Post-processing: everything that happens after the machine finishes

The machine stops and the part is gone. It is inside a block of powder, welded to a steel platform, full of supports and with enough internal stresses to deform as soon as it is cut.

What comes next represents half the time and a large part of the cost, and it's what almost never appears in comparisons or quick quotes. This article covers that half.

Order, which is non-negotiable

#	Step	Mandatory?	What happens if skipped or moved
1	Cool and depressurize the chamber	Yes	Risk with reactive powders
2	Remove and recover the powder	Yes	The most expensive material of the part is lost
3	Stress relief, with the part still on the platform	Almost always	When cutting, the part splits like a banana
4	Cut from the platform	Yes	—
5	Remove supports	If any	Marks, burrs, and risk of damaging the part
6	Heat treatment of the material	According to the alloy	Without aging, a maraging part lacks mold hardness
7	HIP, if required	Rarely	Without it, internal porosity in fatigue parts
8	Surface finish	Almost always	Adhered powder and unfinished appearance
9	Machining of functional faces	If there are dimensions	—
10	Inspection and documentation	By sector	Without this, there is no certifiable part

Step 3 is the one that prevents the most problems. An LPBF part comes off the assembly with large residual stresses, a result of heating and cooling each layer against the cold material beneath it. While it's welded to the platform, this stress is contained. As soon as it's cut, it's released suddenly and the part deforms—sometimes by millimeters. Stress relief is done before cutting, and is discussed in deformation and stress relief.

Supports: The Most Underestimated Game

Removing supports is manual work. On a part with internal supports or in hard-to-reach areas, it can be more expensive than the manufacturing itself, and it cannot be automated because each part is different.

They also leave a mark: where the support was, the surface is imprinted. If that surface is important, it must be machined or polished afterward.

Therefore, the best post-processing decision is made in CAD, weeks in advance: redesigning and adjusting to require fewer supports. This is discussed in supports in metal 3D printing and in design rules for LPBF.

Finishes: what each one achieves

The ranges and details of the roughness for each face are in tolerances and finish. Here's what's important for planning:

Shot blasting. Cheap, fast, evens out surface and removes powder. It's the default finish for almost everything. It doesn't change the geometry: if the surface had steps, it still has them.

Vibration. It rounds edges and reduces roughness effectively, but it's charged by the hour and affects the entire batch at once. Good for many small parts, bad if a sharp edge needs to be preserved.

Electropolishing and abrasive flow finishing. These are the only processes that can reach the inside of a channel. If your part requires a fine internal surface, this decision is made during the design phase, not in the shop floor.

Hand polished. Mirror finish, expensive and non-repeatable. Molds, aesthetics, medical.

What is most often forgotten: oven traceability

A key management detail determines whether a part is certifiable. Each thermal cycle must be recorded: which parts were inside, what ramp, what plateau, what atmosphere, what cooling. If the cycle cannot be demonstrated on the day of the audit, the part is invalid, even if it is perfect.

It is the same logic as the traceability of powder in powder reuse, and is part of what is frozen when qualifying — how an LPBF part is qualified.

How much it weighs in the lead time

Without giving specific numbers, which vary from shop floor to shop floor, the pattern is consistent and should be kept in mind when promising a date:

Manufacturing is what everyone talks about, and it usually accounts for less than half the schedule.
The furnace dictates everything else: cycles are long, production is done in batches, and a batch that isn't ready waits for the next one.
Machining depends on the schedule of another machine and, often, another company.
Inspection seems instantaneous until a report has to be issued.

The practical consequence: the delivery date is determined by the oven and the machining shop floor, not the printer. When someone asks if it can be sped up, the answer is almost never with the machine.

The four most expensive mistakes

Cut before relieving stress. The most common and most expensive: the part becomes deformed and, if it was a perfect oversize, there is no part left.

Machining before heat treatment. Machining a geometry that will change. All the work is lost.

Do not allow for oversize on the faces to be machined. If the part reaches the rough dimension, there is no material left to remove.

Discovering the post-process at the end. If it wasn't in the budget, it appears as a cost overrun; if it wasn't on schedule, it appears as a delay. This is the number one reason why a first additive manufacturing project leaves a bad taste.

How we approach it

When we give a deadline, the post-processing is included. And when we give a price, we say what's included—which is exactly the checklist for how to order a printed part: manufacturing, supports, treatment, finishing, machining of which faces, inspection, and documentation.

A budget that is much cheaper than another is almost always cheaper because it includes less, not because it manufactures better.

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Why the part warps and how to prevent it, in warping and stress relief. What can be ordered in the rough, in tolerances and finishing. And how to design to require fewer supports, in supports in metal 3D printing.

And if you want a number that includes all post-processing costs and not just machine time, that's what the quoter is for.