Weld Distance; Welding Problems And Solutions - Dukane VWA-4300 User Manual

Welding Problems and Solutions

Some of the faults associated with vibration welding are
caused by joint design and some are due to improper weld
parameter settings. Table A-I lists some of the more com-
mon problems, the causes and solutions.
Problem
Overwelding Excessive weld flash. Final
dimensions of part are too
small.
Underwelding Low weld strength.
Final dimensions of part are
too large.
Nonuniform or incon- Excessive weld flash.
sistent weld joints
Low weld strength.
Failure when leak tested.
Part failure in service.
Common Welding Problems and Solutions
Table A- I
Dukane Manual Part No. 403-592-00
Symptom
Weld time too long.
Weld distance too large.
Incorrect flash trap design.
Weld Time too short.
Weld distance too small.
Material difficult to weld due to low
friction coefficient.
Weld ribs flex during weld.
Parts moving in tooling (visible dust
or scratches on parts).
Warped parts.
Uneven weld interface.
Fixture and part are not parallel.
Poor part alignment of parts in
fixture.
Insufficient fixture support.
Vibration stalling.
Walls are flexing during welding.
Excessive filler or uneven distribu-
tion.
Possible Cause
Section 14 - Appendices
Recommended Solution
Reduce weld time.
Reduce weld distance.
Evaluate and correct flash trap design.
Increase weld time.
Increase weld distance.
Degrease joint interface to remove mold release agent.
Consider changing material (avoid PFTE).
Change design to eliminate rib flexing or change direc-
tion of vibration.
Adjust nest to hold part.
Add return flanges to part.
Add vacuum to fixture.
Check part dimensions.
Check molding process conditions.
Shim fixture where necessary. Check that tooling is
true to table.
Redimension parts. Improve part tolerance caused by
cavity variations in multiple cavity molds.
Check for parts shifting during welding. Provide means
for alignment in mating parts.
Evaluate joint constraint due to tooling design or mold
processing.
Redesign parts with reinforcing ribs and/or tongue
and groove joints.
Reduce amount of filler. Improve processing conditions
to ensure even distribution of filler.
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