Why More Buyers Order Machined Parts, Not Raw Profiles
A raw extrusion is a long, uniform cross-section – useful, but rarely ready to mount. Buyers increasingly order profiles already cut, drilled, tapped and CNC-machined, so parts arrive ready for assembly or anodising. Doing this in-house means buying saws, machining centres and the skilled operators to run them. Handing it to a third-party machine shop splits responsibility: tolerance disputes between extruder and machinist become your problem. One-stop sourcing – extrusion, machining and finishing under one roof – keeps tolerance, lead time and accountability in a single chain.
The Standard Machining Menu
Most heat sink and industrial profile orders use the same operations: precision sawing (cut to length with controlled burr), drilling and tapping for mounting holes, milling for steps and mounting surfaces, and full CNC finishing for complex pockets, slots and contours. Heat sinks typically add a milled base or machined mounting face to guarantee flat contact with the heat source, plus tapped holes for fan or board mounting. The key is doing these operations before anodising, so the final surface finish stays clean and uniform.
Machining Quality Starts in the Extrusion
A machinist can only be as good as the material they receive. Wall thickness tolerance decides how much thread a tapped hole can hold; straightness decides how accurately a long profile clamps in a jig; and internal stress – controlled by the T5/T6 ageing process – decides whether a profile distorts after metal is removed. Profiles that are marginal on these points machine badly, no matter how good the CNC cell is. That is why a supplier who controls extrusion and machining together can hold tolerances a separated chain cannot.
How to Order Machined Profiles
Send two drawings: the raw profile cross-section and the machined part view with critical dimensions, hole positions and thread sizes called out, plus the machining datum (the reference surface every operation is measured from). Leave machining allowance on surfaces you plan to finish yourself, and approve a machined sample before mass production. At Siken Aluminum, extrusion, CNC machining and anodising run in-house – send us your part drawing and we will quote the complete machined component, not just the profile.