Automobile parts

At the beginning of last year, we received an urgent technical support request from a Tier 1 supplier of a joint venture brand. They brought us a set of air conditioning valve molds that had been revised three times but still failed to pass PPAP.

This valve is the core moving part of the automotive air conditioning box assembly， with a requirement for flatness ≤ 0.15mm and uniform gap between the edge and the housing. Otherwise， it would cause air leakage， abnormal noise， and even valve jamming. However， the existing molds of the customer had two major problems：

1. Severe warping deformation： The middle part of the long side of the valve arches upwards by 0.35 - 0.50mm， far exceeding the tolerance range.

2. Radiation spots around the nozzle： Not only affecting the appearance， but also becoming a stress concentration point， causing micro cracks during assembly.

The customer had tried adding spacers， extending cooling time， and adjusting the holding pressure， but with little effect. Each mold repair cost approximately 38，000 yuan， resulting in a cumulative loss of over 110，000 yuan， and the project faced the risk of being cancelled by the main manufacturer.

After we took over， we did not rush to modify the mold but initiated a closed-loop process of "diagnosis - simulation - optimization - verification".

Step 1： CAE mold flow analysis - find the real root cause

We imported the 3D data of the customer's original mold into the Moldflow software for full model analysis. The results revealed three hidden fundamental reasons：

• Inappropriate nozzle position： The original used two-point side nozzles， located on both sides of the valve shaft. The melt converged to form a "V-shaped weld line" passing through the entire functional area center， and the end filling pressure was insufficient， resulting in low density and uneven shrinkage at the far end.

• Unbalanced cooling waterway distribution： Due to structural limitations in the central large hollow area of the valve， no cooling waterway was arranged， with a temperature difference of 28℃. The thick-walled area (the shaft seat) overheated， while the thin-walled area (the blades) cooled too much. This temperature difference directly converted into internal stress and warping.

• Low efficiency of pressure transmission： Due to the early solidification of the nozzle， the pressure could not be effectively transmitted to the far end of the product， resulting in a volume shrinkage rate difference of up to 1.8% in the length direction.

Conclusion： This is not a problem that can be solved by trimming the flange or adding spacers. It is necessary to redesign the pouring system and cooling scheme.

Step 2： Targeted optimization - starting from the mold structure

Based on the analysis results， we proposed a "trinity" modification plan：

1. Pouring system reconstruction： From two-point side nozzles to a one-point fan-shaped connect nozzle

• We moved the nozzle position from the side to the bottom of the blind hole on the valve shaft center， using a fan-shaped nozzle.

• Principle： The melt fills uniformly from the center to the periphery， the weld line is pushed to the subsequent processing area at the edge， and the flow balance is improved by 40%.

2. Forming cooling waterway and adding sensors

• For areas where straight holes cannot be drilled， we used 3D printing inserts to make the forming waterway， making the cooling channel closely adhere to the complex surface of the product.

• Add pressure/temperature sensors in the mold cavity (especially at the junction of the thick-walled area of the shaft and the thin-walled area of the blades) to monitor the cooling status of the plastic in the mold cavity in real time.

• Effect： The maximum temperature difference from the mold temperature dropped from 28℃ to within 6℃， and the cooling time was shortened from 32 seconds to 22 seconds.

3. Re-matching process parameters

• With the optimized curve given by the mold flow analysis， we changed the holding pressure from "single-stage holding" to "stepwise decreasing holding"， and achieved precise control of the holding switching point with the feedback of sensor signals.

Step 3： Result presentation - an "unexpectedly cost-saving" "win-win-win"

After the new plan was implemented， the mold achieved satisfactory results in the first trial run：

• Quality improvement: The warpage deformation has been reduced from 0.50mm to 0.08mm, successfully meeting the size requirements of the original manufacturer; the welding line has been moved to the non-functional area, and there are no any defects in the appearance.

• Production efficiency improvement: The cooling time has been shortened by 31%, the forming cycle has been reduced from 55 seconds to 38 seconds, and the single machine daily output has increased by approximately 30%.

• Cost reduction: The original mold had a scrap rate of about 18% for each product due to warping (mainly due to inability to flatten), while after optimization, the scrap rate has dropped to below 1%. Comprehensive calculation shows that the cost per product has decreased by more than 30%. Based on an annual production of 500,000 pieces, the company saved over 800,000 yuan for the customers that year. 

Customer feedback

The project manager of this Tier 1 supplier wrote in the acceptance report: "Haina Mold Factory not only solved the warping problem that had troubled us for half a year, but more importantly, they did not follow the old path of 'testing the mold first'. Instead, they used scientific mold flow analysis to find the root cause. This is one of the most professional automotive mold engineering services we have ever seen."

Summary

This case once again demonstrates that the core of reducing the cost of molds lies not in cutting materials or lowering processing fees, but in eliminating defects fundamentally, shortening the cycle, and improving the yield through CAE simulation, intelligent sensing and lean design.

Haina will also continuously enhance its professional knowledge to be responsible for customers and products. For automotive precision functional parts, a one-time optimization of the mold often brings far greater than expected long-term benefits. 

If you have any questions about mold processing techniques, please feel free to contact us. Contact - hainamould Mould Company Limted