Design for Manufacturability
Engineering best practices by process — so your parts come out right the first time. Our team reviews every file, but starting with these guidelines will save you time and money.
CNC Machining Guidelines
CNC milling and turning are the most versatile manufacturing processes — but good design still matters. The guidelines below apply to 3-axis milling; 5-axis work relaxes many of these constraints.
Thinner walls vibrate during cutting and may deflect. For walls taller than 3×, add 50% to the minimum.
Square internal corners are impossible to machine — all pockets must have a radius equal to or larger than the end mill radius. Adding 30% clearance lets us use standard cutter sizes.
Holes smaller than 0.040" require micro-drilling and add cost. Specify standard drill sizes where possible (e.g., letter, number, or metric sizes).
Deep holes beyond 10× require peck drilling with chip clearing, which adds time. Through-holes are always preferred over blind holes where function allows.
Under-tapped holes strip under load. For blind tapped holes, add at least 2 thread pitches of extra depth below the minimum engagement depth for tap runout.
Deep narrow pockets require long end mills with reduced rigidity. If your pocket exceeds 4:1, add reliefs or discuss with our team.
Sheet Metal Fabrication Guidelines
Sheet metal fabrication involves laser cutting, bending, punching, and welding. Bends create the biggest design challenges — follow these guidelines to avoid unfoldable geometries and springback surprises.
Bending inside the minimum radius causes cracking on the outer bend surface. For material thicker than 0.125", increase the minimum radius to 1.5× thickness.
Holes punched too close to a bend will deform during forming. If you must have holes near a bend, punch them after forming or use slots to relieve stress.
Holes smaller than the material thickness risk punch breakage and poor edge quality. Very small holes in thick material are better drilled after forming.
Bend reliefs prevent tearing at corners where two bends meet. Required when bending sheet metal where a bend runs to the edge of the material.
Tighter bend tolerances require secondary operations and add cost. Design assemblies so that reasonable variation in bends is acceptable.
Very short flanges can't be gripped by standard press brake tooling. If shorter flanges are required, discuss alternate forming strategies with our team.
Injection Molding Guidelines
Injection molding economics reward thoughtful design. Parts that fill properly, eject cleanly, and minimize sink and warp require following these fundamentals from the start — retrofitting DFM issues after tooling is cut is expensive.
Uniform wall thickness is the most important rule in injection molding. Thick-to-thin transitions cause sink marks, warp, and filling hesitation. Transition gradually (3:1 taper) where thickness must change.
Without draft, parts won't release from the tool — or will drag and scuff on ejection. Add draft to all vertical surfaces, increasing angle for deeper features and texture.
Ribs thicker than 60% of the nominal wall will sink on the opposite cosmetic surface. Draft ribs at 0.5°–1° per side for clean ejection.
Isolated bosses sink and crack under load. Connect bosses to nearby walls with ribs. Add generous radii at the boss base to reduce stress concentration.
Undercuts require additional tooling mechanisms (lifters, slides, collapsible cores) that add tooling cost and cycle time. Redesign with a parting line shift or snap-fit if possible.
Sharp internal corners create stress risers in both the part and the tool steel. Generous radii extend tool life and reduce part cracking under load.
3D Printing Guidelines
Design rules vary by 3D printing technology. SLA provides the finest detail; SLS and MJF are self-supporting; FDM is the most cost-effective for large parts. We offer all four.
| Attribute | SLA | SLS / MJF | FDM |
|---|---|---|---|
| Min. Wall Thickness | 0.030" (0.8 mm) | 0.060" (1.5 mm) | 0.060" (1.5 mm) |
| Min. Feature Size | 0.025" (0.6 mm) | 0.040" (1.0 mm) | 0.060" (1.5 mm) |
| Min. Hole Diameter | 0.030" (0.8 mm) | 0.050" (1.3 mm) | 0.075" (1.9 mm) |
| Supports Required | Yes (removed post-print) | No | Yes (removed post-print) |
| Layer Thickness | 0.002"–0.006" | 0.004"–0.006" | 0.008"–0.016" |
| Dimensional Accuracy | ±0.005" | ±0.010" | ±0.020" |
| Max Build Volume | 12" × 7" × 10" | 15" × 15" × 18" | 24" × 24" × 24" |
| Best For | Fine detail, smooth finish | Functional parts, assemblies | Large low-cost prototypes |
Part orientation affects surface finish, support locations, and mechanical properties. Anisotropic strength (weakest in the Z/build direction) must be considered for load-bearing parts. Critical surfaces should face up or forward in SLA.
Printed holes consistently come out smaller than nominal due to resin shrinkage (SLA) or powder sintering (SLS). Upsize holes that need to be tapped or fitted with inserts.
Horizontal spans in SLA and FDM sag without supports. Orient parts to minimize unsupported overhangs, or choose SLS/MJF for complex internal geometries.
SLS and MJF nylon prints can produce functional living hinges. Design the hinge perpendicular to the build direction, flex immediately after printing while still warm.
Tolerances & Fit Classes
Tolerance selection directly drives cost. The table below shows what's achievable by process — always specify the loosest tolerance that meets functional requirements.
| Process | Standard | Precision | High Precision |
|---|---|---|---|
| CNC Machining | ±0.005" (±0.127 mm) | ±0.002" (±0.05 mm) | ±0.0002" (±0.005 mm) |
| Sheet Metal (cut) | ±0.004" (±0.1 mm) | ±0.002" (±0.05 mm) | — |
| Sheet Metal (bend) | ±0.015" (±0.38 mm) | ±0.010" (±0.25 mm) | — |
| Injection Molding | ±0.010" (±0.25 mm) | ±0.005" (±0.127 mm) | ±0.002" (±0.05 mm) |
| SLA 3D Print | ±0.010" (±0.25 mm) | ±0.005" (±0.127 mm) | — |
| SLS / MJF | ±0.015" (±0.38 mm) | ±0.008" (±0.2 mm) | — |
| FDM | ±0.020" (±0.5 mm) | ±0.010" (±0.25 mm) | — |
Common Fit Classes (ISO 286)
Parts always have clearance — shaft is always smaller than bore. Use for moving parts: bearings on shafts, sliding mechanisms, loose assembly requiring easy insertion.
Either clearance or slight interference depending on the specific part. Use for accurate location where parts must be assembled and disassembled: locating pins, dowel pins.
Shaft is always larger than bore — requires press-fitting. Used for permanent assemblies: gear hubs on shafts, bushings in housings, pins in blind holes.