Resources · Design Guide
Aluminum extrusion design guide
How to design a profile that extrudes cleanly, costs less and holds tolerance — wall thickness, fillets, fin limits, tongue ratio and die cost.
Wall thickness
Keep walls uniform. Minimum ≈ 1.0 mm for small sections; change thickness gradually to avoid sink and die imbalance.
Inner fillets
Use radii ≥ 0.5 mm at internal corners. Sharp corners wear the die and can tear the section.
Fin limits
Fin height-to-thickness ratio up to ~40:1 by extrusion. Taller/thinner → skived or bonded.
Tongue ratio
Avoid slender tongues between slots; high tongue ratio dies are fragile and limit tolerance.
Symmetry
Balanced wall flow reduces twist and warpage after exit.
Tolerances
Standard per EN 755-9; tighten critical dims by post-machining.
Tongue ratio, simply
The tongue ratio is the width of a slender feature divided by its length (how far metal must flow to form it). A low ratio is easy and accurate; a high ratio needs a strong die and yields wider tolerance. If your section has deep, thin slots, expect to machine them after extrusion instead.
Before you draw
- Sketch the cross-section and mark critical dims.
- Avoid < 1.0 mm walls and > 40:1 fins unless using skived/bonded.
- Plan machining for holes, threads and tight features.
Extrusion die cost
Tooling is a one-time die cost, then per-part price drops with volume. Die cost rises with section size and complexity; we quote it with the part. For low volume, near-net CNC from plate can beat paying for a die.
Want the exact number? Send the drawing — we return die cost and lead time in the quote.
Get the full checklist
Our one-page extrusion design checklist covers every rule above.