Dispensing plays an important role in manufacturing, especially in the production of products requiring high precision. There are many stringent requirements for accuracy, reliability, repeatability, dispensing speed, and throughput.
With all these complexities of the manufacturing process, the operation of something as fundamental as a dispensing valve is frequently overlooked. Especially when the vendors are not based in Vietnam, the troubleshooting process will take time and money. In this article, Gluditec will give some common errors when using dispensing valves and how to solve them.
1. Incompatible Materials
Although there is a wide range of well-designed dispensing valves with general-purpose that can handle a range of fluid viscosities is a good choice. Best results will be obtained with a dispensing valve’s style and configuration precisely matched to the properties of the fluid being dispensed.
High viscosity fluids
High viscosity fluids include silicone based adhesives or heavy grease, etc. This type of material requires high-pressure dispensing valves to perform efficiently. Moreover, with suck-back feature, the valve can prevent drooling and tailing effects to save the material as well as reduce the rework and cleanup, which are often associated with these challenging assembly materials.
Our Recommendation: High Pressure Valve
High Pressure Valve with maximum viscosity of 1,000,000cps. High discharge accuracy, capable of easily fine tuning the discharge flow.
Applied materials: Grease, Silicone, Oil, Epoxy, etc.
Low to Medium viscosity fluids
Low to Medium fluids like solvents and watery adhesives have many different requirements, especially when very small deposits are needed. For these material’s applications, we often recommend needle dispensing valves to minimize dead volume that can cause dripping or oozing.
For more precise applications, there is even a needle seat in the dispense tip, which can effectively eliminate dead fluid volume between shots, and makes it possible to produce even smaller and more consistent micro deposits.
Our Recommendation: Needle Off Valve
Precision needle dispensing valves apply low-viscosity fluids in accurate, repeatable amounts. Because the stainless steel needle seats in the tip adapter, there is virtually no dead fluid volume between shots.
Applied materials: Marking Inks, Silicone Oils, Solvents, etc.
Tricky Fluids Like Cyanoacrylates (CAs)
With tricky fluids like CAs adhesives, which are primarily characterized by their fast cure time when moisture is present, dispensing valves’ materials will require careful consideration.
For example, wetted parts made of inert, Ultra High Molecular Weight (UHMW) polymers are a good choice because they will not react with the fluid. On the other hand, nylon or metal fluid fittings should never be used with CAs because they absorb moisture and will promote premature curing. We should use polyethylene or polypropylene fittings instead. Chemically inert, polyethylene-lined or PTFE FEP tubing are good choices for fluid feed lines.
Our Recommendation: Diaphragm Dispensing Valve
The design of short opening strokes make operation more easier and increase precision of dispensing. Especially, the wetting part, which directly contacts dispensing chemicals, has various options of material to meet the demand of different dispensing liquids (including: Teflon, PEEK or Acetal).
Applied materials: Anaerobic, cyanoacrylates or UV lacquers, etc.
2. Leak and Drip
Leaking and Dripping happen when the dispensing valves can not block the glue, which leads to material loss and hygiene problems. We can see this phenomenon in two main positions, at the connectors (luer lock) or at the tip of the needle. The main reason is that the equipment is not cleaned clearly as well as maintained regularly so the valves are worn out after a period of operation and unable to seal the liquid. So please note to maintain and replace components monthly to keep the device running smoothly.
3. Glue amount dispensed is not stable
Whether the glue line is dispensed evenly and continuously or not is based on two processes, “opening/closing” and “transportation” process. The function of the dispensing valves is opening and closing the flow of material while compressed air is used to perform the function of transporting materials (or pushing materials in the valves).
If it is ensured that the valve is compatible and there are no errors, it is possible that the unstable glue amount may come from the wrong method of pushing air into the valve. Normally, manually pushing the air will not produce continuous and stable gluing lines. Therefore, the controller should be integrated into the dispensing system. A dedicated controller is an efficient approach to establish shot size and regulate valve operation. Moreover, please keep in mind that each type of dispensing valve may require a certain type of controller to achieve optimal performance.
Gluditec provides sufficient types of controller for a variety of needs, you can check our products here.
Lastly, determining the root cause of the problem will help users save time, money as well as prevent this situation from continuing in the future. When it comes to troubleshooting, Gluditec has a team of expert engineers, nationwide branches, available 24/7, who might know a better way to resolve your issue or improve your setup. Contact us for more details:
Hotline: (+84) 969 469 089