Guide
Design for Manufacturing (DFM): the practical guide.
The tolerance, wall-thickness and fixturing decisions that can double your machining or molding cost, and how to catch them before you request a quote.
What DFM actually means
Design for Manufacturing is the practice of shaping a part so it’s cheap and reliable to produce with the process you’ve chosen — before you commit to tooling or a full run. It isn’t a formality tacked onto the end of a design review; the earlier it happens, the more it saves, because a five-minute CAD edit before you request a quote can avoid an expensive tooling change later.
The 7 checks that move price the most
Tolerances tighter than the function needs
Every step tighter than a standard ±0.1mm roughly doubles inspection and machining time on that feature. Ask: does this dimension actually mate with something, or is it just "tight" out of habit?
Deep, narrow pockets
A pocket deeper than about 4× its width needs a longer, thinner tool that flexes and breaks more easily. Widen it or split it into two shallower passes if you can.
Sharp internal corners
Cutting tools are round. A 0mm-radius internal corner forces a small-diameter tool and a slower feed rate. Add a radius of at least a third of the pocket depth and machining time drops.
Walls thinner than the process likes
Under roughly 0.8mm in metal or 1mm in plastic, a wall vibrates during cutting or warps during cooling. Thicken it, or add a rib instead of a solid wall.
Undercuts and side-actions
Every undercut in an injection-molded part adds a slide or lifter to the tool — more cost, more maintenance. Redesigning the part to open in a straight pull is almost always cheaper than tooling around it.
Missing draft angles
Injection-molded and cast parts need a taper — usually 1–2° — on vertical walls so the part releases from the tool without scarring. Forgetting draft is the most common reason a first-shot mold needs rework.
Threads cut too close to an edge
A threaded hole needs wall material around it — roughly 2× the thread diameter — or it strips under torque. Move it inward, or spec a heli-coil / insert instead of a cut thread.
A quick checklist by process
CNC machining
- Round internal corners instead of leaving them sharp
- Avoid pockets deeper than 4× their width
- Keep wall thickness above ~0.8mm
- Group tolerances — don't tag every dimension ±0.05mm by default
Injection molding
- Add a draft angle to every vertical face
- Keep wall thickness uniform to avoid sink marks
- Design around a straight pull before accepting a side-action
- Radius sharp corners to reduce stress concentration
Sheet metal
- Keep bend radius at least equal to material thickness
- Hold features back from a bend line by 2–3× thickness
- Avoid tight features that fight the grain direction where strength matters
- Standardize hole sizes to avoid extra tool changes
How OperGo applies this to your quote
Before you get a price, your part gets a first-pass review against checks like these — enough to catch tolerance, wall-thickness or fixturing calls that would obviously move cost or lead time. The deep, feature-by-feature DFM pass happens once you accept the quote, ahead of production, where your engineer flags, line by line, the changes that would make the part cheaper. Nothing here replaces that conversation — it's what to expect from it.
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