Design. Validate. Scale. is a five-part fireside chat series from Hawk Ridge Systems and A3D Manufacturing on how a product moves from concept to production. Episode 2, Choosing the Right Manufacturing Path, covers the step between design and production: the CAD model is locked, and someone has to decide how each part gets made — 3D printing, CNC machining, injection molding, urethane casting, or a hybrid of them. Host David Whitten, account manager at Hawk Ridge Systems, puts the questions Hawk Ridge customers ask on real projects to Michael Dymond, product manager at A3D Manufacturing, and the live audience adds their own. Here are the most important takeaways:
Key Takeaways
- Choose a manufacturing process per part, not per product. Steer each part in the bill of materials (BOM) to the process that suits it.
- Tool the large, locked geometry. Keep small, uncertain, or fast-changing parts on the 3D printer.
- Moving to injection molding does not always lower unit cost. A hybrid BOM can cost less than an all-molded one.
- The break-even quantity between 3D printing and injection molding is not a fixed number. Part size and material set it, and teams move off it on purpose.
- Metal 3D printing is rarely a cost play. If a part can be CNC machined, machine it.
Should I 3D Print This Product or Injection Mold It?
Neither, as a single decision. Dymond says the product is the wrong unit; the bill of materials is the right one.
“You can take individual parts and geometries within your BOM and steer them into their strong suits.”
That is what A3D means by hybrid manufacturing. It is not a machine. It is going through the BOM à la carte. Sometimes hybrid is a linear path for the whole product: 3D print the prototype, move to a higher-fidelity print for bridge production, release on urethane casting, then tool for injection molding. Sometimes it is a production unit that ships with 3D-printed parts in it indefinitely, unless user feedback drives a change.
“It’s this mentality of bringing the right-size hammer to the right-size nail.”
Which Parts Should Be Tooled, and Which Should Stay on the Printer?
Tool the large geometry you are confident in. Print the parts that are small, uncertain, or likely to change. The rule comes from the cost shape of each process.
Additive manufacturing has little to no tooling up front, but the unit cost is not great, and it gets worse as parts get bigger and simpler.
“The worst thing you can 3D print is a real big, simple box.”
Injection molding is the complete flip: tens of thousands of dollars in tooling to reach a very low per-part cost. CNC machining sits in the middle, with some NRE in jigs and fixtures and a moderate unit cost.
Dymond’s example is an electronics enclosure. The form factor is well defined and locked, so the main enclosure, the large part, goes to injection molding. The user interface is still up in the air: the screen, the plug-in ports, where the battery installs. So A3D molds the enclosure and 3D prints the face plates, interface plates, and bezels. The customer gets real cost savings against the all-injection-molded plan, plus the ability to change those parts when the hardware updates.
Does Moving to Injection Molding Always Lower My Unit Cost?
No. Whitten admits this is not what he expects: the instinct says the further you move toward set-in-stone traditional manufacturing, the lower the price per part. The enclosure case is the counterexample. Molding everything costs more than molding the housing and printing the parts that are still moving.
At What Quantity Do I Switch From 3D Printing to Injection Molding?
There is no single break-even number. On paper it is a quantity question; in practice, part size and material set the break-even point.
Very small, complex parts can stay on the printer well into the thousands. Complexity is free in 3D printing, and A3D can produce a lot of small parts per run, so the quantity at which tooling is justified is very high. Large parts flip quickly. Dymond sees parts where the break-even is 20 or 40 units, because the part needs a higher-performance plastic and each print is expensive relative to the tool.
Teams also move off the on-paper number on purpose. Some switch to injection molding early: the break-even is 1,000, but they want the molded finish, a specific texture, or a specific resin formulation, so they pivot at 500. Others stay on the printer past break-even because they expect user feedback and a design change six months out, and they want to stay agile.
Can I Get Manufacturing Quotes Before My Drawings Are Done?
For 3D printing, yes. Whitten’s advice for anyone newer to manufacturing services: you do not need dialed-in engineering drawings to quote printed parts. Send a CAD model. If you are iterating, that lets you get parts quoted and made before you spend time on the drawings a traditional process requires.
Some of Dymond’s customers send two or three versions of the same part with minor tweaks at once, to get three learning cycles in one go.
Do 3D Printed Parts Look Like Production Parts?
Yes, with the right technology and finish. The picture most people have is FDM, where 3D printing started, with visible layer lines. Technology has moved on.
For cosmetics, people often think SLA. Dymond is wary of putting SLA parts into the field as finished product: light cures them, and light can over-cure and embrittle them later. For customer-facing production additive, A3D turns to powder-based 3D printing. Parts come off the printer with a matte texture. The lowest-hanging fruit is a black dye, which reads as ruggedized and lands well in defense and government work. At the other end, print in a white material, vapor-smooth it, and gloss it for the clean, medical-device look. Inserts, mechanical smoothing, and premium dyes in reds, blues, and greens sit in between.
“Unless you’re well initiated into the world of 3D printing, you have a hard time picking one out as being a printed part sometimes.”
Can I 3D Print Transparent or Tinted Parts?
For prototypes, yes. For production, you usually have to leave the printer.
For prototyping, there is a 3D printing technology that mixes a clear resin with a pigmented one to get a smoked, fogged, or tinted-clear look. For production, injection molding is relatively easy: start with a clear polycarbonate and mold the pigment into the plastic. For bridge quantities, urethane casting gets you there the same way: a clear urethane, pigment added by the drop until the color is right. In both cases the color is in the part, not a coating that scratches off.
Is Metal 3D Printing a Good Fit for My Part?
More often than not, no.
“If a part could be CNC machined, it should be CNC machined.”
Machining holds tighter tolerances and repeats better, and an apples-to-apples part costs several times more printed in metal than machined. The exception is a part designed in a way that cannot be machined, where the geometry delivers a real performance improvement that justifies the cost. Aerospace engine components and implantable medical devices with organic, super-surfaced geometry are the cases Dymond points to. Outside those, if you are considering metal 3D printing as a cost saver, strike that from memory.
When Is 3D Printing the Right Manufacturing Path?
Two cases: low quantity and performance geometry. Low quantity means prototypes, demo units for a trade show, a sample to get a decision maker to a yes or no. Nobody tools an injection mold for two parts that are going out to get beaten up. Performance geometry means lightweighting in aerospace, or cooling channels and structures that CNC could technically cut but additive handles better.
Traditional manufacturing wins when quantity climbs, when you need a material or performance you cannot get from a printer, or when tolerances tighten toward a few thousandths. Traditional is also a wider menu than CNC and injection molding: urethane casting, compression molding, waterjet, sheet metal, press brake, stamping, die casting, wire forming. Each has a geometry it prefers.
Dymond’s shorthand for choosing the right manufacturing path is Now, Next, Later.
“It’s the NML approach: what do you need now, what are you going to need next a couple months, what are you going to need way down the path later.”
Quantity, geometry, material, then a clock, applied one part at a time. That is the path. If you want help walking a BOM through it, A3D Manufacturing offers manufacturing as a service from prototype to production.
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