Injection Molded Manifolds (Podcast)

In this podcast, Tom Rohlfs talks with John Maher about injection molded manifolds. Controlled Fluidics have the unique capacity to bond injection molded components together to make manifolds, and Tom explains the manufacturing process and design considerations.

John Maher: Hi, I am John Maher. I’m here today with Tom Rohlfs, President and Principal Engineer at Controlled Fluidics, a plastics machining company specializing in precision manifolds. Our topic today is injection molded manifolds. Welcome, Tom.

Tom Rohlfs: Morning, John. Thanks for having me.

What Is an Injection Molded Manifold?

John: Sure. So Tom, what is an injection molded manifold?

Tom: So Controlled Fluidics has a unique capability where we’re able to take injection molded components and bond them together to create a manifold. As far as I know, we’re the only ones doing it.

We have customers in the life science industry as typical. Generally this is used as a consumable. The manifold injection mold manifold tends to be fairly basic, but they need something relatively low cost that can be used as a consumable for a medical device. Typically, point-of-care applications where you have a patient come in, they take some sort of sample from that patient, they use the manifold for testing, whatever they might be testing for, and then that manifold is thrown out after the test is complete.

So we see it a lot on the consumable stage. A full-bonded manifold from us can be quite expensive. Oftentimes a simple two-layer acrylic manifold of four inches by six inches with kind of medium complexity, can run about $200 a piece. Obviously as a consumable, that would be a difficulty for the customer. So this is a way to create manifold channels without the machining process.

And then we complete it via the bonding process, we’ll put on generally single-sided channels and we’ll put on a cover plate. So it’s a nice way to get a low-cost bonded manifold and help the customer achieve their goals to keep things economical.

Cost of an Injection Molded Manifold

John: What would be the typical cost of one of these injection molded manifolds as compared to the $200 bonded one that you mentioned?

Tom: Yeah, they’re very application specific, but we have just straight bonded processes. So we had one application where a customer sent me two halves. I took it out of the bag, I bonded it, put it back into the bag, very simple. And each bond cost around $15 a piece. So 10 to $15 a piece depending on the complexity of the part. So we’re able to do some very low cost bonding applications for some of these customers in the consumable space.

Manufacturing Injection Molded Manifolds

John: Talk a little bit about these injection molded manifolds and the difference in manufacturing these versus the other types of manufacturing that you do, like the bonded manifolds or drilled manifolds.

Tom: Yeah, so oftentimes our biggest challenge, and we have an application currently in shop, is that we require very flat components. In order to bond, you need to have good intimate contact from surface to surface. If the part isn’t flat or it has variation in thickness, we can’t do it.

So with this particular application we have in-house, we end up skimming. We get an injection molded component, we skim both halves to make it very flat and parallel, and then we’re able to bond it together and send it back to the customer. So what’s nice is the configuration of the part is historically or typically a bonded manifold is just a simple rectangle, right.

It’s a cube, it’s a rectangle, it’s a flat plate. Because we need to push on either side, both halves tend to be very flat geometrically. The nice thing about injection molding is that you can have lots of different irregular shapes and we can still hold onto that part and bond it together. It works pretty well. But again, very small parts. These parts are only one inch by four inch.

They don’t tend to be very big. Again, their injection mold parts, they don’t tend to be big anyway. And the manifold channels are relatively simple. Again, our bond strengths with injection molding components, and by the way, we just do this for PMMA acrylic, we don’t do this for any other material. Again, our bond strengths are good, customers run 150 PSI in these small manifolds and it works quite successfully for them.

Materials for Injection Molding

John: Yeah, so I was going to ask about the materials and if there were limitations in terms of what materials you can use with injection molding. So PMMA plastic, that’s the type that you have to use?

Tom: Yeah. Which is acrylic. That’s a generic name for acrylic.

John: And why is it that is what you’re limited to with injection molding?

Tom: Yeah. Sure, because acrylic is so readily bonded, other materials are more difficult to bond and so I think acrylic bonds, we’ve never been requested of it, but I suspect we could do ultem as well. Ultem is readily bondable, but because acrylic is so bond friendly, that really helps us achieve it.

Because this particular part, and often injection molded parts, they’re very irregular shapes. They’re not nice flat plates. They’re irregular shapes, so holding onto them and putting appropriate pressure can be a little tricky. So we need something that’s bond friendly.

John: Right, ’cause you’re taking these two pieces that you make, whether an injection molded part and then a flat plate or whatever, and then you have to bond those together and they have to be able to hold. So you’re limited with the types of plastics that you can use because of that?

Tom: That’s correct.

John: Right.

Tom: They need to be easy to bond, as it is, because of the shape generally, it’s challenging to begin with. Because we have to put consistent pressure across the entire piece in order for it to bond, they have to meet with each other well.

Advantages and Disadvantages of Injection Molded Manifolds

John: So you mentioned cost being the major factor. Are there other advantages or disadvantages of injection molded manifolds?

Tom: Yeah. You can get configurations. This particular manifold that I’m thinking of has a little reservoir built into it. It has geometric shapes that we wouldn’t do, couldn’t do very successfully from a machining front. We could machine it, but we couldn’t machine it economically. The injection molded process is far, far less money in certain applications or in a lot of applications when it comes to plastics.

John: And that would be because you’re only machining the mold once and then after that it’s just injecting the plastic, so you don’t have to do that machining of this difficult shape every single time, you only have to do it once.

Tom: That’s right. I mean, I could imagine that this part from an injection molded perspective probably costs $5, $10. If we were to attempt to machine it would be $50.

John: Yeah, right-

Tom: Something like that. Just a big difference.

John: All right. Well, that’s really great information, Tom. Thanks again for speaking with me today.

Tom: You’re welcome.

Contact Controlled Fluidics to Learn More

John: And for more information, you can visit the website at or call 603-673-4323.