Week 7:- Base Unit Design Challenges 1

Q.1. What is the Base Unit ? What are the typical parts of the Base Unit ?

ANS. Base Unit in BIW Fixture Designing used to mount all the units like pin unit, clamp unit, rest unit, dump unit and slide unit, etc,. Also tooling holes are provided on base plate of base unit. Tapping for eye bolt also given on base plate to lift the whole fixture from one position to other. Image provided below shows all the components in the base unit:

1. Base Plate: Holes are provided on this plate to mount all units, eyebolts. This machined plate of 25mm to 40mm thickness. Material used for this plate are Aluminium or Steel.
2. Pedestal: Pedestal is a component used to connect base plate to floor as shown in figure. Depending upon the size of base plate no. of pedestals are used. It is a std. parts available in different heights, size and inclinations.
3. Trunking Channel: It is the duct or tube consist of electrical cables or wires and pneumatic tubes of different units in a fixture.
4. Valve Box: It is nothing but a control unit of BIW Fixture consist of no. of solenoid valve which is used control valve.
5. Measuring Hole Cover: This Hole Cover are used to protect tooling holes from dust, damages due to welding spatters. This holes are acts as a referance holes for other hole used to mount different units on base plate.
6. Eyebolt: Eyebolts are provided on the base plate to lift the whole fixture from one position to another.
7. Floor Plate: It is also known as foundation plate which is mounted on ground using fix bolts. Min. 10mm of clearance is provided between floor plate and pedestal base plate.
8. Weld Bar: These bars are used to position the fixture. Weld bar is steel plate placed along side of base plate of pedestal.

Q.2. What are the points need to account while designing a Base Unit ?

ANS. The points need to account while designing a Base Unit are as below:

1. Working Height: Depending upon type of operation whether it is manual welding or robotic welding working height of base unit decided. For Manual Welding Fixture working height must be 850mm to 1100mm for ease in welding operation for the operator.
2. Selection of Eyebolt depends upon weight of fixture. According to the weight of fixture tapping for eyebolt is provided on base plate like M24 or M20. Generally four eyebolt are provided on base plate.
3. Depending on no. of units, its sizes and weight base are designed. Generally base designed are made up of square or rectangular tubes or c channels with machined plate.
4. Generally four dowel holes are provide at four corner of base plate with its coordinates displayed on aluminium plate.
5. Base Unit is designed in such a way that there is min. possibility of deflection, vibrations.

Q.3. What is a Dump Unit ?

ANS. Dump Unit is used rarely when there is limited space for designing any unit like clamp or pin unit. It consist of dump cylinder used to perform loading or unloading action which is mounted on unusual riser designed according to the space we have.

FUNCTION:

1. To restrict all degree of freedom and to endusure proper resting of car panel
2. To fix the car panel in fixture using pin or magnet or side block
3. To provide necessary clamping force to clamp car panel

Q.4. What are the points you need to consider whlle designing a Dump Unit ?

ANS. The points you need to consider whlle designing a Dump Unit are as below:

1. 3-2-1 Principle: This is a basic principle while designing any fixture used to locate any car panel in fixture proper.
2. Mass Consideration: Weight of dump unit must be at lesses side. Less the weight of unit less will be the force required to operate this unit. While taking such consideration of mass, strenght will be at maximum side.
3. Time of opening and closing: Time of opening and closing will be less as much as possible.
4. Cylinder Validation: It is one of the important point which is consider while designing such unit. Cylinder is selected such that it is able to take load of unit while operation.
5. Open Condition: It is one of the basic point which is consider in every moning unit like movable pin unit or clamp unit or slide unit, etc. Open condition is check to determine whether the car panel is load-unload proper or not.

Q.5. What is a Slide Unit ?

ANS.

Slide Unit is used for different purposes like clamping or resting or may be as pin unit. Sliding action is performed with the help of pneumatic or hydraulic cylinder or may be by using manual toggle clamp.

This unit has built on a plate which is guided on rail. Stopper block or plate is mounted at the end position to stop the plate on which whole unit is build. This type of unit is used where space available is less.

Classification of Slide Unit:

1. According to the guide ways used:

1. Hardened Guide way
2. LM Guide way

2.According to the type of operation used for sliding:

1. Manual
2. Pnematic or Hydraulic
3. CNC

3. According to the Applications:

1. Horizontal
2. Vertical
3. Angular

Q.6. What are the points you need to consider while designing a Slide Unit ?

ANS. The points you need to consider while designing a Slide Unit are as below:

1. Weight Carrying Capacity: Weight carrying capacity of rails are one of the important point while selecting proper guide rails which perform sliding action without any problem. Different rails have different capacity to carry load of unit assebly.
2. Push and Pull Forces: Pull and Push force should to be less as much as possible. It is majorly consider when slide unit is in inclination.
3. Locking Mechanism: Locking Mechanism is necessary to stop sliding unit at perticular position. While doing operation the slide unit must be locked at some position hence this provision is made is the fixture.
4. Stopper Block: At start and end of stroke of sliding unit stopper block is provided to hold the plate in guide rail on which whole assembly is mounted.
5. Sensor Unit: Basically to check the postion of slide unit sensor unit is designed.
6. Stroke: Stroke is decided while designing this type of unit according to the space availble and some other factors.
7. Open Position: Open position is check to ensure that slide unit is collide with other unit in fixture or to welding gun.