1. About the company

Our customer is a company of more than 50 years old with a presence in 30 different countries worldwide. They have connections with about 16.000 suppliers in several industries. The project shown in this case study took place in the corporation’s factory in Hungary that works mainly with electronic device manufacturers and automotive OEM and Tier 1 suppliers.

2. Goal

The main goal of the cooperation is to discover the possibilities offered by pressure measurement and to examine in what cases the Cavity Eye system can bring benefits for our customer.

In accordance, for this project with our partner we did not choose the mold that makes the most scrap parts but a relatively well functioning one that needs some optimization. The more concrete goal we set was to reduce cavity pressure, achieve a stable process, process monitoring and automatic scrap separation.

3. Challenge

The chosen 8 cavity mold produces fiberglass filled (PA6 GF50) internal functioning parts. After implementing the sensors and measurement device we examined the pressure curve of the original technology setting used by our customers. It was visible that the cavity pressure is rather high causing more abrasion and load in the mold thus negatively affecting its life time. We also experienced longer filling time and pressure maximum differences that implies cavity imbalance problems. The data analysis also revealed a large varience in dosing and cycle times which confirmed the presense of faulty or worn machine parts.

Figure 1. The part

4. Solution

To avoid the problems above, at first, we aimed to decrease the cavity pressure. We achieved this through several steps:

 - Setting earlier switchover

 - Reducing holding pressure

 - Longer holding time

 - Shorter cooling time

 - Using faster injection speed profile – shorter injection time

When modifying the IMM parameters, we had to pay attention that the pressure integrals must be almost the same before and after optimization. This way, because of the relation between the pressure integral and the product size, we can ensure that the parts manufactured with the modified technology are within the appropriate size range.

While taking all this into account we were able to reduce the maximum pressure from ~700 bar to ~400 bar. At lower pressure the thermal load on the mold is smaller thus reducing the heat-induced deformation. Material fatigue and friction can also be decreased, the latter’s effect is especially important in the case of materials with glass fiber. All these factors can result in longer tool life.

 

Figure 2. Pressure curve before and after optimization

In the next step we optimized the cavity balance by modifying the hot runner temperature setting. This way we were able to significantly decrease not just the filling time differences but also the pressure maximum differences cycle to cycle. The deviation of 74 bar decreased to 47 bar after the optimalization, which means a near 35% change.

Figure 3. Pressure maximum difference before and after optimization

Figure 4. Filling time differences before and after optimization

By processing and analyzing the data provided by Cavity Eye system, it is possible to identify where the faulty factors are in the process. In our case we can see when we examine the dosing and cycle times that was a quite big dispersion in the values which implies instable process. To solve this issue, we suggested to check the condition of screw and barrel. After replacement of the worn-out parts and optimization, the dosing times decreased significantly and became almost the same from cycle to cycle. A quite stable process was achieved

5. Results

Thanks to the optimization, based on cavity pressure measurement the internal pressure maximum was reduced by 300 bar which can result increased tool lifetime. By compensating for the pressure integral loss we increased the holding time, we did not experience any variation in quality or size compared to the previous conditions with the new, optimized technology. The automatic separation of the possible defective parts is ensured with the help of the Cavity Eye system. Due to lower cavity pressure, we could reduce the clamping force from 120t to 80t which resulted in better ventilation, better energy efficiency and lower stress on the mold.

In conclusion pressure measurement has many application possibilities beyond scrap separation. The data provided by the system can be used to optimize processes, analyze errors, and help to prove the need for maintenance or component replacement.