For stable molding to make quality products, we require a molding machine, a mold, and durable resin raw materials. Most of the causes of defects can figure out the errors with the mold and the molding machine, but most workers will not be recognized the flaws if the resin’s condition is not durable. For example, if the resin’s moisture content becomes unstable, the melt viscosity becomes unstable. Also, gas is generated, and the silver streak is generated. As a result, the molding conditions must be changed.

The only thing that plastic auxiliary equipment can do is stabilize the moisture level and stably supply materials with less dust, which is the most important thing.

So what are the factors that make it unstable?

The first is the storage condition of raw material tanks, etc. This is a part that we have often overlooked.

The second is the conveying method from the dryer to the molding machine. Moisture may be absorbed immediately after conveying materials to use outside air.

The third is the residual materials inside of the molding machine or the piping.

The sealed raw material bag is stored with a constant moisture level. The condition will change immediately after opening. The graph is expressed with the image of nylon, which has high hygroscopicity, but other materials are also the same. It will change significantly depending on the environment in which it is placed.

The dew point goes up and down means that the content of caution changes depending on whether it is cold or hot. Also, if the dew point is close to 20 ° C, it will absorb moisture shortly.

What changes when the initial moisture is different is that the drying time and the reached moisture content will be change. A dryer is a device that can remove a certain amount of water in a certain time.

In other words, if the condition of the feeding material changes, the moisture content of the discharged material will change. Therefore, it may be one of the causes that silver streak suddenly occurs during continuous production, and the conditions become unstable. Excessive moisture causes silver streak, which is a problem, but if it is dried too much, the melt viscosity will increase, causing short shots and gas generation.

What is happening on the molding machine?

It cannot be dried to 0ppm with a dryer.

When you enter the barrel, which is hotter than the dryer, drying will be accelerated.

Then, the moisture that has no escape is exhausted from the material supply port.

In addition, conveying materials with outside air or undried air may cause moisture absorption, and it may stay in the piping and absorb moisture when it cools.

Furthermore, suppose materials stay in the molding machine hopper for a long time. In that case, they will cool down and be added alternately with the material immediately after drying, which is one of the causes of unstable melt viscosity.

If the initial moisture is not controlled, the condition of the material discharged from the dryer will change significantly. If the retention is long, the moisture content will change gradually.

Therefore, Kawata has some suggestions.

Next, there is the DO-series as a representative device of M-stabilizer technology.

Dry with nitrogen in a closed system.

Regarding nitrogen, we will generate nitrogen air inside the equipment by providing air from the customer.

The big difference from the conventional nitrogen dryer is that the drying air’s nitrogen concentration is about 99%.

Besides, by using a closed nitrogen purge tank as the raw material tank, the condition does not change even if it is stored and conveyed.