Sheet Metal¶
Mental model: Sheet metal parts are cut and bent from constant-thickness stock. The fastest way to ruin sheet metal DFM is to design as if the part were a sculpted solid.
How The Process Actually Works¶
A sheet metal part begins as flat stock. The shop cuts, punches, or lasers the blank, then forms bends and local features, adds hardware if needed, applies finish, and finally assembles the part into a larger product.
That means sheet metal DFM is dominated by bend behavior, feature spacing, handling, and assembly logic. The designer is managing a manufacturing sequence, not only a final shape.
What The Shop Cares About¶
- one consistent material thickness per part
- whether bends can be formed in a sane order
- whether local features distort during forming
- whether edge conditions, hems, curls, lances, and inserts are realistic
- whether tolerance expectations match a bent part rather than a machined block
Common DFM Issues¶
1. Forgetting that thickness is fixed¶
A sheet metal part wants one thickness. Once the design starts acting like a variable-thickness solid, the part often no longer belongs in this process family.
2. Bend-adjacent features that distort or crack¶
Many sheet metal rules are really spacing rules:
- hole to edge
- hole to bend
- formed feature to bend
- formed feature to edge
- distance between neighboring formed features
These rules exist because deformation is local and cumulative. The metal has to stretch, compress, and recover in a real forming sequence.
3. Flanges, hems, curls, and lances that are too small¶
When flange lengths, curl radii, lance depth, or hem geometry get too small relative to thickness, the part becomes fragile, hard to form, or dependent on special tooling.
4. Notches and knife-edge thinking¶
Very small notches, knife-edge conditions, and overly sharp local details often increase cost while also making the part weaker or harder to handle.
5. Tolerance assumptions imported from machining¶
A bent sheet part is not a milled datum block. Tight across-bend tolerances, asymmetric bend layouts, and stack-ups across many formed features quickly become inspection and repeatability problems.
The Practical Design Principle¶
Good sheet metal design keeps returning to the same question:
Can the part stay a simple cut-and-bend part?
If the answer drifts toward repeated special forms, tiny edge conditions, dense local features, or awkward manual correction, the design is leaving the efficient core of the process.
Why This Matters For TextCAD¶
Sheet metal is especially important for enclosures, covers, frames, and industrial hardware, which are all common product archetypes around machinery and equipment. A useful DFM system therefore needs to explain not just that a feature breaks a ratio, but that it likely causes distortion, tooling complexity, or handling trouble.
The rule encoding already exists in C_SHEET. This page is the human-readable process model behind that pack.
Important Caveat¶
The numeric spacing heuristics in sheet metal are highly shop-dependent. Material, press brake tooling, bend method, and supplier preference all matter. The ratios are still valuable, but they are best treated as baseline guidance rather than universal law.
Open Questions¶
- Should this section expand into separate pages for enclosure design, PEM hardware strategy, and welded sheet-metal assemblies?
- Do we want a future "flat pattern thinking" page for designers who model in solids first?
- Should RapidDraft distinguish between prototype sheet metal shops and production contract manufacturers?
Sources¶
C:\Users\adeel\OneDrive\100_Knowledge\203_TextCAD\06_Technical data\06_Manufacturingbooks\310796791-Definitive-Guide-to-DFM-Success.pdfC:\Users\adeel\OneDrive\100_Knowledge\203_TextCAD\01_Product_Project_Management\TextCAD_Wiki\docs\04_DFM_Research\DFM_Rules_Handbook\references\REF-SM-1.mdC:\Users\adeel\OneDrive\100_Knowledge\203_TextCAD\01_Product_Project_Management\TextCAD_Wiki\docs\04_DFM_Research\DFM_Rules_Handbook\packs\C_SHEET.md