cold runner, at a tonnage factor of 3 to 5 US t/in² and a 10% reserve. For electrical housing moulding on a 180 t machine, the resin decides how large a housing fits. The same box in ABS needs about 71 t to 143 t.
Junction boxes, meter enclosures, LED driver housings and appliance bodies can all fit on 180 t. Flame-retardant PC sits near the top of the factor range, though, and leaves little room.
Key Takeaways
- A general PC grade lists a clamp tonnage of 3.0 to 5.0 US t/in² and an ABS grade 2.0 to 4.0, so at the upper end the same housing needs about 20% less clamp in ABS.
- Flame ratings are thickness-specific: one FR PC grade is UL 94 V-0 at 3.0 mm but only V-2 at 1.0 mm.
- Boxes and enclosures to IS 14772:2020 need the BIS Standard Mark under the Electrical Accessories (Quality Control) Order, 2023.
- FR PC must be dried to 0.02% moisture or less and moulded at 80 to 120 °C, which affects auxiliaries and cycle time.
How Large a Housing Can a 180 t Machine Mould?
In a general PC grade at the top of its factor range, about 233 cm² of projected area, runner included, with a 10% reserve. In ABS at its upper factor of 4, about 291 cm². A two-cavity layout roughly halves the area available to each housing.
Projected area here is the housing's footprint seen from the mould opening direction. Cable entries in the side walls do not reduce it, while through-holes in the base, such as fixing holes, can be deducted. The method is set out in the applications article in this series.
Largest housing footprint at 180 t, one cavity, cold runner 10 cm², 10% reserve (a starting margin, not a rule)
| Resin and factor | Largest total area | Largest footprint | Square equivalent |
|---|---|---|---|
| ABS at 2 US t/in² | 582 cm² | 572 cm² | about 239 × 239 mm |
| ABS at 4 US t/in² | 291 cm² | 281 cm² | about 168 × 168 mm |
| PC at 3 US t/in² | 388 cm² | 378 cm² | about 194 × 194 mm |
| PC at 5 US t/in² | 233 cm² | 223 cm² | about 149 × 149 mm |
Deep housings also need opening stroke to clear the core. That check, and when it points to a different build at the same clamp, is in the article on when a standard 180 t machine is enough.
Which Materials Suit Electrical Housing Moulding?
FR PC, PC/ABS, ABS and glass-filled polyamides or PBT are all used, chosen by flame rating, glow-wire performance, tracking resistance and heat. A rating applies at the wall thickness tested, so the material and the wall design must be settled together.
Covestro's page for Makrolon 6555, a flame-retardant PC, shows why. It lists UL 94 V-0 at 3.0 mm but V-2 at 1.0 mm, a glow-wire flammability index of 960 °C at 1.5 and 3.0 mm but 875 °C at 0.75 mm, and a comparative tracking index of 225 V. Thinning a wall to save clamp can drop the housing below the rating it needs.
INEOS's Lustran ABS 248 data sheet lists a clamp tonnage of 2.0 to 4.0 US t/in², small appliance housings among its uses, and UL 94 HB. HB is the lowest UL 94 class, so a general ABS suits covers with no live parts nearby, while live-part carriers need a flame-retardant grade.
In India, boxes and enclosures for electrical accessories in household and similar fixed installations, covered by IS 14772:2020, need the BIS Standard Mark under the Electrical Accessories (Quality Control) Order, 2023, notified on 1 January 2024. The order also covers cable trunking and ducting to IS 14927 Part 2, and excludes goods made for export.
Our view: settle the material and its rated thickness before you size the machine. A switch from ABS to FR PC can move the same housing from comfortable to marginal on a 180 t clamp.
What Processing Demands Do FR PC Housings Add?
Dry resin, a hot mould and enough pressure. Covestro lists drying at 120 °C for 2 to 3 hours to a maximum moisture of 0.02% for Makrolon 6555, a melt temperature of 300 °C and a mould at 80 to 120 °C. Each affects auxiliaries and cycle time.
