Expert Custom Metal 3D Printing Maker

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  How a metal printer actually builds a part
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  Alloys that print well, and alloys that fight you
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  What geometry additive handles better than CNC
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  Why printed parts still go back on a CNC
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  The four checks that keep a printed part on size
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  What to verify before you send a file to a metal printing shop
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  Additive or subtractive: pick by feature, not by habit

A metal powder-bed machine spreads a thin layer of gas-atomized powder, typically 20–60 μm across, then a laser or electron beam melts a 2D slice of the part into that layer. The build plate drops by one layer thickness, a recoater arm pushes fresh powder across, and the next slice is melted on top of the last. Layer thickness is usually 30–60 μm. A 50 mm tall part therefore needs roughly 800 to 1,600 passes of the recoater.

That melt pool is the whole story. Each pass creates a small liquid pool a few hundred microns wide that freezes in milliseconds. The metal around it heats and cools at rates above 10^6 K/s. That is why the grain structure of a printed part does not look like a wrought bar, and why residual stress builds up until the part is stress-relieved in a furnace.

Layer thickness is a trade, not a setting you ignore. Thin layers, around 30 μm, give smoother as-built surfaces and finer feature resolution. Thick layers, around 60 μm, build faster and cost less per part. On a bracket with a visible outer wall, the difference shows up as a rougher texture and more post-machining stock.

The printer is only half the process. Every build needs a stress-relief cycle, removal from the plate, support removal, and usually some machining on the critical faces. An expert custom metal 3D printing maker plans all of that before the file is nested.

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  Laser200–400 W fiber laser, spot size around 70–100 μm
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  Layer30–60 μm typical for DMLS and SLM
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  AtmosphereArgon or nitrogen, oxygen kept below 1,000 ppm
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  Post-buildStress relief, plate cut-off, support removal

Not every metal behaves in a powder bed. The alloys that print reliably form a stable melt pool, resist cracking, and have known heat-treatment routes. Ti-6Al-4V (TC4) is common in aerospace and medical work because it prints dense and responds well to stress relief. 17-4PH stainless is a favorite for functional prototypes: it prints, machines, and heat-treats to around 40 HRC.

Aluminium is a different story. AlSi10Mg prints well because silicon improves the melt pool behavior. Pure aluminium and high-strength 7075 are much harder to print without hot cracking, so a shop that offers them should be able to explain its parameter set. If the answer is vague, treat it as a warning sign.

Inconel and other nickel alloys print into dense, heat-resistant parts that are painful to machine conventionally. That is often the strongest reason to print at all. Copper and its alloys conduct heat away from the melt pool so fast that only specific high-power setups work, which limits feature resolution.

Material choice should follow service conditions, not novelty. A part that sees high temperature, corrosion, or cyclic load needs an alloy with a documented heat treatment, not just a datasheet density value.

Additive wins when the geometry is internal or organic. Conformal cooling channels that follow a curved mold surface, internal lattices that cut weight, and manifolds with smooth transitions instead of drilled right angles are all cases where a cutter cannot reach the feature. If the channel is curved and buried, subtractive methods usually fail.

Minimum feature size is where expectations go wrong. A powder-bed machine can hold holes down to roughly 0.4 mm, but small holes often need drilling after printing because the top of the hole sags. Walls thinner than about 0.4 mm may print but will be fragile and may warp. Overhangs below 45° need support.

Trapped powder is a real design constraint. A closed internal cavity without a drain hole will hold powder that you cannot remove, and that becomes a contamination risk in medical or vacuum service. Add 2–3 mm drain holes at the lowest points of the cavity and plan how they get plugged or left open.

Shrinkage is predictable but not zero. Metal powder-bed parts shrink roughly 0.5–2% during melting and cooling, and the machine compensates with a scale factor. Long, thin parts still distort because the compensation is uniform while the stress is not. Orienting the part to keep the longest dimension flat on the plate helps.

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  Good for additiveConformal channels, lattices, merged assemblies, low-volume complex shapes
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  Better on a millPrismatic parts, tight bores, flat sealing faces, high-volume simple geometry
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  Add drains2–3 mm holes at the lowest point of any enclosed cavity
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  OrientationKeep long thin features flat to limit distortion

As-built surfaces from a powder-bed machine sit around Ra 8–15 μm, and the layer lines are visible. Any mating face, bearing bore, O-ring groove, or thread needs machining. The usual hybrid route is: print near-net, stress relieve, cut off the plate, then finish the critical faces on a 5-axis machine. That gets you internal geometry from additive and sealing surfaces from subtractive.

The tolerance split matters. Additive holds roughly ±0.1 mm on as-built dimensions, and that is fine for internal channels. A CNC finishing pass holds ±0.005 mm (±0.0002 in) on the faces that mate with something else. That is the number to put on your drawing for bore diameters and flatness.

Surface finish follows the same split. A fine machined face lands at Ra 0.2–0.8 μm if the geometry allows it, Ra 0.8–1.6 μm is the everyday range, and as-machined is Ra 1.6–3.2 μm. Specify finish per face. Calling out one blanket finish over a printed part wastes money on surfaces that never touch anything.

This is where a shop with both capabilities saves you a step. If the printer and the 5-axis cell are in the same building, you are not shipping the part twice or arguing about who owns the datum. At GreatLight, printed near-net parts move onto the same 127-machine floor as the rest of the work.

Check one is orientation. The build direction sets which faces need support, how heat leaves the part, and where distortion lands. Put the tightest face vertical or on a stable base, and keep supports off surfaces that must stay smooth. A part that fails inspection usually failed at orientation.

Check two is the stress-relief cycle. Skipping or rushing it lets residual stress release during plate cut-off, and the part bends after it leaves the machine. The alloy and section thickness decide the cycle. Ask for the furnace record, not a verbal assurance.

Check three is the finishing stock allowance. Leave 0.3–0.5 mm on faces that will be machined. Less than that and the cutter may not clean up the layer texture; much more and you waste print time and risk hitting a thin wall.

Check four is inspection. A printed part needs the same discipline as a machined one: material check, in-process monitoring, and a final dimensional report. For critical bores, a CMM report on the finished faces closes the loop.

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  OrientationDecide support placement and distortion before nesting
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  Stress reliefFurnace cycle matched to alloy and section
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  Stock0.3–0.5 mm on faces to be machined
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  InspectionFinal dimensional report on request

Start with the machine list and the alloy list. A shop that prints titanium, stainless, aluminium, and nickel alloys needs separate parameter sets and, in most cases, separate machines or at least verified changeover procedures. Cross-contamination between powders ruins a build, so ask how powder is handled, sieved, and stored.

Ask who owns the post-processing. Printing is one step. If the shop sends parts out for stress relief, support removal, or machining, your lead time depends on a supplier you never met. A single-site workflow keeps the datum and the schedule in one place.

Confirm the quality system against your industry. ISO 9001:2015 covers general process control. IATF 16949:2016 matters for automotive and EV work, ISO 13485:2016 for medical devices, and ISO 27001:2022 for how your files and drawings are protected.

Finally, test the communication. Send a real part with a real tolerance and see what comes back. A DFM note that flags a 0.3 mm wall or a trapped cavity before the build is worth more than a low quote. GreatLight returns a quotation and DFM analysis within 12 hours, and production can start within 24 hours.