HYBRID FABRICATION ROBOT

HYBRID FABRICATION ROBOT

ADITHYA NARAYANA .K.S BHARATH.R.S4th sem mechanical 4th sem mechanical

(Email-kadamba_adi@rediffmail.com) (Email-bharathshetti@gmail.com)

KALPATARU INSTITUTE OF TECHNOLOGY

TIPTUR-572202

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HYBRID FABRICATION ROBOT

HYBRID FABRICATION ROBOT1 ADITHYA NARAYANA.K.S, 2BHARATH.R.S

Audi_kadamba@rediffmail.combharathshetti@gmail.com

Abstract:

Robotics is a technology with a future and it is a technology for the future. There is a large class of applications in which the robot actually performs work on the part. This work almost always requires that the robot’s end effecter is a tool. The type of tool depends on the processing operation that is performed. The purpose of this paper is to present an idea of building a Hybrid fabrication robot that will do continuous arc welding, remove the chips on welded joints by wire brushing and also do spray coating on the joint of a pair of long and flat sheet metals.

1. Introduction:-

Robots are employed in a wide assortment of applications in industry. Today most of the applications are in manufacturing to move materials, parts, and tools of various types. Future applications will include nonmanufacturing tasks such as construction work, exploration of space, and medical care. At some time in distant future, a household robot may become a mass produced item, perhaps as common place as the automobile is today.

For the present, most industrial applications of robots can be divided into the following three categories:

1 . Material-handling and machine loading and –unloading applications. In these applications the robot’s function is to move materials or parts from one location to other location. The MAKER 110 in fig 1 is shown performing material-handling operation. Loading and/or unloading of a production machine is included within the scope of this material-handling activity. The Unimate 2000 in fig 2 is performing machine load/unload operation for a machine tool.

2 . Processing applications. This category includes spot welding, arc welding, spray painting, and other operations in which the function of the robot is to manipulate a tool to accomplish some manufacturing process in the work cell. Welding represents particularly important applications in the processing category.

3 . Assembly and inspection. These are two separate operations which we include together in this category. Robotic assembly is a field in which

industry is showing great interest because of economic potential. The SCARA robot shown in fig 3 is performing an assembly operation. Inspection robots would make use of sensors to gauge and measure quality characteristics of manufacturing product.

2. Processing Operations:-

There is a large class of applications in which the robot actually performs work on the part. This work almost always requires that the robot’s end effector is always a tool to perform certain processing operations. Accordingly, the use of a tool to perform work is a distinguishing characteristic of this group of applications. The type of tool depends on the processing operation that is performed. We divide the processing operations that are performed by FABRIBOT-2009 into the following categories for purposes of organizing this paper:

a) Continuous Arc weldingb) Wire brushingc) Spray coatingd) Sensors used

a) Continuous Arc Welding

Continuous arc welding is used to make long welded joints in which an airtight seal is often required between the two metal pieces being joined. The process uses an electrode in the form of a rod or wire of metal to supply high electric current needed for establishing the arc. Currents are typically 100 to 300 A at voltages of 10 to 30 V. the arc between the welding rod and the metal parts to be joined produces the temperatures that are sufficiently high to form a pool of molten metal to fuse the two pieces together.

For robot applications, two types of arc-welding seem the most practical:

1. Gas metal arc welding (GMAW)2. Gas tungsten arc welding (GTAW)

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HYBRID FABRICATION ROBOT

Fig. 1 MAKER 110

In these welding processes the wire is continuously fed from coil and contributes to the molten metal pool used in the fusion process. The welding wire serves as the electrode in the arc-welding process. GMA welding is typically used for welding steel. In GTA welding (also called TIG welding for tungsten inert gas welding), a tungsten rod is used as the electrode to establish the arc. The GTA process is typically used for welding aluminum, copper and stainless steel. In both GMA and GTA welding, inert gases such as helium or argon are used to surround the immediate vicinity of the welding arc to protect the fused surfaces from oxidation.

b) Wire brushing

In this processing operation a power spindle is attached to the robot’s wrist. The spindle is used to rotate the wire brush that will be used for chip removal after the continuous arc welding process.

