The governing equation for flow is shown here: A good example is the design and manufacturing of a slot die for fluid coating operations. If you have a fixed lip slot die that utilizes a body shim to control the fluid flow, then the difference between different body shim thicknesses are compounded by the flow control equation.
In the world of manufacturing, an engineer learns a lot by getting out on the shop floor and turning some knobs. With this knowledge, an experimental design can be developed around these factors and a coating window established.
You have to be careful with shear sensitive fluids however, and manage the flow control with the rheological properties.
The basis of this pre-metered system is that there are two die body slot die lip design that are slot die lip design together to form a slot for fluid to be deposited on a substrate. The goal of the manifold is to place the fluid exiting the slot at a consistent velocity so the flow phenomena is predictable when interacting with the substrate.
The interfacial chemistry of the fluid and substrate are enough to understand without having to deal with irregular fluid vectors exiting the slot die.
This design perspective will help lead front line manufacturing projects as companies look to improve efficiencies and drive down production costs. The opposite end of this slot is where the fluid is fed in and distributes along a manifold or flow chamber.
July 02, If you'd like to hear from Mark Miller's own lips rather than read his column titled, "Coating Matters Slot Die Design Considerations," click on his podcast below: And you thought the vendor was useful just when you wanted to buy something! This may be a couple thousand cP for some fluids, while only a handful of cP for other fluids.
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While the manifold of the slot die slot die lip design the fluid uniformly within the slot die, the lip land and slot die lip gap controls the final fluid flow as it exits the slot die. Similarly, if you are operating a flexible lip slot die, it is important to start with the lip opening at a well tuned opening via feeler gauges and remember that a small adjustment can create a large effect.
This simple equation shows that the slot die lip gap change and the subsequent shim thickness should be shifted slightly to see the effect. What is awesome about the physical capability of the slot die is that the manifold can be designed for fluids ranging from 1—, cP and still perform as required for product performance.
This insight can be garnered by engaging in a dialogue with the vendor in question, especially if you have access how to make money blackjack the individuals who are involved in the design of the equipment.
So if you have heard of curtain coating, this is simply a slot die coater arranged to drop a fluid curtain down from a height, while draw coating is positioning a slot die in a horizontal arrangement farther away from the substrate than in a slot die lip design proximity arrangement. The slot die is typically designed as two pieces of metal that are either separated by a body shim or adjusted by lip adjusting bolts working against a hinged lip design.
The key to uniform flow is distribution and stable pressure, velocity, and volumetric flow at exit. I would caution the slot die operator to make a minor change and then wait for the response to show before chasing the high or low spot in coating.
The boundary conditions of these factors, in addition to the temperature, pressure, and surface energy of the fluid and substrate, predict the flow behavior of the slot die.
I am pointing out the robustness of the technology, not the capability of one piece of equipment. Remember, however, that one manifold cannot coat this entire range! The other amazing characteristic of the slot die technology is the ability to coat from any position around a substrate—horizontal, vertical, above, below….