research design and manufacture 3d printer using delta mechanism

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<b> </b>

<b>TECHNOLOGY AND EDUCATION</b>

MINISTRY OF EDUCATION AND TRAINING

<b>HO CHI MINH CITY UNIVERSITY OF </b>

<b>RESEARCH, DESIGN AND MANUFACTURE 3D PRINTER USING DELTA MECHANISM</b>

<b>LECTURER: Ph.D VO XUAN TIEN </b>

<b>STUDENT: NGUYEN THANH LUAN HUYNH XUAN BANG</b>

<b> TRINH XUAN DUCGRADUATION THESIS </b>

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HO CHI MINH UNIVERSITY OF TECHNOLOGY AND EDUCATION

<b>FACULTY FOR HIGH QUALITY TRAINING *********** </b>

<b>GRADUATION THESIS </b>

<b>RESEARCH, DESIGN AND MANUFACTURE 3D PRINTER USING DELTA MECHANISM </b>

<b>Supervisor:</b>

<b> </b>

<b>Ph.D VO XUAN TIEN</b>

<b>Student’s name: NGUYEN THANH LUAN</b>

<b> STUDENT ID: </b>

<b>19143081 HUYNH XUAN BANG</b>

<b> STUDENT ID: </b>

<b>19143065 TRINH XUAN DUC</b>

<b> STUDENT ID: </b>

<b>19143064 </b>

Academic year: 2019 – 2024 Ho Chi Minh city, March 2024

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<b>HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION FACULTY FOR HIGH QUALITY TRAINING </b>

_______________________

<b>GRADUATION THESIS </b>

<b>RESEARCH, DESIGN AND MANUFACTURE 3D PRINTER USING DELTA MECHANISM </b>

Supervisor:<b>Ph.D VO XUAN TIEN</b>

<b>HUYNH XUAN BANG</b>

STUDENT’ ID:

<b>19143065</b>

<b>TRINH XUAN DUC</b>

STUDENT’ ID:

<b>19143064</b>

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HO CHI MINH UNIVERSITY OF TECHNOLOGY AND EDUCATION

<b> HIGH QUALITY TRAINING FACULTY </b>

<b>GRADUATION PROJECT TASKS Semester I/School year 2023 </b>

Instructor: Ph.D Vo Xuan Tien

<b>1. Project ID number: CTM-103 </b>

<b>-Topic name: RESEARCH, DESIGN AND MANUFACTURE 3D PRINTER </b>

<b>USING DELTA MECHANISM </b>

<b>2. Initial figures and documents: 3. Main contents of the project: </b>

- Learn the theory of delta printer.

- Create printed project to use in education, industrial,… - Complete delta 3d printer.

- Collect and analyze results.

<b>4. Expected products: 3D printer using delta mechanism 5. Project submit date: __/03/2024 </b>

<b>6. Date of delivery of the project: 15/07/2023 7. Presentation Language: </b>

 Permitted to present the research project: ………. (Instructor sign, specify full name)

<b>SOCIALIST REPUBLIC OF VIETNAM </b>

<i><b>Independence - Freedom - Happiness </b></i>

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<b>Topic name: RESEARCH, DESIGN AND MANUFACTURE 3D PRITERS </b>

<b>USING DELTA MECHANISM </b>

<b>Instructor: Ph.D Vo Xuan Tien </b>

<b>Class: 19143CLA3, 19143CLA2, 19143CLA2. </b>

Thesis submission date: __/03/2024.

Commitment: “We promise this is an article that we researched. We do not copy or arbitrarily use materials, quotes, or articles without citing the source. If there is a violation, we will take all responsibility.”

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... ...

...

3. Disadvantage: ...

6.Grade:……….(Word:...)

Ho Chi Minh City, date… month… year 20… Instructor

(Sign & write full name)

<b><small>SOCIALIST REPUBLIC OF VIETNAM </small></b>

<i><b><small>Independence - Freedom - Happiness </small></b></i>

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... ...

...

3. Disadvantage: ...

6.Grade:……….(Word:...)

Ho Chi Minh City, date… month… year 20…

<b><small>SOCIALIST REPUBLIC OF VIETNAM </small></b>

<i><b><small>Independence - Freedom - Happiness </small></b></i>

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<b>Acknowledgement </b>

Ph.D. Vo Xuan Tien, your wealth of knowledge and mentorship have been crucial in guiding us towards excellence. Your constructive criticism and tireless commitment to our project's quality have truly made a significant impact on our work.

