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Frequently Asked Questions

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  • Laser Welding
  • Ultrasonic Insertion
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  • Vibration Process

Laser Welding

What types of plastics can be welded?

Most commonly used thermoplastics can be welded with the exception of fluoropolymers.

What color plastics can I weld?

Both could be clear or both could be pigmented or just the bottom part can be pigmented.

Does the bottom or inner part need to be Black?

It is not required when using the 2-micron laser.

How large of a part can I weld?

To date, we have welded parts up to 700mm diameter. There are really no limitations as each system is custom designed based on the customer’s requirements.

Do my parts need a joint design?

Yes and Dukane will advise you for the optimum joint design. In many cases flat-on-flat surfaces are acceptable.  A good fit between mating surfaces is critical.

How fast can I weld? (inches/mm per minute).

This depends on the material properties and thickness of the upper part.

What shapes can I weld?

Moderate curvature is possible without any special tooling.

Can a laser system by integrated into automation?

Yes, in fact the laser welding systems are flexible and the systems are easy to automate.

What safety precautions are there for using a laser?

Our laser work cell enclosures are Class 1 CDRH certified with laser-safe glass viewing window.

Laser Welder Tooling: Do I need to have glass clamp my parts?

Not necessarily.  Some parts can be clamped using metal (aluminum or stainless steel).

Can I use a transparent plastic?

No, due to the 2-micron laser beam is absorbed by the polymer itself.

Applications and Troubleshooting – Why do I have so much smoke/fumes when I weld?

Fumes or smoke are an indication of thermal decomposition of the thermoplastic material. So process optimization is critical.

Should or can the laser system be calibrated? How often?

Yes, in many cases an annual calibration is sufficient, but calibration frequency is guided by your quality control requirements.

Ultrasonic Insertion

Why does the insert lack retention strength?

Probable Causes and Solutions:
  • There is insufficient interference between hole and the insert.
    • Ensure proper hole size per insert the manufacturer guidelines.
  • The screw bottoms out in the hole. (Applies to internally threaded insert)
    • Try using a shorter screw or increase the depth of the hole.
  • The insert gets pushed into the plastic before the plastic melts.
    • Use slower iQ Servo Weld Speed, use a hydraulic speed control, increase the amplitude and/or decrease the gauge pressure, or use pre-triggering.
  • The ultrasound remains on after insertion is complete.
    • Reduce the primary weld parameter.
  • The horn retracts before the plastic around the insert is solidified.
    • You need to increase the hold time.

Why do I keep having inconsistent insertion of multiple inserts?

Probable Causes and Solutions:
  • The plastic is not melting consistently around all inserts.
    • You need to increase the amplitude.
  • Inserts are pushed into the plastic before the plastic has melted.
    • Use slower iQ Servo Weld Speed, use hydraulic speed control, reduce the down speed, or use pre-triggering.
  • Inserts are seated at different heights.
    • Weld to a position or absolute distance, use pre-trigger, or level fixture.

How can I stop the cracking during/after insertion?

Probable Causes and Solutions:
  • The insert is pushed in before the plastic has melted.
    • Try using pre-triggering, reduce the down speed and/or gauge pressure, or use slower iQ Servo Weld Speed.
  • The weld force is too high.
    • You need to reduce the gauge pressure.
  • The boss wall is too thin.
    • You need to increase the wall thickness of the boss.
  • There is too much interference between the insert and the hole.
    • You need to decrease interference.
  • Weak molded “knit” or “weld” lines.
    • Ensure correct molding parameters.

Why is the insert not driven to the desired length?

Probable Causes and Solutions:
  • The ultrasound is not on long enough.
    • You need to increase the primary weld parameter.
  • Flash fills the hole (Applies to an internally threaded insert).
    • Increase the depth of the hole.
  • There is insufficient gauge pressure and/or power.
    • Increase the gauge pressure or change to a higher power rated generator.

Why is the cycle time so long?

