PLASTIC COMPONENT & MANIFOLD FABRICATION PROCESSES

Whether you're a seasoned engineer or entirely new to plastic manifold fabrication, the information below will help in guiding you to creating and manifesting high-performance plastic manifolds tailored to your unique needs.

We will cover the most important processes here: drilling and bonding along with their associated details. Let's get started.

Along with our traditional machining for single layer manifolds and bonding processes, we offer 3D printing services (additive manufacturing) for quick-turn manifold prototypes and short-run applications. This chart illustrates some of the reasons why a designer may decide to utilize 3D printing.

They also offer more flexibility considering material choice. Without restrictions on which material to use, this opens up doors to other design possibilities that may not have have been available before. However, we always recommend keeping the product's requirements in mind concerning the needed strength, chemical resistance, and temperature resistance (among other factors).

We must also note the limitations concerning drilled manifolds here as well. Here, manufacturers have to restrict the geometry of such manifolds to straight lines, reducing some possibilities. However, with drilling and plugging techniques, designers can create internal bends in the flow path. Manufacturers also have to limit L/D ratios for drilling within manifolds as this threatens the product's integrity as that ratio increases. This holds true for both traditional twist drills and gun drills.

Regarding Component Size 

The maximum size for a non-bonded drilled manifold is 81.3cm*45.7cm*30.5cm (32”*18”*12”). The limitations of drilling channels does impact the ultimate size of the manifold. Length to diameter ratios of 40:1 is reasonable. Up to 60:1 is possible, but this becomes increasingly difficult, especially in smaller diameters (<1.27 mm (0.05")). 80:1 is challenging.

A workaround for through-holes is to drill from two sides and meet in the middle. Ratios up to 160:1 become possible.

However, the downside to the approach is that the drills will not match perfectly and often leave a small step. For fluidic or pneumatic manifolds, this is generally not a concern when creating through holes from two sides. Deep intersecting holes at an angle could be problematic as drill drift can be up to 25.4μ/2.54cm (.001 in/1 in) length.

Right now, more applications are causing an increased demand in bonded manifolds, calling for greater complexity and larger sizes. When manufacturers bond two separate manifolds together, it adds an element of customization fit for complex operational demands. With drilled manifolds, they limit the kinds of internal channel patterns capable. However, with separate pieces crafted using an overhead view, machinists can more easily create those complex channels and routings than machining only from the outside and with one big block. These resolve deep hole drilling challenges and allows for non-straight channel solutions.

We'll look at size and layering in this section.

Manifold Thickness

For layering, manifolds usually consist of two or three layers and don’t go beyond five layers. Why? Going beyond five layers diminishes most returns because of fallout/scrap from its creation. Also, for each layer bonded, some opportunities exist to create a flaw that renders the manifold unusable. The more layers, the greater the opportunity for scrapped parts.

This holds true for physical size as well. The greater the surface area, the more likely a defect will render the part unusable. Most finished manifolds will have thickness less than 7.5 cm (3 in) thick to retain functionality. In microfluidics, a 0.75 mm or 750 μm (0.03 in) cover plate is common but can be thinner with secondary machining. We suggest making a manifold as small as possible with efficient tight component placing to create that balance. When a manifold exceeds 100 in² or four layers, consider two separate manifolds instead of one.

Although every project will have different pricing, we can give a rough estimate, if only to give an idea of the potential costs. Ball-park pricing for an acrylic bonded manifold measuring 10 cm*15 cm (4 in * 6 in) with an average channel density is approximately USD$200 for 100 pcs. Each subsequent layer typically adds an additional USD$100.

Pressure Limitations

Pressure limitations depend highly on channel and any reservoir or accumulator size. While most fluidic applications are less than 60 psi, typical standard operating pressures fall somewhere up to 150 psi (10 atm or 1MPa) to vacuum. With small channels, bonded manifolds are capable of handling up to 800 psi (54 atm or 5.5 MPa) working pressure.

Injection Molded Bonded Manifolds

Injection molded bonded manifolds offer some benefits over other manifold types. These are best for those projects that need a high quantity with a more economical price point. Often used as an IVD consumable, the manifolds are simpler in configuration and/or where the geometry is difficult to machine. Manufacturers often offer either two molded manifold layers or a molded manifold layer with a machined layer.

With injection molded bonded manifolds, most designers most often choose acrylic as it often meets most requirements while maintaining a reasonable price point. Bonding costs for this material can come in as low as USD$10 per bond.

For these types of manifolds, we must state some design considerations. For one, the designer has to consider the flatness of the mating surfaces for success as most times an initial development order is required. Special fixturing is often needed to support the manifold layers properly. Moreover, manufacturers often prefer single sided channels in either a square or D-shape for easier machining.

When creating these, we have two options for sourcing. Either we can source injection molded parts from a third party, or the customer provides them to us for further processing.

About Layer Count & Cost Reduction

Layer count factors as a strong driver of cost increases for bonded plastic manifolds. More layers means higher cost, but nominally so as each individual layer typically comes in at around the same cost. A single layer, drilled solution has a significantly lower cost than a multilayer bonded solution as they consist of only one layer versus two or more that require more machining. As such, two-layer bonded manifolds contain three parts in one here with two layers bonded and the final finishing "layer".

When thinking about price per manifold, a good rule of thumb is a medium size and complexity two layer manifold costs about USD$200 in quantity (100 pcs). Three layers is USD$300, and four layers totals around USD$400 each.

How do we eliminate the bonding while still getting the nice benefit of all top mount connections? Designers can accomplish this with angled holes. If your application allows, simplify the design by incorporating angled holes. Traditionally, designers have avoided this approach because of cost. Extra angled fixturing increased that price quickly, but times have changed. With the arrival of low-cost 5th axis trunnions, angle holes are the same cost as straight drilled holes. Angle choice is flexible, and the trunnions can reach any position with ease.

About Other Cost-Affecting Factors

Feature density will determine the manifold's machining time. More complex, longer channel runs are more expensive than simpler layouts. Cycle times average to be over one hour for channel machining.

Physical size also factors as cost determinant. Large manifolds use more material and generally have longer channel runs, and in turn, can add up quickly if designers don't consider these factors before production. When manifolds get large or require many layers, consider splitting them into two. This can better support field servicing and potentially reduce cost.