Chapter 15
How To Set Off Contact & Using Pallet Adhesives
An important setting on your manual rotary textile screen printing press is the off contact, also known as snap or snap off. This is defined as the distance between the screen and the substrate before printing, when the screen is lowered into its printing position.
This off contact distance prevents the screen from being in direct contact with the substrate before the printing action avoiding smearing or ghosting. It also allows the tightly stretched mesh to rise from the substrate immediately following the squeegee stroke. This snap off action also helps improve the shear factor between squeegee, ink, and the substrate creating an even more consistent ink deposit.
Proper off contact settings are normally higher with manual textile presses but overall lower off contact settings will reduce distortion and improve registration. The ideal off contact distance is determined by screen dimensions, printed image, mesh tension, and ink characteristics. The desired print result may also be a factor.
Off contact distance is directly related to mesh tension and snap off motion. If any one of the three is altered, the others must be adjusted as well. Squeegee stroke speeds can also affect the drag between the squeegee and the screen depending on the off contact distance causing registration problems.
Other factors determining off contact distance are:
The type and thickness of the substrate.
Type of frame, metal, or wood.
The give or potential movement of the substrate such as fleece.
Wood frames in general have less tension than that of metal frames and require a greater off contact distance. Personal preference will also be something to consider when setting off contact. Different printers will suggest different distances based on their experiences. Distances can range from as little as a 1/16". Ideally speaking 1/16th of an inch is ideal in most cases.
Because off contact is the distance between the substrate and the screen, it must be set with the intended substrate to be printed in place on the pallet. This will ensure that when you engage in the actual print run the off contact will be correct for that product. There are many different methods and even tools to set off contact on manual textile presses.
Whatever method you use, you should keep in mind many presses are old and are unable to hold a screen parallel to the pallet arm due to give in the equipment. If you want to use a piece of a specific thickness Plexiglas or some wood board to set off contact and make the screen parallel to the pallet, add some distance to the end closest to the printer to compensate for armature sag. This added incline will depend on your press arm's ability to hold the screen in a fixed position consistently.
All your pallets must be level before you can effectively set your off contact. Each print head must have the off contact set individually. The result of setting off contact properly is to have the screen be parallel to the pallet at a set distance when in the lowered position.
Having your manual textile screen printing press assembled and adjusted properly to manufactures specifications is a great place to start with any press. All your press settings and functions will affect the quality and ability of your printing. It is also important to note that newer manual rotary textile presses like the Ranar Vista and Elite have a secondary off contact on the pallet arm which makes it very easy to set.
There is another setting on the print head called screen angle or warp that is worth mentioning. This setting will compensate for screen frames that are not quite perfectly parallel or square. It is often used in conjunction with off contact settings to be sure the screen is parallel to the pallet. When the aluminum frames are made for screens, they are extruded and then cut and welded together. Many times, the rectangular pieces are not exactly parallel to one another. This means that when you mount the screen on one end it may tilt upward and when you mount it on the other end it could tilt down. Check with your equipment manufacturer to find out if you have this adjustment and how to set it.
VIDEO: Initial Set Up With Off Contact And Screen Angle
VIDEO: Using Off Contact On The Press
VIDEO: Ranar Elite Rotary Press Off Contact Settings Are Easy As Pie!
VIDEO: How Much off Contact Is Too Much?
Pallet Adhesives For Screen Printing
Pallet adhesives are used on manual rotary screen printing presses as well as other types of presses to hold the garment in a fixed position during printing. Keeping the garment securely affixed to the pallet during printing will improve print quality as well as registration. In fact, it is impossible to print a multi colored job without pallet adhesive to hold the shirt to the printing pallet. There are 3 basic types of pallet adhesives which are; spray tacks, bulk adhesives, and adhesive paper or sheets.
Which type of pallet adhesive you choose to use will really depend on the quantity of printing you are doing. For medium to high quantity printing, spray tacks are easy to use and cost effective. For very high volume printing in mass production situations a bulk adhesive will be much more economically practical. And finally for the lower end screen printer who is doing very low quantity printing, an adhesive paper roll or sheet may work just fine.
Any one of the 3 basic types of pallet adhesives may be used for any volume of printing. In the end it will come down to the preference of the printer and shop owner.
The following is a brief description of each of the types of screen printing pallet adhesives and their usages:
Aerosol Spray Tacks - These are probably the most common of all pallet adhesives because they are very easy to use and store. The product will last forever inside the can and may be used efficiently in low quantity printing situations as well as high quantity printing. Aerosol spray tacks are also very versatile in that they come in a few different formulas which are specifically designed for certain printing applications.
There are flash tacks designed to be used with a flash cure unit and resist heat. Spray tacks also come in a web type spray which is well suited for fleece such as hoodies or sweatshirts. The standard type of aerosol spray tack is a mist. These products most often come in a metal aerosol can containing about 14 to 16 ounces of product. The biggest drawback is the over spray of the adhesive product in usage.
VIDEO: Aerosol Spray Adhesives And Screen Openers
Spray adhesive mist - This is used for all knit fabrics that will not be flash cured on press. Any multi-color printing or jobs where you will print the design twice for any reason will require a pallet adhesive.
Spray adhesive flash mist - This is used for all knit fabrics that will be flash cured on press. Anytime you want to print a screen, flash, and print again you will need this pallet adhesive.
Spay adhesive web tack - This is used for all fleeces including but not limited to hoodies, sweat pants, and sweatshirts. Again, this product is intended for screen printing without using the flash cure on press.
Spray adhesive flash web tack - This is used for all fleeces including but not limited to hoodies, sweat pants, and sweatshirts. This product however is intended for screen printing when using the flash cure on press.
Screen opener - This is NOT an adhesive but it is an aerosol so it is included here. Screen opener is used to remove stubborn clogs on press. It is great at removing stains from mesh and clearing clogs in the stencil.
VIDEO: How To Use Screen Opener For Clogs On Press
Bulk Pallet Adhesives - These pallet adhesives are most often liquids of various thicknesses that are intended to either be manually applied to the pallet or sprayed onto the pallet using a compressed air delivery system. Manual printing applications may be done by brush and bulk applications on automatic presses are often done by a pneumatic system in which compressed air is used as the propellant.
These may also come in a variety of formulas depending on the manufacturer. This type of adhesive will often come in quarts, gallons and five gallon containers. The biggest drawback is the over spray of the adhesive product in usage when applied by compressed air. When applied by hand with a brush or spreader, there is no over spray to be concerned with. many people chose this method to keep the shop and equipment cleaner while also reducing breathable airborne contaminants.
Paper Roll or Sheet Adhesives - This is a type of pallet adhesive that is like pallet tape but it has adhesive on both sides. It is much like double sided or double stick tape. It may come in pre-cut sheets as well as rolls. The adhesive poses application and storage challenges. It is not the easiest to apply and it is not the best as far as storage longevity is concerned.
This pallet adhesive may also become so fixed to the pallet that it can become very difficult to remove and replace. Much like using pallet tape, this adhesive is best when replaced on a regular schedule rather than waiting until it loses all its stickiness.
VIDEO: How To Use Pallet Tape
For beginners and intermediates aerosol spray tacks are recommended for their long shelf life and ease of use. They are versatile and cost effective when used properly. The only drawback to aerosol spray tacks is that there is an over spray that may build up on the press itself and any closely surrounding items too.
Never keep screens and other items that need to remain clean near the pallet or press you are using spray tacks on. The over spray will not only build up on the press itself but it will also collect dust and dirt. Remember, it is important to keep your rotary screen printing press clean and well lubricated for best performance.