Probable Causes and Solutions:
  • There is too much interference between the hole and the insert.
    • Increase the hold diameter (if possible) or use a smaller insert.
  • The area of the part being inserted is not being rigidly supported.
    • Support the part directly under the boss or install a metal post directly under the part being inserted.
  • The down speed is slow.
    • Increase the down speed/increase iQ Servo weld speed.
  • Insertion force too low.
    • Increase weld force by increasing weld speed or pneumatic down force.

How can I stop melted plastic from filling the hole (Applies to internally threaded inserts).

Probable Causes and Solutions:
  • The insert is too long, or the hole is too shallow.
    • Use a shorter insert or make the hold deeper.
  • There is too much interference between the hole and the insert.
    • You need to decrease interference.
  • The insert is being driven too deep.
    • You need to decrease the primary weld parameter.

Ultrasonic Staking

Why is there a ragged or irregularly shaped stake head being formed?

Probable Causes and Solutions:
  • The staking cavity is too large.
    • Change to a smaller cavity in the horn.
  • The volume of plastic in the stud is insufficient.
    • You need to increase the stud height/diameter.
  • The stud is melting at the base.
    • See the problem section below titled, “The base is melting before the head forms”.

Why is there excessive flash around the stake head?

Probable Causes and Solutions:
  • The staking cavity is too small.
    • Use a larger cavity in the horn.
  • The volume of plastic in the stud is excessive.
    • Decrease the stud height and/or the diameter.
  • The stud is not centered in the horn cavity.
    • Center the stud under the horn cavity.

Why is the surface below the stake head distorted?

Probable Causes and Solutions:
  • The part is not supported directly beneath the stud being staked.
    • Support the fixture with a metal post under the stud being staked.
  • The trigger force is too high.
    • Reduce the trigger force or use pre-triggering.
  • Weld distance is too high.
    • You need to decrease weld parameter.
  • Weld Amplitude is too high at end of cycle.
    • Use Amplitude profiling to decrease at end of cycle.

Why is there a loose fit between the staked head and the part being attached?

Probable Causes and Solutions.
  • The hole diameter relative to the stud diameter is too large.
    • You need to reduce the hold diameter.
  • The holding force was removed before the stud head could solidify.
    • If using a dual pressure system, use pressure 2 in the hold portion of the weld cycle (Pressure 2 should be higher than Pressure 2), use Dynamic Hold to ensure appropriate compression during hold phase, increase the hold time/distance, increase the stud diameter, or reduce the size of the staking cavity.
  • Insufficient force is being applied to the staked head during the hold time.
    • Use Dynamic hold to ensure appropriate compression during hold phase.

Why is the stud collapsing at its base?

Probable Causes and Solutions:
  • There is a sharp corner near the base of the stud.
    • You need to radius the stud at the base.
  • The stud Is not centered in the horn cavity.
    • Center the stud under the horn cavity.
  • Too much pressure is applied before the ultrasound is activated.
    • Use pre-triggering or decrease down speed or iQ Servo Weld Speed.
  • The trigger force is too high.
    • Reduce the trigger force.

Why is the base melting before the head forms?

Probable Causes and Solutions
  • There is a sharp corner near the base of the stud.
    • Radius the stud at the base.
  • Trigger Force is too high.
    • Decrease Trigger Force.
  • The Amplitude is too high.
    • Pre-trigger the ultrasound, decrease the amplitude by changing to a lower gain booster or reduce amplitude percentage setting, or use amplitude profiling to decrease at end of cycle.
  • The downstroke speed is too fast.
    • Use hydraulic speed control or use a slower downstroke speed.

Why does the formed stud stay in the staking cavity as the horn retracts?

Probable Causes and Solutions:
  • The head has not solidified before the horn retracts.
    • You need to increase the hold time.
  • The horn tip is heating and not allowing the head to solidify.
    • You need to cool the horn tip or use afterburst.

Ultrasonic Welding

Why am I seeing a Flash?

