Production Cycle Optimization - How to Reduce Injection Time 2025

Introduction - the value of every second

Injection molding cycle time is the most important economic parameter in mass production. Reducing the cycle by just 5 seconds when producing 3 million parts annually means saving 4,167 machine hours – equivalent to €50,000-€125,000 in annual savings.

In Polish injection molding industry, average cycle times are 28-45 seconds for automotive parts and 15-30 seconds for packaging. Studies show that in 60-75% of cases this time can be reduced by 10-30% without quality compromises.

Why is cycle optimization critical?

• Production costs: Shorter cycle = more parts per hour = lower unit cost
• Capacity: 20% cycle reduction = 25% productivity increase without new machines
• ROI: Optimization investment (€10-30K) pays back in 3-12 months
• Competitiveness: Shorter cycle time = lower quote price = more contracts

Key insight: In a typical injection molding cycle, cooling accounts for 50-70% of total time. This is the biggest savings potential.

Anatomy of the injection molding cycle

To effectively optimize cycle time, it's necessary to understand what phases it consists of and where the biggest savings potential lies.

5 main phases of the injection molding cycle

Phase	Time [s]	% of cycle	Reduction potential
Mold closing	2.8	8%	Low-medium (5-15%)
Injection + filling	1.2	3%	Medium (10-30%)
Packing/holding	8.5	24%	High (20-40%)
Cooling	22.0	62%	VERY HIGH (20-50%)
Opening + ejection	3.5	10%	Medium (10-20%)

Conclusion: Cooling is 62% of the cycle – the first area for optimization. Even a 27% cooling time reduction translates to 25% total cycle reduction.

Cooling optimization (50-70% of cycle)

Cooling is the biggest time consumer in the injection molding cycle and simultaneously the area with the greatest optimization potential.

1. Mold temperature optimization

Problem: Higher mold temperature = better filling, but longer cooling. Lower temperature = shorter cooling, but risk of short shots.

Solution: Find the minimal acceptable mold temperature (MAMT)

DOE Method:

1. Set baseline mold temp (e.g. 50°C for PP)
2. Run series with temperatures: 45°C, 40°C, 35°C
3. Monitor: cooling time, surface quality, filling, dimensional stability
4. Select lowest temperature meeting all quality requirements

Example: Reducing mold temp from 50°C to 40°C (PP)

• Cooling time reduction: 18s → 14s (-22%)
• Annual savings: 3.3M parts × 4s × €0.05/min = €11,000

2. Conformal Cooling - mold cooling revolution

Traditional cooling channels are straight, drilled. Conformal cooling uses 3D printing to create channels that follow the cavity shape, ensuring uniform cooling.

Benefits:

• 20-40% cooling time reduction
• Uniform cooling → less warpage
• Ability to cool difficult geometries
• Higher surface quality

Challenges:

• Cost: €15,000-€80,000 additional for mold
• Break-even: Typically 300,000-1,500,000 parts

ROI example:

• Investment: €35,000
• Cycle time reduction: 42s → 32s (-24%)
• Annual production: 800,000 parts
• Savings value: €100,000/year
• Payback period: 4.2 months ✅

3. Precise temperature control - TCU ±0.5°C

Standard temperature control units (TCU) have accuracy of ±2-3°C. Premium TCU achieve ±0.5°C.

Benefits:

• More repeatable solidification time
• Can reduce cooling time closer to minimum without variability risk
• Typical savings: 3-8% of cycle time

Cost: €8,000-€18,000 | ROI: 12-24 months for high-volume production

4. Hot runner systems

Cold runner: Runner must cool before ejection → additional 3-8 seconds

Hot runner: No runner to cool → immediate elimination of 3-8s from cycle

For high-volume applications (>500K parts/year) hot runner is a game changer. See details in hot runner economics section.

