Manufacturing Processes: Comparisons and Techniques
TIG Welding vs. MIG Welding
| Sr. No. | Feature | TIG (Gas Tungsten Arc Welding) | MIG (Gas Metal Arc Welding) |
|---|---|---|---|
| 1 | Electrode | Non-consumable electrodes (tungsten or tungsten alloys) | Consumable electrodes (bare welding wire of desired composition) |
| 2 | Electrode Function | Generates an arc; does not melt | Generates an arc and melts |
| 3 | Application | Easier for thin plates and small parts | Widely used for thick plates (above 4mm) |
| 4 | Welding Torch Cooling | Water-cooled | Air or water-cooled |
| 5 | Metal Joining | Used for joining dissimilar metals | Used for joining similar metals |
| 6 | Process Speed | Slow process | Faster process |
| 7 | Filler Material | Separate filler material is used | Metal electrode acts as filler material |
| 8 | Equipment Cost | Lower than MIG | High |
CO2 Molding
- In this process, carbon dioxide is used to harden the mold.
- The mold is prepared by ramming clean sand mixed with sodium silicate around the pattern.
- Carbon dioxide gas is then fed into the mold, which hardens the mold immediately.
- The process can be easily used for all sizes of casting and can also be mechanized.
- Dextrin, coal powder, wood flour, and sea coal may be added to improve collapsibility.
- The strength of the mold increases as the fineness of sand increases up to 80 mesh but decreases afterward.
- Since very high compressive strengths are reached in carbon dioxide molding, the problem of collapsibility may sometimes be faced.
- Carbon dioxide molding results in high accuracy and good surface finish. There is no need to harden the mold, thus considerably reducing manual work and cost.
Brazing vs. Soldering
| Brazing | Soldering | |
|---|---|---|
| 1. Melting Point of Filler Metal | Above 400°C | Below 400°C |
| 2. Joint Stability | More stable joints | Less stable joints |
| 3. Effect of Pressure and Temperature | Joints are not affected | Joints are affected |
| 4. Equipment Cost | Higher | Very low |
| 5. Definition | Brazing is when a filler metal or alloy is heated to its melting temperature above 450 °C. | Soldering is the joining of metals using a filler material of a lower melting point than that of the parent metals to be joined. |
Open Loop vs. Closed Loop Systems
| Open Loop System | Closed Loop System | |
|---|---|---|
| 1. Build Complexity | Easier to build | Difficult to build |
| 2. Accuracy | Accurate if calibration is good | Accurate because of feedback |
| 3. Stability | Generally more stable | Less stable |
| 4. Optimization | Not possible | Possible |
| 5. Reliability | Not reliable | Reliable |
| 6. Feedback | Not using feedback | Using feedback |
| 7. Accuracy | Less accurate | More accurate |
| 8. Construction | Simple | Complicated |
| 9. Control Optimization | Not possible | Possible |
| 10. Maintenance & Cost | Easy maintenance, lower cost | Difficult to maintain, higher cost |
Rolling: Spread, Elongation, and Draft
- Spread: Absolute spread is the change in width between the stock entering and leaving a stand. Spread depends on several factors, including:
- Draft
- Roll diameter
- Stock temperature
- Roll material
- Material being rolled
For a given stock size and reduction, the bigger the roll diameter, the greater the spread; the lower the temperature, the greater the spread.
Elongation: Elongation is the increase in length of the stock due to the reduction in area. Elongation usually defines the total elongation from billet to product, or in a specific section of the mill (e.g., the roughing mill or finishing block).Draft:- Draft is the reduction in bar height in the pass. Absolute draft is expressed in linear units and is the difference between the entry height and exit height of the stock.
- Relative draft is the reduction in height expressed as a percentage of the entry height.
Cold Working vs. Hot Working
| Cold Working | Hot Working | |
|---|---|---|
| 1. Temperature | Below recrystallization temperature | Above recrystallization temperature |
| 2. Mechanical Properties | Decreases properties like elongation, reduction of area, and impact values | Increases mechanical properties |
| 3. Crystallization | Does not take place | Takes place |
| 4. Material Uniformity | Not uniform after working | Uniform throughout |
| 5. Risk of Cracks | More risk | Less risk |
| 6. Internal Stresses | Internal and residual stresses are produced | Internal and residual stresses are not produced |
| 7. Energy Required | More energy for plastic deformation | Less energy (metal becomes more ductile and soft at higher temperatures) |
Classification of Production Processes
There are four different types of production commonly used. The type of production a company should use depends on the product type, product demand, and raw material supply. Considering these factors, the four types of production are:
- Unit or Job Type Production: This type is used for producing a single unit of a product, such as tailored outfits or custom-made cakes.
