Probing delivers shorter lead-time

A machine tool probe is an inexpensive and easy-to-use machine tool accessory that can deliver significant reductions in production time and cost. Machine tool probing potentially makes sense at nearly every stage of the process.

Advances in machine tool accuracy and probing technology make machine inspection viable for process control by allowing a machine to be used to verify the accuracy of parts it machines. Once a machine tool's performance as a measuring instrument has been established, the probe becomes the operator's CNC gage.

On-machine probing is gaining widespread application for process improvement-automating and speeding part processing, even eliminating parts of the process. The growth is being driven by shifts to flexible machining, shorter lead-times, tighter accuracy specifications and automated processing-all areas where on-machine probing yields time, quality and productivity improvements.

This represents a fundamental change in the way inspection is performed. Rather than a post process check performed off-line on parts after machining, probing on the machine makes inspection part of the process, as well as a powerful process improvement tool for machining parts to spec in the shortest possible time.

Steve Randerson, Production Manager at Boxtrees Precision Engineering Ltd, Halifax, UK has employed a Renishaw OMP400 high accuracy touch probe and NC4 non-contact laser tool setting system on a Mazak Integrex 200-IV ST to radically reduce non-productive setting. Improvements have also been seen in component accuracy and the consistency of cycle times, with a direct effect on production scheduling, plus the vast majority of post-machining inspection has been eliminated.

The OMP400 is Renishaw's compact probe for small- to medium-size machining centres, combining the miniaturisation of the popular OMP40 probe, with high accuracy RENGAGE strain gauge technology. It has excellent 3D performance, which allows probing of contoured surfaces whilst maintaining very high accuracy.

Boxtrees make all the machined parts for a large range of educational machine tools supplied by sister company Boxford, along with other sub-contract work.

Randerson explains, "Five years ago I did a detailed analysis of our machining operations and found that 40% of machine time was used setting jobs. This had to change, and what better figure to aim for than 0%? That is where we are now. Many companies have moved production out of the UK to reduce costs, we have chosen to cut costs by improving our operation here. We make what we need when we need it, there are no components that have cost us money to produce sat on the shelf not earning us money. The majority of work now is in very small batches, including single parts, but crucially that makes no difference to the productivity."

The Mazak Integrex, originally fitted with the Renishaw systems when supplied, has been installed at Boxtrees for 11 months, one of three CNC machine tools in active use in a very large machine shop now containing increasingly inactive manual machines.

In that time Randerson has created machining programs for over 200 different components, which can be machined in many different materials, usually mild steel, cast iron or aluminium. Every one of these programs relies on Renishaw part setting and tool breakage detection macro routines to control the process, making the most of the flexibility offered by the Mazak multi-axis mill-turn machine.

Tool life is more important than cutting time

"Everyone talks about reducing the time taken to cut the part," says Mr. Randerson. "I'm more interested in minimising tool wear to keep tooling costs down, so we don't cut as fast as we used to, and now get 20% more tool life. I'm also keen to identify that occasional scrap part aAir Max 90 YEEZY 2 SP