Quick tips for better, cheaper parts.
Short, practical advice from our shop floor — organised by theme. Each tip is a small change that cuts cost, avoids a defect or speeds a part to production. For the long version, see our engineering blog.
Cost reduction
Small design changes cut real money off a part — usually without touching its function.
Loosen the tolerances that don't matter
A general ISO 2768-m block is effectively free. Every ±0.01 mm callout adds inspection, slower finishing and scrap risk — reserve tight tolerances for mating, sealing and bearing features. See the tolerance chart.
Cut the number of setups
A part machined from one or two faces costs less than a five-sided part. Group features onto fewer faces and leave a flat, square edge for work-holding.
Keep pockets shallow
Deep, narrow pockets force long tools and slow cuts. Keep depth under ~4× the tool diameter, or open the pocket so a bigger, rigid tool fits.
Use standard hole sizes
Match hole diameters to standard drills; odd sizes need boring or custom tooling. See the drill chart.
Leave non-cosmetic faces as-machined
As-machined finish is included in the price. Anodising or polishing faces that don't need it just adds cost.
Ask for quantity price breaks
Unit price falls with volume as setup is amortised — quote 1, 10, 50 and 100 to see where the curve bends. Try the instant quote.
Avoiding defects
The most common manufacturing defects are designed in — and designed out — at the CAD stage.
Stop sink marks
Thick sections behind ribs and bosses cool slowly and sink. Keep ribs ≤ 60% of the adjoining wall and core out heavy masses.
Prevent warping
Non-uniform walls cool unevenly and warp in molded, cast and printed parts. Keep wall thickness uniform — see the wall thickness guide.
Kill chatter on thin walls
Thin walls and long tools vibrate, ruining finish and accuracy. Add support ribs, or leave stock for a light finishing pass.
Define your edge breaks
Sharp edges break out as burrs. Call out an edge break (e.g. 0.1–0.3 mm) so deburring is specified, not guessed.
Avoid cracking at sheet bends
A bend radius below material thickness over-stretches the outer fibre and cracks it. Keep the inside radius ≥ thickness.
Control cosmetic surfaces
Name the show surface and its finish on the drawing; leave hidden faces as-machined to keep cost down.
Tolerances & GD&T
Tolerancing is where cost and quality meet. Control what functions; let everything else float.
Always state a general-tolerance block
A default ISO 2768-m (or -f) block lets the shop hold the obvious dimensions without you tolerancing every one.
Use position, not coordinate, for holes
A round true-position zone gives roughly 57% more usable area than the square ± box — fewer good parts rejected. See GD&T basics.
Dimension from a single datum
Chained dimensions accumulate. Locate critical features from one datum edge to control stack-up — read stack-up analysis.
Use MMC on clearance holes
Apply maximum material condition to clearance-hole position for bonus tolerance where assembly clearance is the real concern.
Don't over-control surfaces
Reserve flatness and profile for sealing or bearing faces — controlling every surface adds inspection for no function.
Material selection
Pick by the one property the part cannot compromise, then optimise for machinability and cost.
Start from the hardest requirement
Strength, temperature, corrosion or weight — shortlist by the governing property first, then compare cost. Browse materials.
Default to 6061 aluminium
6061-T6 balances strength, machinability and cost for most parts. Reach for titanium or 7075 only when you genuinely need the strength-to-weight.
Choose 303 stainless for fast machining
303 cuts faster than 304; use it where its slightly lower corrosion resistance is acceptable. Compare stainless grades.
Use POM for precision plastic parts
Acetal (Delrin) is stiff, low-friction and dimensionally stable — the default for machined plastic. See POM.
Match material to finish
Aluminium anodises, steel needs plating or coating, stainless passivates — factor the finish into the material choice.
CNC machining
A machinist can only cut what a tool can reach, hold rigidly and measure. Design for the tool.
Maximise internal corner radii
Bigger, consistent internal radii let a rigid standard end mill reach them; tiny radii force slow, deflecting micro-tools. More in design for CNC.
Tap threads to a sensible depth
Threads deeper than ~1.5–2× diameter add no strength and raise tap-breakage risk. See the tap chart.
Engrave rather than emboss text
Recessed text cuts only the characters; raised text clears the whole surrounding field and costs more.
Design around standard tools
Internal undercuts need specialty cutters. Use standard geometries or move the feature to an accessible external face.
Sheet metal
Bends drive sheet-metal cost and quality. A few rules keep parts forming accurately.
Standardise one bend radius
Each unique radius may need a different press-brake tool. Use one inside radius across the part. See the bending guide.
Keep holes back from bends
Holes within 2–3× material thickness of a bend distort into ovals as the metal stretches.
Respect minimum flange length
A flange shorter than ~4× thickness slips into the die and forms inaccurately.
Add bend reliefs
Notch where a bend meets a feature edge so the metal doesn't tear at the corner.
Molding & casting
Anything that solidifies from a liquid follows the same rules: uniform walls and clean release.
Add draft to vertical faces
1–2° of draft lets molded and cast parts release cleanly from the tool.
Keep walls uniform
Uniform wall thickness prevents sink marks, warpage and internal voids.
Fillet internal corners
Sharp inside corners concentrate stress and impede material flow — add fillets.
Core out thick sections
Replace solid masses with ribbed, uniform-wall geometry to keep cooling even. See molding design.
Want these checked on your part?
Upload your CAD for an instant estimate and a free DFM review — our engineers apply every one of these before we cut.