The methods for dispensing adhesives, epoxies, grease, silicone, oils, sealants, and a multitude of other assembly fluids cover a wide spectrum of techniques—from manual applications like squeeze bottles, toothpicks, and hand-plunger syringes to semi-automated tabletop dispensing robots. Each dispensing method presents unique challenges as manufacturers attempt to scale the sophistication of their fluid dispensing processes to meet requirements for quality, volume throughput, and cost efficiency.
Looking at a series of in-depth research studies conducted over a five-year period focused specifically on fluid dispensing in assembly processes, Nordson EFD has identified the top most common dispensing challenges. Here we share key guidelines for solving these challenges to improve process control.
Sponsored by Nordson EFD and conducted by Clear Seas Research, the market studies were conducted over a five-year period (2014-2018) in three separate waves. The studies used largely identical questions and comparably sized respondent bases from similar geographic sections of the country and industries; results from the three studies were then combined to achieve trending data.
Participants included 890 respondents from manufacturing companies throughout the U.S. Respondents were qualified as being involved in deciding which assembly fluids and dispensing equipment are used by their organizations’ manufacturing processes.
Highest-Scoring Dispense Challenges
The highest-rated challenging factors relating to dispensing systems, based on data from the 2018 respondents, include:
- Shot-to-shot repeatability
- Shot-to-shot accuracy
- Equipment maintenance
- Need for faster production
- Fluid waste
- Operator training
- Rework, rejects
A needle dispensing valve applies grease in an automotive application.
This challenge appears to be more prevalent when using squeeze bottles and medical syringes to dispense assembly fluids for low-volume production. 44% of respondents from 2018 said shot-to-shot repeatability was the biggest challenge when using these manual methods. This is not surprising, considering that the repeatability of the process likely varies from operator to operator.
Shot-to-shot repeatability becomes less of a challenge as manufacturers use more sophisticated dispensing equipment to apply assembly fluids in their production processes. Consider that 37% of respondents cited shot-to-shot repeatability as a challenge when using air-powered benchtop dispensers. 32% of respondents that used pneumatic valves systems cited shot-to-shot repeatability as a challenge, while only 26% of respondents using positive displacement dispensing systems said this was a challenge.
Though improving the sophistication of dispensing equipment can solve the problem of shot-to-shot repeatability, other simple guidelines such as ensuring there is no air in the assembly fluid being used can help as well. Air bubbles in fluid are undoubtedly one of the top culprits in ruining deposit consistency for manufacturers.
Many methods are effective in preventing air entrapment from ruining deposit consistency, including:
- Using a centrifuge to purge air from fluid in syringe barrel fluid reservoirs prior to dispensing
- Using the proper high-quality dispensing components designed to purge air as dispensing takes place
- Following the guidelines for thawing frozen assembly fluids to prevent freeze-thaw voids in fluid
A centrifuge can purge air from fluid prior to dispensing and prevent air entrapment from ruining deposit consistency.
Perhaps not surprisingly, more respondents reported shot-to-shot accuracy as a challenge when using squeeze bottles and medical syringes to apply fluids than when using air-powered dispensers: 41% vs. 35%, respectively, according to 2018 respondents. Dispensing accuracy becomes less of a challenge when using pneumatic valve systems such as diaphragm and needle dispense valves.
Precision increases as manufacturers use advanced jetting systems, such as electro-pneumatic jet valves and piezoelectric jet valves. These latest advances eliminate the barrier between speed and accuracy when dispensing assembly fluids.
Recent advancements in air-powered dispensers are also helping to solve the dispense accuracy challenge. Improvements in software allow features like multi-shot capabilities, which enable an operator to program the dispenser to dispense multiple, accurate deposits with a single press of the foot pedal. This feature can also help speed production.
Recent advancements in air-powered dispensers can improve the accuracy of manual applications.
Entrapped air in assembly fluids can also impact shot-to-shot accuracy. Purging any air-entrapped fluid through the valve system or syringe barrel reservoir prior to use is key to experiencing consistent, accurate dispensing.