We would like to once again thank Ph.D. Vo Xuan Tien and all the faculty committee professors for their tremendous support and encouragement throughout this journey. We are truly grateful for their belief in our abilities and the opportunity to learn from their expertise. Our experience under their mentorship has undoubtedly shaped us into better individuals, equipped to tackle future challenges.

We also extend our heartfelt appreciation to all the faculty committee for their

insightful input, valuable critiques, and continuous support. Their diverse perspectives and encouragement have enriched our project and expanded our understanding of the subject matter. Their encouragement has fueled our determination to strive for

greatness. Furthermore, we express our gratitude to the entire faculty for providing us with the necessary resources and creating a nurturing environment that allowed us to successfully complete our project. Their unwavering support and commitment to our academic advancement have been invaluable.

We are deeply grateful and in awe of the immense support and guidance provided by Ph.D. Vo Xuan Tien throughout our graduation project. His expertise, feedback, and unwavering dedication have been instrumental in helping our team achieve success. We are honored and grateful for the opportunity to have worked under the guidance of these esteemed individuals. Their passion, dedication, and unwavering support have played a pivotal role in our academic and professional growth.

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<b>SUMMARY </b>

<b>❖ The urgency of the topic. </b>

In today's world, applications of rapid forming, meeting practical needs are the foundation for the development of rapid prototyping machines (3D printing – 3D printer). Applicability in many fields such as product model manufacturing, healthcare, education, architecture ...

The development of 3D printing technology will help the production process as well as the design stage shorten the time to create products, bringing ideas into real objects for easier analysis, helping designers to be more flexible and creative when coming up with ideas without having to fear how to create that product, and how long it takes to form it. So 3D printing is the best rapid prototyping tool.

<b>❖ Scientific and practical significance of the topic. </b>

For the purpose of learning and researching the field of 3D printing, the group chose the topic "Design and Manufacture of 3D printers based on parallel configurations" with the following objectives:

Participate in research and learn 3D printing rapid prototyping technology. Application of 3D printing in practice.

Research products that meet commercial needs.

<b>❖ Research objectives of the project. </b>

Learn and calculate the kinematics of the machine.

Design drawings and hardware fabrication of the machine.

Development of 3D printers based on parallel robot configurations according to 3D printing method FDM.

Learn some of the printing errors of the 3D printing method and offer solutions based on experiments.

<b>❖ Subjects and scope of research. - Research subject. </b>

Translational structure Delta parallel robot.

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<b>- Scope of research. </b>

Research and manufacture parallel structured 3D printers.

Print the largest specimens with a diameter of 220mm and a height of 300mm. The printing material is PLA plastic fiber.

<b>❖ Research methodology. </b>

Choose the main method of analyzing and summarizing experience, but also practical research methods and study materials to give accurate results.

From practical research, come up with ways to design, manufacture and repair the system.

Step 1: Learn quick prototyping methods on the internet, books and newspapers.

Step 2: Analyze the selection of feasible rapid prototyping methods and proceed with the design by comparing the advantages and disadvantages of prototyping methods.

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❖ Scientific and practical significance of the topic. ... viii

❖ Research objectives of the project... viii

❖ Subjects and scope of research. ... viii

- Scope of research. ... ix

❖ Research methodology. ... ix

- Specific research methods. ... ix

LIST OF TABLES... xv

<b>LIST OF ACRONYMS ...xvi</b>

CHAPTER 1. RESEARCH OVERVIEW ... 1

1.1. Introduction to rapid prototyping. ... 1

1.1.1. General principles... 1

1.1.2. Character... 1

1.2. The birth and development of rapid prototyping. ... 2

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1.3. Application of rapid prototyping. ... 3

1.3.1. New product development... 3

1.3.2. Check the working function of the product... 4

1.3.3. Rapid Tooling. ... 5

1.3.4. Application in medicine... 5

CHAPTER 2. THEORETICAL BASIS ... 8

2.1. Rapid prototyping methods. ... 8

2.1.1. SLA methodology (Stereo lithography apparatus)... 8

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2.4. Delta parallel robot structure applied in the topic. ... 22

