Prototyping Methods Compared: How We Actually Use FDM, SLA, SLS and DLP

Every 3D printing technology has a marketing niche; accuracy, speed, surface finish, cost per part. What matters far more in practice is which technology answers the specific question you’re actually asking at that stage of a project.

Early on, that question is often ‘does this basic geometry work?’ Later, it might be ‘will this survive being handled a thousand times a day?’ Different questions call for different tools.

Rather than run through the technical specifications in the abstract, it’s more useful to show how prototyping actually plays out on a real project. So here’s one: a complex injection moulded part we developed to let two different handheld computer ranges interface and dock into the same accessory ecosystem for a major retail client.

The brief: one interface, two incompatible devices

The client needed a single accessory part, essentially a bridge component, that would let a Zebra RFD8500 RFID sled work interchangeably with either a Zebra TC58 or a Honeywell CT40 handheld computer. Devices from different manufacturers, none of them designed with each other in mind, all needing to interface through a moulded part with tight tolerances and a positive, reliable mechanical fit.

That’s a harder brief than it sounds. Each handset has its own body geometry, its own connector position, its own retention mechanism. The interface part had to accommodate all of that without becoming bulky, without compromising the fit of any individual device, and without adding failure points to a piece of retail hardware that would be picked up and put down hundreds of times a shift.

Starting with 3D scanning, not a blank sheet

Where existing CAD data for the handsets was incomplete or unavailable, which can be common with third-party hardware, we used 3D scanning and reverse engineering to fill the gaps. Scanning the physical devices gave us accurate surface topology to design against, rather than working from datasheet dimensions or approximate models that can hide small but critical inaccuracies in exactly the areas that matter most, such as connector alignment and retention features.

This is a step that’s easy to skip under time pressure, and it’s almost always a mistake to skip it. An interface part is only as good as the accuracy of the surfaces it has to interface with.

FDM prototyping: cheap, fast, and exactly right for this stage

Once the interface geometry was modelled, we moved straight to FDM (Fused Deposition Modelling) 3D printed prototypes. FDM isn’t the most dimensionally precise or the finest-finished printing technology available, but at this stage of the project that’s not what we needed. What we needed was to physically hold the part, test it against real hardware, and find problems fast — and FDM is unbeatable for exactly that.

Low cost per iteration, fast turnaround, and good enough accuracy to validate fit and function.

We used the printed prototypes for three specific checks.

First, confirming the part worked correctly not just with the handsets themselves but with the other hardware in the ecosystem, including charging stations, where a part can fit the device perfectly and still foul on a dock.

Second, verifying the fit of each handset variant. Does it seat correctly and securely into the shared interface.

Third, and just as important, ease of use. Checking that insertion and release of the handset felt right in the hand.

“A part that fits perfectly on screen and feels wrong in the hand is still a failed design. Physical prototyping is the best way to catch that.”

From validated prototype to production tooling

Positive results from physical testing meant we could move quickly from FDM prototype to production tooling, without a long cycle of redesign and re-testing.

That speed only works because the earlier stage was done properly, accurate reverse engineering with FDM prototypes that resolved the fit and clearance issues that would otherwise have shown up expensively at the tooling stage instead.

For injection moulded production, we work with specialist tooling suppliers who offer two routes depending on volume. For modest batch runs, aluminium tooling is a genuinely cost-effective option. Quicker and cheaper to produce than steel, while still giving a production-quality moulded part. For higher volumes, hardened steel tooling is the right investment, offering a much longer tool life suited to sustained, high-quantity production.

Matching the tooling approach to the actual volume required, rather than defaulting to the most expensive option, is part of getting the economics of a project right and not just the engineering.

Beyond FDM — choosing the right process for the question you're asking

This project is one example among many where 3D printed prototyping has been central to getting a design right before committing to tooling — but FDM isn’t always the right tool for the job. The technology should match the question being asked at that stage:

–  FDM (Fused Deposition Modelling) is fast, low-cost iteration for fit, clearance and general function testing. Our default choice for early-stage validation, exactly as used on this project.

–  SLA (Stereolithography) has much finer surface finish and higher dimensional accuracy, better suited to parts where fine detail, smooth surfaces, or presentation-quality models matter.

–  SLS (Selective Laser Sintering) produces genuinely functional parts in nylon-based materials without support structures, useful for testing complex geometries or components that need real mechanical durability during testing.

–  DLP (Digital Light Processing) is fast, high-resolution printing suited to small, highly detailed parts where accuracy at a small scale matters more than build volume.

Choosing between them isn’t about which is ‘best’ in the abstract, it’s about matching the process to what you’re actually trying to learn at that point in the project. Early fit or clearance checking on a large interface part like this one, FDM every time. Fine surface detail on a small cosmetic component, SLA. A working mechanism that needs to survive genuine handling during testing, SLS. Intricate parts with features measured in microns, DLP.

These are just some of the options available. The right prototype, at the right stage, using the right process — that’s what turns a complex design into a part that goes from prototype to production tooling without expensive surprises along the way.

MAKE manages the full prototyping journey — from 3D scanning and reverse engineering through FDM, SLA, SLS and DLP prototyping to production tooling.

Get in touch to discuss your project.