The balancing of Vibration Weld Tooling is critical to the longevity of any manufacturer’s vibration welding equipment. With proper design of the moving half of the vibration tools used in the Linear Vibration Welder, the manufacturer can expect a much longer life from his welding equipment. Also by running unbalanced tools you can significantly shorten the life of your machine and incur tens of thousands of dollars in repair costs.
First let’s discuss the dynamics of the moving half of the tool in a vibration welding tool set. Usually this is the upper half of the tool. The partial g loading chart below shows that at 1.8 mm amplitude and 240 Hertz we get 208 g’s of dynamic load. Therefore, a 100 pound tool moving at 240 Hertz and 1. 8 mm peak to peak displacement becomes 20,800 pounds of dynamic load on the machine.
The following table is g loading calculations (click table for larger view):
So let us assume that a tool is 20 pounds out of balance, 12 inches from the center line of the tooling. This would mean that we have:
(20 pounds) X (12 inches) X (208g) = 49,920 inch pounds of torque on the machine.
This will cause the Linear Vibration head to move in a non linear fashion. It will damage components in the head and make the frequency drives work harder to keep the tool running the application. This eventually will take critical components in the vibration head to a fatigue failure point, thus causing the expensive repair bills.
If you look at the weld tool representation, you will see lightening holes on the upper tooling plate to the back side of the tool. These are there to counter balance the thick portion of the poured urethane nest, thus bringing the tool into balance.
Extensive use of tool balancing was used on the tool illustrated below. Here, not only was the tool plate lightened but the tooling segments themselves needed to be weight reduced to balance the tooling.
The use of steel counter balances can also be used, just remember the upper tool must fall within the manufacturer’s recommended tool weight specifications. The use of good CAD tools can also aid in the balance analysis of a tool before you even cut the materials.
Finally, the tool being balanced in the direction of welding is not as critical. The tool balance from front to back in most machines or 90 degrees to the direction of vibration or along the direction of the weld axis is what must be considered for all good vibration tooling.
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