Probable Causes and Solutions:
  • The Energy director could be too large.
    • Reduce the size of the energy director and the gauge pressure and use an interrupted energy director.
  • The Shear interference is too large.
    • Reduce the amount of interference.
  • The primary weld parameter is too large.
    • Reduce the weld parameter.
  • The amplitude setting is too high.
    • Reduce amplitude % or booster ratio.
  • The amplitude is too high at the end of weld cycle.
    • Reduce the amplitude during the weld cycle and use Dynamic Hold Distance.
  • The IQ Servo Weld Speed is too low.
    • Increase IQ Servo Weld Speed or use Melt Match® speed profiling.
  • The Trigger Force is too high.
    • Reduce Trigger Force.
  • There are Non-uniform joint dimensions.
    • Re-dimension the joint, redesign the joint to be a shear joint or a tongue-in-groove joint, and check the mold processing conditions.
  • The part fit too tight.
    • Increase part to part spacing.

Why is there a misalignment of the welded assembly?

Probable Causes and Solutions:
  • The parts are not self-aligning.
    • Add a means of alignment (e.g., pins and sockets) to the mating part halves.
  • There is improper support in the fixture.
    • Redesign the fixture for proper support.
  • There is wall flexure.
    • Add ribs or gussets to the part and add a rigid gusset to unsupported sections in resilient fixtures.
  • The joint design Is not properly dimensioned.
    • Re-dimension the parts.
  • There is incorrect part tolerance/poor molding.
    • Tighten the part tolerance and ensure correct molding conditions.

How do I stop internal components from being damaged during welding?

Probable Causes and Solutions:
  • There are sharp internal corners/thin sections.
    • Try to radius all sharp corners and damp any damaged area (if possible).
  • There is excessive amplitude.
    • Try reducing the amplitude by changing to a lower gain booster or reduce amplitude percentage.
  • There is excessive weld time.
    • Try decreasing the primary weld parameter, increasing the amplitude, increasing the gauge pressure, and increasing the iQ Servo Weld Speed or use Melt-Match® speed profiling.
  • There is internal part stress.
    • Ensure correct molding conditions, perform mold flow analysis, follow standard design practice to reduce residual stress in molded parts, reduce the amplitude by changing to a lower gain booster or reduce amplitude, and use amplitude.

How can I stop melting or fracturing of the part (outside of the joint area)?

Probable Causes and Solutions:
  • There are sharp internal corners/thin sections.
    • Try to radius all sharp corners and damp any damaged area (if possible).
  • There is excessive amplitude.
    • Try reducing the amplitude by changing to a lower gain booster or reduce amplitude percentage.
  • There is excessive weld time.
    • Try decreasing the primary weld parameter, increasing the amplitude, increasing the gauge pressure, and increasing the iQ Servo Weld Speed or use Melt-Match® speed profiling.
  • There is internal part stress.
    • Ensure correct molding conditions, perform mold flow analysis, follow standard design practice to reduce residual stress in molded parts, reduce the amplitude by changing to a lower gain booster or reduce amplitude, and use amplitude.

Why are the internal components welding together?

Probable Cause and Solution:
  • The internal components are made of the same material.
    • Make sure the internal components are made out of a dissimilar resin, lubricate the internal parts, or consider using a higher frequency system.

Why do I keep experiencing diaphragming?

Probable Cause and Solution:
  • The internal components are made of the same material.
    • Make sure the internal components are made out of a dissimilar resin, lubricate the internal parts, or consider using a higher frequency system.

Why am I experiencing over welding?

Probable Cause and Solution:
  • There is too much energy being transmitted to the part.
    • Try reducing the gauge pressure, reduce the weld time/primary weld parameter, reduce the amplitude by changing to a lower gain booster or reduce generator amplitude percentage setting, use slower downstroke speed, increase the amplitude by changing to a higher gain booster to decrease weld time, and increase IQ Servo Weld Speed or use Melt-Match® speed profiling.

Why am I experiencing under welding?

