Fused Deposition Modeling - 3D Printing

Fused Deposition Modeling - 3D Printing

Fused deposition modeling is an additive layer manufacturing process also known as layer by layer manufacturing process because in this process a 3 dimensional object is made by adding very thin 2 dimensional layers. Process starts with generating the computer aided design (CAD model) of the component which needed to be manufactured. Then second step is to convert the computer aided design file in to STL (standard triangulation language) file, this file format is internationally accepted by all additive layer manufacturing machines. Third step is to slice the 3 dimensional STL file into 2 D cross sections, this is done by the additive layer manufacturing machine. In fourth step the physical development of the desire component is done. After complete manufacturing of the component the post processing is required which is fifth step where finishing process like cleaning and curing is done and final the component is read to be used. 

1.0 Working

In fused deposition modeling the material which is in form of solid filament, is feed from the roller into the head of the machine where the material is first melted and then extruded out through the preheated nozzle of the machine. Material is extruded on to a table called build plate form whose temperature is maintained below the material melting temperature. As material is feed through the controllable nozzle which move only in the horizontal direction and deposit the molten material on the building plate form to make a thin layer two dimensional profile. 

After one layer is deposited the building plate form is lower down equal to the thickness of the layer to be deposited and after that second two dimensional layer of the material is deposited above the first layer. When second layer solidified it make a weld like connection with the lower layer and like this with more two dimensional layers, a three dimensional component is obtain. In the case of over handing feature in the component design, some support material will be required for processing that overhanging feature. The support material is deposited just before the overhanging feature is required with the help of a second nozzle.  After the manufacturing process is completed, the semi-finished product is taken for post processing like cleaning and removing of support material form the main part and after that the component is ready for use. 

2.0 Materials

Material used in the fused deposition modeling is supplied in the form of wire with diameter of about 1.5 millimeter and the materials that are used are elastomer, eutectic metals, wax, glass fiber reinforced material, thermoplastics and ceramics. Build material in the form of pellets can also be used instead of the filament form. Material used for the support material is mostly nylon and wax type material. The support materials used are either broken away or it may be water soluble. 

3.0 Applications

Fused deposition is mostly used for the development of the conceptual models of the products and for the products like pattern, cores and other tooling used in other manufacturing processes. Fused deposition modal is also used for the production of the medical related models and products. To some extend fused deposition modeling is used for the production of functional prototypes which are used to test the design of a product. 

By RepRap.me [GFDL 1.2], via Wikimedia Commons

4.0 Advantages of Fused Deposition Modeling

• Fused deposition modeling have low labor cost

• Fused deposition equipment cost is moderate

• Cost related to finishing in fused deposition modeling is very low

• Fused deposition modeling is environment friendly process as it has very good material utilization

• Fused deposition modeling have the ability to produce the layer thickness in the range of 0.05 to 0.75 mm

• Fused deposition modeling have the ability to produce the minimum sectional thickness of about 0.3 mm

• Building material of different color can be used in fused deposition modeling

• Component made from the fused deposition modeling have almost zero porosity

• Fused deposition modeling process has the ability to provide the tolerance of about 0.1 to 0.25 mm

• The surface roughness of the parts made form fused deposition modeling is in the range of 6 to 12 micro meter Ra

• In fused deposition modeling no post curing process is required which make this process little faster and more economical than some other additive layer manufacturing methods like selective laser sintering 

• Fused deposition modeling process support more material than other additive layer manufacturing process like selective laser sintering 

• Fused deposition modeling can be used anywhere because its environmental friendly and non-toxic process. 

5.0 Disadvantages of Fused Deposition Modeling

• Product building speed of fused deposition modeling is between slow to medium but it truly depends on the size and type of the product. Building speed is very slow for solid parts but medium for hollow parts

• Lead time in fused deposition modeling is between one to two weeks

• Build and support material used in fused deposition modeling are very expansive

• Fused deposition modeling is only economical for very small production quantity

• Product dimensions in fused deposition modeling are limited to 600 mm, 600mm and 500 mm

• In fused deposition modeling finishing processes are required to improve the surface condition of the final product

• Stair stepping case effect is a big problem associated with fused deposition modeling

• Surface finish produce by the fused deposition modeling is not as good as produce by the other additive layer manufacturing process like selective laser sintering and 3 dimensional printing.