- Batch Type Production: Commonly used in consumer durables, FMCG, and similar industries with large product varieties and variable demands. Products are manufactured in batches.
- Mass Production (Flow Production): Also known as assembly line production. Common in the automobile industry and where continuous production is required. It focuses on specialization, with multiple workstations.
- Continuous Production (Process Production): Often confused with mass production, but the key difference is the amount of mechanical work involved. In continuous production, most work is done by machines, operating 24/7.
Closed Die Forging vs. Open Die Forging
| Sr. No. | Parameter | Closed Die Forging | Open Die Forging |
|---|---|---|---|
| 1 | Process | Metal is confined in a die cavity and compressed. | Shaping is done by compressing the workpiece between two flat dies. |
| 2 | Metal Deformation | Metal flows and fills the die cavity completely. | Shape is given by specified blows on different faces of the workpiece. |
| 3 | Use | Used in drop forging and die forging operations. | Includes most shaping operations. |
| 4 | Accuracy | Accuracy depends on the die cavity design. | Accuracy depends on the operator’s skill. |
| 5 | Complexity of Products | More complex shapes can be produced, especially with multiple impression dies. | Simple shapes like styles, discs, and rings are produced. |
| 6 | Die Cost | Higher | Lower |
| 7 | Post-Forging Operation | No final machining is necessary. | The product may need to be finished by machining. |
Pattern Allowances
Pattern allowances are made to compensate for dimensional and structural changes during casting:
- Shrinkage Allowance: Metals shrink volumetrically after solidification. Patterns are made larger to compensate.
- Draft Allowance: A taper is provided on the pattern to facilitate easy removal from the mold and reduce edge damage.
- Finishing or Machining Allowance: Additional material is provided to compensate for metal removed during machining.
- Shake Allowance: Pattern dimensions are reduced to compensate for enlargement of the mold cavity during pattern removal.
The Internet of Things (IoT) in Production
The Internet of Things (IoT) has revolutionized production by creating an interconnected ecosystem of devices. IoT in production involves embedding sensors, actuators, and smart devices into the manufacturing environment, enabling real-time data collection and communication.
IoT relies on a network of physical objects with sensors and actuators, connected through protocols like Wi-Fi, Bluetooth, or Zigbee. This connectivity facilitates information exchange, enhancing monitoring, control, and automation.
Sensors collect data on variables like temperature, humidity, and machine performance. In conclusion, IoT transforms production through connectivity, automation, and data-driven decision-making, improving productivity and competitiveness in Industry 4.0.
Thread Rolling
- Thread rolling produces external threads by cold forging, not cutting.
- It involves subjecting a thread blank to pressure between two hardened steel dies.
- The die surfaces carry the reverse form of the thread.
- The blank diameter is approximately equal to the thread’s pitch diameter.
- Pressure causes plastic flow of the material.
- The die thread forms the roots, while displaced material forms the crests and flanks.
- Dies can be grooved blocks or threaded rolls.
- Thread rolling can be done on materials that withstand forging pressure.
- Generally used for small diameter workpieces and small pitches.
Rolling Defects
- Folds: Occur with very small reduction per pass during plate rolling.
- Lamination: Small cracks appear with high thickness reduction.
- Edge Cracking: Caused by low ductility or uneven deformation. Cracks in cold rolling occur if the metal becomes too work-hardened. Cracks on the edge of hot-rolled coils are due to excessive quenching.
- Fins: Formed when metal forces itself between rolls, potentially leading to folds and cracks.
- Alligatoring: Splitting of the workpiece along a horizontal plane on the exit side, occurring during slab rolling of aluminum alloys.
- Wavy Edge: The roll part consists of middle position bend or deflection due to compressive load on work rolls resulting in more thickness than the end of the workpiece.
Cloud Manufacturing
Cloud manufacturing integrates cloud computing into production, revolutionizing resource and information management. It involves using centralized cloud platforms to share and coordinate manufacturing resources (software, models, equipment) over the internet. This enhances collaboration among designers, suppliers, and manufacturers.
Benefits include cost efficiency (reduced upfront investments, scalable pay-as-you-go model), flexibility, and global collaboration. Challenges include security and data privacy. Overall, cloud manufacturing increases agility, innovation, and efficiency.