Robotics Project - Assignment Solution

Rationalization / Re design of the components:

We have selected the piston sub assembly for the project. The assembly consists of mainly 5 components and the main block where the components are assembled by an industrial robot.

The components are:

1) Nuts.

2) Cover plate.

3) Spring.

4) Piston stop.

 5) Piston.

We have decided to remove some parts and replaced their purpose with re design of the remaining components. The parts we decided to remove are nuts and piston stop.

The piston stop is re designed as the extension of the cover which is transformed into a cap. The nuts are also removed and the purpose is served by the cap itself by fixing the assembly in to the block by tightening of cap in to the block.

 Re-Design of Cover:

The actual shape of the cover is a rectangle which is made up of steel. The design of this component has been transformed into a Cap like structure as shown in the figure. The dimensions of the cap is Ø30 mm on the top. And the height of the cap is designed as 25 mm. The bottom of the circular top is chamfered to 5mm which gives ease for the robot Jaw to pick the part and hold the part with ease. The Cap is given threading cuts on the vertical wall structure which is helpful to tight the cap into the main block which also has the threading inside it. The diameter of the threading is given as Ø1 mm. The material used for the Cap is steel. 

  COMPONENT:  Cap

MASS             :  26.6 Grams

VOLUME        :   70.2 mm^3

DENSITY         :   0.3 Grams /mm^3  

MATERIAL      :   Steel

Re-design of Spring :

The spring actually given was very thin in its material structure and has very high pitch. So these types of springs are very difficult to feed from a feeder as there can be point of tangling if springs. This is highly observed with the springs which have high pitch. So we have decreased the pitch of the spring and also increased the radius of circle in helical sweep. This also avoids some percentage of the tangling of springs. So the both constraints together will reduce the tangling on springs to a larger extent. The height of the spring is maintained same as 40mm and the Radius is kept at Ø25 mm. The material used is steel. 

Component: Spring

Material      : steel 

Volume       :  26.1 mm^3

Density        :  0.3 Gram /mm^3

Mass            :   10.1 Grams.

Re-Design of Piston :

Piston in this assembly is the first part to be assembled into the block. So the piston should be stable when it is placed inside the block and must be enough strong to hold the other parts with good stability. So the bottom of the piston has rod which is re deigned to rectangular cube like structure with 2mm length and width so that is placed in the hole provided in the fixture and attain stability. The rod of the piston is 10 mm in height, out of which half of the rod is inserted in to the fixture hole. The total height of the piston is about 25 mm height out of which the tip circular head is 5mm of the total height and the cylindrical part in the middle is about 10mm in height.

The top base has diameter of Ø 26 mm which later on hold the spring on its surface in the assembly process.

Component: Piston

Material      : Steel

Volume        : 84.3 mm^3

Density         : 0.38 gram/mm^3

Mass             : 32 Grams.

1.4 Re-design for Main Block: 

Block is the one of the main part of the assembly which holds all the components in it. The Block is designed in such a way that the components are placed with good stability. The block is a rectangular cube with a height of 30mm from the top of the base of the table where it is placed. The fixture is clamped on the table so that is fixed on the table during the assembly. The cube has a hole of Ø 30mm diameter on the 32 mm head of the cuboid. The rectangular cuboid has an orifice at 25mm depth with 5mm which is made for the piston rod to get inserted to maintain stability. Then the spring and cap are assembled after the piston. The assembly is closed by tightening the cap into the block. For this we have designed the hole of the cube with internal threads which helps the cap to tighten the assembly.

The above figure demonstrates how the Block looks and the assembly process is like the piston is first component inserted in the hole of the cube. Then the spring is placed on top of the piston. Then the cap is placed over the spring and the cap is pressed downwards to make the cap to get contact to the threading of the cube. Then the cap is rotated by the robot to make sure the assembly is closed. The cap and fixture tightening is as same as the bolt and nut tightening.

2 FXTURE DESIGN: 

  The fixture is something which will hold the base block and does not allow the block to move while assembly process. We have designed a clamp like structure where the block is inserted into the clamps on the table. These clamps are of 2mm x 2mm dimensions. The block is inserted by an industrial robot which later followed by the assembly process.

•  FEEDERS:

2.1.1 PISTON FEEDER: 

The main requirement to choose a feeder is to check the number of orientations of the component. Piston has one orientation which is top base resting upside down as shown. And the other orientation is lying side wards which is not constant orientation. We have selected the reciprocating fork hopper to feed the piston components. The feeder has a rotating bowl which has the piston components in bulk. When the bowl rotates the pistons cannot stand on the base orientation due to centrifugal force they may be pulled sideways. So the reciprocation fork which has its fork gap same as the diameter of the cylinder starts it’s up and down ward motion. The components gets struck in the fork when they are rotating in the bowl. So the fork picks up the components that get struck in the fork and transfer then in to the delivery chute.

So this way the piston components are fed by the feeder and delivery chute has a stock of components ready for robot for the assembly.