Thai Automotive Interior Factory Case Study: 27% Cycle Time Reduction with ZILLION Cooling System Upgrade

Introduction

Automotive interior and exterior plastic components — dashboards, door panels, headlamp lenses, bumper fascias, and climate control housings — are manufactured at volumes that make even small per-part defect rates financially significant. A Tier 1 automotive supplier producing 2 million parts per year with a 2% scrap rate is discarding 40,000 parts annually — at material, energy, and cycle time cost — before the part ever reaches the assembly line.

Cooling system performance is the dominant variable in automotive plastic injection molding productivity. Mold temperature directly controls cycle time — every degree of additional mold temperature allows faster filling, shorter pack time, and earlier ejection. But automotive grades of PP-EPDM (TPO), ABS, and PC/ABS also require careful temperature uniformity to achieve the surface appearance standards demanded by OEM customers.

This case study covers how a Thai automotive interior components supplier solved a chronic cycle time and quality problem by redesigning their cooling system around a ZILLION industrial water-cooled chiller and cooling tower installation, ultimately reducing cycle time from 52 seconds to 38 seconds — a 27% productivity improvement — while simultaneously reducing defect rate from 3.1% to 0.6%.

The Challenge: Slow Cycle Time and High Scrap in Automotive PP-EPDM Molding

Background

The customer operates a Tier 1 automotive interior components plant in the Eastern Seaboard Industrial Zone of Thailand, supplying instrument panels, door panels, and glove box assemblies to three automotive OEMs. Their main production line runs a 650-ton injection press molding glass-filled PP-EPDM (PP-EPDM-T20) for instrument panel substrates at a nominal cycle time of 45 seconds.

Despite a relatively modern press, the plant was averaging 52-second effective cycle times and experiencing a defect rate of 3.1% — primarily warp and sink marks on parts exceeding 600mm in length. The root cause investigation pointed consistently to the cooling system.

Problem 1: Mold Temperature Too Low for Glass-Filled PP-EPDM

The plant had been operating the mold at 35 degC mold surface temperature — a holdover from their previous material (unfilled PP) which processed well at low mold temperatures. However, glass-filled PP-EPDM behaves very differently: the high filler content creates significant differential shrinkage between the glass-rich skin layer and the core, and low mold temperature locks in this differential before the part has fully packed. The result is warp — particularly in large, flat sections of the instrument panel substrate.

The mold design allowed surface temperatures of up to 65 degC at the gate area and 50 degC at the part edges — but the existing air-cooled chiller could only maintain 35-38 degC consistently during Thailand's hot season (ambient temperatures 34-38 degC in the plant).

Problem 2: Cooling Channel Scale Restricting Heat Transfer

Water-cooled molds with hard water cooling channels develop scale deposits over time. The plant had not chemically cleaned the mold cooling channels in over 18 months. Thermal imaging of the mold during production revealed surface temperature differentials of up to 15 degC between different areas of the cavity — far exceeding the plus/minus 3 degC uniformity required for warp-free molding of large glass-filled parts.

The cooling channels most distant from the gate — where the material arrives coolest and most viscous — were running 8-10 degC below design temperature, creating localized thick frozen skins and subsequent sink marks on the Class-A surface visible from the driver's eye position.

Problem 3: No Closed-Loop Cooling Tower — Open Basin in Tropical Climate

The plant's existing "cooling tower" was a simple open evaporation basin with no fan, no fill media, and no water treatment. Makeup water from the municipal supply was added manually, and the basin was cleaned quarterly. During Thailand's hot season, basin water temperatures reached 36-38 degC — meaning the chiller's condenser was receiving water at temperatures that severely compromised its capacity. The chiller's leaving water temperature at 38 degC ambient was 30 degC — but the mold required 50 degC supply water, forcing the plant to run the process with a 20 degC approach that the MTC could not bridge.

The Solution: ZILLION Water-Cooled System with Proper Cooling Tower

System Design

ZILLION's engineering team conducted a complete heat load analysis for the instrument panel mold, accounting for:

• Material heat content: PP-EPDM-T20 at 250 degC melt, 50 degC mold surface
• Cycle time target: 38 seconds (from current 52 seconds)
• Required heat extraction per cycle: calculated at 18.5 MJ per part
• Heat load at 38-second cycle: approximately 486 kW average, 520 kW peak

The selected system:

Why a Cooling Tower Was Non-Negotiable

Thailand's climate presents extreme challenges for air-cooled cooling: ambient temperatures of 34-38 degC are common for 8 months of the year, with relative humidity of 70-85%. Under these conditions, a 60 kW air-cooled chiller loses 25-30% of its rated capacity. To achieve the mold temperature of 50 degC required for the PP-EPDM material, the chiller would need to produce leaving water at 45 degC — an extreme condition that no standard air-cooled chiller is designed to handle continuously without severe compressor wear.

A properly sized counterflow cooling tower operating at 32 degC entering water temperature allows the ZL-60WS to produce leaving water at 27 degC — comfortably below the 50 degC required by the MTC — with 23 degC approach temperature. This leaves ample capacity margin for hot weather operation and future capacity expansion.

