A Metal Part Sourcing Checklist: Laser Cutting, Press Brake Forming, Injection Molding, and Desktop Metal

Who this checklist is for

I'm a manufacturing engineer who has handled custom metal parts orders for eight years. I've personally made—and documented—14 significant mistakes, totaling roughly $27,000 in wasted budget. This checklist exists so my team doesn't repeat them.

It's for engineers and R&D teams ordering small to mid-volume metal parts: laser-cut brackets, formed stainless assemblies, and parts that need a tight tolerance hole. It assumes you're working with outside shops or setting up an in-house desktop-metal workflow. My experience is based on around 230 orders in carbon steel, 304/316 stainless, and aluminum. If you work with Inconel or hardened tool steel, add your own checks.

Five years ago I would have told you the only options for small metal parts are CNC and waterjet. In 2025, the list is bigger. What was best practice in 2017 may not apply now. But the fundamentals still matter: define the part, choose the process, verify the result.

Step 1: Put the requirement on paper before choosing a process

Before you contact any supplier or press 'buy' on a machine, write down the part function and the constraints: material, max thickness, tolerance, volume, and mating parts. A lot of expensive mistakes happen because someone starts with a machine preference instead of a part definition.

• Material grade: 304 vs 316 stainless is a different price and different bend behavior.
• Volume: a prototype run of 5 parts and a production run of 5,000 need different processes.
• Critical features: holes that locate components, edges where a burr can't be tolerated.

Checkpoint: if you can't hand the drawing to someone else and have them explain the function back to you, it's not ready. I learned this in 2017 when I submitted a DXF that worked on my screen but the nested file was mirrored on the laser cutting bed. 75 parts, $1,400, straight to scrap.

Step 2: Match the cutting process to the sheet metal

For sheet metal prototypes, a desktop laser cutter for metal is often the first tool people consider. If you're cutting material under about 3 mm, a 100 W fiber laser with proper exhaust and enclosure can be genuinely useful. Keep two things in mind:

• Kerf width changes with power, focus, and material. Cut a test coupon from the same batch, measure the slot, then set compensation.
• A desktop laser cutter metal setup is a production machine, not a toy. If it's a Class 4 laser, ANSI Z136.1 applies: controlled access, enclosure interlocks, and proper eyewear.

My mistake: I bought a 'good enough' desktop laser cutter and trusted the default kerf table. The first bracket slots came out 0.35 mm too narrow. Not a disaster, but it killed 80 parts. That's when I learned to put kerf verification on the checklist.

If your volumes are higher or the tolerance is tight, skip the desktop unit and send the file to a cutting service. The machine size matters less than the quality of the nest and the operator.

Step 3: Design for press brake forming before you quote

When a part has a bend, stainless steel press brake forming services are usually the right answer. The process itself isn't complicated; the setup is. The shop needs to know material grade, thickness, grain direction, and the inside bend radius you expect.

Rule of thumb for 304 stainless sheet: keep the inside bend radius at least 1× the material thickness. If you design a sharp 90-degree flange on 1.5 mm 304 and the shop uses a 0.3 mm punch, you're asking for cracks. I learned this on an $870 order where 20% of parts cracked at the bend line.

Also specify the bend direction relative to the material grain. Bending parallel to grain makes stainless much more likely to split. A good shop will catch this; don't assume yours will.

Checkpoint: before quoting press brake forming, confirm the bend line, radius, and springback allowance in writing.

Step 4: Know your process definitions

This is where I slow people down. A lot of ordering delays come from process terms being used loosely. So let's answer the one definition clients ask about: what is injection molding definition?

Injection molding is a manufacturing process in which molten thermoplastic is injected under high pressure into a closed mold cavity. The material cools and solidifies inside the mold, then the part is ejected.

That definition is from the SME Tool and Manufacturing Engineers Handbook, and it matters because injection molding is not the same as metal injection molding (MIM) or metal binder jetting. I've watched purchase orders fail because someone assumed injection molding automatically means any molten material in a mold. It doesn't. It's a plastic process, designed for high-volume parts.

If your assembly includes plastic components, get this process definition right before ordering molds. Likewise, if you need metal parts, don't ask for injection molding—ask for metal injection molding or binder jetting, and the tooling rules are different. To be fair, the term is confusing. That's why we write it down.

Step 5: Plan secondary operations — get the expansion hand reamer on the routing

The step I keep forgetting is secondary operations. A laser-cut hole or a 3D printed hole is never a finished hole. If you need a dowel pin to fit snugly, or a bearing seat to hold tolerance, reaming is usually the answer.

Honestly, an expansion hand reamer is one of those tools you hardly need until you need it badly. The blades can be expanded slightly with a screw or wedge, so one tool can finish a range of hole sizes. It's used by hand through a pilot hole, with cutting fluid, to clean up the surface and get to the target diameter.

The September 2022 failure changed how I think about this. I approved 60 parts with 'reamed hole H7' on the drawing but never specified the reaming sequence. The shop used a standard chucking reamer, left micro-galling on the hole walls, and 60 parts failed fit. $2,300 wasted, one week late.

Checkpoint: any hole that locates something gets a callout: size, tolerance, and whether an expansion hand reamer will be used for final pass.

Step 6: Use Desktop Metal for geometry CNC can't handle

Now the part of the checklist people ask about: when should you use Desktop Metal? Desktop Metal is a company that makes production metal binder jetting systems, desktop CNCs, and laser cutters. The phrase desktop-metal describes a category of machines as well. For small-lot metal parts with complex internal geometry, a binder jetting system like the Production System P-50 is a real option.

Five years ago, a desktop-metal 3D printer was a lab curiosity. In 2025, it can handle production short runs. The fundamentals haven't changed—geometry, material, tolerance—but the execution has transformed. It does not replace CNC machining, and it shouldn't. It handles geometries that are difficult or impossible to machine: internal cooling channels, consolidated assemblies, bionic shapes.

If the part can be laser cut and bent, that's probably cheaper. If it needs complex features, binder jetting may make sense. Compare part cost at the volume you actually forecast. Include finishing time—not just the print time, because all metal additive parts need some post-processing.

Checkpoint: ask 'could this be machined or formed?' before you call it a 3D printed metal part only because you have a desktop metal machine available.

Final pre-send checklist

Before I send any order to a shop or start a job in-house, I run a 22-item pre-send list. The core is this:

• Drawing is checked against the part function, not just geometry.
• Material grade and thickness are explicit.
• Kerf compensation is verified on the actual material.
• Bend radius, grain direction, and springback are on the press brake drawing.
• Process names are defined—especially injection molding, so the shop quotes the right process.
• Reamed holes have a tolerance and a reaming operation assigned.
• Desktop Metal or another additive option is chosen because it earns the cost, not because it's cool.

This list has caught 47 potential errors in the past 18 months. Most were small; a few were $400+ redo mistakes. None were public disasters. That's the point of a checklist: catch the error before it becomes a cost.