Product Introduction of BLT-S400 Metal 3D Printer

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  What the BLT-S400 metal 3D printer actually is
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  How laser powder bed fusion builds a metal part
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  Alloys the S400 runs and what each one is for
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  Geometry that prints well on the S400
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  Where the S400 stops making sense
• 6
  BLT-S400 versus CNC machining: which to choose

The BLT-S400 metal 3D printer is a laser powder bed fusion system. A recoater spreads a thin layer of metal powder, typically 20 to 60 μm, across a build plate. A fiber laser then melts a cross-section of the part into that layer. The platform drops by one layer height, powder is spread again, and the cycle repeats until the part is complete.

The build envelope is 400 × 250 × 400 mm in L × D × H. That is the maximum bounding box, and it is smaller than it sounds once you add a base plate, support structures, and a recoater clearance margin. Realistically, a part that fills the plate edge to edge leaves no room for the support lattice the process needs.

Laser power comes in two configurations: 500 W × 2 and 500 W × 3. More lasers means more melt tracks running in parallel, so a tall build finishes faster. It does not change the physics of a single melt pool, and it does not automatically improve surface finish or density.

The S400 sits in the middle of the BLT range. It is large enough for a manifold, a heat exchanger core, or an impeller, and small enough that a single operator can manage powder handling and depowdering without a dedicated cell.

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  ProcessLaser powder bed fusion, layer by layer
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  Envelope400 × 250 × 400 mm (L × D × H)
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  Laser options500 W × 2 or 500 W × 3 fiber lasers
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  Typical layer20–60 μm depending on alloy and detail

Each layer starts as loose powder. The laser scans the 2D slice, and the powder absorbs energy and melts. The melt pool is roughly 100 to 200 μm wide at 500 W, and it cools at rates in the range of 10⁶ K/s. That fast cooling is why LPBF parts have a fine, directional grain structure.

Fast cooling is also why residual stress builds up. The top of the part cools and contracts while the layers below hold it in place. Thin walls and long unsupported spans curl. This is not a machine fault; it is the process telling you the geometry needs support or a different orientation.

Support structures do two jobs. They anchor overhangs and conduct heat away from the melt pool. Supports are not optional decoration. Removing them adds a manual step, and on internal channels they can be hard to reach. Design for LPBF means designing for support access.

After the build, the plate goes into a stress relief cycle. Then the part is cut off, supports are removed, and any mating surface is machined. A printed part is a near-net shape, not a finished part.

The S400 supports titanium alloy, aluminum alloy, high temperature alloy, stainless steel, high strength steel, cast steel, and copper alloy. In practice, a handful of grades cover most work: Ti-6Al-4V (TC4), Inconel 718, 316L stainless, 17-4PH, and AlSi10Mg.

Ti-6Al-4V is the workhorse for aerospace brackets and medical implants. It prints well, machines slowly, and needs stress relief before you cut it off the plate. If a part is small and simple, machining titanium from bar stock is often cheaper than printing it.

Inconel 718 and other nickel alloys suit hot sections and rocket hardware. They are hard to machine, which is exactly why printing them makes sense: you skip the roughing operations that eat tooling. Thermal post-processing is usually required to get the properties you want.

AlSi10Mg prints fast and is light, but it is not a structural substitute for 7075. Copper alloy is useful for thermal and electrical parts, though the high reflectivity of copper at 1 μm pushes the laser to its limit and needs careful parameter development.

316L is the safe choice for corrosion resistance and food or medical contact. It prints dense and welds well. If your part needs a mirror finish, plan a post-machining pass; as-built surfaces sit around Ra 8–12 μm.

Minimum wall thickness depends on alloy and orientation, but 0.4 mm is a practical floor for a stable wall. Below that, the laser re-melts the wall on the next pass and the geometry distorts. Walls under 0.4 mm should be a deliberate choice, not an accident.

Overhangs below 45° from the build plate generally need support. The exact threshold moves with alloy and laser parameters, but 45° is the number to design against. Holes printed horizontally come out oval; keep holes vertical or drill them after printing.

Internal channels are where LPBF earns its place. A channel with a 1.0 mm diameter can be printed and cleared, though powder removal gets harder as the channel lengthens. A straight channel is easy. A serpentine channel with tight bends traps powder, and trapped powder inside a sealed part is a real problem.

Thermal distortion grows with part size. A 400 mm tall build accumulates more stress than a 50 mm one. Splitting a large part into printed sections that are later joined is a common compromise when the envelope is close.

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  Wall thickness0.4 mm practical minimum for stable walls
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  Overhang angleAbove 45° from the plate needs support
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  Printed holesHorizontal holes distort; drill after printing
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  Internal channels1.0 mm diameter is printable; powder removal is the limit

Printing is not the answer for a simple bracket with three holes. A machined part in 6061 will be cheaper, stronger in the grain direction you control, and ready in days. Printing it costs more and adds a heat treat step for no gain.

Large flat parts are a poor fit. The envelope caps you at 400 mm in one axis, and flat plates warp as they cool. If a part is mostly flat and mostly prismatic, sheet metal or machining wins.

Parts that need a mirror finish should be planned as a hybrid: print the shape, then machine the critical surfaces. We do exactly this on our 5-axis centers after LPBF, and it is the normal route for sealing faces and bearing bores.

If the part has to meet a tight tolerance across the whole body, printing the whole body to that tolerance is not realistic. Print to near-net, then machine to spec. That combination is where the S400 pays off.