• With fused deposition modeling it is very difficult to produce features like thin walled members, sharp edges and acute angle

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Analysis of current material and manufacturing process of flywheel

Analysis of current material and manufacturing process of flywheel

Flywheel is a mechanical device used to store the rotational kinetic energy. The main application of the flywheel is to provide the kinetic energy whenever the load torque is greater the drive torque. Amount of energy store in a flywheel depends on three things geometry of flywheel, angular velocity of flywheel and density of material used. Whereas the flywheel ability to handle the stresses and range of angular velocity at which it can rotate safely, depends on the material of the flywheel. Therefore the material selection is one of most important aspect of flywheel manufacturing.  

Flywheel which is discussed in this report is for an electric motor, manufactured form aluminum casting alloy using sand casting. 

Current material selection and issues related with it. Currently aluminum casting alloy was selected by manufacturer to manufacture flywheel for given job because of following four reasons. 

1. Manufacturing properties required

According to the requirements listed by the customer following are the properties required by any material to perform the job perfectly and safely. (Mikell P. Groover, 2010, Chapter 10)

• Cast-ability

• Good Fluidity

• Pouring Temperature

• Good machinability

• Shrinkage during solidification

Cast-ability means how much easy it is to manufacture a quality finished product without the machine processes like surface finish and property enhancing process like heat treatment. Material fluidity means molten material ability to flow into the mold cavity. More the fluidity less will be the damage done to cavity walls and better will be material distribution into the cavity. Low pouring temperature will help us to work at low temperature. As metal melting temperature is also its freezing temperature so low melting temperature means material will solidify at lower temperature and also solidify quickly. 

Machinability of a material means the ease with which machine operation like drilling and surface finishing can be done. Material with good machinability usually required fewer forces which directly increase your tool life and decrease the time of machining. Every material has three phase liquid contraction, phase changing contraction and thermal contraction. Material having greater value of linear shrinkage need larger pattern than material having lower value of linear shrinkage. Shrinkage of material causes defects in material like void and shrinkage cavity formation.  

2. Mechanical properties required

According to the requirements listed by the customer following are the properties required by any material to perform the job perfectly and safely. (Mikell P. Groover, 2010, Chapter 3)

• High ductility

• Low density

• High yield strength

• Corrosion resistance

• High material index

A material having high ductility have a clear change in its shape before it breaks or burst (flywheel burst like pressurize cylinder upon failure). 

This property will help us to replace the part before it causes any serious damage to machine but high ductility affect the working of flywheel in such a way that at very high rpm it start to lose its shape, affecting the working where flywheel is enclose inside a machine. Low density of a material allow you to have minimum mass under a given geometry, making your flywheel light weight, easy to carry and easy to assemble and disassemble but low less mass result is less kinetic energy of flywheel at given rpm which directly affect your output. 

High yield strength of a material enables him to restore its original shape after elastic deformation. It will help flywheel of resist the high rpm without being permanent deformed. Giving desire shape to a material required machining and for this good machinability is required. For long life material should be stable and should not react with surrounding atmosphere to form oxides. For this flywheel material should have good corrosion resistance. Material index is the most important property which shows material strength to density ratio enables us to select the best material.

3. Local Market Condition

Local market condition greatly affects the selection of material. Material you select should be easily available, cheap and should have continuous supply for nonstop manufacturing and reducing the throughput and inventory cost of material. 

4. Environment affects

Material you select should not affect the environment that is melting of it should not emit harmful gases and waste material can be recycled. 

5. Company ability to process material

Selection of material depends on the manufacturing facilities available and technical skills of labor working there.

