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.
3D Printing Advantages
- Higher design freedom
- Channels not constrained to 2 axis
- Single part flow
- Short lead time
- Very accessible, easy to find vendors or in-house
- Inexpensive for small quantities
- Many resin choices
- Clear or opaque parts
- Improves breadboarding
- Minimal training to produce your own
- Low cost for equipment
3D Printing Drawbacks
- Expensive for large batches
- Rough/poor surface finish
- Ok for air but not liquids
- Makes cleaning much more difficult
- Hard to make small channels
- Secondary operation needed for small holes and cleanout
- Difficult to get truly round channels
- Base materials are light-cured acrylics
- Not very strong along printing axes
- Low Z axis feature accuracy
Drilled plastic manifolds offer several benefits. For engineers looking for a more economical and easier-to-design alternative, drilled manifolds have less manual involvement as a majority of the process relies on machining action. Drilled manifolds also do not use layering techniques and involve one layer for its creation. This, in turn, tends to lower costs overall.
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 Part/Component Size
The maximum size for a non-bonded drilled manifold is 32”x18”x12”. 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 with increasing difficulty especially in smaller diameters (less than .050). 80:1 is challenging.
A work around for through holes is to drill from two sides and meet in the middle. Ratios up to 160:1 becomes 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 .001”/1” 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.
Size & Number of Layers
Typical Footprint & Sizes for Plastic Manifolds
- Maximum: 15” x 15” (610 mm sq) – Material dependent
- Common: About 4”x 8” (102 x 152 mm)
- Smallest: no theoretical lower limit
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 3 in (7.5 cm) thick to retain functionality. In microfluidics, a .03” (0.75 mm, 750 micron) 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 4” x 6” (10 x 15 cm) with an average channel density is approximately $200 for 100 pcs. Each subsequent layer typically adds an additional $100.
When Considering Future Maintenance Costs
Manifolds can get damaged during the assembly process. Retaining screws for valves are small and easy to over-torque. In the event that a manifold is damaged during field servicing, the cost to replace one of two manifolds is much less than an entire single block.
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.
Features on a Bond Line
We can place most features on the bond line including drilled holes, threaded holes, and counter bores. Flat bottom ports will seal successfully across the bond line. We can also place tapered pipe threads on the bond line, however, we generally discourage this with stress sensitive plastics. Please reach out to our engineering team if this is a design requirement for your product.
Additionally, with our bonded manifolds, we can say that we have no history of field failure delamination or leakage/cross-talk.
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Multiplanar Bonding
To use more sides of a manifold, engineers can consider multi-planar bonding. Channel planes run both horizontally and vertically, and components can be attached to the sides for greater design flexibility.
In a typical manifold with a single or multiple bonds, the bond planes will all be parallel. Components tend to be top or bottom mount, but they can also be on the bond line as is acceptable.
Bonded in Components
By utilizing different components within the manifold, we can create unique functionalities that need to serve a particular purpose. However, an anticipated component to that assembly must have the capability to withstand the bonding temperature and pressure to have that happen. We also suggest consideration to both the assembly's and component's longevity as non-serviceable items. This means that once those components are within the manifold, further work on those is near impossible.
Here is a list of components that can be bonded into a manifold:
- Flow meter impellers
- Metal strips for conductivity and other electrical process measurements
- Orifices
- Check valves
- Silicone diaphragms for valving or pumping
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 $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, or the customer provides them to us for further processing.
Potential Cost Influencers When Creating Bonded Manifolds
Decisions made about material choice, number of layers, feature density, and physical size affect cost the most. Other factors, such as special polishing or specifically tight tolerance requirements, can influence this as well.
Designers often cite materials and resins as the leading factors when it comes to the cost of a manifold. To the right is a chart to compare the prices of different materials we bond. As we can see, UltemⓇ is quite expensive when compared to other materials. Using another material, like acrylic or polycarbonate, can save dollars. Research the material choices versus reagents carefully to make an informed decision. If needed, we can provide sample manifolds for chemical testing.
For Controlled Fluidics customers, they can take advantage of our special partnership with Quantum AEP to get special pricing available nowhere else.
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 2 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 $200 in quantity (100 pcs). Three layers is $300, and four layers totals around $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.
Comparing Single-Layer, Multilayer, and 3D Printed Manifolds
| Single Layer Machined Manifolds | Multilayer Machined Manifolds | 3D Printed Manifolds | |
|---|---|---|---|
| Footprint | 40” x 20” (100 x 50 cm). Limited by drilling capabilities | 24” x 24” (45 x 30 cm) Material dependent | Varies widely – machine dependent |
| Flexibility | Material and size of manifold | Channel shape and size Generally 2D | Can create very complex geometries, 3D possible |
| Surface Finish | Great | Great | Limited. Can be polished externally to improve |
| Chemical Resistance | Very wide range of materials means great choices for chemical resistance | Limited options however Ultem® and COC/COP have broad chemical resistance | Limited options |
| Temperature Resistance | Very wide range of materials means great capabilities for temperature resistance | Very wide range of materials means great capabilities for temperature resistance | Limited to SLS (Selective Laser Sintering) to achieve high temperature resistance |
| Accuracy | Standard ±.005” to precision +/- .0002 | Standard ±.005” to precision +/- .0002 | Lower accuracy especially in the vertical axis. Dependent on machine |
| Threads | Standard process, any location | Standard process, any location including the bond line | Can’t be done well in 3D printing, needs to be done as a secondary operation |