What is the appropriate curing speed for hot melt adhesive particles? A tutoring printing factory reduced the scrap rate from 6% to 0.8%

Direct answer:Hot melt adhesive pelletsThere is no standard answer to ‘the faster the better’ for the curing speed of. Book and magazine packaging usually requires an opening time of 3-8 seconds and a complete curing time of 10-20 seconds; Sealing and pressing require 1-3 seconds for shaping. Curing too quickly, the glue has not yet wetted the paper before it forms a crust; Curing is too slow, and the book is still shifting after pressing. The appropriate range should be pushed backwards with the machine speed.

The real process of a tutoring printing factory

A certain educational printing factory in Guangdong received a batch of 280000 workbook orders during the peak season of autumn last year, using an automatic gluing line with a machine speed of 4500 copies per hour. On the third day of online launch, problems began to arise: about 6% of the books were found to have partial empty glue during random inspections, and the middle section of the spine would open easily when bent. The first reaction of the workshop was that the amount of glue was not enough, so the amount of glue applied was increased by 15%. As a result, the overflow glue stained the pages of the book, and the scrap rate did not decrease but instead increased.

Troubleshooting: The problem lies in the mismatch between curing speed and machine speed

The technicians broke down the time nodes of the entire line and calculated them:

• Milling back to glue: 1.2 seconds
• Glue up to clamping and pressing: 4.6 seconds
• Press and hold: 6 seconds

The problem lies in the 4.6 seconds from “gluing to pressing”. The opening time of the adhesive particles they used at that time was only about 3 seconds. By the time the cover was covered, the surface of the adhesive layer had already formed a crust, and no matter how hard they pressed it, they could not effectively wet it, resulting in a false adhesive that could not be seen by the naked eye and could be easily broken.

Adjustment: Changing glue is faster and more effective than adjusting the machine

The transformation of the machine’s rhythm requires a shutdown, and it cannot be stopped during peak seasons. The factory has changed to a new type of adhesive particle, choosing a specification with an opening time of 6-7 seconds and a complete curing time of about 15 seconds, while also reducing the amount of adhesive to the original level. After changing the adhesive, the first batch of 2000 samples were randomly inspected, and the phenomenon of empty adhesive disappeared. The page pulling force increased from an average of 3.4 N/cm to 6.1 N/cm.

Three weeks later, the binding scrap rate of the entire batch of orders decreased from 6% to 0.8%. Based on a direct cost of 4.2 yuan per volume, the scrap alone saved over 100000 yuan, which is much more important than the money saved on adhesive prices.

Reusable judgment methods

• First, measure the actual number of seconds from gluing to pressing, which is the only basis for selecting the opening time.
• The opening time should be 1-2 seconds longer than this, leaving room for speed fluctuations.
• The compression holding time should cover the initial curing, usually not less than half of the complete curing time.
• The change in environmental temperature during seasonal changes will alter the curing rate, and in winter, if the temperature in the workshop is below 15 ℃, it needs to be re verified.

The role of Sunlife hot melt adhesive in such projects

When Guangzhou Sunlife Trading provides selection services for book and magazine customers, they first require a set of on-site data: machine speed, seconds from gluing to pressing, and workshop temperature. Sunlife hot melt adhesive recommends the opening time range based on these three data points and provides small batch trial installation to avoid customers gambling with whole batches of goods during peak seasons.

Frequently Asked Questions

How to estimate the opening hours on site?

Draw a glue line on a piece of paper, use a stopwatch to time it, and press another piece of paper every second. The final moment when the fiber tears out is the effective opening time.

Will slow curing affect subsequent cutting?

meeting. Cut three sides before fully curing, as the spine of the book is prone to burrs. It is recommended to let it sit until the adhesive layer has completely cooled before cutting.