From available material for flywheel, aluminum casting alloy is the best candidate but still there are some problem associated with its casting. First is to make the mixture of materials, which need complete technical knowledge of all the materials involve. Second is the melting of mixture, melting the mixture at higher temperature to melt the material having high melting temperature will do the work  but too much high temperature will boil the low melting materials resulting the metal oxides of that material because its vapor reacts with oxygen. (Tomasz Stuczyñski, 1997)

Current manufacturing process selection 

and issues related with it

After the selection of material the process of selecting the manufacturing process starts and like material selection this selection also has some important factors govern the manufacturing method selection. Some of them are as follow (K. G. Swift and J. D. Booker, 2013, Chapter 2)

1. Production volume

It is the number of pieces to be produce and it decide whether to use expandable mold or permanent mold and this factor also decide whether the organization should go for automation of the process or do it manually. If the volume is high the organization should go for automation to reduce the unit production time and cost but if the volume is small and design variation is high the organization should think of the integration of designing and manufacturing to have the fastest response to change in design of product. 

2. Product Size

Dimensions of the product is really important for determine of the manufacturing process because of the factors associates with the size like mold size, amount of molten material, pouring rate, cooling rate and total solidification time. 

3. Product shape features

Product shape features defines the complexity involves in the manufacturing of the product for example irregular external shape and core for internal cavity can resist the flow of molten material.

4. Product Value

Product value means the sensitivity of the function which it is going to perform. Product associated with human life security need more careful manufacturing.

Sand casting which is most widely used manufacturing process was selected by manufacturer because of low production volume, small size, simple shape and low product value. This can produce near net shape and also can provide you desire mechanical properties by the use of chillers or by careful design of mold V/A ratio. Sand use in this process can be reused again and again and waste material because of molding can be recycled making this process highly economical. Automation of sand casting can also be done to reduce the unit production time. Sand casting is a simple process but still there are some problems associated with it. (Mikell P. Groover, 2010, Chapter 11)

One of the most important is human health security issue because the molten metal is usually pored manually by the workers and any accident here can seriously damage human life also the heat and gases coming from the molten metal are harmful for human health. To overcome this, a manual operated mechanical system can be established so that worker does not come in direct contact with molten metal. (Mikell P. Groover, 2010, Chapter 11)

Another issue which is associated with sand casting of aluminum alloy is the creations of defects due the reason that alloy solidify at a range of temperature rather than at single temperature. Defects usually occur near hub of the flywheel because this is the place which solidifies in last. To overcome this, externals chills can be used near hub so that cooling process can be speed up there. (Mikell P. Groover, 2010, Chapter 10)

As already mention that these flywheels are being manufactured for an electric motor therefore an assembling process should be there to mount flywheel on electric motor shaft. This was done by making a key way on shaft of motor and also in the hub of flywheel and then after placing the flywheel was hammered onto the shaft of motor. This need experience because little carelessness can damage the shaft and bearing of the motor thus making the whole electric motor useless.

Quality control was a big problem in the organization because only destructive testing method was available. For testing the flywheel one from every batch was rotated at rpm which increase slowly until the flywheel have permanent deformation. The rpm at which the flywheel fails is then compared with rpm at which it was design to rotate. ( K.Gopinath and M.M.Mayuram, n.d, pg 8)

There was no recurring and non-recurring coat associated with this project but to manage the inventory cost delivery system was made on weekly bases and to handle the material cost recycling of the waste material was done.

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Analysis of three different material for flywheel

Analysis of three different material for flywheel

Current selection of material and manufacturing process for the flywheel has been clearly described and critically evaluated in Project 2 - Analysis of current material and manufacturing process of flywheel but there are other materials and manufacturing process that can be used instead of current material and manufacturing process to increase the performance, reliability and cost effectiveness of flywheel. Three of these materials and their manufacturing process are discussed below.

Proposed Alternative Materials

Three materials for the flywheel other than aluminum alloys are high strength steel, titanium and titanium alloys and carbon fiber composite. These materials are selected after comparing them with aluminum alloys on the bases of mechanical properties and factors involves in material selection.

Mechanical Properties

According to Mouleeswaran Senthil Kumar and Yogesh Kumar (2012) following are the material mechanical properties which affects the flywheel factor of safety, maximum rpm, weight and kinetic energy.

·         Allowable stresses

·         Yield Strength

·         Density

·         Material Index

Allowable stress is point above which flywheel will burst like a pressurized cylinder and yield strength of a material allows him to go elastic deformation and to avoid sudden fracture. Allowable stress and yield strength of all the suggested materials is greater than the aluminum alloy which makes them better candidate for safer operation.