Injection and holding optimization

Multi-stage injection profiling

Instead of constant injection speed, use 2-5 stage profile:

Stage	Position [mm]	Speed [mm/s]	Goal
1	0-15	60	Gentle start (no jetting)
2	15-85	180	Maximum filling speed
3	85-100	90	Gentle finish

Benefits: Shorter fill time (1.8s → 1.3s, -28%), better quality, more uniform packing.

Gate freeze detection - critical technique

Problem: Holding time is often set "for safety" - 2-5 seconds longer than actually needed.

Gate freeze study method:

1. Set holding time definitely too long (e.g. 15s)
2. Run series with holding time: 12s, 10s, 8s, 6s, 4s, 2s, 0s
3. Weigh 10 parts from each series
4. Gate freeze time = point where further holding time increase does NOT increase part weight
5. Set production holding time = gate freeze + 0.5-1.0s (safety margin)

Typical savings: 2-5 seconds at zero investment – always the first optimization step!

Hot runner vs cold runner - economics

System comparison

COLD RUNNER:

• Material flows through cold sprue and runner
• Runner must cool → additional 3-8s cooling time
• Wasted material (runner = 15-40% shot weight)
• Lower mold cost (€30K-€80K cheaper)

HOT RUNNER:

• Heated manifold maintains material molten
• Elimination of 3-8s runner cooling time
• Zero material waste
• Higher initial cost: €20,000-€150,000

ROI calculation example - automotive part 180g PA6, 2-cavity mold

Parameter	Cold runner	Hot runner
Mold cost	€85,000	€133,000
Cycle time	38 seconds	33 seconds (-13%)
Material waste	20.9%	0%
Parts/year (3-shift)	1,661,000	1,912,000 (+15%)
Annual savings	-	€66,900

Payback period: €48,000 / €66,900 = 8.6 months ✅

Recommendations:

• Hot runner recommended: Production >500K parts/year, long runs, expensive materials
• Cold runner acceptable: Low volumes (<200K/year), frequent material/color changes

Case study - reduction from 45→32 seconds

Real cycle time optimization case study conducted by TEDESolutions for a Polish tier-1 automotive manufacturer.

Project profile

• Part: Center console cover, ABS+PC, 285g
• Machine: Tederic NEO.H260
• Annual production: 420,000 pieces (2-shift)
• Baseline cycle time: 45 seconds

3-month optimization program

Phase 1: Low-hanging fruit (Week 2-3, €0 investment)

• Mold temp reduction: 65°C → 60°C → -2.5s cooling
• Gate freeze study → -3.3s holding
• Faster mold close/open speeds → -0.7s
• Result: 45.0s → 38.5s (-14%)

Phase 2: Process profiling (Week 4-6, €0-€5K)

• 3-stage injection profile → -0.3s
• Holding pressure decay profile → -1.2s
• Aggressive cooling cut → -1.7s
• Result: 38.5s → 35.3s (-8%)

Phase 3: Equipment upgrade (Week 7-12, €22,300)

• Premium TCU ±0.5°C (€9,800) → -1.8s
• Cooling channel upgrade (€12,500) → -1.5s
• Result: 35.3s → 32.0s (-9%)

Final results

Parameter	Start	End	Improvement
Cycle Time	45.0s	32.0s	-28.9%
Parts/hour	80	112.5	+40.6%
Cpk (dimensional)	1.28	1.52	+18.8%
Scrap rate	2.8%	1.2%	-57%

ROI:

• Total investment: €37,300 (€22,300 equipment + €15,000 consulting)
• Annual benefits: €70,780/year (increased capacity, reduced scrap, energy)
• Payback period: 6.4 months ✅

Key takeaways

1. Low-hanging fruit most important: Phase 1 (zero investment) delivered 14% reduction
2. Gate freeze study critical: 3.3s saved just through proper holding time
3. Cooling dominates: 67% of total reduction came from cooling optimization
4. Quality improved: Aggressive optimization did NOT degrade quality - opposite (Cpk +18%)

Troubleshooting and pitfalls

Cycle time optimization is a balance between speed and quality. Here are the most common problems:

Problem 1: Warpage after cooling reduction

Cause: Part didn't solidify sufficiently - internal stress causes deformation.

