Key Differences: Subtractive vs. Joining
Machining is a "subtractive" process. Utilizing CNC milling, turning, or drilling, it removes material from a solid block (such as 16Mo3 steel) to achieve a final shape. It is synonymous with high precision and tight tolerances that welding simply cannot match.
Welding is a "joining" process. It uses heat to fuse separate metal parts into a single structure. Welding is the go-to for large-scale structural frames and complex assemblies where carving from a single block is impractical.
Cost Comparison: Which is More Expensive?
Generally, machining is more expensive per unit for complex parts due to:
1.Material Scrappage: Significant amounts of expensive raw material are turned into chips and waste.
2.Machine Time: High-end CNC machines have high hourly rates, and complex geometries take time to program and execute.
3.Tooling Costs: Harder alloys like 24CrMo4 require specialized, expensive cutting tools that wear down quickly.
Conversely, welding costs are labor-intensive. Certified welders (required for DIN EN ISO standards) command high wages. Additionally, post-weld processes like Non-Destructive Testing (NDT) and surface grinding add to the bill. For large, less precise structures, welding remains the more cost-effective solution.
Can Machining Replace Welding?
- Yes, through "Monolithic Manufacturing."
In high-performance engineering, "machining from solid" can replace a welded assembly. - The Benefit: By eliminating welds, you remove the Heat Affected Zone (HAZ), which is often the weakest point in a structure. This results in superior strength and fatigue resistance.
- The Drawback: It is often prohibitively expensive. Milling an "L-shaped" support from a giant solid block involves massive material waste compared to welding two plates together.
Conclusion
The decision hinges on the loads and tolerances. If your drawing specifies micron-level precision, machining is mandatory. If you are building a robust structural frame, welding is the industry standard. For companies like Witzenmann or Sealergy, a hybrid approach—welding for the frame and machining for the contact surfaces—is often the optimal balance of cost and quality.