Hot Runner vs Cold Runner Payback Calculator
A hot runner removes the sprue and runner from every shot, but it costs real money up front. This calculator compares the extra tool cost against saved resin and shorter cycles so the purchase can be justified, or rejected, with numbers.
Your numbers
Hot runner system, controller and added mold work minus the cold runner cost it replaces.
Sprue plus runner plus any cold slugs, not the parts.
Share of resin value you recover by regrinding and reusing the runner. Zero if it is scrapped.
Often from shorter runner cooling and no runner ejection. Zero if cooling of the part sets the cycle.
Your results
Excludes hot runner maintenance, color change scrap, higher startup scrap and heater failures. Add those costs to the extra mold cost for a fuller view.
Net 5 year benefit vs annual shots
Sweeps Annual shots from 50000 to 1000000, holding your other inputs fixed.
Quantify runner and scrap waste from ERP data
Optional: we can look at how scrap and regrind are posted in your ERP and show how to report waste per mold.
Optional. The tool and every export work without this. No spam.
How to use it
Enter the extra cost of the hot runner mold over a cold runner version, the weight of sprue and runner per shot, resin price, and how much of the runner value you recover by regrinding. Then enter annual shots and any cycle time reduction. The payback is the extra cost divided by monthly saving. The chart shows how the five-year benefit changes with volume, which is usually the deciding factor.
Method behind the numbers
Material saving per shot is runner weight times resin price times the share of value lost. If you regrind and reuse half the runner at full value, you only lose the cost of grinding and the risk of quality drift, so enter a high recovery. Machine time saving is shots times seconds saved, converted to hours and priced at the machine rate. It is only a cash saving if that time can be used for other jobs or avoids overtime.
- Low volume and cheap resin favor cold runner
- Expensive resin, large runners and high volume favor hot runner
- Engineering resins that cannot be reground favor hot runner strongly
Worked example
A 14 g runner at $2.80 per kg with 40 percent value recovered wastes about $0.0235 per shot. At 400,000 shots that is roughly $9,400 a year. A 1.5 second cycle saving at $55 per hour adds about $9,200. Total near $18,600 a year against $18,000 extra cost gives a payback of about 12 months.
Common mistakes
Counting the full resin price when regrind is reused, claiming cycle savings that do not exist because part cooling is the limit, and leaving out hot runner running costs such as nozzle tips, heater replacements and slower color changes. Quality also matters: sprue vestige, gate type and thermal degradation in the manifold can decide the choice regardless of payback.
Frequently Asked Questions
When does a hot runner not make sense?
For low volume, short runs, frequent color changes or small runners with cheap resin, the extra cost and maintenance can outweigh savings. Cold runners are also easier to troubleshoot and cheaper to modify.
Does a hot runner always shorten the cycle?
No. It removes runner cooling and ejection as limits, but if the part wall cooling already sets the cycle, the saving is near zero. Enter zero seconds in that case and judge on material and quality.
How much runner can I regrind?
It depends on the resin, the part requirements and customer specifications. Many parts allow a limited percentage of regrind, and some regulated or optical parts allow none. Enter the value you can actually recover.
What other costs should I include?
Controller, spare tips and heaters, extra startup scrap, longer color changes, and the added mold maintenance labor. Add them to the extra cost field or reduce the saving to be realistic.
Netray can read your ERP job history to show real shot volumes and scrap by mold, so a hot runner decision rests on actual runner waste rather than estimates.
Related Tools
Injection Molding Machine Hourly Rate Calculator
Build a defensible press hourly rate from machine cost, utilization, energy, labor, maintenance and overhead, then convert it to cost per shot and per part.
Discrete ManufacturingInjection Molding Cooling Time Calculator
Estimate the cooling time of a molded part from wall thickness, resin thermal diffusivity, melt, mold and ejection temperatures, and see how it drives total cycle time.
MES & Shop FloorInjection Molding OEE Calculator
Calculate availability, performance, quality and overall equipment effectiveness for a molding press from a shift or day of production data.
Discrete ManufacturingBarrel Residence Time Calculator
Estimate how long resin sits in the barrel and how much of the machine capacity a shot uses, to spot degradation risk from oversized presses.
More Costing & Finance tools
See all- SAP QM Inspection Effort and Cost Calculator
- SAP Standard Cost Estimate BOM Rollup Calculator
- Legacy ERP Retirement Cost and Payback Calculator
- JD Edwards World Month-End Close Procedure Template
- Distributor Customer Credit Application Template
- Distributor Customer Profitability Worksheet
- Distributor GMROI and Inventory Turns Calculator
- Vendor Early Pay Discount Worksheet
- SyteLine Cost Rollup Variance Calculator