Project
CNC Fixturing for Large-Format Machining
SSI Shredding Systems · 2021–2022
The Problem
SSI had just invested in a brand new large-format CNC machine. The promise: machining very large steel weldments with accuracy across the full machine envelope. These are heavy, welded assemblies that go into industrial shredding equipment.
The reality: without proper fixturing, every time the machinist needed to work on a different area of the weldment, they'd have to crane the part out, physically reposition it on the table, re-align, and re-zero. For parts this size and weight, that's not a five-minute operation. It's hours of downtime per repositioning, and some parts needed multiple setups.
The Constraints
Extreme weight. These aren't aluminum prototypes. They're heavy steel weldments that need to stay locked in place during cutting operations with zero movement.
Full-envelope accuracy. The fixture had to maintain machining accuracy whether the part was at one travel limit or the other, across the entire working volume of the machine.
No crane dependency. The whole point was eliminating the crane-and-reposition cycle. The fixture had to allow shifting weldments across the table mechanically.
The Approach
I designed a custom fixture system that interfaces with the CNC's T-slot table and allows weldments to be shifted across the full table without lifting. The clamping mechanisms lock the part securely during machining, then release for repositioning. No overhead crane needed.
The design had to account for the forces generated during heavy milling operations, thermal expansion of the fixture under sustained cutting, and the practical reality that machinists need to operate this quickly and repeatedly without complex setup procedures.
The Result
The fixture turned a capable machine into a productive one. What had been a multi-hour repositioning cycle became a quick mechanical shift. The machine could now do what it was purchased to do: machine large weldments accurately and efficiently, without the bottleneck that was defeating the whole investment.
Standard off-the-shelf solutions didn't exist at this scale and weight class. This was a custom problem that needed a custom solution.