Probable Causes and Solutions:
  • There is insufficient energy being transmitted to the part.
    • Try increasing the gauge pressure, increasing the weld time/primary weld parameter, changing to a higher gain booster to increase the amplitude, decreasing iQ Servo Weld Speed, and changing to a higher power rated generator.
  • The energy is being absorbed into the fixture.
    • Try changing the type of fixture being used.

Why am I experiencing uneven welding?

Probable Causes and Solutions:
  • There is a warped part(s).
    • Try checking part dimensions, ensure there are correct molding conditions, use a higher Trigger Force/Trigger Delay, use a higher Hold Pressure, and increase Melt-Detect™ percentage.
  • The energy director varies in height.
    • Redesign the energy director to ensure uniform height and use an interrupted energy director.
  • There is lack of parallelism between the horn, the fixture, and the part.
    • Try level tooling to the part and ensure correct part dimensions.
  • Wall flexure is occurring.
    • Add ribs to the part and incorporate fixture component to prevent outward flexure.
  • The knockout pin location is in the joint area.
    • Redesign the part so the knockout pin is not in the joint area. (Make sure knockout pins are flush with the surface).
  • There is insufficient support in the fixture.
    • Redesign the fixture to improve the support in critical areas (underneath weld region), use a more rigid fixture, and add a rigid backup to unsupported sections in resilient regions.
  • The part dimensions are incorrect.
    • Ensure correct part dimensions and molding conditions.
  • The parts are improperly aligned.
    • Check for part shifting during welds, the alignment of mating parts, and for parallelism of the horn, the part, and the fixture.
  • There is a lack of intimate contact around the joint area.
    • Ensure correct part dimensions and tolerances, ensure knockout pin marks are not in the joint area, and check for misalignment of the mating part halves.
  • Non-uniform horn contact is occurring.
    • Check for sinks in the molded parts, check the fit of the part to the horn, and check for proper support in the fixture.
  • There is mold release on the joint surface(s).
    • Clean the mating surface and use paintable grade mold release.
  • There is a non-uniform distribution of filler/reinforcement in the plastic material.
    • Ensure correct molding conditions and check the mold design.
  • There is a material or resign grade incompatibility problem.
    • Consult with a resign supplier(s) or Dukane Application Engineering.
  • The Regrind percentage varies.
    • Consult with the molder and ensure correct molding conditions.
  • There is moisture in the molder parts.
    • Specify the parts to be “dry as molded” and dry the parts by heating prior to welding.

When I am welding why are the parts marking?

Probable Causes and Solutions:
  • The part does not match CAD data used to cut tooling.
    • Try polishing tooling and/or recut with larger offsets.
  • There is too much energy is being transmitted to the part.
    • You need to reduce the gauge pressure, reduce the weld time/primary weld parameter, reduce the amplitude by changing to a lower gain booster or reduce amplitude percentage, use a slower downstroke speed, increase the amplitude by changing to a higher gain booster to decrease weld time, increase IQ Weld Speed or use Melt-Match® speed profiling.
  • The horn temperature increase causes marking.
    • Try to cool the horn using forced convection, confirm that the horn and booster interfaces are clean and flat, ensure horn, booster, and transducer interfaces are appropriately torqued per Dukane specifications, and visually check the horn for cracks.
  • The use of raised letting causes marking.
    • Use recessed lettering or relieve the horn around the lettering.
  • The part doesn’t fit the tooling properly.
    • Check the tooling for proper support, place polyethylene film between the horn and the part or use Dukane film feeder, check for cavity to cavity variations, and redesign the remanufacture the fixture.
  • There is oxide from the horn being transferred to the part.
    • Place polyethylene film between the horn and the part or use Dukane film feeder, use a chrome-plated horn and/or fixture, or use polished Titanium horns.
  • The filler content varies in part.
    • Ensure correct molding conditions and reduce the amount of filler in the plastic.

Why am I having inconsistent weld results on a part-to-part basis?

