Why Do Results Change Day by Day?
“Yesterday it was perfect, but today it is full of streaks.” “The film thickness changes between morning and afternoon.” We hear this constantly in dip coating labs.
If your liquid viscosity and withdrawal speed are exactly the same, but your results are changing, the problem is not your machine or your liquid. The problem is the air in your lab.
Dip coating is not just about pulling a part out of a liquid; it is also about how that liquid dries. Controlling this drying process is the secret to getting perfect, repeatable results every single day.
How Airflow Ruins Your Film Thickness
The moment your part leaves the liquid surface, the solvent starts to evaporate. The speed of this evaporation is highly sensitive to the airflow around it.
A slight breeze from the lab’s air conditioner, or even the air movement from someone walking past the machine, can speed up evaporation in specific spots. When evaporation speeds up, the liquid gets thicker and stickier. This causes uneven film thickness, streaks, and drag marks. If you are using fast-drying solvents like alcohol or thinner, even a tiny draft will cause major defects.
The Fix: Create a Draft-Free Space
The most reliable way to fix this is to put a clear cover, or a chamber, over your entire machine.
A chamber completely blocks room drafts. It also traps a little bit of the solvent vapor inside. This slows down the overall evaporation rate, giving the liquid enough time to spread out evenly (leveling) before it dries. With a chamber, you get the exact same quality every time, no matter what the air in the lab is doing.
From Controlled Chambers to Contract Services
In professional R&D and mass production, a chamber is practically mandatory. SDI offers custom-fitted chambers for our dip coaters. We can also build advanced systems that control the exact temperature and humidity inside the chamber.
If controlling your lab’s environment is simply too difficult, let us do the work for you. SDI’s Contract Coating Service runs your parts in our own fully controlled environments, ensuring flawless results without the headache.
▼ We offer testing services in controlled environments. Learn more.
https://www.sdicompany.com/en/jutaku/