Role of Pneumatic/ Hydraulics in BIW welding fixture design

Pneumatic system-

v  System operated with Air.

v  Open loop system

v  Generally used for low pressure

v  Generally delivers less force compared to hydraulic system

v  Cheaper compared to hydraulic for basic cost. But compressor running cost is more

Hydraulic system-

v  System operated with  fluid - oil.

v  Closed loop system

v  High pressure system

v  Generally used for heavy force delivery

v  Initial cost is high

v  More expensive

Pneumatic system  is mostly preferred over  hydraulic system  in BIW welding fixture.
All toggle clamp, pin cylinder, slides are operated via pneumatic.
Generally cylinder are designed to operate max pressure 12-13 bar. As it expensive and difficult to maintain 10-12 bar in shop floor it is preferred to do design pneumatic systems at 6 bar pressure

Types of Spot Welding Guns

IT- Integral Transformer
Non-IT- Transformer is separate from gun body.
MFDC- Medium Frequency DC Gun.
Depending upon the application IT and NON IT Guns are selected.

It has been observed that for under body welding application where floor width is more it is better to used Non IT gun.
In under body guns arm length is longer due to spot distance .Due to this weight increase and it is better to use NON IT gun. Transformer is mounted/hanged on top.

Many OEM not preferring MFDC guns nowadays. MFDC are costlier.