Operators blame the former when cups warp. Often the chiller is 3–5 °C too warm or flow is shared with the roll stack. Split circuits: one loop for extrusion rolls, one for molds.
A usable sizing sketch
Cooling load scales with kg/h × specific heat × temperature drop, plus ~20% margin, then convert to refrigeration tons. Deep PP cups dump more heat than shallow PET lids. Our cup machines list 2.5–4.0 m³/min air — that is air, not water; do not size the chiller from the air line.
| Loop | Job | Failure if shared |
|---|---|---|
| Roll stack | Lock sheet gauge | Thickness bands, brittle wind |
| Mold / plug | Freeze the cup | Warp, long cpm, sticking |
| Hydraulic oil (LS/HSS) | Keep oil in window | Slow force, leaks in heat |
Worked example — 500 kg/h PP, molds 15 °C ΔT
Order-of-magnitude: 500 kg/h × 1.9 kJ/kg·K × 15 K ≈ 4.0 kW thermal from the cups alone, before rolls and inefficiency. Add rolls, motors, and 20% and you are shopping a real industrial skid, not a 3-ton comfort unit. Send cup mass and cpm; we size LS-Chiller on the layout.
Write the formula in the RFQ
Q (kW) ≈ ṁ (kg/s) × Cp × ΔT, then ÷ 0.8 for inefficiency, then add the roll stack (often larger than the mold on a thick PP web). Convert kW / 3.5 ≈ refrigeration tons as a shopping number. Send mass, ΔT, and whether oil needs its own loop — we will not size from “same as last factory.”
Scale closes channels in months. Closed loop + filter. Open tower water in the tool is a false economy. Air conditioning does not replace process water.
Fault map — what the line is telling you
| Symptom | Likely cause | First check |
|---|---|---|
| Cups warp; operator blames the former | Chiller 3–5°C too warm or one loop for rolls + molds | Split circuits; check actual tool metal temperature |
| Gauge bands on the sheet | Roll stack sharing mold water | Dedicated roll loop |
| Hydraulic press slows after lunch | Oil loop missing or undersized | Oil cooler is not the mold chiller |
| Channels scale shut in months | Open tower water in the tool | Closed loop + filter; hall AC is not process water |
| Bought a 3-ton comfort unit for 500 kg/h PP | Sized from air-con logic | Use ṁ × Cp × ΔT + 20% + rolls |
RFQ checklist — send this in one email
Fill what you know; blank is better than a guess. Attach it on Get a Quote with photos of resin or flake.
- Cup mass, cpm, cavities, and resin (for heat load)
- Desired mold ΔT and roll-stack temperatures if known
- Whether oil needs its own loop (LS / HSS)
- Water quality (scale, tower vs closed) and hall peak °C
- Existing chiller tons and whether it already serves another line
Frequently asked questions
Can I use a cooling tower only?
For some oil or plant water, maybe. Not as the only fluid through fine mold channels.
Why 3–5 °C too warm matters?
PP will not freeze in time. You drop cpm or ship oval rims.
One chiller, two zones?
Yes if it has two independently controlled loops. One thermostat for everything is the failure mode.
Does servo need less cooling?
Drives like cooler air. The mold still needs the same water for the same plastic mass.