Fused deposition modeling, and when the part needs to be metal.

FDM is the 3D printing most engineers meet first. It is fast, cheap and good at what it does. This guide explains what it does, where it stops, and when to move the same file to laser powder bed fusion.

AME does not run fused deposition modeling. We are a metal shop, and we say so up front because a surprising number of the files we receive have been through an FDM printer first, which is exactly the right order. Here is how the two processes relate.

Sectioned metal 3D printed part revealing internal passages that no plastic process could make

Layer, LPBF vs FDM: 0.04mm, against 0.2 mm typical for FDM
Service temperature: 650°C for Inconel 718; about 150 °C for the best FDM polymers
Tolerance: ±0.1mm for LPBF; ±0.3 mm typical for FDM
Density: 99.5⁺percent, pressure tight; FDM beads leave voids

What fused deposition modeling is.

Fused deposition modeling (FDM, also fused filament fabrication or FFF) pushes a thermoplastic filament through a heated nozzle and lays it down in beads, layer on layer, at 0.1 to 0.3 mm per layer. The materials are polymers: PLA, ABS, PETG, nylon, polycarbonate, and at the high end PEI (ULTEM) and PEEK, often with chopped carbon fibre. The machines run from a few hundred dollars on a desk to industrial systems with heated chambers.

It is the right tool for form and fit checks, jigs, fixtures, enclosures, ergonomic mock ups, and a great many end use plastic parts. It is fast, the material is cheap, and a part can be in your hand the same afternoon.

Where FDM stops.

Temperature. ABS softens around 100 °C, ULTEM 9085 around 150 °C. Inconel 718 carries structural load at 650 °C and GRCop-42 past 700 °C. If the part sees heat, FDM is a model of the part, not the part.
Strength and anisotropy. A printed bead bonds to its neighbour more weakly than to itself, so FDM parts are weakest between layers, often at half the strength of the print direction. LPBF parts after heat treatment are close to isotropic and meet wrought minimums.
Pressure and sealing. Beads leave micro voids. FDM parts weep under pressure unless coated; a fully melted metal part is pressure tight as printed.
Tolerance and surface. FDM holds ±0.2 to 0.5 mm with visible layer lines. LPBF holds ±0.1 to 0.2 mm and machines to whatever the drawing says.
Feature size. A 0.4 mm FDM nozzle cannot make a 0.5 mm wall or a 1 mm cooling channel. A 90 micron laser spot can.

What about metal FDM?

Bound metal filament, a polymer loaded with metal powder that is extruded like FDM and then debound and sintered in a furnace, exists and has its place: small brackets and fixtures in 17-4 PH or 316L stainless. The parts shrink 15 to 20 percent in the furnace, finish at around 96 to 98 percent density, and the alloy list is short. It is not the route to an Inconel 718 manifold or a GRCop-42 chamber, and it is not what most people mean by industrial metal 3D printing. Laser powder bed fusion is.

The sensible order of operations.

Print it in plastic first. Check the fit, the routing, the hand feel, the assembly sequence. Change what is wrong. It costs almost nothing.
Design for metal. Once the shape is right, adjust it for LPBF: 45 degree self supporting angles, powder escape holes, machining stock on interfaces, consolidation where an assembly can become one part. We review this with you.
Print the functional article in metal. Same STEP file, now in Inconel 718 or GRCop-42, heat treated and inspected, ready for test.

If you are in Huntsville or Madison County there are good polymer shops for step one, and the universities and makerspaces run FDM too. For step three, bring us the file.

When to go straight to metal.

The part will see temperature above about 150 °C.
It carries pressure, or fatigue load, or both.
It has internal channels that must be leak tight.
It is the actual test article and the schedule does not allow a plastic pass.
The material itself is the point: thermal conductivity, creep resistance, oxidation resistance.

FDM and laser powder bed fusion, side by side.

Typical figures. Every polymer and every alloy has its own numbers, but the gaps are the same order of magnitude.

	FDM, thermoplastic	Laser powder bed fusion, metal
Materials	PLA, ABS, PETG, nylon, PC, ULTEM, PEEK	Inconel 718, GRCop-42; other alloys on request
Layer thickness	0.1 to 0.3 mm	0.04 mm
Tolerance, typical	±0.2 to 0.5 mm	±0.1 to 0.2 mm, machined where tighter
Tensile strength	30 to 90 MPa, by polymer	1240 MPa and up, Inconel 718 heat treated
Service temperature	About 60 to 150 °C	650 °C for 718; above 700 °C for GRCop-42
Density	Bead structure with micro voids	99.5 percent plus, pressure tight
Isotropy	Weak between layers	Near isotropic after heat treatment
Cost per part	Dollars to low hundreds	Hundreds to thousands
Lead time	Hours to days	Weeks, including heat treatment
Best use	Form and fit, jigs, enclosures, plastic end use parts	Flight and functional metal hardware: hot, loaded, pressurised

Questions we get asked.

What is fused deposition modeling?

A 3D printing process that melts a thermoplastic filament in a heated nozzle and lays it down in beads, layer on layer, to build a plastic part. It is the most common form of 3D printing, from desktop machines to industrial systems with heated chambers.

Is FDM the same as FFF?

Yes. Fused deposition modeling is the Stratasys trademark; fused filament fabrication is the generic name for the same process.

Can FDM print metal?

Only in the form of bound metal filament, which is sintered in a furnace after printing. Parts shrink 15 to 20 percent, finish at 96 to 98 percent density and are limited to a few alloys such as 17-4 PH and 316L stainless. It is not a route to Inconel 718 or GRCop-42 flight hardware.

Which is stronger, FDM or metal 3D printing?

Laser powder bed fusion metal, by more than an order of magnitude. Heat treated Inconel 718 has an ultimate tensile strength above 1240 MPa; the strongest FDM polymers are below 100 MPa, and weaker still across the layers.

Does AME offer FDM printing?

No. We run laser powder bed fusion in metal only. We are glad to look at an FDM prototype, or the file behind it, and quote the metal version. See the metal 3D printing service page for what that includes.

Can I send the STL from my FDM prototype?

Yes. STEP is better for a metal part because we add machining stock and check features against the design rules, but an STL is enough to start the conversation.

How much more does metal cost than FDM?

Typically tens to hundreds of times more per part, because the machine, the powder and the post processing are in a different class. Compare it against what the part has to do, not against the plastic model. The cost guide explains what drives the metal price.

Go deeper.

Service

Bring the file. We’ll make it in metal.

Send the STEP file behind the prototype and the material you need. If it can be built, we will tell you what it costs and how long it takes.

Call the shop(256) 929-2332 Request a quote

Fused deposition modeling, and when the part needs to be metal.

What fused deposition modeling is.

Where FDM stops.

What about metal FDM?

The sensible order of operations.

When to go straight to metal.

FDM and laser powder bed fusion, side by side.

Questions we get asked.

Go deeper.

Metal 3D printing service

Laser powder bed fusion

Metal 3D printing cost

Inconel 718 3D printing

GRCop-42 3D printing

Metal 3D printing in Huntsville, AL

Bring the file. We’ll make it in metal.