Help you select the mold of PA66 thermal break strips

Every thermal break strip manufacturer wants to provide PA66 thermal break strips with perfect size and high quality. So how can we produce PA66 thermal break strips with perfect sizes? Mold places a very important role.  
The mold determines the cavity number, the PA66 strip shape and the PA66 strip sizes.   

When you choose the mold, the first factor you care about must be the mold material.
After years of trial and improvement, we have tested various materials and hardness of mold plates, and finally summarized the following points based on actual usage and customer feedback:
If the mold material is too soft, it is not easy to crack and the cutting surface has a high smoothness. However, it is easy to wear and tear. After using for a period of time, the produced strips will exceed the tolerance.
If the mold material is too hard, it is easy to crack in comparison. The cutting surface is not extremely smooth, but it is wear-resistant and has a long usable cycle.
If you want to know the most suitable hardness, please contact our sales team.

The second factor that affects the mold quality is the cutting way of the mold.
For other companies, they prefer use medium-speed wire cutting machine(also known as WEDM-MS) to process the cold plate. The electrode wire material of WEDM-MS is molybdenum wire, and it is recycling, so the electrode wire continues to wear during processing, result in the machining accuracy is around 0.01-0.02mm. The surface roughness of Ra is around 1.0-1.7μm.
The cutting surface of this kind of mold is not smooth enough, so there is a lot of resistance when starting up. And the production speed will be slow, it means the yield is low. Producing the same quantity of thermal break strips takes longer time, which invisibly increases production costs. Besides, the strip surface in the early stage will be relatively rough.

For our company, we use low-speed wire cutting machine(also known as WEDM-LS) to process the cold plate. The electrode wire material of WEDM-LS is copper wire, and it is not recycled, which greatly improves the machining accuracy to be 0.002-0.01mm. The surface roughness of Ra is around 0.05-0.2μm. With WEDM-LS, the cutting surface is smooth and flat, which is close to the grinding level. So it will be more easier for customer to produce strips with mold processed by WEDM-LS. And the produced strips in the early stage can have a beautiful surface and a high yield.  

The third factor that affects the mold quality and PA66 strip production is the design of conical degree.
If the conical degree of cold plate is too large, then the pressure of the mold cavity on the strip will be too small. It will cause that the strip’s density being too low, result in not bright strip surface.
If the conical degree of cold plate is too small, then the resistance between the strip and the mold cavity is too strong, therefore not all strips can come out from each cavity. Even if strips are formed, their edges and corners are likely to being incomplete.  

Besides, molds with different shapes have different levels of conical degree. For molds with complex shapes, the conical degree of different parts are also different.
How to choose a suitable conical degree depends on years of production experience. To achieve a suitable conical degree, modifications may be required twice or three times based on test results.

Last but not least, the control ability of size accuracy is also a key factor affect the mold quality.
Every mold supplier can cut any shape of the mold. But in our eyes, cutting mold doesn’t mean success. We only consider the mold to be qualified when qualified PA66 strips are produced through this mold. There are 4 factors affect the strip sizes:

1.Shrinkage of raw material.
Our factory has been doing research and development of raw materials from the beginning, so we have a certain understanding of the shrinkage rates of raw materials in different formulations. When cutting the mold, the shrinkage of the raw material must be taken into consideration.

2.The temperature of the cooling water.
The room temperature is different in winter and summer, so does the water temperature. There will be seasonal errors in strip sizes. To reduce seasonal errors, we suggest using a temperature controller to set the water temperature at 25±5°C. For PA strips with special shapes or high demands on sizes should be produced in a constant temperature workshop.

3.Mold production for complex strips
For some complex shapes, firstly we will make one set of test mold. According to the test results, we may scrap this test mold, then make a new set of mold. Sometimes we may even need to make two sets of test mold. This also means that our production costs will increase in order to increase the qualification rate of the strip sizes.
In China, mold suppliers usually only guarantee 1-2 main dimensions. But we can guarantee most important dimensions.

4.Mold test
After the mold is produced, we will test the mold. And we will provide a detailed mold testing report to the customer based on our company's high delivery standards. Only when the strip sizes are qualified, we think the mold is qualified.

When customers review mold quotes, they usually just see the mold price and not the elements that make up the mold price.
However, these elements are the basic of the mold qualification. So we cannot choose molds only based on mold price.