Mold Flow Analysis in Practice: Single-Point vs. Two-Point Gate

Mold Flow Analysis in Practice: Single-Point vs. Two-Point Gate – Choosing Optimal Solution?

Time：2026-03-16 08:15:04 / Popularity： / Source：

In actual injection molding production, gate design is one of key factors affecting product quality, cycle cost, and mold life. Single-point and two-point gates are two common gate methods, each with its own advantages and disadvantages. How to choose the right one scientifically has become a focus of attention for many engineers and manufacturers.
This article, based on a real mold flow analysis report and combined with actual parameters of a Haitian 160T injection molding machine, guides you step-by-step through analyzing differences between two solutions and provides suggestions for trial molding process parameters to help you avoid detours in production.

I. Why Perform Mold Flow Analysis?

Mold Flow Analysis (MFA) uses computer simulation to observe flow, cooling, and shrinkage of plastic in a mold, predicting and optimizing production problems in advance, such as:
Is filling balanced? Are there weld lines or air pockets? Are shrinkage marks and warpage controllable? Are injection pressure and clamping force within machine's range?
Mold flow analysis allows us to identify problems and optimize designs before mold opening, significantly reducing trial molding costs and timelines.

II. Single-Point Injection vs. Two-Point Injection: Key Indicator Comparison

Taking a carbon fiber reinforced material (Stat-Kon DE002ER) as an example, we compare performance of two injection methods on same product:

Indicators	Single-Point Injection	Two-Point Injection
Injection Pressure	68.9 MPa	55.3 MPa
Clamping Force	Higher	Lower
Filling Time	0.537 s	0.438 s
Runner Weight	2.71 g	3.64 g
Shrinkage Risk	Lower	Low
Warpage	Excellent	Slightly Higher
Weld Lines	Fewer	More

III. How to Choose? Consider Your Product Priorities

✅ Choose single-point injection if: Product has high requirements for flatness and dimensional stability; You want to save material and reduce runner waste; You can accept slightly higher injection pressure and clamping force.
✅ Choose two-point injection if: High product appearance is required, avoiding noticeable shrinkage marks; Limited machine tonnage, requiring lower injection pressure; Long filling path, necessitating faster filling speed.

IV. Recommended Trial Molding Process Parameters (Can be directly used in workshop)

�� Single-Point Injection Scheme

Parameters	Setting Values	Descriptions
Melt Temperature	300°C	Recommended for same material
Mold Temperature	95°C	Cavity/Core Consistent
Injection Time	0.60 s	Slightly longer than mold flow filling time
V/P Switching	98% Stroke	2% Buffer Reserved
Holding Pressure	80% Peak Pressure	First Mold Reading Peak Pressure
Holding Time	10.0 s	Strictly Follow Mold Flow Settings
Cooling Time	20.0 s	Strictly Follow Mold Flow Settings

�� Two-Point Injection Scheme

Parameters	Setting Values	Descriptions
Injection Time	0.48 s	Slightly longer than mold flow filling time
Injection Speed	70%~80%	Medium to High Speed Adjustment
Holding Pressure	80% Peak Pressure	First Mold Reading Peak Pressure
Storage Stroke	~88 mm	Including 5mm Retraction

⚠️ Key steps in trial molding:
1. Use "staged injection method" to accurately locate V/P switching point;
2. Read peak pressure in the first mold as holding pressure benchmark;
3. Monitor residence time to prevent material degradation.

V. Summary: Data-driven, scientific trial molding

Whether it's single-point or two-point injection, there is no absolute "optimal," only "most suitable." Through mold flow analysis, we can:
Predict filling behavior; Optimize holding pressure curve; Assess defect risks; Develop a scientific process window.
It is recommended that in actual trial molding: use parameters provided in this article as a starting point, and make fine adjustments based on results of the first mold to gradually approach optimal production state.
Gate Detail