2.4.1. General introduction of Delta parallel robots. ... 22

3.1. Analyze some of the essentials of a Delta 3D printer... 25

3.2. Make a design plan from the requirements given. ... 25

3.3. Analysis of truss frame design selection. ... 27

❖ Option 2. ... 27

3.4. Analysis of powertrain selection. ... 28

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3.6.1. 3D printing material nozzle construction. ... 33

3.6.2. The effect of temperature on the operation of the print head... 34

CHAPTER 4. CALCULATION, DESIGN ... 39

❖ Design options. ... 39

4.1. Consider the parallel robot structure to find out the number of degrees of freedom of the structure: ... 40

4.2. Actuator selection... 40

4.2.1 Design of the Stepper Motor... 40

❖ Stepper Motor Specifications: ... 41

❖ Choosing a GT2 pulley for machine design: ... 43

4.3. Mechanical components. ... 44

4.4. Kinematic calculations for mechanical hands. ... 46

4 .4 .1 .Prismatic delta robot configuration analysis... 46

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CHAPTER 5. EXPERIMENTATION AND EVALUATION ... 60

5.1. Finished Delta 3D printer texture... 60

<b>5.2. Experimentally measure the error of the printed sample ... 61</b>

5.3 Evaluate and fix errors... 64

5.3.1 The phenomenon of product warping... 65

5.3.2 The phenomenon of opening the upper surface... 66

5.3.3 Openings between layers. ... 67

5.3.4 Some notes before printing the template. ... 68

5.4 Errors in the FDM prototyping process, optimizing technological parameters affect the accuracy of the sample. ... 69

5.5 Optimizing technological parameters affects the accuracy of the sample.705.5.2 Determine the accuracy of the sample generated by the 3D printer based on a parallel configuration. ... 70

5.6 Measurement of nozzle height error with the print bed. ... 72

HAPTER 6. CONCLUSION AND DIRECTION OF DEVELOPMENT ... 74

6.1. Conclusion... 74

6.2. Petition. ... 75

BIBLIOGRAPHY... 76

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<b>LIST OF TABLES </b>

<b>Table 5.2: Nozzle error with the print table ...69 Table 5.3: The sample tested on the printer has the following specifications: ...72 Table 5.4: The value of empirical parameters ...73 </b>

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<b>LIST OF ACRONYMS </b>

ABS: Acrylonnitrile Butadiene Styrene CAD: Computer Aided Design

CAE: Computer-aided engineering CAM: Computer-aided

manufacturing CMM: Coordinate Measuring Machine FDM: Fused Deposition Manufacturing LOM: Laminated Object Manufacturing PLA: Polylactic Acid

FDM: Fused Deposition Manufacturing RP: Rapid prototyping

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<b>CHAPTER 1. RESEARCH OVERVIEW 1 .1 . Introduction to rapid prototyping. </b>

Rapid prototyping is a method of quickly creating product models from 3D data by building them layer by layer under computer control. Rapid Prototyping is also known variously as Layered Manuafacturing, Additive Manuafacturing or 3D Printing.

Rapid prototyping technology can also be understood as a type of technology that can directly create a three-dimensional object in a very short time, usually through only 1 element. With the help of CAD software, create physical models as databases for rapid prototyping machines. The model object is created using an appropriate material depending on the method of the rapid prototyping machine .

3D printing is one of the methods of rapid prototyping that creates a 3D object by stacking layers of material on top of each other until the object is completely shaped. Each layer is a thin and horizontal slice of matter .

<b>1 .1 .1 . General principles. </b>

The material added (additive) and bonded together to form the sample is not material cutting like traditional machining methods where the sample is created in a layered pattern, the latter layer is created on top of the previous layer .

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<b>1 .2 . The birth and development of rapid prototyping. </b>

The prototyping process is divided into three stages. The latter two periods have only been born in the last 20 years or so. Similar to computerized prototyping, the physical properties of samples were only developed in the third period.

<b>1 .2 .1 . Early stage: Manual prototyping. </b>

The first period was born several centuries ago. During this period, typical samples are not highly complex, and fabricating an average sample takes about 4 weeks. The prototyping method depends on workmanship and performs the work in an extremely heavy lifting way. To this day this method of manual styling is still quite popular, in art universities with a Posing major, this method is still used .