Equipment maintenance appeared to be a challenge across the board, regardless of the dispensing method (aside from those using cotton swabs, toothpicks, squeeze bottles, and medical syringes) to apply assembly fluids. Responses broken down by fluid dispensing method include:
- 46% of 2017 and 45% of 2018 respondents rated this as the top challenge when using positive displacement dispensers
- 39% of 2017 and 33% of 2018 respondents using pneumatic valve systems rated this as a challenge
- 35% of 2018 respondents rated equipment maintenance as a challenge when using pneumatic jetting valve systems
While it is interesting that more respondents rated positive displacement dispensers as a challenge when it comes to equipment maintenance vs. pneumatic valve and jet valve systems, it is not surprising. Positive displacement dispensers such as volumetric pumps generally feature more intricate parts that require more time to disassemble and clean. The benefit of positive displacement systems is that they provide continuous, repeatable dispensing, regardless of fluid viscosity or changes in viscosity over time. For many types of applications, the benefits outweigh the downside of taking longer to clean.
Recent advances in dispensing technology, including pneumatic valves and piezoelectric jetting valves, reduce maintenance time through innovative product design. Quick-release clasps integrated into the valve design allow operators to quickly remove the fluid body while keeping the valve mounted to automated systems. Not having to remove the valve to clean it and return it to service saves a great deal of maintenance time. In fact, if a manufacturer had more than one fluid body prepped ahead of time, the switch could be seamless, minimizing downtime for service to only a few minutes.
Jet valves with fluid bodies that are easy to remove without dismounting the valve can help minimize equipment maintenance time.
Need for Faster Production
The need for faster production was reported as a top challenge for manufacturers using cotton swabs and toothpicks to apply assembly fluids. 44% of 2018 respondents expressed this as the main challenge of this dispensing method.
Surprisingly, 43% of respondents using tabletop automated systems also said the need for faster production was a top concern. When higher throughput is required, an automated tabletop dispensing robot often increases the speed of production by allowing faster dispensing on a batch of parts vs. one-by-one applications when dispensing fluid manually with a toothpick or squeeze bottle. One reason respondents may have cited faster production as a pain point of automated dispensing systems could be that some manufacturers purposely design robots to move more slowly so they don’t require being enclosed in safety guarded systems.
Recent advances in tabletop dispensing robots include purposeful product design decisions for decreasing dispense cycle times. These newer robots feature ball screw actuation instead of belts for that very purpose. They also achieve best-in-class positional repeatability at ± 0.003 mm.
Fluid Waste, Operator Training, and Rework
The final three factors in the ranking of top fluid dispensing challenges for manufacturers were: fluid waste, operator training, and rework/rejects. Fluid waste can certainly be a costly challenge, depending on the type of fluid used in the assembly process. One way to reduce fluid waste is to use disposable dispensing components (e.g., syringe barrels and pistons) that are right for the fluid type to prevent leaving any fluid left in the barrel after dispensing. Some components are designed to work as a system to reduce waste.
Shorter fluid feed tubing between the fluid reservoir and dispense valve can also help reduce waste. Using dispense valves designed with zero dead fluid volume inside the valve can also help ensure all the fluid is being dispensed so there is minimal waste.
The next challenge, operator training, is more of a concern with sophisticated jetting systems and tabletop robots. One way to overcome this issue is to work with a dispensing equipment provider that will test the assembly fluid and application in-house on the equipment prior to purchase. This not only provides confirmation that the equipment will deliver the desired result but also generates documented parameters to use as a guide when setting up the equipment and training operators.
Recent upgrades in proprietary software used to program tabletop automated dispensing systems can also significantly reduce the time it takes to train operators. Some equipment vendors have invested a great deal in developing an intuitive software interface to simplify setup and programming of dispensing robots to reduce operator training requirements.
Upgrades in proprietary software used to program automated dispensing systems reduce the time it takes to train operators.
Lastly, rework and rejects are obviously a significant challenge. However, using the right dispensing equipment can greatly minimize the amount of rework and rejects. The more sophisticated the dispensing system, the less likely the chance of creating rework and rejects. Working with a partner that understands the nuances of all the different types of dispensing equipment and the type of setup required for a specific application is key.
Optimizing fluid dispensing processes to make production operations run faster, smoother, and with a heightened return on investment can be achieved by using the right equipment and working with an experienced partner with a wide range of solutions to offer. Minor process improvements, such as making sure assembly fluids are air free prior to dispensing, can also help optimize fluid dispensing processes.
For more information, visit www.nordsonefd.com.
Note: Images courtesy of Nordson EFD.