Term of the Week: Optical Encoders

jerid hill

Throughout the years, Jerid Hill has written articles, blog and forum postings, created informative videos and taken the time to speak to many direct-to-garment (D2) users to assist in moving the D2 industry forward. Hill has been a thought leader in the D2 industry pursuing new technologies for better quality and output. In 2018, BelQuette merged with the ColDesi group of companies in Tampa and Jerid now serves at DTG Product Manager for ColDesi Inc. You can rely on Jerid’s unique perspective in the garment industry, focusing on the end user’s experience. He has extensive technical knowledge of D2 printing as well as details and tips for preparing artwork, pre-treating garments, expert level tips, and best overall practices for the garment printing realm.

Often, getting back to the basics in any given situation will provide you with a solution to problems. The direct-to-garment (D2) market is no different. Through the years, there have been significant changes in printing equipment, but the basics of D2 have remained the same. Understanding how your printer functions is a crucial element in keeping it running at its best, and a printer's encoder is one element you don't hear about often. 

There are many types of encoders, but with D2 systems, there are usually two optical encoders used. An optical encoder is either a strip or a disc that appears gray in color. The coloration comes from printing thin black lines in a row, usually beginning at 1,000 or more across a span of 1". The former is typically called an encoder strip, encoder scale, or linear encoder. This is the strip that's behind the print head carriage and runs left to right. There is an encoder sensor behind the carriage that reads these lines so that it knows the position of the head at all times and when to fire a nozzle.

A dirty or scratched linear encoder will cause problems during printing. These problems could include unwanted lines printed, misregistered prints, the print head carriage traveling further than its allowed distance, and other strange issues. In these cases, the system is not able to understand where the positioning of the head is and where the nozzles need to fire due to a miscount of these lines. Cleaning this strip off throughout routine maintenance procedures will prevent many of these types of issues from occurring.

The image on the left shows a linear encoder while the image on the right is a rotary encoder, both of which can be found in D2 printers. 

On some machines, the second optical encoder may require attention, while others are inaccessible or even absent. The second optical encoder, which is almost always a disc, is most often hidden and not exposed, so cleaning is not necessary. If it can be seen, then cleaning is essential. The linear encoder effects prints from left to right, whereas the rotary encoder effects prints from top to bottom. If there is an inconsistency with prints in this manner and you can see the rotary encoder, cleaning it off with a lint-free cloth and isopropyl alcohol should fix the issue. If it doesn't, contact the manufacturer or distributor for additional assistance.