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Volume 6, Issue 1                                                January/February 2005

IG INSTRUCTIONS  

The Slinky® Dog
You Don’t Want Him in your IG Department
by Mike Burk

Do you remember the Slinky Dog? This toy was introduced in 1955 and grew in popularity through the sixties. As the front of the dog is pulled forward, the back end stays in place. After a short delay the back end starts to move and catches up with the front of the dog. This action is intensified with sudden starts and stops and speed changes while it moves. The action of the Slinky dog is very similar to the movement of components through many insulating glass (IG) production lines.

"I hear some IG supervisors boast of the ability to produce ten or more units per minute. A closer look at the operation shows peak production for short periods with reduced quality followed by periods of zero production. Bursts of production speed can create many quality and safety issues. "

No Need for Speed
There is a need to produce insulating glass as quickly and efficiently as possible. In some managers and production associates this creates the desire to make the various processes of the IG manufacturing line move as fast as possible. When customers inquire about new equipment, often the first question is how fast it will go, or how many units will it produce? Take a moment to look at the speed adjustment on your own glass washer; it is more than likely set at maximum speed. Most operators prefer to run the washer as fast as possible, and then stop it when necessary to allow production to catch up. This method of glass washer or automated machinery operation is very similar to the movement of the Slinky dog.

Faster is not necessarily better when we consider the process of manufacturing insulating glass. Level loading or consistent and smooth operation is the goal. I hear some IG supervisors boast of the ability to produce ten or more units per minute. A closer look at the operation shows peak production for short periods with reduced quality followed by periods of zero production. Bursts of production speed can create many quality and safety issues. 

Washing glass faster than necessary with a washer that is not maintained properly could result in dirty glass, insufficient rinsing action or wet glass, leading to a loss of adhesion and premature unit failure. 

When the stackers or assemblers are rushed, alignment issues increase. The misalignment may not be detected until the unit is glazed or fractures after installation. Increased speed may also cause additional injuries as operators attempt to handle glass at an unsafe rate. Excessive conveyor speeds at the washer or oven may cause the glass to collide creating impact damage. What appears to be minor edge damage on the lite will someday run and cause the lite to break. 

If units are processed through the heating and compression at an excessive speed, the sealant glue line may not reach the temperature required to assure proper bonding. This could result in adhesive failure or a reduced moisture vapor barrier. 

Reduce Speed
It is a tough sell to convince a supervisor to slow down the process and work at a slower, more even rate. However, in many cases reducing the speed of the line will increase quality, reduce remakes and increase production. Consider a line producing four units per minute consistently. Four units per minute over a seven-hour period would produce 1,680 units. This pace allows the production associates 15 seconds for each operation. Utilizing 15 seconds at each operation can increase throughput by minimizing stoppages and increase quality by improving inspection time.

The washer loader is able to place lites on the entrance conveyor with the correct spacing, matching the pace of the stackers, eliminating conveyor stoppage. At this slower rate the stackers are able to align the spacer and glass while inspecting the glass for scratches and contaminates. The units are able to reach correct sealant glue line temperatures in the heating and compression sections with no impact damage. The off loader is given sufficient time to inspect the assemblies before sorting the finished units onto the IG carts. 

Look for the Slinky dog effect in your IG department. If you find it, remember it “doesn’t do much.” You might want to consider slowing things down. 

Mike Burk serves as training manager for GED Inc. in Twinsburg, Ohio.


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