Case studies

Vol.1

DENSO Corporation / Air Gap Sensor

Prevent machining defects with CNC machine tools
using precise workpiece seating confirmation.
Not noticing seating failures of ABS actuator parts
produces defectively machined goods.
Our biggest headache was having to stop the line for a full inspection...
In Denso's Driving Safety Production Division, ABS actuator parts must be manufactured with a high machining accuracy.
In the past, when cutting using a CNC machining center, a pneumatic "gap sensor" was employed to verify the seatingof the workpiece and the chuck.
However, the repeatability of 20 - 30 μm obtained with the conventional
pneumatic "gap sensor" was unstable and unable to detect trapped cutting chips
or workpiece float, leading to defective products due to seating failure.
Since the machined workpieces are all subject to a full inspection,
sending defective machined parts to the next process means that the line
has to be stopped during the inspection process and productivity goes down.
Murata:"Using a conventional pneumatic gap sensor, 20 μm was the limit ofconfirmable seating detection.
We called it a ‘sensor to detect workpiece presence’ , not a seating sensor.
Our goal was to find a detection method for defective workpiece seating
using an entirely new technique to detect failures before cutting,keeping the next processes free of defective parts. "Required accuracy of 5 μm!
Everyone said "you can't get that accuracy in mass production...",
but they set out in collaboration with chuck manufacturers todevelop new workpiece seating confirmation.

Firstly, high-accuracy chucking wasachieved using a precision diaphragmchuck.
The challenge was the Z-axis
seating accuracy.

With 24-hour operation, continued
machining without noticing that theseating of the workpiece isincorrect will reduce the yield andcause a drop in productivity.

DENSO Corporation
Driving Safety Manufacturing Division
Shoichi Murata

1. Workpiece before machining
A 5 μm seating accuracy was
required in order to preventmachining defects.

2. Workpiece during precision
machining
Lathe→drilling processes arefollowed by machining actuatorparts.

DENSO Corporation adoption example

confirmation
× Seatingusing a conventional pneumatic "gap sensor"
Air↓ChuckWorkpiece

Allowabletolerance
5μmCuttingchip→Seating signal
Conventional pneumatic gap sensor
20μm Repeatability
Accurate seating of workpiece: UndeterminableWorkpiece
stopper surface

AirAir nozzle

Problems

× The repeatability of a conventional pneumatic "gap sensor" is a low 20 μm, meaning that the accurate seatingof the workpiece cannot be detected when held in the chuck.

× Defective machining results in stopping the line for a full inspection, decreasing productivity.
The opportunity to adopt a Metrol sensor came in the form of the M-TECH Mechanical Components & Materials TechnologyExpo held in 2013 at Tokyo Big Sight.
We received an inquiry after a chance visit to the Metrol booth,featuring a demo performance of our "Air Gap Sensor" precision seating sensor.
Murata:"I saw the Air Gap Sensor seating demo at the exhibition and thought 'That's it!'Exactly the precision seating sensor I had been looking for.
I immediately asked for a trial sample, and started evaluation tests with thechuck manufacturers."

Air Gap Sensor〈DPA-A2〉

Conventionally, the pneumatic "gap sensor" adopted for machine tools had been used
for detecting machined workpieces, but with a low repeatability of 20 μm, it was limited,at best, to simply confirming the presence or absence of the workpiece.
Accurate seating confirmation of the jig and workpiece was impossible

Technology which picks up on defects before cutting.
Incorporating a mechanism into the production process
to prevent machining defects.

Murata:"Seriously, confirming precision seating with a 5 μm allowable tolerance!?
I was very dubious at first, but the chuck manufacturer's evaluation results were,in fact, ±1 μm.
The moment I heard this, I thought, 'That will do the trick!' ""Since it is also necessary to consider the precision of the machine tools
themselves, it was very hard to get stable accuracy, but with this, the machining
line can get moving! I made the decision immediately. "After that, through rigorous evaluation tests over 4 months, the decision was made toformally adopt it on the machining line.
Detects workpiece seating defects due to cutting chips before machining can takeplace, preventing machined defect products.
The inspection process no longer stops the line, and there has been an overall
improvement in yield.

DENSO Corporation adoption example

Seating Confirmation with the "Air Gap Sensor"
Air↓Diaphragm chuck

Workpiece
Cuttingchip

Allowabletolerance
5μm→Seating signal
Air Gap Sensor±1μm Repeatability

Workpiece
stopper surface

Air nozzle

Accurate seating of workpiece: Determinable

Air

Results
The "Air Gap Sensor" allows accurate seating confirmation with the workpiece chucked.
Prevents machined defect products during the production process. Productivity is improved significantly.

Air nozzle▲ Interior of the CNC machining centerPrecision diaphragm chuck + Precision seating sensor "Air Gap Sensor" = The unbeatable pair eliminates defective products▲ Exterior of the CNC machining center
Installation is straightforward since the air piping of the conventional pneumatic "gap sensor" can be re-used as is,while the sensor is simply retrofitted.

DENSO Corporation adoption example

Continuing the drive for ultra-precise machining andimproved productivity.
Murata:"After adoption, operation has been trouble-free.
Reliable awareness of 'poor seating' keeps
defects from moving on to the next process.""The next challenge is to construct a newmachining line to suit the digital age.
We are driving on with the goal of highly
accurate parts machining which unites bothpeople and equipment!"

The "Air Gap Sensor" adopted here has earned a high reputation within DENSO itself, and at the moment is being
deployed company-wide as machining lines in one department after the next take it up.
Thank you very much for your cooperation, Mr.Murata.
Cooperated with DENSO Cooperation Driving Safety Manufacturing Divisionwww.denso.co.jp/en▶For further information about the products presented here

Air Gap Sensor Series

Effectively prevents CNC industrial machined defect products.

NEW!!

NEW!!

Air Gap Sensor

1−100 µm detection distance

80−350μm detection distance

DPA-A2

Short Range Detection TypeLong Range Detection TypeDPA-SR1

DPA-LR1

Precision Mechanical Type

Excellence Award
in “Tokyo Venture Technology Award” 2015

The specifications and descriptions are subject to change without notice due to improvements in products.

METROL CO., LTD.
1-100 Takamatsu-cho Tachikawa, Tokyo 190-0011 JAPAN
Tel: +81 50 5558 7366 / Fax: +81 42 528 1442
E-mail: touchsensor@metrol.co.jp
APP-DNS-E-K003