Page 1
Technolog
Ultrasonic Welding Trouble Shooting Guide
PROBLEM PROBABLE CAUSES SOLUTIONS
Overweld Too much energy into the part. Reduce pressure, trigger force and/or down speed
Weld time too long. Reduce weld time/energy/ collapse.
Too much collapse. Change to lower ratio booster to reduce amplitude.
Digitally reduce the amplitude %.
Use Amplitude Profiling.
Reduce down speed.
Change to lower gain horn if lowest booster is already in use.
TL-24
Absolute distance too high.
Underweld Insufficient energy into the part. Increase pressure, trigger, and/or down speed.
Insufficient weld time. Increase weld time/energy/ collapse.
Insufficient amplitude. Use higher ratio booster to increase amplitude, if horn allows.
Energy loss into fixture.
Presence of mold release.
Absolute distance too low.
Moisture absorption by
hygroscopic material.
Non-uniform Warped part(s).
weld around
the joint
Non-uniform horn face amplitude.
Lack of parallelism between horn,
fixture and part.
Insufficient support in the fixture.
Recalibrate absolute distance and adjust.
Change to higher gain horn if highest booster is already in use.
If fixture is urethane, change fixture to rigid material such as
aluminum, stainless steel.
Evaluate part fit in fixture.
Eliminate use or clean parts after molding.
Increase absolute distance.
Dry parts as required.
Check part dimensions and flatness
Check molding conditions.
Use higher trigger pressure.
Have horn tested (and modified if needed) to establish uniformit
Shim fixture where necessary, or level adjustable plate.
Check part dimensions/flatness.
Check part fit with horn using carbon paper.
Improve support in critical areas.
Change to a rigid fixture.
If large sections of urethane are deflecting, add rigid backup
y.
Page 2
PROBLEM PROBABLE CAUSES SOLUTIONS
Non-uniform
weld around
the joint
(continued)
Inconsistent energy director height.
Wall flexure.
Knock-out pin location in joint area.
Improper alignment.
Non-uniform horn contact.
Part tolerance.
Mold release.
Correct mold to ensure uniform energy director height.
Check molding conditions.
Add internal ribs to part.
Increase wall thickness.
Modify fixture to prevent outward flexure.
Move knock-out pin location from joint area.
Make sure knock-out pin marks are flush with surface.
Check for part shifting during welding.
Check alignment features in mating parts.
Check for parallelism of horn, part, and/or fixture.
Check fit of part to horn.
Check part fit with horn using carbon paper.
Check for sinks.
Check for proper support in fixture.
Tighten part tolerances.
Check molding conditions.
Clean mating surfaces.
If mold release is required, use a paintable/printable grade.
Inconsistent
weld results
part-to-part
Accumulation of fillers in one area.
Moisture in joint area.
Mold release.
Part tolerances.
Cavity-to-cavity variations.
Regrind/degraded plastic.
Check molding conditions.
Reduce the amount of filler.
Use only short fiber fillers
Dry parts as required.
Clean mating surfaces.
If mold release is required, use a paintable/printable grade.
Tighten part tolerances.
Check part dimensions.
Check molding conditions.
Run statistical study to see if a pattern develops with
certain cavity combinations.
Check part tolerances/dimensions.
Check for cavity wear.
Check molding conditions.
Centralize gate location.
Check with molder for percentage of regrind
Check molding conditions.
Reduce percentage of regrind (maintain below 10%).
Improve quality of regrind.
Page 3
PROBLEM PROBABLE CAUSES SOLUTIONS
Inconsistent
weld results
part-to-part
(continued)
Marking Lack of parallelism.
Drop in air line pressure.
Filler content too high.
Non-uniform distribution of filler.
Incorrect joint design.
Poor part fit.
Incompatible materials or resin
grades or lots.
Moisture in molded part.
(Usually nylon parts.)
Raise compressor output pressure.
Add surge tank with a check valve.
Check air supply line capacity vs. number of welders supplied.
Reduce percentage of filler.
Check molding conditions.
Change type of filler, i.e., short- to long-glass fibers.
Check molding conditions.
Check mold design.
Redesign joint, check with Branson applications engineering.
Improve part dimensions.
Improve part tolerances.
Check molding conditions and improve.
Check Branson Technical Information Sheet PW-1.
Check with resin supplier specifications.
Check with Branson Applications Lab.
Receive parts dry-as-molded, bagged and sealed.
Dry parts, then weld.
Readjust for parallelism between horn, part, and fixture.
Check horn/part fit.
Check part/fixture fit.
Level fixture where necessary.
Shear interference too great.