c) Spray Coating

This method involves the use of spray guns to apply the paint spray system comes in various designs, including conventional air spray, airless spray and electrostatic spray. The conventional air spray uses compressed air mixed with the paint to atomize it into a high velocity stream. The stream of air and paint is directed through a nozzle through a nozzle. This causes the liquid to break up into fine droplets due to the sudden decrease in pressure in front of the nozzle. The electrostatic spray method makes use of either conventional air spray or airless spray guns. The electrostatic spray method makes use of either conventional air spray or airless spray guns. The feature which distinguishes the electrostatic method is that the object to be sprayed is electrically grounded and the paint droplets are given a negative charge to cause the paint to adhere to the object better at the object to be painted. The airless spray does not uses compressed air. Instead the liquid paint flows under high fluid pressure through a nozzle. This causes the liquid to break up into fine droplets due to the sudden decrease in pressure in front of the nozzle. The electrostatic spray method makes use of either

conventional air spray or airless spray guns. The feature which distinguishes the electrostatic method is that the object to be sprayed is electrically grounded and the paint droplets are given a negative charge to cause the paint to adhere to the object better.

Fig. 2 UNIMATE 2000

3. Hazards of the following operations when accomplished manually:-

a. Continuous Arc Welding

i. Arc from the welding process emits ultraviolet radiation which is injurious to human vision. To be protected from this the welder wears a helmet with a dark window. This dark window filters out harmful radiation, but it is so dark that the welder is virtually blind while wearing the helmet except when the arc is struck.

ii. The high temperatures created in arc welding and the resulting

Fig.3 SCARA ROBOT

molten metal’s are inherently dangerous.

iii. The high electrical current used to create the arc is also unsafe.

iv. Sparks and smokes generated during the process and these are a potential threat to the operator.

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HYBRID FABRICATION ROBOT

b. Spray coating

i. Fumes and mist in the air. These result naturally from the spraying operation. Not all of the paint droplets become attached to the surface of the object. Some remain suspended in the atmosphere of the spray painting booth. To protect the human operators, ventilation systems must be installed in the booth and protective clothes must be worn. Even with this protection, the environment is uncomfortable and sometimes toxic for humans.

ii. Noise from the nozzle. The spray gun nozzle produces a loud shrill noise. Prolonged exposure by humans can result in hearing impairments.

iii. Fire hazards. Flammable paint, atomized into a fine mist and mixed with air, can result in flash fires in the spray painting booths.

iv. Potential cancer hazards. Certain ingredients used in modern paints are believed to be carcinogenic, with potentially unsafe health consequences to humans.

4. Hybrid Fabrication Robot:-

Hybrid Fabrication Robot is an idea of building a fabrication robot that can weld, wire brush the joints to remove chips and spray paint the two long sheet metals. Before designing we’ve to keep n mind the following features:

1. Work volume and degrees of freedom: The robot’s work volume must be large enough for the sizes of the parts to be welded. A sufficient allowance must be made for manipulation of welding torch

2. Motion control system. Continuous-path control is required for arc welding. The robot must be capable of smooth continuous motion in order to maintain uniformity of the welding seam.

3. Precision of motion. The accuracy and repeatability of the robot determines to a large extent the quality of the welding job.

4. Programming. Programming of the continuous arc welding must be considered carefully. For straight welding paths, the robot should possess the capability for linear interpolation between two points in space.

5. Hydraulic drive. Hydraulic drive is preferred over electric or pneumatic drive in spray painting applications.

6. Blower should be situated at the bottom near power spindle attached with wire brush so that the chips removed are blown away and the area is made clean for spray painting.

7. Sensor. A vision camera should be mounted on the robot near the welding torch to view the weld path. Highly structured light is usually required for the camera sensors to function reliably. Single pass system is preferred over double pass system. Deviations from the programmed seam location are detected and corrected in the weld path. The obvious advantage of the single pass systems, compared to the two pass system is that time is saved by eliminating the need for a second pass along the weld path.

Parts of Hybrid Fabrication Robot

1. Spray gun2. Welding electrode3. Wire brush4. Camera

a. At spray gunb. At welding electrode

5. Machine unita. Welding machineb. Air compressorc. Electrical circuits and wiring

6. Guide track

5. Conclusion:-

This Hybrid Fabrication Robot is a very promising technology which has to be considered by any fabrication industry. It is worth to have such robot that combines various operations in a single unit. This is just an idea but we look forward to implement it if necessary support is offered

6. References:-

1.“Robotic Configurations” Industrial Robotics by M. P. Groover.

2. “Sensors in Robots”- www.robots.com/sensors.txt.in

3. “Advanced Applications of Industrial Robots” A paper by S. K. Mathur Prof. of Mechatronics from IIT Powai Bombay.

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HYBRID FABRICATION ROBOT

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