Probable Causes and Solutions:
  • A mold release agent is used.
    • Clean the mating surface of weld interface. If a mold release agent is necessary, use a paintable/printable grade.
  • There are incorrect part tolerances.
    • Tighten the part tolerances, check the part dimensions, and ensure correct molding conditions.
  • There are cavity-to-cavity variations.
    • Ensure part dimensions and tolerances are within specification, check for cavity wear, ensure correct molding conditions, and perform a statistical study to see if a pattern develops with certain cavity combinations.
  • The resign contains regrind or degraded plastic.
    • Consult with the molder, ensure correct molding conditions, reduce the percentage of regrind, ensure consistent percentage of regrind, or improve the quality or the regrind.
  • There are fluctuations in the AC line voltage supplied to the generator.
    • You need to upgrade to a generator with line load regulation.
  • There are fluctuations in the air line pressure.
    • Upgrade to iQ Servo welding system, upgrade to a system with electronic pressure regulation, add a surge tank with a check valve to the airline, and raise the compressor output pressure.
  • The plastic’s filler content is too high.
    • Reduce the percentage of filler in the plastic, ensure correct molding conditions, or change the type of filler (e.g., from short to long glass fibers).
  • The horn doesn’t fit the part correctly.
    • Check the part dimensions, check for cavity-to-cavity variations, or consult Dukane to modify existing horn.
  • There is a lack of parallelism between the horn, part, and/or fixture.
    • Check for parallelism between the horn, check the horn/part fit, check the part/fixture fit, or level the fixture where necessary.
  • The rigid fixture reflects vibratory energy.
    • Damp the energy by using Teflon. Neoprene, cork or urethane in the nest of the fixture.

Vibration Machine

Why will the machine not cycle in auto mode?

Check top status bar on HMI to find out why it is not ready for cycle.

  • Make sure back doors are closed
  • Check all e-stops are cleared
  • Make sure the machine is in auto mode
  • Make sure machine is in home and “ready for cycle”
  • Make sure all part presence switches are made.

What periodic maintenance needs to be performed?

See operation manual section 11. Main items listed below:

  • Change air filter on 15 psig drop or every 2 years
  • Check hydraulic fluid levels weekly
  • Change hydraulic filter yearly
  • Change hydraulic fluid every 10,000 hours or when discolored
  • Grease all 8 zerk fittings on bearings once or twice a year. (grease only bearings rails do not need grease on them.

Can you shut down the machine without a coordinated shut down of HMI?

Yes, the industrial HMI can be shut down at any time. It will not hurt the function of the machine or HMI.

What is tool weigh compensation?

This is the way you Zero the weight of the tool and the table. Allow you to know that the force you are developing is what you are putting on the part during weld. In some machines you enter the tool weight directly and the machine knows the weight of the table and subtracts both from the pressure in the system. The more accurate way to do this is called “Float the Table”. In this case you load the tooling and run a process of increasing pressure until the table moves. That is where the force to lift is zero. Then this pressure is subtracted from the force of the system.

How often should the hydraulic oil be replaced?

The oil should be changed out every 10,000 hours or when it is discolored.

Why use all bolts in upper tooling?

The bolts in all spring and lamination carriers must be used. The upper moving tool develops up to 208g’s. This means a 100 pound tool will dynamically produce 20,000 pounds + of dynamic load. Electrically we can see one bolt missing and the head to begin to run not in a desired mode. Multiple bolts missing will damage the machine and void a warranty.

Why is a balanced tool so important?

An un-balanced tool will not run linearly. It will start to move in a orbit form. This stresses the lamination carriers and the Coils. A balanced tool is the single most important thing you can do to make the machine last longer.

What is tool ID?

Tool ID in a Dukane machine is simple binary input to the machine through the tooling connector. By wiring 24 volts to the correct pins it is possible to give a tool a unique tool ID. In using this each time you plug in the tool the program associated with the tool will be pulled up in the PLC/HMI. So there is no chance to get the wrong weld parameters for a given application and no reason to set up parameters when you load the tooling.

