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Squeegees

Squeegees are made from 3 basic types of materials: Rubber, Neoprene, and Polyurethane. At Discount Screen Supply We offer all Polyurethane squeegees, they are the most common type used in the screen print industry today, while slightly more expensive, they offer better chemical and abrasion resistance than other materials on the market.


Durometer:

When selecting a Squeegee, the first task is to determine your desired durometer, or hardness. The durometer is the value that reflects the physical hardness of the Squeegee material. The Squeegee durometer values from 50A to 95A. This is measured by a durometer gauge, and measured based on standards established by ASTM procedures. (American Standard Testing materials) . For the sake of simplicity, we will call soft - 60A, medium - 70A, and 80A - a hard Squeegee, and 90A -extra hard. Most manufacturers of Polyurethane Squeegees color-code their Squeegees based on the hardness of the material. By color-coding, it makes the Squeegee easier to define for a particular job. For Example, one manufacturer has a color scheme of 60A - red, 70A green, and 80A blue. Others use an orange, blue, and red color-code system. Unfortunately, there aren't any standards for colors. The printer knows if they want a heavy ink deposit, they should use a 60 durometer, but it could be red or orange, or even another color.


Squeegee Profile:

A screen printer can purchase a squeegee with many different profiles. The profile of the Squeegee determines the thickness of the ink deposit laid down, and the effectiveness of the Squeegee on different substrates. See chart for enclosed profiles. Available edge profiles include a square edge, a square edge with rounded corners, a round edge, a double-sided beveled edge, and a single beveled edge. Squeegees with a square edge are the most common, and mainly used on cylinder, textile, and manual presses. Rounded Squeegees are generally limited to the textile industry, and are used when a very heavy deposit is required. Beveled Blades are typically used for printing rounded surfaces where fine definition is required. While double sided beveled blades are more efficient on high-speed automatic machines. Single Beveled blades produce excellent results when printing heavy solids.

Some printers will round the Squeeegee with a small radius to get more ink deposit. There are tools available or grinding wheels for putting different radiuses/profiles on Squeegees. However, the most effective, and the best shearing edge is still a 90 degree or a straight edge profile. The reason being is the following: Anytime you round a squeegee or put a tapered edge on it, the the blade looses it sharpeness or cutting edge. A rounded Squeegee isn't really shearing or transferring the ink, but rather the blade is now spearing the ink across the screen. A good test of the principle is to look at the screen when the blade is done printing, Is there any ink left in the screen? There are many different parameters that can changed in the printing process to achieve the same results: ink viscosity, mesh count, mesh tension, & off contact. I am firm believer that a Squeegee job is to transfer the ink, and the best angle of attack is a 90 degree edge. If you want to lay an adhesive down, then I will agree a rounded edge may be the right choice.

Maintenance & Storage:

Proper Squeegee maintenance is vital to producing quality printed images. For example, when printing with aggressive inks, each side of the blade shouldn't be used for more than 4 hours. Implementing a rotation schedule with the blades will dramatically increase the overall life of a Squeegee. By using the Squeegee for 4 hours at a time, and then replacing with a new one, the blade will last much longer. Squeegees are like car tires. If you rotate them every 5000 miles or 4 hours, they will last longer, and not develop a curl or swell to them. Do not use the Squeegee till Failure. This will cause problems with the blade when re-sharpening. Excessive swelling and softening can result from printing with the same Squeegee edge for an excessive period of time. If ink residue begins to build up on the inside of the screen, the Squeegee should be replaced with a new one. A used Squeegee will recover after 24 to 48 hrs, and can be resharpened and returned to the printing press. The Squeegees should be laid out flat when not in use. Polyurethane Squeegees should always be stored in a dry and relatively cool area. (60 to 70 degrees F). The material should be laid out flat to eliminate any curl to the Squeegee rubber. Manufacturers and distributors ship the material in coil form for shipping purposes only. You should always lie out flat as soon as the material is received into your facility. Occasionally, Squeegees stored below 60 F will increase in hardness. This will not affect the performance of the rubber, but it will affect the ink deposit performance of the blade. It is a good idea to test Squeegees with a durometer gauge during a long production run. Some materials will soften when exposed to solvents for a long period of time. If the rubber softens to more than 5 to 7 points, it is recommended that you replace the material.

Squeegee Innovations:

One of the biggest innovations in the past 25 years is the multi durometer blades. The reason stems from the increase in the need for better print quality. More and more printers are being pushed to the upper limits of Screen printing, and thus the increase in the number of Squeegee innovations to the market place. Referencing back to the durometer section of this article, the most popular blade regardless of industry is the 70 durometer, or medium hardness blade. The reason is that a 70 durometer is in the middle of the road: (not soft, not hard). However, when problems arise on a press, most printers will increase the Squeegee pressure to get more ink lay down. The increased pressure on the blade will cause the blade to bend or roll over. Therefore, by using a dual durometer stacked, dual durometer vertical, triple durometer, or a fiberglass composite Squeegee, the printer can get better print quality by using a blade that is supported right down to the edge of the Squeegee. Multi-durometer Squeegees use a softer material on the printing edge, and then use a harder material or fiberglass product to give the blade some rigidity.