Friday, August 27, 2010

Vibration Welding and Compatibility of Materials

For most applications you weld the same material to the same material. Example (ABS to ABS) To bond two thermoplastic parts it is necessary that the materials be chemically compatible. Otherwise, even though both materials melt at the same temperature no molecular bond will occur. A good example of this is polypropylene and polyethylene. Both are semi-crystalline materials and have a similar appearance and many common physical properties. However they are not chemically compatible, and therefore are unable to weld to each other.
So we need to look at the chart below for compatible materials. If you notice you see that ABS is compatible to ABS/PC, PMMA, PS, PVC and SAN. If we get these two compatible materials we may be able to weld them together with success. (Click chart for larger view)


Now that you know you have two materials that have similar structure you need to answer two more questions.
  1. What is the melt temperature of each of the materials. These two melt temperatures must be within 40 degrees F (20 degrees C). The reason for this is that we are using a friction based process. If one melt temp is below more than 40 degrees F from the other, the lower melt temperature material will go to a complete melt and not melt the higher melt temperature material. This is true for both Ultrasonic and Vibration welding.
  2. The next question you need to answer is the melt flow of the two materials. This is basically a viscosity rating on the material at its processing temperature. Melt flows in the 0-3 and 20-30 range are extrusion grade materials. Melt flows in the 4-12 range are injection grade materials. For vibration welding these melt flows must be within 3 to 4 of each material. Also know that in ultrasonic welding the melt flows should be within 1 of each other.
So now you are asking where do I find all this information? Well you can contact the material suppliers and they are more than happy to share the data sheets on the materials with you. Also the next best thing is to get some 4” x 6” plaques and weld them together. This way you can see a welded “T” plaque of the two materials. Then you can test these materials as well.

If you have any further question please contact Dukane at (630) 797–4900. Or visit our website at http://www.dukane.com/us

Raymond M. Laflamme
Worldwide Automotive Marketing Manager
47757 West Road, Suite C101
Wixom, MI 48393
(248) 613 - 5722

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