WHAT IS FIXTURE
A device which is used to hold, locate and support the component in the manufacturing industry is called fixture. Fixtures ensure to provide the stability to the part when any process is being done on that part. That process can be welding, riveting, grinding, drilling etc. In BIW fixture design Fixture works on 3-2-1 principle.
WHAT IS 3-2-1 PRINCIPLE
Basically 3-2-1 principle is used to lock all six degree of freedom.
The 3-2-1 principle is a Component holding principle where three pins are located on the 1st principle plane, i.e. either XY, YZ, ZX. And two pins are located on the 2nd plane which is perpendicular to the 1st plane, and at last one pin on the plane which is mutually perpendicular to the 1st and 2nd planes.By using this method Componet can be arrested in all six degrees of freedom.
Assembly Line :
An assembly line is a process in which car panel/car body parts are joined as the semi finished assembly moves from one station to another station until the final product is produced.
In the process of joining in assembly line , panels are moved from one section to another sections.Those sections are called Station.
In BIW fixture designing we have various stations which are used to locate the panels so that joining processes can be done.
Some of these stations are:
- Geo Station
- Respot Station
- Pedestal Weld/Rivet
- Loading Station
- Buffer Station
- Marriage station
- Sealing station
- Curing station
1. Geo station:
In this station geometry of two parts are fixed. it can be either using welding or riveting . In this station precision and geomatry of the finished product is defined Locating pins have closer tolerence of 0/-0.15.
Suppose the hole dia of panel is 16mm then the pin dia minimum can be 15.85.
Diameter of locating pins should be lesser than the panel hole dia. So Tolrence in locating pin is given in negative value.
2. Respot Station :
Once product comes out of the Geo Station and there are left out spots where spot welding or riveting is to be done. then it is moved to another station , that station is called Re-spot station.
These left out spots may be the due to clamp plan, cycle time,robot reach ability or any other various reasons.
In this station pins ahve tolrence upto 0/-0.28.
3. Pedestal Station :
In this station , Pedestal gun is mounted on a tool and panel is manipulated manually or by robot to weld the panels.
Pedestal station is generally a Re spot station.
Re spot station and Pedestal station, both perform same kind of operation . but to decide whether to go for pedestal or a re-spot station some parameters needs to consider like cycle time, floor space, no. of welds, clamp plan, or size of the panel.
4. Loading Station :
This station is used for loading of panel and same station is used to change the orientation of the if it is required in the upcomin station.
Sometime this station is used when Robots are unable to transfer panel from one station to another.
5. Buffer Station :
This station is used to make the balance between the process.
Some stations carry out procees in lesser time as compared to their respective stations.In that case panels can be stored in one sation so that assembly line process remains smooth.
6. Sealer Station :
In this station Sealant application is carried out.This process can be carried out manually or by using robots. Sealer is used in between two panels so that panels do not flatter due to friction.
7. Marriage Station :
In this Station inner and outer panels are joined. In this station to avoid the imprssion on the outer panel(A class surface), copper strips are used in betweenn the weld tip and A-class surface.
8. Curing Station :
In this Station product recieved after sealing application, is kept idle at ambient temperature, which allows sealent to get dry with better bonding between the panel.