THE TOP 5 WAYS TO GET YOUR GLUE UNDER CONTROL TODAY
We’ve used robotics to automate a variety of adhesive dispensing processes over the years. But, we can’t do that effectively until you get your glue under control. When starting a new project we see the same issues over and over. Often times, companies look to automation to solve production issues. Many customers come to us to increase throughput and quality. What we find is that they don’t fully understand their current process and no amount of robotics or automation can solve that problem. Taking a step back to methodically define what you are really trying to do can offer immediate savings… even without a robot.
We’d like to share what we’ve learned so you can start off on the right foot and get your glue under control.
1) What’s your spec?
Most processes that we see don’t have a measurable, attainable specification. Specifications for a process can be wide ranging from technical requirements to defining how a user will interact with the process. Every specification should be associated with an acceptance criteria that can be clearly verifiable.
Often, a process is transferred rapidly from R&D into production and not enough testing has been completed to characterize a process. Processes are implemented that are heavily dependent on operator consistency and training. New operators can have negative impacts on device quality.
With adhesives we prefer to see specifications that have been developed with data based on testing with known volumes of adhesive and tensile or functional tests. Often times this leads to multiple specifications.
For example, a poor specification:
Apply enough glue to attach component X to component Y
This has a lot to be desired because the amount of adhesive is not defined and we don’t know how strong the joint between the components don’t need to be.
Adhesive bead should be greater than ¼” wide
Force to remove component X from component Y must be greater than 5 lbf
These are much better specifications as the volume of glue is defined and detail about how “attached” component X and Y need to be is also defined. A specification like this also leads to a process that can be validated. This means that if you can show that a set of parameters on a robot (pressure/speed) always (statistically) lead to a bead with of ¼” and a force that meets the requirement then less testing over time will be required. Using proper specifications to get your glue under control will further reduce manufacturing costs.
2) How do you inspect it?
Not having a verifiable method to determine if your process meets specification can also be a headache. Visual inspections that rely on operator judgement are the most common and can lead to a host of downstream quality issues.
Moving to a verifiable test method may require the engineering to do a bite more characterization but will be worth it in the end. Replacing visual inspection with dimensional inspections, go/no go gages, vision systems, etc will all make for a robust (and cheaper) manufacturing process.
3) How much glue do you need?
To get your glue under control you need to know how much glue you need. Specifying the number of “drops” of glue to apply does not make for a robust process!
While volume is the best way to measure the amount of adhesive applied, it’s not always practical. Using a robot with a pre-defined speed and pressure parameters can get you what you need. By setting upper and lower bounds for speed and pressure and testing at the worst case, you can much better define “how much” glue to apply.
Additionally, if you are applying dots or “drops” you can also use the diameter of the resulting adhesive bead to define how much.
Get a consistent bead with our robotic adhesive dispensing kit. Learn more HERE.
4) Do you have the right type of adhesive?
The most common reason we here for an adhesive being chosen is that, “we had it in the R&D lab when we started developing the project.” This is especially challenging to overcome because if there’s no real reason that it was chosen in the first place, it’s hard to compare a better option.
In this case, we recommend having an adhesive manufacturer like Henkel/Loctite or Dymax help you choose an adhesive. While this can be difficult after a product has been put into production it will likely save you in device quality costs in the future. Working with a manufacturer will help get you the correct adhesive to join specific materials but it will also take into consideration the manufacturing process for applying that adhesive as well as the end use of the product. While a thin cyanoacrylate might be easy and cheap to prototype with, it may be a nightmare to try and apply when device manufacturing quantities ramp up.
5) Validate your process
If you’ve taken the time to properly define 1-4 above, then you should be able to develop a robust manufacturing process that can be validated. Validation of a process does not need to be as hard and labor intensive as many make it out to be. Define your specifications properly with the right inspection methods and it should be very straightforward. We prefer to use the Installation Qualification/Operational Qualification/Process Qualification (IQ/OQ/PQ) method to properly validate a process.
The IMDRF has posted guidelines on testing for medical devices that has detailed info that you may want to read about HERE.
Installation Qualification (IQ): This ensures that the equipment has been installed correctly. Does it have the correct voltage, air pressure, etc.
Operational Qualification (OQ): This defines the maximum and minimum parameters that a process can be operated at and this test is a challenge at those maximum and minimum values. This could be a range of air pressure that adhesive is dispensed at, speed of a robot, diameter of jaws of a crimper, etc.
Process Qualification (PQ): This is a test that is run at the nominal system parameters that will be encountered in production and will demonstrate that the process is consistent enough to produce acceptable product.
We hope this gave you a solid starting point to get your glue under control. By focusing on these 5 areas you should be able to quickly see returns on your manufacturing line that will result in a reduction in quality issues and an increase in throughput:
- Glue volume
- Choosing the right adhesive