Hot off the press: how load cells keep printing presses rolling
A few years back, business leaders went crazy for the concept of the ‘paperless office’ or indeed, a Utopian ‘paperless world’. While it’s certainly true we all print out information a lot less (when did you last print an email?), it’s also true that we still need printed items, from books and newspapers, to food packaging and information leaflets. Even the much-touted COVID vaccination ‘passport’ cannot be entirely app-based, as it discriminates against those without smart phones (and those with smart phones but flat batteries!).
Keep ’em rolling
Load cells have been helping keeping printing presses running for decades, from the massive rolling sheets of newsprint to the digital presses producing full colour takeaway menus. The key is maintaining the correct tension in the material being printed. Accurate tension control reduces waste and printing press downtimes, and resolves issues such as:
- Out of registration printing (misalignment)
- Web breaks
- Stretching
- Coating inconsistencies
Load cells sit within the system to ensure tension is maintained, enabling presses to run at optimum speed and be varied for different applications and materials.
All lined up
The whole point of printing information is that it must be clearly legible. Any smudges, smears, or misalignments will render the printed item useless. Load cells help ensure the quality and clarity of printing on almost any material by regulating the amount of force the printer applies to the materials in question. This is particularly crucial when printing on something as thin as shrink wrap. Too much pressure, and the film could tear or break. Too little, and the text/image might be muddy, incomplete or misaligned.
As an article in FLEXO magazine (for flexographic printers, press manufacturers, and premedia service providers) says:
“Accurate tension control is important in any web application, including flexographic printing, where registration, print quality and speed are vital to making the best product as efficiently as possible. In the past, manual systems required the operator to continually decrease the output as the roll got smaller. Advances in tension control, like automatic open loop systems … have freed the operator.”
Dancers and load cells
Dancer systems have traditionally helped maintain accurate tension control through positive feedback. This is particularly effective when the roll of substrate being printed on may be “out-of-round”, i,e, got a flat spot or uneven from top to bottom. (For a real world examples of this, check out your next nine pack of loo rolls!)
As Flexo mag explains:
“Today’s load cell controls can continually monitor the frequency of the flat spot on an unwind and adjust the output as it is about to happen rather than always chasing the velocity change, eliminating the need for expensive, large and difficult-to-design dancer control systems.”
Variable tensions
Not every part of the printing process requires the sam tension. As Packaging Impressions magazine says:
“The web (material) must maintain an optimum tension as it passes through various points in the process. And because processes vary, multiple tension control options exist to fit the needs of any application… For example, the tension level needed in unwinding a web will usually differ from the tension level needed as the web passes through the press.”
Load cells can signal to a controller unit when the tension is not at the optimum level, allowing the controller to adjust accordingly. As the magazine explains:
“Controllers can be particularly helpful in a dynamic tension zone such as an unwind, as they help ensure constant tension as the reducing size of the roll will naturally cause tension fluctuation..”
Tighter tolerances = more opportunities
The more accurate a press can be in terms of tension, the more opportunities it presents to the business owner. The ability to print onto a wide variety of materials will increase the profitability of each machine, reducing downtime.
“The ability to produce web to tighter tolerances minimizes the costs associated with nonconforming web. It also increases the web producer’s accessible market to include products with tighter tolerance requirements.”
Looking for load cells for perfect printing?
Call us to discuss your requirements, including load cell replacements, calibration and upgrades. Call us too if you are an OEM and need specific load cells for a future product or system. We design and manufacture our own load cells right here in the UK, reducing development times and ensuring speedy delivery of in-stock items. (So no worries about load cells stuck in the Suez Canal or waiting for a container in Asia.)