Low density of carbon fiber will result into a light weight flywheel and high density of titanium alloy and high strength steel will result into heavy weight flywheel than the aluminum alloy flywheel. Low density of carbon fiber composite leads to less mass which result into small amount of kinetic energy stored at fix rpm. Aluminum and titanium alloys have intermediate values and high strength steel have high density resulting into maximum amount of kinetic energy stored in a flywheel.

Material index is directly proportional to the angular velocity of flywheel, carbon fiber composite have highest value of material index means it can rotate at highest rpm than any other material. Aluminum alloys, high strength steel and titanium alloys have very small difference in material index value, so their rpm range is almost same. So at fix mass carbon fiber will have maximum kinetic energy followed by aluminum alloys, then titanium alloys and high strength steel will have least amount of kinetic energy stored.

Material	Allowable stresses MPa	Density Kg/m^3	Material Index M Pa (m^2)/Kg	Melting Temperature (oC)
Aluminum Alloys	400	2700	0.148	463 - 671
High Strength Steel	900	8000	0.113	1425 - 1540
Titanium Alloys grade 4	550	4500	0.123	1670
Carbon Fiber composite (epoxy resin)	750	1550	0.483	150

Manufacturing Properties

According to Mikell P. Groover (2010) and Prof. Dr. Ahmet Aran (2007),  following are the manufacturing properties of a material that should be considered during material selection.

1.      Cast-ability

2.      Fluidity

3.      Pouring temperature

4.      Machinability

5.      Shrinkage

Cast-ability means how much easy it is to manufacture a quality finished product without the machine processes like surface finish and property enhancing process like heat treatment. Cast-ability of high strength steel, titanium alloy and aluminum alloy are almost the same but surface finish of the product made from carbon fiber is far better than other three materials.

Material fluidity means molten material ability to flow into the mold cavity. Due to the high density high strength steel have least fluidity value and aluminum alloy with less density have the highest value of fluidity.  More the fluidity less will be the damage done to cavity walls and better will be material distribution into the cavity. Carbon fiber composite have no concern with this property.

Pouring temperature is the temperature of the material at which it is poured into mold. Titanium alloy have the highest melting temperature among the other two metals and aluminum alloy have the least melting temperature. So more energy will be required for melting the titanium alloy than aluminum alloy, which increase the manufacturing cost of the product and also will take more time to solidify increasing the production time of product.

Every material has three phase liquid contraction, phase changing contraction and thermal contraction. Material having greater value of linear shrinkage need larger pattern than material having lower value of linear shrinkage. Shrinkage of material causes defects in material like void and shrinkage cavity formation. As the solidification start from outer walls toward the center and alloys solidify at a range of temperature rather than at fix temperature, this makes high concentration of one material at outer walls and concentration of other material at inner side of product. Usually material with low melting temperature solidifies at outer walls and material with high melting temperature usually solidifies at inner side.

Local Market Condition

Local market condition greatly affects the selection of material. Availability of high strength steel and aluminum alloy is good but availability of carbon fiber and titanium alloy is not as good because they are mostly use in aerospace industry.  Material you select should be easily available, cheap and should have continuous supply for nonstop manufacturing and reducing the throughput and inventory cost of material.

Environment affects

Material you select should not affect the environment that is melting of it should not emit harmful gases and waste material can be recycled. High strength steel, titanium alloy and aluminum alloys can be recycle easily but carbon fiber composite can be recycled directly.

Company ability to process material

Selection of material depends on the manufacturing facilities available and technical skills of labor working there. Manufacturing of parts using carbon fiber composite required highly skilled labor and special equipment’s where aluminum alloys, titanium alloys and high strength steel required intermediate skills and their equipment’s are also not much expansive.

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Design and Development of Automated circle drawer

Aim of this mechanical engineering project is to design and develop an automatic circle drawer which can be used to draw circles of different diameter. This task is a perfect mechanical engineering semester project which can enables students to learn about design an development of product. 