<b>1 .2 .2 . Second era: Prototyping software or virtual prototyping. </b>

The second period of styling developed very early, around the mid -70s. In this period there was prototyping or virtual prototyping software. The application of CAD / CAE / CAM has become very popular. Prototyping software will sketch on the computer new ideas and ideas. These samples are like a physical model: Tested, analyzed as well as stressed and calibrated accordingly if they are not satisfactory. For example, analysis of fluid surface stress and tension can be accurately predicted because it is possible to accurately determine the properties and properties of materials.

Moreover, the patterns during this period became much more complex than in the early period (about more than two times). Therefore, the time required for prototyping tends to increase to about 16 weeks, the physical properties of the sample still depend on the basic prototyping methods first. However, the use of precision machining machines has better improved the physical properties of the sample.

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<b>1 .2 .3 . The Third Period: Rapid Prototyping. </b>

The physical properties of each part of the product during rapid prototyping are also known. Hollow prototyping is suitable for production on lifting tables or layer manufacturing technology. This technology represents the process of prototyping development in the third period. The invention of rapid prototyping equipment was an important invention. These inventions met the requirements of the business world during this period: Reduce production time, increase sample complexity, reduce costs. At this time consumers demanded products both in terms of quality and design, so the complexity of the part also increased, three times the complexity that the parts were made in the 70s. But thanks to rapid prototyping technology, the average time to form a part is only 3 weeks compared to 16 weeks in the second period. In 1988, more than 20 rapid prototyping technologies were studied. We see that the need to create the initial product model is a necessity in the production process, ....

Along with the advancement in the field of rapid prototyping in the third era, there is great help of the virtual prototyping process. However, there is still controversy about the limitations of rapid prototyping technology such as: Material limitations (either because of high cost or different uses for each material to create parts).

<b>1 .3 . Application of rapid prototyping. 1 .3 .1 . New product development. </b>

This is the most important application of rapid prototyping, in the process of developing new products, it shows the physical phenomena of designs that cannot be observed on computer models, including design aspects, helping designers evaluate the best product before putting it into mass design .

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<b>1 .3 .2 . Check the working function of the product. </b>

Based on the 3D model, it is difficult to ensure that the product when produced can meet the requirements of working operation, assembly ... Especially with gears, gearboxes, cams, eccentric shafts or couplings, joysticks ... Rapid prototyping will help engineers and designers deal with those problems. Rapid prototyping technology can now "3D print" assembled parts, even in many different colors.

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<b>Fig 1.2: Creating mold with 3D printer.[12] 1 .3 .4 . Application in medicine. </b>

In the field of medicine, rapid prototyping technology is used to make medical models, bone replacement implants, and surgical aids .

Artificial bones: There are accidents that cause a part of the bone on the body to break and cannot be recovered. The requirement is to reconstruct the corresponding bone for high-precision implantation. To do that, reverse engineering is used. Rapid prototyping technology is also widely used in dentistry .

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<b>Fig 1.3: The joints were created from a 3D printer to replace osteoarthritis </b>

patients.[13]

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<b>CHAPTER 2. THEORETICAL BASIS 2 .1 . Rapid prototyping methods. </b>

<b>2 .1 .1 . SLA methodology (Stereo lithography apparatus). </b>

As a technique that uses a laser to harden liquid materials to create serial layers until the finished product, the thickness of each layer can reach 0.06mm at most, so it is very accurate. This technique can be visualized as follows: Placing a platform in a container of liquid material, the laser beam moves (by design) onto the top of the liquid material in the shape of a cross -section of the product, causing this layer of material to harden. The pedestal containing the already hardened layer of material is lowered to create a new layer, the other layers are carried out continuing until the finished product.

<b>Fig 2.1: Prototyping method principle SLA.[14] </b>

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<b>- Advantage: </b>

Rigid and fully automated system.

High dimensional accuracy. Typical size tolerance is about 0.0125mm. Good surface gloss.

High resolution to suit intricate details.

With the support of QuickCastTM software enables rapid and accurate prototyping of metal die casting processes.

<b> - Disadvantage: </b>

The product is warped. Expensive prices.

Materials used are restricted.

Must go through the post-processing stage. High operating and maintenance costs.

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<b>2 .1 .2 . SGC (Solid) method Ground Curing). </b>

Also the method of layer-by-layer hardening. Unlike SLA, this does not use a point laser source, but uses a beam of ultraviolet light to shine on the entire surface, which has been shielded through a mask. The bright open material will solidify into one layer. The mask is a negative film of the cut cross section .