Filling-lsoline curves

Fill results

Global deformation

Trial Molding Direction Reference Machine Parameters and Suggestions
Haitian 160T Machine Parameters (Based on Shenzhen No. 7 160T Haitian)
Screw Diameter (Barrel Diameter): 35mm
Maximum Glue Weight: 210g (Based on polystyrene standard density 1.0g/cm³)
Barrel Volume: 210cm³ (Calculated based on maximum glue weight and standard density)
Melted Glue Length: Approximately 218mm (Calculation method: Barrel Volume = Π * (Screw Diameter / 2)² * Melted Glue Length; Substituting values: 210 = Π * (3.5 / 2)² * L, solving for L ≈ 21.8cm).
Raw Material Parameters
Material: Stat-KonDE002ER (containing carbon fiber)
Raw Material Density: Calculated from weight and volume in analysis report:
Two-point injection: Density = Total weight / Total volume = 9.30449 / 7.9725cm³ ≈ 1.167 g/cm³
One-point injection: Density = Total weight / Total volume = 8.47789 / 7.2175cm³ ≈ 1.175g/cm³
Calculation Explanation:
Weight of Raw Material in Barrel: In actual production, volume of molten adhesive in barrel is usually set to twice injection volume (to ensure stable injection). Therefore, weight of molten adhesive in barrel = 2 * injection volume * raw material density.
Total Molten Volume: The total volume obtained directly from analysis report (including parts and runners).
Cycle Time: Holding pressure end time obtained from analysis report, approximated as the total cycle time (including filling, holding pressure, and cooling).
Product Weight and Cold Runner Weight: Obtained from holding pressure stage end results in analysis report (more consistent with actual production).
Dwell Time: Calculated as (weight of raw material in barrel * cycle time) / injection weight (injection weight is the total weight at the end of filling).
Calculation results for two-point injection scheme:
Bug diameter: 35mm
Bug melt length: 218mm (based on maximum capacity, but actual usage)
Total melt volume: 7.9725cm³
Raw material density: 1.167g/cm³
Raw material weight in the barrel: 18.61g (Calculated: 2 * 7.9725cm³ * 1.167 g/cm³)
Cycle time: 30.5s
Product weight: 6.1204g
Cold runner weight: 3.6359g
Dwell time: 61.0s (Calculated: (18.61g * 30.5s) / 9.3044g)
Calculation results for a single-point injection scheme:
Bucket diameter: 35mm
Bucket melt length: 218mm (based on maximum capacity, but actual usage)
Total melt volume: 7.2175cm³
Raw material density: 1.175g/cm³
Raw material weight in the bucket: 16.96g (Calculated: 2 * 7.2175cm³ * 1.175 g/cm³)
Cycle time: 30.6s
Product weight: 6.1270g
Cold runner weight: 2.7129g
Dwell time: 61.2s (Calculated: (16.96g * 30.6s) / 8.4778 g)
Comparison of key parameters based on mold flow analysis report:

Parameters	Two-Point Injection	One-Point Injection	Advantages and Disadvantages
Maximum Injection Pressure	55.28 MPa	68.91 MPa	Two-point injection has lower pressure, resulting in less wear and tear on machine and mold, and is more energy-efficient.
Maximum Clamping Force	6.93 tonne	9.83 tonne	Two-point injection has lower clamping force, suitable for smaller machines, reducing risk of deformation.
Average Volumetric Shrinkage	3.3646%	3.2594%	One-point injection has slightly lower shrinkage and slightly better dimensional stability.
Maximum Sink Mark Index	2.2647%	2.7949%	Two-point injection has a lower risk of shrinkage and better surface finish.
Maximum Warpage	0.283mm	0.125mm	One-point injection results in less warping and higher part flatness.
Runner Weight	3.6359g	2.7129g	One-point injection has a lighter runner weight, less material waste, and lower cost.
Fill Time	0.4383s	0.5373s	Two-point injection fills faster, improving production efficiency.
Weld Line Risk	Possibly High	Possibly Low	One-point injection has fewer weld lines, but two-point injection may result in weld lines due to multiple gates, affecting strength and quality.

Summary:

Advantages of two-point injection: lower injection pressure, lower clamping force, faster filling, and lower risk of shrinkage marks. Suitable for applications requiring high surface quality and minimizing machine load.
Advantages of one-point injection: less warpage, less runner material waste, and slightly lower shrinkage. Suitable for parts requiring high dimensional stability and flatness.
Recommendation: If low pressure and surface quality are prioritized, choose two-point injection; if low warpage and material efficiency are prioritized, choose one-point injection. Actual choice should be weighed based on product requirements.
Please note that above calculations are based on analysis report and equipment list. Adjustments to process parameters may be necessary in actual production. Further verification through trial molding is recommended.
Trial Molding Process Parameter Sheet
1. Single-Point Injection Scheme Parameters:

Parameter Category	Parameter Name	Setting Value	Setting Basis and Notes
Temperature Setting	Melt Temperature	300℃	Based on mold flow analysis report.
Temperature Setting	Mold Temperature	95℃	Based on mold flow analysis report, same for cavity/core sides.
Injection Settings	Injection Time	0.60s	Slightly longer than mold flow filling time (0.537s), providing a safety margin.
V/P Switching Position	Switch from 98% injection stroke to holding pressure. Mold flow analysis switches at approximately 99% volume fill, reserving a 2% buffer.
V/P Switching Position	Injection Speed	60%~70%	Average flow rate of mold flow analysis is approximately 13.4cm/s, corresponding to approximately 10% of machine's maximum injection rate (~210cm³/1.5s=140cm³/s). It is recommended to start debugging from low to medium speed.
Holding Pressure Setting	Holding Pressure	80% of peak filling pressure	Mold flow holding pressure is set to 80% of filling pressure. Upon startup, inject at 100% speed and read peak pressure of first mold (estimated ~70MPa), then use this value as a baseline.
	Holding Pressure Time	10.0s	Strictly follow mold flow analysis process settings.
	Holding Pressure Method	One-stage holding pressure (80%), followed by pressure release after 10 seconds.	Follow holding pressure curve from mold flow analysis.
Cooling and Cycle Time	Cooling Time	20.0s	Strictly follow mold flow analysis process settings.
Cooling and Cycle Time	Total Cycle Time	~31s	Estimated (injection 0.6s + holding pressure 10s + cooling 20s + mold opening/ejection -0.5s).
Key Metering Parameter	Injection Retraction Position (Material Pad)	5mm	Recommended initial setting to ensure there is still material pad after VIP switching to prevent material shortage.
	Buffer volume	5 mm
	Molten material (storage) stroke	~44 mm	Calculation basis: Injection volume 7.22cm3/[Π*(3.5/2)2]=75mm, plus 5mm retraction, totaling approximately 80mm. The storage position can be set to 80mm.

Two-Point Injection Scheme Parameters

Parameter Category	Parameter Name	Setting Value	Setting Basis and Notes
Temperature Setting	Melt Temperature	300℃	Same as "One-Point Injection" scheme.
Temperature Setting	Mold Temperature	95℃	Same as "One-Point Injection" scheme.
Injection Setting	Injection Time	0.48s	Slightly longer than mold flow filling time (0.438s), providing a safety margin.
VP Switching Position	Switching from 98% injection stroke to holding pressure; mold flow analysis switches at approximately 99% volume fill, reserving a 2% buffer.
VP Switching Position	Injection Speed	70%~80%	Mold flow analysis average flow rate is approximately 18.2cm³/s; higher flow rate is required, it is recommended to start debugging from medium to high speed.
Holding Pressure Setting	Holding pressure	80% Filling Peak Pressure	At startup, inject at 100% speed first, read peak pressure of the first mold (estimated ~55MPa), and then use this value as a reference.
	Holding pressure time	10.0s	Strictly follows mold flow analysis process settings.
	Holding pressure method	One-stage holding pressure (80%), followed by pressure release after 10 seconds, following holding pressure curve from mold flow analysis.
Cooling and cycle time	Cooling time	20.0s	Strictly follows mold flow analysis process settings.
Cooling and cycle time	Total cycle time	~31s	Estimated (injection 0.5s + holding pressure 10s + cooling 20s + mold opening/closing ejection -0.5s).
Key metering parameters	Injection retraction position (material pad)	5 mm	Recommended initial setting.
	Buffer amount	5 mm
	Material storage (molten plastic) stroke	-83mm	Calculation basis: Injection volume 7.97cm³/[Π*(3.5/2)²]=83mm, plus injection retraction 5mm, total approximately 88mm. Material storage position can be set to 88mm.

Trial Molding Operation Focus and Comparative Analysis
1. Core Differences and Advantages/Disadvantages
Injection Pressure: Maximum injection pressure required for two-point injection scheme (55.3MPa) is significantly lower than that for the one-point injection scheme (68.9MPa), making it more friendly to mold and machine, which is its main advantage.
Runner Weight: Cold runner of one-point injection scheme is lighter (2.71g), resulting in higher material utilization and lower cost.
Fill Balance: Two-point injection scheme shortens flow path, resulting in faster and more uniform filling, but may introduce more weld lines.
Selection Recommendation: If product has high appearance requirements and no weld lines requiring high strength, two-point injection scheme can be prioritized to reduce injection pressure. If the lowest material cost and a simpler runner system are desired, then one-point injection scheme should be chosen.
1. Trial Molding Start-up Procedure
Step 1: Set all temperatures and allow them to stabilize.
Step 2: Manually inject material into air to observe plasticization and melt quality.
Step 3: Use "staged injection" method, i.e., injecting without holding pressure, to find correct V/P switching point. Increase injection stroke each time until approximately 95% of product is filled; injection stroke for next mold is V/P switching point.
Step 4: Set holding pressure and time, and begin formal production cycle.
1. Key Monitoring Points
Dwell Time: Calculated dwell time for both schemes is approximately 61 seconds, which is within an acceptable range. However, if cycle time is significantly lower than 31 seconds, material storage amount needs to be adjusted to prevent material degradation.
Dimensions and Appearance: Focus on checking shrinkage marks of single-point injection scheme, location and strength of weld lines in two-point injection scheme.
Please bring this parameter sheet to workshop as a benchmark for debugging. Fine-tuning will be required based on results of the first mold in actual production.

Gud Mould Industry Co., Ltd