Main topics which will be covered int this mechanical project are as follow

• Concept Designing
• Concept Design Selection
• CAD modeling
• Design detail description
• Manufacturing considerations 

Concept Designing

Concept Design one

First concept design was the made by keeping in view the regular compasses design. Regular compass have one limitation that it can only draw smalls circles usually used to draw circle on papers. This new concept design has removed this limitation. Its arm can move forward and backward through the rod which enables it to draw big circles. Biggest disadvantage of this concept is that it is very difficult to operate when drawing circle at vertical surface.

Concept Design Second

Second concept design was made by keeping in view the need of drawing the large concentric circles. In this design concept one end of arm is connected with motor and other end is connected a tire. Tire is provided for support. Arm is provided with a slider which enables the design to draw concentric circles rapidly. Disadvantage of this system is that it can only draw circles at horizontal surface.

Concept Design Three

Third concept design was made by keeping in view the need of rapidly drawing concentric circles at any surface. This concept have gun like shape with an arm at its front face. This arm can slide left and right in the cavity of connecting rod which enable it dram circle of any diameter. With the gun like shape it can draw circle at horizontal and vertical surface easily. It will be electrical powered which make it easy to operate.

Concept Comparison

	Concept Design One		Concept Design Two		Concept Design Three
Criteria	Details	Grade	Details	Grade	Details	Grade
Operations	Horizontal  operation  Only	Satisfactory	Horizontal  operation  Only	Satisfactory	Horizontal and Vertical operation	Good
Handling	Difficult	Bad	Easy	Good	Easy	Good
Working	Manual Operation	Satisfactory	Electrical Power	Good	Electrical Power	Good

From the Concept comparison perform above it is clear that the concept design three is the beat design as it provide easy handling, automatic working and operation in all planes.

Introduction

Automatic Circle Drawer Design

1.    Electric gear motor 

2.    DC electric battery 

3.   Connecting Rod

4.    Arm 

5.    Plastic body

Electric geared motor and battery are enclosed inside the plastic body and arm attached with connected rod are outside of plastic body. One end of connected rod is connecting with the shaft of gear box using a pin and other end contains the arm of the automated circle drawer. Battery provides the DC voltage to the gear motor which rotate at a constant rate and along with it the connecting rod and arm rotates.

Gear Box Design

The gear box of motor have three planetary gears which are used to reduce the speed and increase the torque. In each planetary gear set input is provided to the sun gear which transfers it to three planetary gears. Planetary gears rotate at their own axis and transfer their motion to the annulus ring. Annulus gear of first planetary gear set with the help of front gear plate transfer its motion to the sun gear of the second planetary gear set.

Manufacturing Consideration

Table 9 Manufacturing Consideration

Component	Material	Process	Design Consideration	Reasoning
Body	Acrylonitrile butadiene styrene (ABS),	Injection molding	2mm uniform wall thickness, draft angle of 1 degree at least, minimum spacing between ribs [3]	Injection molding process is selected because it is the easiest and fastest process to manufacture plastic production in mass production case.
Motor	---------------	Purchase	----------------------------	Available at amazon.com
Gears	POM	Integrated with motor	----------------------------	----------------------------------
Connecting Rod	Steel	CNC Machining	Gear box shaft diameter, Shear strength of material and maximum torque is considered while selecting diameter of rod [4]	After selecting diameter of rod, just purchase it form market and then machine it required diameter and make required amendments.
Arm	Steel	CNC Machining	Gear box shaft diameter, Shear strength of material and maximum torque is considered while selecting diameter of rod [4]	After selecting diameter of rod, just purchase it form market and then machine it required diameter and make required amendments.

Conclusion

The task of making an economical, high quality, user friendly and technical useful product is completed. Product is light weight, log lasting and easy to use. Its battery can provide 60 hour working life in a single charge. To ensure safety all electrical component and mechanical component are inside the plastic body.  

The main manufacturing process involve in this project is the injection molding process for making the plastic body for the product. This process look expensive but in mass production, its fast production rate and easy working will safe much more time and the product will be delivered in market on time.

Before the mass production, many prototypes have to build to check that the design work perfectly. Although the calculation show that the design is perfect and it will not fail but it is better to test it to check that is there is any kind of material defect or any unexpected failures before investing money.

As this product starts as a conceptual design, research work has to be conducted on it to improve its design and performance or to make it even cheaper. 

 

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