Energy director too large.
No joint design (butt surfaces).
Improper fit of part to fixture.
Weld cycle is too long.
Reduce interference.
Reduce energy director size.
Check for proper support.
Redesign fixture.
Check for cavity-to-cavity variations.
Check part dimensions.
Check for cavity-to-cavity variations.
Obtain a new horn.
Reduce weld time by adjusting amplitude and/or pressure.
Adjust Dynamic Triggering pressure.
Page 4
PROBLEM PROBABLE CAUSES SOLUTIONS
Marking
(continued)
Flash (see also
non- uniform
welding)
Horn heats up.
Localized high spots in part.
Raised lettering.
Aluminum oxide (from horn).
Overwelding: control mode
(time, energy, collapse or
absolute distance, peak power,
force) too high.
Weld time too long.
Non-uniform joint dimensions.
Check for loose tip.
Reduce weld time. Cool horn with ambient or refrigerated air.
Check coupling between horn and booster.
Visually check for cracked horn.
If horn is titanium, change to chrome-plated aluminum.
Check part dimensions.
Check fit of horn to part in fixture.
Use polyethylene film between horn and part.
Relieve horn.
Use recessed lettering where possible.
Chrome-plate or clear anodized horn and/or fixture.
Use polyethylene film between horn and part.
Readjust control parameters.
Reduce weld time.
Redimension joint.
Check molding conditions.
Misalignment
of welded
assembly
Energy director too large.
Shear interference too great.
No joint design (butt surfaces).
Lack of proper alignment feature
between mating parts.
Improper support in fixture.
Wall flexure.
Reduce size of energy director.
Reduce weld time.
Reduce pressure.
Use textured surface.
Reduce amount of interference.
Redesign joint to direct flash as required by application.
Add alignment feature to the mating part halves (i.e., pins and
sockets).
Redesign fixture for proper support.
Shim fixture where necessary.
If large sections of urethane are deflecting, add rigid backup.
Add ribs or gussets to part.
Increase wall thickness.
If large sections of urethane are deflecting, add rigid backup.
product nameTL-24
Page 5
PROBLEM PROBABLE CAUSES SOLUTIONS
Misalignment
of welded
assembly
(continued)
Internal
components
damaged during
welding
Joint design improper dimension.
Part tolerance/poor molding.
Overwelding.
Too much energy into the part.
Long weld time.
Components improperly mounted, i.e.,
mounted too close to joint area, etc.
Location of components.
Redimension parts.
Tighten part tolerances.
Check molding conditions.
Reduce weld time/energy/pressure.
Reduce amplitude by changing to a lower gain booster, or utilize
Amplitude Profiling.
Reduce pressure and/or down speed.
Reduce weld time/energy.
Adjust Dynamic Trigger pressure.
Investigate the use of alternate frequencies.
Reduce weld time by adjusting amplitude and/or pressure.
Adjust Dynamic Triggering pressure.
Make sure internals are properly mounted.
Isolate internal components from housing.
Move components away from areas of high energy concentration.
Use nodally-mounted device to dampen energy locally.
Components should be in fixture part.
Melting/fracture
of part sections
outside of joint.
Too much energy into the part.
Sharp internal corners.
Excessive amplitude.
Internal stress.
Knit/flow lines.
Improper molding conditions.
Gate located near joint.
Reduce weld time.
Decrease amplitude.
Decrease pressure.
Adjust Dynamic Triggering pressure.
Radius all sharp corners.
Reduce amplitude by changing to a lower gain booster, or
step amplitude.
Reduce horn amplitude if lowest booster is already in use.
Monitor/improve molding conditions.
Check part design.
Check molding process parameters.
Check molding conditions.
Move gate area away from joint.
Page 6
Ultrasonic Welding Trouble Shooting Guide
PROBLEM PROBABLE CAUSES SOLUTIONS
Technolog
TL-24
Diaphragmming Excessive amplitude.
Long weld time.
Gate location.
Horn type and/or
placement.
Thin wall section.
Internal parts
welding
Internal parts same
material as housing.
Reduce amplitude.
Utilize Amplitude Profiling.
Reduce weld time by increasing amplitude and/or pressure.
Check gate placement.
Check molding conditions.
Change shape of gate.
Add stiffening ribs to the part.
Increase thickness of material on the underside of the gate area.
Eliminate horn contact over diaphragm area.
Check for horn/part fit.
Use a horn with a nodal plunger.
Add vent hole in horn.
Increase wall thickness or add ribs.
Change material of internal part to incompatible material. Lubricate
internals.
Reposition internal parts to prevent contact during weld cycle.
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