Working Principle, Operation, and Maintenance of Dispensing Machines

Working Principle and Operation of Dispensing Machines

Working Principle:
Dispensing machines primarily utilize compressed air or pressure systems to transfer adhesive from the reservoir to the dispensing nozzle, with precise control of adhesive flow rate and direction achieved through control valves. During operation, the machine applies adhesive accurately onto workpieces at predetermined positions and shapes, based on preset parameters such as adhesive flow rate, speed, duration, and the machine’s movement path.

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I. Usage of Dispensing Machines

1. Preparing Adhesive:
   • Inject adhesive into the reservoir and secure it onto the machine.
2. Setting Parameters:
   • Configure the machine’s working parameters, including adhesive flow rate, speed, and duration, as required.
3. Placing Workpieces:
   • Position the workpiece requiring adhesive on the machine’s workbench and secure it in place.
4. Starting Up and Setting:
   • Turn on the dispensing machine’s power switch and, following the instructions on the operation panel or touchscreen, set the dispensing position and shape for the workpiece.
5. Checking and Starting:
   • Verify that the adhesive flow rate and workbench movement speed meet requirements, then start dispensing to ensure uniform application of adhesive on the workpiece.
6. Ending and Cleaning:
   • After dispensing, turn off the machine’s power switch and clean the machine, dispensing nozzle, and other components to prevent adhesive from drying and causing blockages.

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II. Common Faults and Repair Methods

1. Nozzle Blockage:
   • Cause: Incomplete cleaning of the adhesive valve or needle, impurities in the adhesive, or mixing of incompatible adhesives.
   • Solution: Replace with a clean needle, use higher-quality adhesive, and clean the adhesive valve promptly.
2. Adhesive Valve Dripping or Leakage:
   • Cause: Needle diameter too small, affecting bubble venting, leading to backpressure and post-dispensing dripping.
   • Solution: Replace with a larger needle, add a suction function, use less bubble-prone adhesive, and perform de-bubbling before use.
3. Slow Flow Rate:
   • Cause: Excessively long liquid transfer tubing causing unstable air pressure loss.
   • Solution: Shorten tubing length, adjust dispensing outlet and air pressure to increase flow rate.
4. Bubbles in Fluid:
   • Cause: Excessive feed pressure and short valve-opening time, introducing air into the liquid.
   • Solution: Reduce feed fluid pressure and use a conical luer needle.
5. Inconsistent Dispensing Size:
   • Cause: Unstable pressure pump or feed pressure.
   • Solution: Ensure control pressure of the adhesive valve reaches at least 60 psi and avoid using the low-pressure section of the pressure gauge.
6. Stringing or Tailing:
   • Cause: Inadequate adjustment of process parameters, such as small needle inner diameter, high dispensing pressure, or large distance between needle and PCB.
   • Solution: Adjust process parameters, replace with a needle with a larger inner diameter, reduce dispensing pressure, adjust needle height from PCB, or heat the dispensing needle to lower viscosity.
7. Satellite Dots:
   • Cause: Tailing and needle disconnection or incorrect jet height during non-contact jetting.
   • Solution: Check for needle damage, adjust equipment parameters to prevent tailing, and adjust jet head height from PCB.
8. Popcorn or Voids:
   • Cause: Air or moist gas entering the adhesive.
   • Solution: Use low temperature for slow curing, extend heating time, shorten the time between placement and curing, and perform de-bubbling for self-filled adhesives.
9. Empty Dispensing or Insufficient Adhesive Output:
   • Cause: Bubbles in the adhesive, needle blockage, or insufficient air pressure.
   • Solution: Perform de-bubbling on the adhesive in the syringe, replace with a clean needle, and appropriately adjust machine pressure.
10. Intermittent Adhesive Dots:
    • Cause: Needle plunger landing on the soldering pad.
    • Solution: Replace with a different needle, increase delay, or adjust the ratio of pressure to cycle time.
11. Component Displacement:
    • Cause: Uneven adhesive dots, inappropriate placement height, or excessive adhesive.
    • Solution: Adjust the placement machine’s working status, replace the adhesive, and specify PCB placement time in the process documentation.
12. Component Falling Off After Curing or Wave Soldering:
    • Cause: Low curing temperature, insufficient adhesive, or contaminated components/PCB.
    • Solution: Retest the PCB’s curing curve, adjust curing temperature, and inspect components or PCB for contamination.

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III. Brands and Models of Dispensing Machines Repaired by Longi Ectromechanical Company

1. Nordson EFD:
   • Ultimus V
   • Performus X100
   • 794 Series
   • 736HPA
   • Liquidyn P-Dot CT
2. Musashi Engineering:
   • Shotmaster 300DS
   • SuperΣ CMII
   • Image Master 350PC Smart
   • Smart Dispenser 300
3. Asymtek (Nordson Asymtek):
   • Spectrum S-820
   • Quantum Q-6800
   • ACJ-3 Controller
   • DispenseMate D-583
   • Helios SD-960
4. Fisnar:
   • CV629
   • F1300N
   • F4200N
   • DC100
   • I&J123-D
5. Techcon Systems:
   • TS5000DMP
   • TS8100 Series
   • TS9000 Jet Tech
   • TS5540
6. GPD Global:
   • MAX Series
   • Island Series
   • PCD Series
   • NCM5000
7. VERMES Microdispensing:
   • MDS 3010+
   • MDS 3200A
   • MDS 3250+
8. Camalot (ITW EAE):
   • Prodigy
   • XyflexPro+
   • FX-D
9. PVA (Precision Valve & Automation):
   • Delta 6
   • Delta 8
   • Sigma
   • FCS300
10. Valco Melton:
    • FlexSpray
    • D4 Series
    • 524 System

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Longi Ectromechanical Company specializes in the long-term maintenance of dispensing machines, with nearly 30 years of experience in quick repairs for various instruments. We also buy and sell used dispensing machines. For inquiries, please contact us.