Mold Cooling Circuit Redesign

Along with the chiller upgrade, the plant undertook a mold cooling circuit redesign:

• Thermal imaging survey of existing mold to identify cold spots and bypassed channels
• Installation of additional cooling circuits in the gate area and long-flow sections
• Balancing valves on each cooling circuit to equalize flow distribution
• Chemical descaling of all cooling channels to restore full heat transfer
• Installation of individual circuit flow meters and temperature sensors on each zone
• Upgrading from a single-zone to dual-zone MTC to separately control the gate area (60 degC) and peripheral areas (45 degC)

Results After 12 Months

Cycle Time Reduction

Quality Improvements

Financial Summary

Key Lessons for Automotive Plastic Moldors

• Glass-filled and mineral-filled materials require significantly higher mold temperatures than unfilled grades — PP-EPDM-T20 requires 45-55 degC mold temperature for warp-free molding, not the 30-40 degC suitable for unfilled PP. Attempting to process these materials at low mold temperatures is a root cause of warp and sink mark defects.
• Cooling channel maintenance is not optional — scale deposits as thin as 1mm can reduce heat transfer by 10-15%. An annual chemical descaling of mold cooling circuits should be standard maintenance practice in all high-volume molding operations.
• Cooling towers are essential in tropical climates for any mold requiring above 40 degC — air-cooled chillers simply cannot deliver the approach temperatures required for high-mold-temperature processes when ambient temperatures exceed 32 degC. The marginal cost of a cooling tower installation is always recovered through improved cycle time and reduced scrap.
• Dual-zone mold temperature control pays for itself on large parts — controlling gate area and peripheral areas separately with independent MTC zones allows optimization of fill and pack conditions simultaneously, reducing both warp and sink marks in the same part.
• Mold thermal imaging is the fastest way to diagnose cooling problems — a THB 50,000 thermal imaging survey identified 6 bypassed and restricted cooling channels in this mold within 2 hours. The alternative would have been months of trial-and-error mold modifications.

Equipment Used

• ZILLION ZL-60WS Water-Cooled Industrial Chiller (60 kW, dual-scroll, R410A)
• ZILLION ZCT-80 Counterflow Cooling Tower (80 kW heat rejection, FRP)
• ZILLION MTC-SO-36 Oil-Feded Dual-Zone Mold Temperature Controller (36 kW, 180 degC)
• Automatic water treatment system (conductivity control, scale inhibitor, biocide dosing)
• Dual condenser water pumps with standby configuration
• Mold cooling circuit balancing valves and flow meters

Frequently Asked Questions

Q: Can this cooling approach work for paint shop plastic parts (Bumper fascias, etc.)?
A: Yes — painted automotive exterior parts require even tighter surface temperature control because paint appearance (orange peel, gloss) is directly affected by mold surface temperature during the injection-cooling phase. Paint-ready bumper fascias typically require mold temperatures of 60-80 degC to achieve the surface conditions necessary for high-gloss painting. Oil-feded MTC systems (like the ZILLION MTC-SO series) are standard for these applications.

Q: What is the typical cooling system maintenance cost for automotive molding?
A: Annual maintenance for a ZILLION water-cooled chiller and tower system serving automotive production typically runs 3-5% of the capital cost per year, including: quarterly water chemistry testing and adjustment, annual cooling tower fill inspection, annual chiller service (refrigerant check, electrical testing, coil cleaning), and mold cooling channel inspection every 6 months. This compares to typical unplanned downtime costs of THB 200,000-500,000 per day in automotive Tier 1 operations.

Q: How do I calculate the ROI of a cooling system upgrade?
A: The key variables are: (1) current cycle time and target cycle time, (2) number of cavities and parts per hour, (3) material cost per kg and per-part material weight, (4) current defect rate and target defect rate, (5) selling price per part and margin per part. The formula: Annual Benefit = (Cycle time reduction hours x Parts/hour x Margin/part) + (Scrap reduction units x Material cost). Divide total investment by Annual Benefit for payback period.

Q: What cooling capacity should I specify for a 650-ton press running glass-filled PP?
A: Rule of thumb for glass-filled PP at 45-55 degC mold temperature: 80-100 kW of chiller cooling capacity per 100 tons of clamping force, as a starting point. A 650-ton press running PP-EPDM-T20 at 50 degC mold temperature with a complex multi-cavity mold typically requires 50-70 kW. ZILLION's technical team provides free heat load calculations based on your specific mold design and material data.

Conclusion

The 27% cycle time reduction and 81% defect rate improvement documented in this case study were achieved through a combination of correct cooling system specification (water-cooled chiller with properly sized cooling tower), proper mold temperature for the material (50 degC, not 35 degC), and systematic maintenance of the mold cooling circuits. Each of these elements was necessary; none was sufficient alone.

The payback period of 3.7 months demonstrates that cooling system upgrades are among the highest-return capital investments available to high-volume automotive plastic molders. For any plant running cycle times above 40 seconds or defect rates above 1.5% on glass-filled or mineral-filled materials, a cooling system audit is the logical first step in an improvement program.

Contact ZILLION's technical team to discuss a cooling system assessment and upgrade proposal for your specific automotive plastic molding application.