Vibration Process

The machine ran a cycle but did not reach melt down distance, why would this happen?

Check the weld time of the machine. It is very probable that you have exceeded the maximum weld time. You will need to add more time or increase clamp pressure or amplitude to make distance in desired amount of time.

Should I weld in time or melt down distance?

If possible, it is usually better to weld in melt down distance. This is the only closed loop welding method. You can change pressure, amplitude, and even surface area of weld part to part and still make the same distance giving you consistent welds.

How much weld pressure should I use on my application during weld?

You need to calculate all the surface area of the top of the weld beads. Then multiply this area by 250 lbs / square inches of area. This is a good starting point it can vary by a lot based on application.

How much hold pressure should I use on my application?

Hold pressure should not exceed weld pressure. In fact it is nice to reduce hold pressure by 10% or so. When a welder goes into hold mode you get “post weld collapse” and this is a thinning of the heat affected zone. This thinning is a reduction in weld strength. You need hold pressure but excessive pressure can yield a cold weld.

I have scratches on the part from the vibration process. How do I get rid of marks?

In general the marks are from the part moving in the nest (could be upper or lower nest or both). You need to increase weld pressure so the parts lock up in the nest better. This usually solves the problem. If not finding a way to lock the part on the tool may be required. The use of locators and return flanges in your part usually will work fine.

Can I use dissimilar materials?

Yes you can use the Dukane Material compatibility chart available on the website to determine what materials are weldable to each other. Then you need to answer two more questions:

  • Material must have similar melt processing temperatures within 20 degrees C of each other.
  • Material melt flow must be within 4 of each other.

I have welds in areas not intended to weld. (causing defect such as flash in visible area)

We need to be thinking pressure and amplitude. If you have a weld in an area where you do not want a weld you need to remove the pressure or remove the amplitude. Usually this means you need to clear the supporting nest in this area relieving any chance that pressure is applied to the area of unwanted weld. Only in rare occasions is it possible to reduce or eliminate the amplitude.

Why or when do I need to run an auto tune?

Auto tune is the matching of the natural resonance of the head to the digital drive. When this matching of the frequency occurs, you get lowest possible power draw from the power supply. A small deviation of even 1Hz can mean a lot of lost power. This excess power will show up in your coils of the vibration head causing excessive heat which over time can damage the coils and or lamination carriers. An auto tune can and should be done at every change in tooling. It also can be done in between tooling changes. Dukane machines can be autotuned on a set number of cycles.

What is a melt map?

A melt map is usually done at 0.5mm or half the desired weld depth. By welding the part at minimum weld depth tearing the part and looking at all weld beads you will find areas of no weld. You would add shims to the tooling until you get around 80% of all areas welded. Then weld the part at full melt depth and check to see if you are making all critical characteristics of the part that are required.

When I tear the parts apart (MELT MAP) the weld beads are not all welded

What you need to think of are pressure and amplitude.

  • Tools are usually segmented so as they can be shimmed.By adding a shim in the un-welded area, you increase the pressure in that area creating more weld.
  • If when shim is added and then more shim is added and the un-welded area grows you could have a problem with amplitude. This usually means you have a weld bead 90 degrees to the direction of amplitude. Adding shims exacerbates the problem and reduces the relative motions between the parts. In this case you may need to remove shims and even lower the shim by cutting off the bottom of the detail. Most cases require the part to be changed so the wall is stiffer and does not move during welding.

What is hold time and how much do I need?

Hold time, is a period of time after weld is completed where the head rings back down to center position and then part stays clamped in the nest until the molten plastic part solidifies. Generally accepted rule is if the parts welds in “X” seconds you need “1/2X” amount of hold time. If you are not cycle time constrained just make hold time equal to weld time.

Are Leak Proof seals possible?

Yes, we weld parts all the time that hold significant pressure without leaking. Example of some of these applications are Tail lamps, Intake Manifolds, Electronic modules, Toilet tanks, and many others