Many paster failures (or splice failures as some say) are the result of trauma to the running web during the paste cycle.  For an offset newspaper printing press the average paster failure, because of downtime and wasted consumables, costs ~$700 per incident.  This can represent a staggering amount of wasted money to pressrooms incapable of resolving their paster failures. Conversely, this can represent a large cost savings if this article resolves your problem. Yay metaprinter!

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One of the most overlooked mechanical components resulting in paster failure is the floating roller and floating roller bellofram cylinder.  Here I will go through the theory and components, then highlight how to troubleshoot and resolve the problems.

Theory

1. The Floating Roller maintains the tension setting on a running web during paste cycle.  If your full roll reel tension is set to run at 30kg’s then the floating roller’s job is to maintain that setting throughout the paste cycle. Why does reel tension fluctuate during paste cycle?

• Reel arms index to paste position
• Old Roll wind at core (tight, loose)
• Brush impact trauma
• Slight speed mismatch at brush contact
• New Roll out of round
• Reel arms index home

2. How does the floating roller maintain the setting?  The roller is a freely spinning pipe roller attached to a linkage with swings in an arc.  See the image below.

Components

The component which controls the movement within that arc is the floating roller bellofram cylinder.  A schematic of the cylinder is shown below.  The rod would be attached to the floating roller linkage.  Notice that air can only flow out the vent when the diaphragm is leaking.  This is important because it is a telltale sign of failure.

The bellofram will look something like the photo below which is from a Mitsubishi MHI press.  You can also see a shock absorber on the other side of the linkage.  As the name implies this acts to absorb shock.  It rarely fails, but a telltale sign is oil leaking out of the cartridge.  If you are curious, that green thing on the left side is the Hi/Lo clutch activated by the dancing roller and driving the infeed roller.

Troubleshooting

I have put together a powerpoint presentation for the troubleshooting portion of this post.  There is just too much data to upload to the site.  Click on the image below to proceed and let me know if this is helpful.

Click for Floating Roller Troubleshooting PowerPoint

As you can see, the floating roller and its related components play a major role in maintaining web tension during the paste cycle.  Components that have failed or are failing will result in a noticable increase in paster failures.  It can be suggested from this presentation that a simple check for air leaks at the bellofram vent can be an inexensive preventative maintenance item.  I hope this helps minimize your paster failures and saves you time and money.   Cheers!

Related posts:

1. Troubleshooting & Resolving Newspaper Web Wrinkles
2. How is a newspaper printed?