The same page gives a shot-to-cylinder size of 30 to 70% and a back pressure of 50 to 150 bar. A mould at 80 °C or more needs a water or oil temperature controller rather than chilled water, and the dryer must be sized for the hourly resin throughput.
Shrinkage is listed as 0.60 to 0.80%. On a 170 mm side, that 0.2% spread is about 0.34 mm, which decides whether a lid and base still mate along their full length. The toolmaker needs the exact grade before cutting steel.
Pressure is the last check. A data sheet for Makrolon 2558, a general PC grade, lists an injection pressure of 69 to 138 MPa, so a long-flow housing can need the upper part of a machine's injection pressure range.
What Should You Send for a Housing Job?
Send the housing drawing with footprint, depth and wall thickness, the resin grade and its rated thickness, the cavity count and the runner type. The clamp, drying and mould temperature checks can then be run together. See the 180 ton horizontal injection moulding machine page.
Frequently Asked Questions About Electrical Housing Moulding
Can a 180 t machine mould a distribution board enclosure?
Smaller enclosures can fit, but a large board enclosure in FR PC can exceed the area a 180 t clamp holds at a factor of 5, which is about 233 cm² including the runner. Split large designs into a base and a separate cover, or size the machine on the largest part in the set.
Should I choose PC or PC/ABS for an enclosure?
It depends on the flame, impact and heat ratings the end product needs. A PC/ABS blend can flow more easily than PC, which can lower the tonnage factor, but ratings vary by grade and thickness. Compare data sheets at your actual wall thickness and confirm against the end-product test standard.
Why do FR PC housings show splay or silver streaks?
Moisture is the first thing to check. PC must be dried to very low moisture before moulding, and Covestro lists a maximum of 0.02% for its FR grade. Splay can also come from high melt temperature or long residence time. Check the dryer's dew point and the shot share of the barrel next.
Do cable entry knock-outs affect the mould design?
Yes. Knock-outs are thin, partly sheared sections that must stay in place during handling and break out cleanly on site. They need a consistent thin section, good venting and gating that stops the melt hesitating there. Knock-outs in side walls can need slides, which adds width and cost to the mould.
How long does an FR PC housing take to cool?
Longer than a PP part of similar size, because the mould runs at 80 to 120 °C. Cooling time grows with the square of wall thickness, so a 3.0 mm wall needs about 44% more cooling than a 2.5 mm wall. Set the timer from a trial or a mould-flow study, not from a PP job.
Related Articles
- What Can You Make on a 180 Ton Injection Moulding Machine?
- 180 Ton Machine for Food Containers, Bowls and Trays
- When a Standard 180 Ton Machine Is Enough and When to Move Up
Sources & References
- Covestro: Makrolon 6555 product page
- Bayer MaterialScience (now Covestro) via IDES: Makrolon 2558 datasheet
- INEOS ABS via UL IDES: Lustran ABS 248 datasheet
- Gazette of India (DPIIT): Electrical Accessories (Quality Control) Order, 2023
Technical Disclaimer
Disclaimer: The information provided in this document is for general informational and educational purposes only. It is based on technical references and industry information available at the time of preparation and may be subject to change. It does not constitute engineering, technical, commercial or professional advice, nor does it constitute a quotation, specification, warranty or contractual commitment by Pratishna Engineers.
Actual injection moulding machine and process requirements vary according to the component design, material, mould, production volume, machine configuration and operating conditions. The information, examples, calculations and recommendations provided should be independently evaluated and verified for the specific application before making any equipment, process or production decision. Information obtained from third-party sources remains subject to the accuracy and limitations of those sources.
Limitation of Liability: Pratishna Engineers makes no representation or warranty, express or implied, regarding the completeness, accuracy or suitability of the information for any particular application. To the extent permitted by applicable law, Pratishna Engineers shall not be liable for any loss, damage, cost or consequence arising from reliance on or use of the information contained in this document. Final machine selection, configuration and application suitability should be confirmed with Pratishna Engineers based on complete and accurate project requirements.
