Common dispensing challenges and solutions

Almost 900 plant engineering and management personnel from diverse industries within the United States weigh in on specific challenges they face relating to their dispensing methods. Find out how to address some of these challenges to improve control in manufacturing processes.

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. Having long been a key player in the design and manufacture of precision fluid dispensing systems for benchtop assembly processes and automated assembly lines, the company shares key guidelines for solving these challenges to improve process control (photo 1). 

Methodology and challenges

Sponsored by Nordson EFD and conducted by Clear Seas Research, the market study was conducted over a five-year period, in three separate waves, from 2014 through 2018.  Using largely identical questions, and similar size respondent bases from similar geographic sections of the country and industries, results from the three studies were then combined to achieve trending data. 890 respondents participated from manufacturing companies throughout the United States.  Respondents were qualified as being involved in deciding which assembly fluids and dispensing equipment are used by their organizations’ manufacturing process. These are the highest rated challenging factors relating to dispensing systems, based on data from the 2018 respondents: shot-to-shot repeatability, shot-to-shot accuracy, equipment maintenance, need for faster production, fluid waste, operator training, rework and rejects. 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 and 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, and only 26% of respondents using positive displacement dispensing systems said this was a challenge. Although, improving the sophistication of dispensing equipment can solve the problem of shot-to-shot repeatability, so can following other simple guidelines like ensuring there is no air in the assembly fluid being used. Air bubbles in fluid are undoubtedly one of the top culprits in ruining deposit consistency for manufacturers. There are many ways to prevent air entrapment from ruining deposit consistency, including: using a centrifuge to purge air from fluid in syringe barrel fluid reservoirs prior to dispensing (photo 2); using the proper, high-quality dispensing components designed to purge air as dispensing takes place (photo 2a); following the guidelines for thawing frozen assembly fluids to prevent freeze-thaw voids in fluid. 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 piezo-electric jet valves. These latest advances eliminate the barrier between speed and accuracy when dispensing assembly fluids (photo 3). Recent advancements in air-powered dispensers are also helping solve the dispense accuracy challenge. Improvements in software allow features like multi-shot capabilities where an operator can program the dispenser to dispense multiple, accurate deposits with a single press of the foot pedal. This feature also can help speed production (photo 4). 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. Here’s how it breaks down by fluid dispensing method: 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 interesting that more respondents rated positive displacement dispensers as a challenge when it comes to equipment maintenance versus pneumatic valve and jet valve systems, it is not surprising. Positive displacement dispensers, such as volumetric pumps, generally have more intricate parts that require more time to disassemble and clean. The plus side 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 piezo-electric jetting valves, reduce maintenance time through innovative product design. Quick release clasps integrated into 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 (photo 5).

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 said the need for faster production was a top concern. Often when higher throughput is required, an automated tabletop dispensing robot increases the speed of production by allowing faster dispensing on a batch of parts versus 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 slower 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 and operator Training

The final three 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, such as 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. Operator training is the next challenge. This is true more so with sophisticated jetting systems and tabletop robots. One way to overcome this challenge 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 (photo 6). 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 who understands the nuances between 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.

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