Mold transfer with the Cavity Eye method
-
Company
Our partner is a more than 50 years old company with locations in 30 countries. They have interests in several industries, but their most significant market is OEM and Tier1 suppliers of automotive and electrical industries. The presented project took place at their Hungarian plant.
-
Goal
Our customer’s goal was to reduce the mold transfer time while ensuring constant product quality, properties and dimensions within tolerance limit. To achieve this, they decided to use the Cavity Eye method for mold transfer which based on data gained from pressure measurement system.
-
Challenge
Two molds, one with 2 and the other with 8 cavities, were transferred during the project. Both were used in series production of functional parts. To be able to measure cavity pressure and monitor the conditions inside the mold, both tools were equipped with 2 and 8 Cavity Eye sensors respectively. The 2-cavity mold was transferred between Engel machines with different screw diameters, while the 8-cavity mold was moved from an Engel to Krauss Maffei machine.
The traditional mold transfer done by copying the parameters that were used on the original machine. Despite the same input parameters, it cannot be guaranteed that the same processes will be happening inside the tool on the second machine because of different machine conditions, types, model or other circumstances. This can result in different product quality, properties or dimensions. To find the right parameter combinations to reach the suitable product quality, the changes in the setting often not data-based or even made by random experimentation. This usually leads to several iteration steps which means several rounds of mold trial, sampling, measuring, thus resulting in significant costs and time loss.
1. figure Cost factors of mold transfer
-
Solution
Our solution is to ensure the reproducibility of the process independently of time and place. To achieve this, we need to know what is happening inside the mold.
With the Cavity Eye method, we use pressure measurement to monitor the processes during injection molding. This way we will have the data required to make the right decisions to set the right technology
Mold transfer process with Cavity Eye method:
- Production start with the usual settings on the original machine
- Data collection during production
- Record cavity pressure curve with Cavity Eye system
- Measure tool surface temperature
- Measure melt temperature
- Take samples to check product dimensions
- Tool change and production start on the second machine
- Use the same as on the original machine: movements, temperatures, dosing parameters
- Set injection parameters according to the pressure curves on the original machine
- Monitor and control production
- Measure tool surface and melt temperature
- Adjust machine settings to match the original pressure
- Take samples for measurement
We can conclude that the goal was to replicate the pressure curve not the parameters.
Following the described transfer process, we can see that after the fine tuning of the machine parameters the pressure curves on the second machine are almost identical to the original in the case of the two-cavity mold. Due to the different machine types, there are significant differences in the set process parameter values., but the product quality is constant.
.
2. figure The 2 cavity mold’s pressure curve before (dark blue lines) and after (orange lines) transfer
The transfer of the 8-cavity mold from the Engel to Krauss Maffei machine was also done according to the Cavity Eye method. It is easy to see the changes in the parameter values here as well. Because the same switchover could not be achieved on the second machine, we faced some difficulties in reproducing the pressure curves. Still, we managed to set up a stable process as well.
3. figure The 8 cavity mold’s pressure curve before (dark blue lines) and after (orange lines) transfer
-
Result
In conclusion, both mold transfers were successful and took considerably less time than the traditional way. There was no significant dimension difference between the products made on the original and the new machines and all the dimensions were inside the tolerance range. Checking the dimensions confirmed what we saw on the pressure curves. In case of the two-cavity tool, where the reproduction of the pressure curves was almost perfect, the biggest difference in dimensions was 0,03%..
At the 8-cavity mold, the new machine was not able to reach the same injection speed and the switchover was also different, so the pressure curves could not be perfectly reproduced. Because of this we expected a little bit bigger deviation, and the measurements confirmed it. The maximum difference in product dimensions was 0,28%, which was still easily inside tolerance.
Our partner successfully achieved their goal with the Cavity Eye method. The mold transfer time was significantly reduced. They could finish both transfer in one shift while ensuring the constant good product quality.