What Are Semi-Finished Products?
Semi-finished products are industrially pre-manufactured starting forms from which finished parts are created through CNC machining. Selecting the right stock shape is an important cost factor — the closer the starting form matches the final geometry, the less material is removed and the faster production proceeds.
The Most Important Stock Shapes
Round Bar
The standard for CNC turning. Available as extruded, drawn or precision-ground bar. Typical diameters: 5–300 mm. More on the differences between drawn and extruded material in our detailed comparison.
Flat Bar and Square Bar
Ideal starting material for CNC milling of prismatic components. Available in many standardised dimensions. Flat bar is suitable for plates, brackets and flat components.
Plate Material
For large-area, flat components. Plates are available in thicknesses from 2 mm to >100 mm. Milled-all-over plates (MIC-6 for aluminium) offer the highest flatness and are ideal for precision components.
Tubes and Hollow Profiles
For components with large bores, tubes can save considerable material and machining time compared to solid bar. Important: wall thickness must be sufficient for finishing machining.
The Right Stock Shape for Your Part
Rotationally Symmetrical Parts
→ Round bar, ideally drawn or precision-ground. Diameter as close to the final dimension as possible.
Prismatic Parts (Housings, Plates)
→ Flat bar or plate. Length, width and height as close to the final dimension as possible.
Parts with Large Internal Bores
→ Tube instead of solid bar. Saves material costs and machining time.
Material Efficiency: Why It Matters
In CNC machining, removed material is waste. The "buy-to-fly ratio" describes the ratio of input material to finished part weight:
- Optimal: 1.5:1 to 2:1 — little waste, efficient starting form
- Average: 3:1 to 5:1 — standard practice
- Wasteful: > 10:1 — indicates a poorly chosen starting form
Higher material efficiency not only reduces material costs but also shortens machining times considerably.
Frequently Asked Questions (FAQ)
Where can I buy semi-finished products?
Specialist metal distributors stock a broad range. For CNC contract manufacturing, the manufacturer typically handles material procurement — they get better prices and know which quality is needed.
Can I supply my own material?
Yes, that is possible. However, note that the manufacturer needs material certificates and clear material identification. Without traceable material data, the manufacturer cannot guarantee quality.
Conclusion: The Starting Form Determines Efficiency
The right choice of semi-finished product is a simple but effective lever for saving costs in CNC manufacturing. Talk to your manufacturing partner about the optimal starting form.
Questions about materials? Contact us — we advise you on the ideal starting material for your component.