Solution:

• Step back: increase cooling time by 2s
• Reduce cooling in 1s steps, test 50 parts after each change
• Measure parts immediately and after 24h - compare
• Consider cooling jig for hot parts

Problem 2: Sink marks after holding reduction

Cause: Insufficient packing - gate froze too early.

Solution:

• Increase holding pressure: +50-100 bar
• Optimize switchover: earlier injection→holding transition
• Long-term: redesign part for uniform wall thickness

Problem 3: Flash after injection speed increase

Cause: High dynamic pressure opens mold during injection.

Solution:

• Increase clamp force: +10-15%
• Multi-stage injection: slower speed at end of fill
• Check mold maintenance: parallelism, wear, sealing surfaces

Golden rule of optimization

"Optimize aggressively, but validate rigorously"

• Each change: test minimum 50-100 parts
• Measure dimensional, visual, functional quality
• Monitor Cpk - don't accept drop >10%
• If in doubt → step back and re-assess

Summary and roadmap

Key conclusions

1. Cycle time is the most important economic parameter

Reduction by 5 seconds at 3M parts/year = €50K-€125K annual savings. In most cases 10-30% reduction is achievable without quality compromises.

2. Cooling is the biggest potential (50-70% of cycle)

• Mold temperature optimization (DOE study)
• Conformal cooling (20-40% reduction, ROI 4-12 months)
• Premium TCU ±0.5°C (3-8% variability reduction)

3. Holding time optimization - low-hanging fruit

Gate freeze study can save 2-5 seconds at zero investment.

4. Hot runner = game changer for high volume

Elimination of 3-8s + zero waste. Payback <12 months for >500K parts/year.

5. Moldflow simulation = fastest route to optimum

Investment €5K-€15K, return €60K-€200K+. ROI often <1 month for new molds.

Optimization roadmap - Step by step

PHASE 1: Low-cost optimization (0-2 weeks, €0)

1. Gate freeze study → optimal holding time
2. Mold temp DOE → find MAMT
3. Faster dry cycle speeds
4. Target: 8-15% reduction

PHASE 2: Process profiling (2-4 weeks, €0-€5K)

1. Multi-stage injection profiling
2. Holding pressure decay profile
3. Aggressive cooling time cut (quality monitoring)
4. Target: 5-12% additional reduction

PHASE 3: Equipment upgrades (2-6 months, €10K-€80K)

1. Premium TCU ±0.5°C (€8K-€18K)
2. Cooling channel modifications (€5K-€25K)
3. Conformal cooling (€15K-€80K) - new molds, high volume
4. Hot runner (€20K-€150K) - for >500K parts/year
5. Target: 10-25% additional reduction

TOTAL POTENTIAL: 23-52% cycle time reduction

Tederic machine capabilities

NEO Series (hydraulic): Mold close speed up to 280 mm/s, repeatability <0.5%, responsive hydraulics for multi-stage profiles

DREAM Series (electric): Ultra-fast cycles (400 mm/s), repeatability <0.3%, 30-50% lower energy consumption, precise temperature control ±1°C

Typical ROI for different optimizations

Optimization type	Investment	Cycle reduction	Payback
Process only (Phase 1-2)	€0-€5K	10-20%	Immediate
Premium TCU	€10K-€18K	3-8%	4-14 months
Conformal cooling	€15K-€80K	15-30%	4-18 months
Hot runner	€25K-€150K	10-25%	6-24 months

Best practices - checklist

✅ Planning

• Start with cycle breakdown analysis - where is the time?
• Set clear, realistic targets (10-30%)
• Prioritize cooling optimization

✅ Execution

• Incremental changes - not everything at once
• Validate rigorously - minimum 50-100 parts
• Monitor Cpk - don't accept degradation
• Document everything

✅ Investment decisions

• Calculate ROI properly - include capacity increase value
• Hot runner - strongly consider for >500K parts/year
• Conformal cooling - evaluate for new high-volume tools