Week 7:- Base Unit Design Challenges 1

What is the Base Unit? What are the typical parts of the Base Unit?

Answer- A base unit is the unit design to mount all the other units(Clamp unit,Pin unit,Rest unit etc.)of the tool,also oter parts like pneumatic valve box,trunking cable path will also be mounted in a base unit.

Parts that are used to create base unit are belows:

• Base plate
• Pedestal
• Trucking channel
• Valve box
• Eye bolt
• Floor plate

Base plate:

-It consists of 25-40mm plate thickness.

-The base plate has no.of drilled holes are done for mounting purpose of different units.

Pedestal:

It is used to connect base plate with a floor plate.

-The pedestal can be a standard part or a make part,depending on size and height of the fixture.

-Pedestal are available in different height and different inclinations.

-Depending on the size of a base plate,for load distribution no of pedestal can be used for a fixture.

Trucking channel:

-For carrying all the electrical and pneumatic connections i.e wires/pipes for units of tool.

Valve Box:

-Valve box is a standard enclosure part which contains all the valves for a pneumatic units.Inside the box there are different types of solenoied valves are used for provide air pressure,so that air inlet and outlet done inside it.The box protect inside parts while operation is perform.

Eyebolt:

-These are the bolts that are the used to lift fixture for transportion by inserting hooks into them,usually M20 bolt is provided in base unit for lift,it can be varries according to load.

-Some times forklift holes are provided for transportion purpose.

Floor plate:

-They are also knows as foundation plate.It is grounded by a fixed bolt.

-10mm clearance should be given between pedestal base plate and floor plate.

-Weld bar is needed to used after levelling is done by levelling screw.Weld bars are along the sides of the base plate of a pedestal.

-Wel bars are also used to position permanently.

What are the points need to account while designing a Base unit?

working height:

• Working height depends on the nature of the manual or robotic welding fixture. For manual fixture we need to consider the working height 850-1100 mm, depending upon the working height of the worker standard of specific country will apply.
• If base structure is made with base plate having tubular structure welded below it we can reach to height 100 mm to ~250 mm. In this case to reach the working welding height we need to provide additional some leg structure which may have top and plate plate welded to tube.

3. What is a Dump unit?

When we have some geometrical constraints them it is difficult to place unit like clamp unit etc .
In this case the dump unit is used . dump unit is the complex unnit to design due to space constrains there is less space available & have to adjust all the parts in available space . it consist of dump cylinder to perform the operation of clamping & unclamping car panel.The first cylinder dumps the assembly carrying clamp mylars , pin and then this unit , we should make sure that in the open position of the open position of the panel , we should be able to remove the panel.

Function of the dump unit:-

• To ensure proper resting of the panel being welded and to restrict its motion.
• To ensure there are not rotation in the panel and to fix it it either by pins or side blocks or magnets.

What are the points you need to consider while designing a Dump unit?

Consideration for the dump unit:-

A dump unit can have a slide cylinder or a clamp cylinder attached to it . cylinder validation is important in case of a dump unit as the weight can be too heavy for the cylinder to dump . in such case , calculation are done force excerted by the cylinder is checked against the weight of the load being carried if cylinder force is more , it is validated or we use a more powerful cylinder.

-Slide units are positioning units which are used to position the fixture, weld gun, units, robots into position for further operations.

-Slide units can be classified into two types on the base of the type of guide-ways used as

1)hardened guide ways

2)LM guide way

-Slide units can be classified into three types on the base of the prime mover used

1)Manual slides

2)Hydraulic/pneumatic slides

3)CNC slides

it may also be classified depending on application as

1)Horizontal slide

2)vertical slide

3)angular slide

-slide unit are used when we have some space constraints . so we don't have spce to design different special unit & to assembly it . in those case we use sliding units.

What are the points you need to consider while designing a slide unit ?

A sliding unit comes under the category of complex unit . few points that need to be considered while designing a slide unit are:

1.Weight carrying capacity

There are different kind of guid rails in avialable in the market ,each having a different load capacity . hence we calculate the weight of our assembly and calculate the weight capacity of rail . hence , we choose rail based on its load - carrying capacity.

2.Push and Pull Forces

We need to check the puch and pull force and check if it is enough to push and pull the slide especially when the slide is at an inclination.

3.Locking Mechanism

Stopper blocks are used to stop the slides at the required position . it is important as if the slides unit has rest mylars and pins, they need to be stopped at their respective position for proper resting and location without a stopper . it may dent the panel.

4.Stopper Blocks:-

Stopper block are used to stop the slides at the required position . it is important as if the slides unit has rest mylor and they need to be stopped at their respective position for proper resting and location without a stopper , it may dent the panel.

5.Sensor unit:-

Sensor unit helps to check the position of the slide when the operation is going to start , the operator pushes the button and slide moves

forward , the sensor gives this signal of the presnece of the unit to the PLC which then performs the next operation.

6.Stroke

We need to select the length of stroke bassed on the work area we want to get cleared .

7.open position

The only moving parts are that one the slides , so we need to check the following with a gun or other unit nearby . only after this has been checked that we can approve the design.