MECHANICAL FABRICATION
GRIPPER:
It consists of the following: -
1) 0.3 Kg.cm stepper motor
2) Rear Housing Plate
3) Front Housing Plate
4) Arm Supports
5) Gripper Arms
6) Wooden Gripper Ends
7) Four Bar Linkage Mechanism
8) Worm Gear Pair
1) Stepper motor:
The stepper motor used is a DC step synchronous motor, manufactured by Srijan Stepper Motors, Pune.
2) Rear Housing Plate:
This is an aluminium plate of square cross-section. It consists of a central hole which is connected to a shaft fits into the wrist assembly. There are four holes at the corners so that it can be connected to the motor.
3) Front Housing Plate:
This is also an aluminium plate of square cross-section. It consists of a central hole to allow the motor shaft to pass through. There are four holes at the corners so that it can be connected to the motor.
4) Arm Supports:
These are rectangular section aluminium flats, which are welded to the front and rear housing plates. They are connected to the arms at the font end with screws.
5) Gripper Arms:
These are aluminium flats connected to the arm supports at one end and hinged to the wooden grippers at the other. They also house the four bar linkage mechanism.
6) Wooden Gripper Ends:
The wooden gripper ends are the object holding ends. They have pads to prevent crushing, of the object. They are hinged at one end to the arm and connected to the four bar linkage mechanism.
7) Four Bar Linkage Mechanism:
The four bar linkage mechanism has been used in order to keep the gripper ends parallel to each other in any position of opening.
8) Worm Gear Pair:
A hylam worm gear pair has been used with a reduction of 1:40. The gear pair transmits the motion from the motor to the arms.
WRIST ASSEMBLY:
It consists of: -
1) 0.3 Kg.cm stepper motor
2) Motor Housing
3) End Effector Shaft
4) Wrist Roll Gear Pair
5) Wrist Pitch Worm Pair
6) Wrist Pitch Motor
7) C - Clamp
1) 0.3 Kg.cm stepper motor:
The stepper motor used is a DC step synchronous motor, manufactured by Srijan. This is mounted on the motor housing and the motor shaft is connected to the spur gear pinion made of hylam.
2) Motor Housing:
It is an aluminium block which has a through hole in the front to receive the end effector shaft, which in turn, is connected to the end effector assembly. The shaft rests on bearings inside the motor housing.
At the back, the shaft projects to receive the spur gear. At the side, the motor housing, houses a worm gear, which is outside the C - clamp.
3) End Effector Shaft:
This is a mild steel stepped shaft passing through the motor housing at one end. The stepped end is hollow and houses the end effector.
4) Wrist Roll Gear Pair:
The spur gears used are made of hylam and have a reduction of 1:3.
5) Wrist Pitch Worm Pair:
The worm gear pair has a reduction of 1:40. The worm gear is mounted on a shaft on one side of the motor housing. While the worm shaft is connected to a mild steel shaft, which rests on the wrist pitch motor. The worm shaft ends in a bush bearing.
6) Wrist Pitch Motor:
This is a 3 Kg.cm motor. It has a nipple to receive the shaft connected to the worm shaft used for the pitching motion of the wrist.
7) C – Clamp:
This consists of two aluminium plates of rectangular section connected to each other with a mild steel plate, which in turn is attached to the elbow link. The C - clamp allows the pitching action of the wrist assembly with the help of the worm gear pair.
ELBOW ASSEMBLY:
It consists of the following: -
1) Elbow Link
2) Wrist Pitch Motor Housing
3) Elbow Motor
4) Worm Gear Pair
5) Counter Weight
6) C clamp
1) Elbow Link:
This is a mild steel hollow box section, which is connected to the C - clamps at both ends. The link has many holes drilled on it to reduce weight. The advantage of using a hollow section is weight reduction as well as passage for wires.
2) Wrist Pitch Motor Housing:
The wrist pitch motor is housed on this link by means of two mild steel plates.
3) Elbow Motor:
This is a 13 Kg.cm DC step synchronous motor manufactured by Sanyo Denki, Japan. This motor houses a nipple, housing the shaft which is connected to the worm shaft used to pitch the elbow.
4) Worm Gear Pair:
The worm gear used to pitch the elbow is made of cast iron while the worm shaft is made of mild steel. The worm pair had a reduction of 1:40. The worm shaft ends in a bush bearing
5) Counter Weight:
On practical evaluation, the efficiency of the elbow was found to be much better with the application of a counter weight of 1 Kg. The necessary box section mild steel link was formed to make the axis of the counter weight parallel to the axis of the elbow link.
6) C – Clamp:
This consists of two aluminium plates of rectangular section connected to each other with a mild steel plate, which in turn is attached to the shoulder link. The C - clamp allows the pitching of the elbow link. The C clamp is connected to the elbow link by means of a shaft and bearing.
SHOULDER ASSEMBLY:
It consists of the following: -
1) Shoulder Link
2) Elbow Pitch Motor Housing
3) Shoulder Motor
4) Worm Gear Pair
5) Worm shaft housing
6) Counter Weight
7) C clamp
1) Shoulder Link:
This is a mild steel hollow box section, which is connected to the C - clamps at both ends. The link has many holes drilled on it to reduce weight. The advantage of using a hollow section is weight reduction as well as passage for wires.
2) Elbow Pitch Motor Housing:
The elbow pitch motor is housed on this link by means of two mild steel plates.
3) Shoulder Motor:
This is a 28 Kg-cm DC step synchronous motor manufactured by Sanyo Denki, Japan. This motor is placed on the base plate and connected to the worm shaft.
