Week 7:- Base Unit Design Challenges 1

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

ANS:- Base unit is used to mount all the assemblies of different units like pin unit clamp unit, etc. It is important component in the BIW fixture design as it holds all the assemblies together. It includes various parts like base plate, pedestal, trunking channel, valve box, eye bolt and floor plate.

a. Base plate:- It is the main plate over which all the assemblies will be mounted. It ensures stability of the assemblies. The base plate size should cover all the units with its outer periphery. It is a machined plate with the thickness of ranging between 25 to 40MM . The base plate should be drilled with datum holes called as measuring holes. The number of datum holes depends on the size of the base plate. Generally they are provided in the pitch of 1000MM.

b. Pedestals:- Pedestals connects base plate to the floor plate. It raises the height of base plate from the floor plate. Generally pedestals are standard parts. They are available in different sizes. The number of pedestals depends on the load to be carried by base plate. In some cases it is welded frame integrated with the baseplate. It ensures proper load distribution over floor plate.

c. Trunking channel:- It is a duct over base plate which accommodates all the pneumatic and electrical hoses and wires. It can be of varying length and shape depends on movement of hoses.

d. Valve Box: It is simple box which accommodates various actuators or valves for the units. It is mostly standard part.

e. Eye bolt:- It is mount over base plate for the transportation purpose. We can transport whole assembly of base plate with the help of hooks mount in the eye bolts. These are standard parts available in different sizes according to the weight to be lifted.

f. Floor plate:- Floor plate connects the whole assembly of base plate via pedestals to the ground. It is fixed over the ground with the help of bolts. It is also called as foundation plates.

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

ANS:-Base unit is used to mount all the assemblies of different units like pin unit clamp unit, etc. It is important component in the BIW fixture design as it holds all the assemblies together. Base unit mast cover periphery of all fixtures. It includes various parts like base plate, pedestal, trunking channel, valve box, eye bolt and floor plate. Following are various points which sould be consider while designing the best plate:-

a. Load of all units:- While designing base unit we need to consider weight of all units. Base plate is a machined part which ranges from thickness of 25MM to 40MM. So depending upon the weight to be carried we need to machined our baseplate. Also according to the load to be carried we need to provide eye bolts. Number of pedestals depends upon load to be carried. So load calculation is must while considering designing of base unit.

b. Working height:- Working height depends on whether fixture is manually operated or is robotic operated. For manual operation of the fixture we need to consider height of base plate according to ergonomics of human body.

c. Material:- Material of base plate depend on the load and the size of best plate. We can use either aluminium or steel. Most of the times tubular sections are welded below the base plate so we consider steel as material. We can use aluminium in lightweight applications.

d. Other:- Generally 4 eyebolts are provided for hanging of the base unit. But it may be changed according to way to be lifted base unit. Pedestal is standard components and they are mainly used to lift the base unit above the ground from floor plate. So the number of pedestals and size of pedestals are depends on the working height and load to be carried. Also we can choose different locations for pedestals according to the uses of base unit. There must be adequate and sufficient fastening to the ground as while working different fixtures may exert deflection load. So for the stability of fixture and smooth working operation we need to fastern base unit to the ground firmly. Tubular sections should be welded below the base plate to give structure rigidity. In case of small fixtures and lightweight application we may neglect tubular sections.

3. What is a Dump unit?

ANS:- Dump unit is complex type of unit. It is used for constrained the panel in a specific way which cannot be done by traditional units like clamp unit or pin unit. It consists of cylinder called as dump cylinder to clamp and unclamped the panel. While designing dump unit constraint space is available. Dump cylinder must ensure enough clamping force while working process like welding. Panel must not displaced or move while working. As we have to design various components like pins, mylars, clamps in constraints space so the overall designing of dump unit get complicated. So usually dump unit is not used it is only used in special cases.

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

ANS:- Dump unit is used to constraint the car panel in specific way which cannot be done by traditional units like clamp and pin unit. Dump unit is used in constraint space. So it's designs get complicated and we have to ensure following points while designing dump unit:-

a. 3-2-1 principle:- As we know 3-2-1 principle is must while designing any fixture for holding of the car panel. So while designing dump unit 3-2-1 principle must be validated. As well while holding of car panel positional accuracy must have to be maintained. So validation of 3-2-1 principle is must while designing dump unit.

b. Clamping force:- To hold car panel firmly adequate forces is required. It will ensures the stability of car panel while working otherwise welding may get distorted and positional accuracy of various joining parts will not be maintained. To give enough clamping force is difficult task in case of dump unit. As while designing various parts like mylars, swing arm we have space constraints.

c. Space considerations:- As dump unit is used in constraint space we have to ensure the enough space between car panel and different components of the dump unit. Except mylar and pin all other parts of the dump unit must be at least 10 mm away from the car panel. Also while loading and unloading of panel there must not be obstacle of different components.

d. Timely operation:- While loading and unloading of car panel, clamp of dump unit must open and close exactly on time. If dump unit is failed to do so it may create obstacle for car panel and it may damage car panel. Dump cylinder must provide enough force to firmly clamp car panel that to on exact time.

5. What is a Slide unit?

ANS:- Slide unit is used where we have geometrical constraints to use normal units. As the name suggest, this unit is different from other as it slides to clamp car panel. When we have to hold panel, slide unit slides forward and clamp th panel with the help of mylar or clamp then while unloading it opens clamp and slides back. Slide units are plcaed where space requirement in low. If panel is small and various operations need to do then we can use slide unit. So that slide unit slides does its work and comes out clearing space for other units.

Slide unit also has sensors. So that accurate positioning while sliding can be maintain. With the help of feedback mechanism accurate positioning and holding of panel can be done. It has guide rails to slide. We can plce any unit on slide so that it can be act as multi-functional. It also has locking mechanism, so that it can be locked at a placed and work can be done with holding panel firmly. Slide unit has 3 types according to direction of slide:-

1. Vertical slide

2. Horizontal slide

3. Angular slide

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

ANS:- Slide unit is used where we have geometrical constraints to use normal units. As the name suggest, this unit is different from other as it slides to clamp car panel. As itis designed where space constrained. So it need to consider various considerations while designing:-

a. 3-2-1 principle:- As we know 3-2-1 principle is must while designing any fixture for holding of the car panel. So while designing dump unit 3-2-1 principle must be validated. As well while holding of car panel positional accuracy must have to be maintained. So validation of 3-2-1 principle is must while designing dump unit.

b. Accurate positioning:- As this unit slides to achieve correct position of working, it need to use sensors to guide unit over guide rails accurately. So accurate measurement of length of travel and matching with stroke of cylinder will be critical.

c. Sensor unit:- Sensor unit is essential in slide unit as it help in achieving accurate positioning with the help of feedback.

d. Weight:- As various units can be mounted over slide unit, so different weight get exerted over slide unit. For better operation of slide unit this weight calculation is necessary.

e. Clamping forces:- As this unit is use in constraint space, clamping forces can be issue. Because while clamping we cannot use bulky parts to exert large clamping force. So for proper clamping of car panel, force calculations is to be done.