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Currently, the squeegee used for screen printing is mainly made of urethane rubber.
Urethane rubber is the most suitable material for squeegees because it is resistant to solvents and hard to wear.
Well, there are three ways to make this urethane squeegee.
There is no big difference in appearance, but there is a difference in characteristics depending on how it is made.
This time, I summarized how to make a urethane squeegee and its characteristics.

・ Compression molding method
This manufacturing method is similar to the method of making taiyaki.
The rubber raw material is a resin that feels just like clay. This is mixed with compounding agents such as a curing agent and put into two upper and lower molds, and the two molds are put together and heated and pressed with a press machine. Raw materials for rubber harden into urethane rubber through a chemical reaction with a hardening agent. Heating is also called “baking”, so it is the same as baking “taiyaki”. “Taiyaki” is often grilled with a gas fire, but rubber is grilled with an electric heater.
This method is not limited to urethane rubber, but is also used for synthetic rubber and silicone rubber.
However, it is difficult to make a long squeegee with this method. To make a long squeegee, you need a large die and a large press to press it. Also, as the press machine becomes larger, it becomes difficult to press uniformly, making it difficult to create stable squeegee performance.
Therefore, it is no longer used for anything other than the production of synthetic rubber squeegees.

・ Casting method
The place where the mold is used is the same as the compression molding method.
However, the state of the source material is different. The raw material is liquid.
First, a liquid rubber raw material is mixed with a curing agent and put into a mold. The big difference from the compression method is that a press is not required. Put the raw material into the mold and heat it in the oven. A liquid rubber raw material hardens into urethane rubber through a chemical reaction with a curing agent. I think you can imagine the feeling of making pudding or tofu. The raw material is liquid, but when hardened, a hard squeegee with a hardness of 90 degrees can be made.
Long squeegees can be manufactured because a large press is not required. Various shapes of squeegees can be made depending on the mold. In addition, liquid materials have the characteristic of being easy to handle. Currently, it is the most common method in the production of urethane rubber.
However, since it takes time to make a squeegee, the price is high, but by using a mold, you can make a high quality squeegee.

・ Centrifugal method
It is a method using a rotating drum. Think of the rotating drum as a large drum-type washing machine.
A liquid raw material is put in this and it is rotated at high speed. I'm sure you've seen the laundry stuck to the laundry after dehydration in the washing machine. Similarly, when raw materials are put into a drum and rotated, the raw materials stick to the surface of the drum. At this time, when heated, the raw materials on the drum surface harden due to a chemical reaction, creating a large cylinder. Cut this to make a squeegee.
With this method, many squeegees can be made at once, so the manufacturing cost can be reduced. Also, no mold is required. Furthermore, you can easily make squeegees of various sizes by changing the cut dimensions.
Increasing the cutting accuracy eliminates the need for squeegee polishing at the beginning of use. For example, it is effective when you want to make the squeegee disposable.
However, the squeegee remains slightly distorted compared to the method using a mold.The squeegee curls slightly because it is cut from a cylindrical object. That said, recent improvements in manufacturing conditions do not affect printing.

In this way, the performance and price of the squeegee change depending on how the squeegee is made. When evaluating squeegees, it is important to evaluate not only the hardness and dimensions, but also the differences in how they are made.

 

· bonus 
Will a soft urethane squeegee (e.g. hardness 60 degrees) melt at high temperatures? I've been asked.
There are two types of urethane: thermosetting and thermoplastic. Thermoplastics are what we call plastics. Plastic products will melt at high temperatures. Similarly, thermoplastic urethane melts at high temperatures.
However, the urethane rubber used for the squeegee is thermosetting urethane. Therefore, even if the squeegee is soft, it will not melt at high temperatures.