Drilled Manifolds

Plastic manifolds are used to control fluid flow, either gas or liquid. Manifolds can be a simple block of plastic with drilled holes allowing for a single input being split into multiple outputs. Alternatively, they can be a complex multilayer device with multiple input and output ports. They can be designed to support both gas and liquid simultaneously while managing flow with pumps, valves, pressure sensors and the like.

Deciding what is the right fit is often an early decision point for an engineer in fluidic system design. Deciding which approach is right is project dependent. Cost, simplicity, desired material, availability all play an important role.

For engineers looking for a low cost, easier to design manifold solution, consider a drilled manifold. Drilled manifolds are as it sounds, created by machining action alone, no use of layers. Machining approaches are typically utilizing end mills and drills to create channels and ports for fluid flow.

The most important advantage is the flexibility of material choice. Material is limited only to the availability of the plastic allowing designers freedom in selecting the right choice given strength, chemical, temperature etc. requirements.

Alternatively, an important disadvantage is that the geometry is limited to straight lines. Design layout is constrained by straight lines created by the tooling, reducing the overall possibilities. This concern can be mitigated by a process called “drilling and plugging”. Designers create internal bends in flow paths by cross drilling two holes. The channel is plugged with a cylinder of parent material or a ball of alternative material such as ceramic or SS.

Another notable limitation to drill manifolds is the L/D ratio for drilling. Designers must carefully consider the ability of drill to form proper holes as the L/D ratio increases. Size, finish and straightness can degrade as the L/D ratio increases. This is true for both traditional twist drills and gundrills.

Advantages of a drilled manifold

• Lowest cost machining method
• Unlimited material choice
• Can be made with conventional machining methods
• Can source quickly

Disadvantages

• Design limited to straight channels.
• Design limited to standard drill depths
• More complex designs require plugging.
• Intersecting holes can harbor chips