4) Worm Gear Pair:
The worm gear used to pitch the elbow is made of brass while the worm shaft is made of mild steel. The worm pair had a reduction of 1:40.
5) Worm shaft housing:
The worm shaft is supported by two mild steel plates, which are in turn welded onto the base plate. This assembly is critical as the worm shaft and wheel must have the right centre distance.
6) Counter Weight:
On practical evaluation, the efficiency of the shoulder was found to be much better with the application of a counter weight of 5.5 Kg was suspended at the base of the shoulder link and another counter weight of 3 Kgs was suspended as an extension from the worm wheel shaft.
7) C - Clamp:
Two mild steel plates of rectangular section of uneven sizes were welded on to the base plate. One of the sections was kept shorter so that it does not obstruct the elbow motor.
BASE
It consists of the following: -
1) Base Plate
2) Spur Gear Pair
3) Base Motor
4) Base Shaft
5) Base Structure
6) Sheet Metal Covering
1) Base Plate:
It is a mild steel plate, which supports the entire structure. The base plate is connected by a clamp to the base shaft. The entire weight of the structure is borne by a thrust bearing, which is placed in housing at the bottom of the base.
2) Spur Gear Pair:
The spur gear has a reduction of 1:4 and is made of mild steel. The spur gear is placed on the base shaft while the pinion is placed on the motor.
3) Base Motor:
This is a 13 Kg-cm DC step synchronous motor manufactured by Sanyo Denki, Japan. The motor is mounted on a plate, which is connected to the base structure with the help of bolts.
4) Base Shaft:
This is a mild steel stepped shaft. The base of the shaft passes through a thrust bearing while at the mid section, the shaft passes through a roller bearing. Both the bearings are seated in their respective housings. The top of the shaft, being connected to the base plate through the plate clamp.
5) Base Structure:
The frame is made mild steel box sections. The shape is a combination of a hollow cylinder and cuboid. The shape has been designed in such a way as to help in the stability of the robot.
6) Sheet Metal Covering:
These are mild steel sheets, which have been bent, in the required form so as to cover the base from all sides. This has the dual function of keeping the interiors dust free and to make it aesthetically appealing.
FINISHING TECHNIQUES :-
Drilling is the process of producing Cylindrical either through or blind holes in the solid material. Different kinds of drilling machines are used for this purpose .They are as listed below :-
1 ) Portable drilling machine
2 ) Bench drilling machine
3 ) Pillar drilling machine
4 ) Multiple spindle drilling machine
5 ) Gang drilling machine
6 ) Radial drilling machine
During a drilling operation the material flows through the flute of the drill bit. On removal of the drill bit from the hole drilled we notice material clinging on to the edges of the drilled hole which appear as frayed edges. These are called burrs. The process of removal of this excess material is called burring.
Deburring is done by using the immediate next sized drill bit and just drilling a few millimeters such that the burrs are removed.
Grinding or abrasive machining is the process of removing metal in the form of minute chips by the action of irregularly shaped abrasives particles . These particles may be in bonded wheels, coated belts, stones or simply loose. The two types of abrasive materials are
1 ) natural
2 ) artificial.
Emery, sand stone, quartz corundum and diamonds are the different natural abrasives . Aluminium oxide, silicon carbide cubic boron nitride and the artificial diamond are the artificial abrasives.
There are three different methods of grinding, namely
1 ) Surface grinding : In this process the grinding wheel revolves on a spindle and the workpiece, mounted on either, a reciprocating or rotary table is brought into contact with the grinding wheel . Flat, angular and irregular surfaces may be produced by grinding.
2 ) Cylindrical grinding : it is the process of grinding the circumferential surfaces of cylindrical pieces. These pieces may be straight or tapered or contoured.
3 ) Centerless grinding : Centerless grinding method is employed for circumferential grinding of long slender rods which cannot be ground by cylindrical grinding due to lateral thrust of the wheel on the workpiece.
Electroplating is the process of coating the material with a protective layer such that the deposited layer of protective coating prevents the material from rusting , and also other wear occurring due to various causes.
In this method basically the material to be used as the protective layer is taken as the anode and the material to be coated is taken as the cathode. A suitable solution is taken as the electrolyte based on the coating material and the material to be coated. When a current is passed through the system of anode , cathode and electrolyte a reaction takes place and the anode splits into its ions and deposits on the cathode thus coating the object.
This process is used to provide a coating of paint on the object to prevent the object from rusting and other wear caused due to use. It also provides a good surface finish and aesthetic looks.
In this process the object is first scrubbed with an abrasive material to remove any dirt and waste material . It is then coated with a primer paint which has putty in it to help in providing an initial coating. the paint is taken in a tank from where it is blown out through a nozzle of small diameter by compressed air coming out of a compressor which splits the paint droplets into minute drops and helps in even spreading of the paint. the paint gets atomised as it comes out of the nozzle due to the velocity of the compressed air thus providing an even coat of paint on the body of the object thus providing a good finish and aesthetic looks.
This process is used for the removal of burrs and unwanted material on the surface of the object to provide a good finish. There are different kinds of files that are used based on the application. For example, in the removal of large sized burrs from the surface of the object bastard files are used. In each kind of file various sizes are also available. Depending on the finish to be got different files are used and by judgement of the person who is filing the object different pressures are applied to conform to the size constraints of the object.
All the drawings have been drafted using AutoCAD Release 13 and are available for download.
The fabrication details are available in the form of freehand drawings which we have scanned using a REALLY old 300dpi scanner and attempted to retouch digitally. If you do want to have a look at these click here.