<b>Fig 2.2: SGC Prototyping Method Principle.[15] </b>

<b>- Advantage: </b>

Parallel processing system: Prototyping and fine processing occur in parallel, thus saving time by 25-50%, reducing internal stress and product warping.

Homogeneous product characteristics.

Can manufacture multiple products at the same time.

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High operating and maintenance costs.

The wax must be removed from the product when it is finished making.

<b>2 .1 .3 . LOM method (Laminated Object Manufacturing). </b>

Use sheet materials coated with adhesive (mainly paper but can also use plastic sheets, metal sheets, etc.). The laser source creates each layer of the cross-section by cutting the sheet of material along the boundary of the object cross-section. The sectional layers are glued one after another thanks to the heating roller system

<b>Fig 2.3: LOM Prototyping Method Principle [16]</b>

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High speed, faster than other layering methods because the laser does not cut the entire area, but only scans according to the outer perimeter. Therefore, thick and thin materials have equal cutting speeds .

There is no phase change during the fabrication of the part, so the shrinkage of the material is avoided.

Non-toxic and polluting the environment.

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<b>2 .1 .4 . SLS Method (Selective Laser Sintering). </b>

It is a laser sintering method. After the roller spreads out on the work table a layer of powder with a predetermined thickness, the laser source scans the coating on the surface to be layered. In that region, the material particles will stick together to form a layer. Each vertical move of the equipment system will form the next layer. The 3D Printing method works on the principle of "inkjet printing". A special glue ink is sprayed onto a layer of plastic powder that has been flattened and solidified. So we created a layer and layer by layer gradually created the object .

<b>Fig 2.4: Prototyping method principle SLS.[17] </b>

<b>- Advantage: </b>

The high amount of material put into the process (Hight Through -put) makes the

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Fabricate multiple parts at the same time.

Changing materials requires thorough cleaning of the machine .

<b>2 .1 .5 . FDM 3D Printing Method (Fused Deposition Manufacturing). </b>

Using flowable wire materials, such as 3D printed ABS, PLA ..., the wire through the heating head will plasticize and be spread on the substrate according to the cross-sectional profile of the sample, in layers with a thickness equal to the cutting layer thickness. The flexible plastic will bond in layers until the pattern is complete.

<b>Fig2.5: The principle of FDM prototyping method.[18]</b>

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Save a lot of materials compared to traditional processing methods, because this is a non-chip processing method.

No need for support structures.

High speed, faster than other layering methods because the laser does not cut the entire area, but only scans according to the outer perimeter. Therefore, thick and thin materials have equal cutting speeds .

There is no phase change during the fabrication of the part, so the shrinkage of the material is avoided.

Non-toxic and polluting the environment.

<b>- Disadvantage: </b>

The warping of the part is often the main problem of the LOM method . Surface gloss is not high.

There are veins between the layers

May need support mechanisms (support)

Temperature fluctuations throughout the production process can lead to poor cohesion between layers, so the strength in the Z-direction is poor, and the machining speed is limited.

The above introduces some typical methods in rapid prototyping technology using different forms of materials (liquid, powder, sheet, wire) with different properties. The general thing is that they are all processed through each layer one by one. Tomography, layering, and tomography are all not simple and have a great impact

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<b>2 .2 . Classification of fast machining methods based on printed materials . </b>

Because there are many aspects of production, there are many types of rapid prototyping systems on the market, to broadly classify rapid prototyping systems based on the basis of production materials. In this type of classification, all rapid prototyping systems can be easily classified into three categories: :

<b>2 .2 .1 . Liquid form. </b>

Rapid prototyping systems are based on a liquid platform starting with material in a liquid state. The prototyping process is a vulcanization process, where the material converts from a liquid state to a solid state. The following are some rapid prototyping methods based on liquids:

3D Systems SLA stereoscopic prototyping equipment Cubital's SGC cube processor.

Sony SCS Block Prototyping Equipment.

The ultraviolet printing device creates Misuibishi's SOUP cubic object . EOS Floating Imaging Device.

Teijin Seiki's Block Imaging Equipment.

Meiko Rapid Prototyping Equipment for Jewelry Industry. Denken's SLP Rapid Prototyping Equipment.

Mitsui's COLAMM Rapid Prototyping Equipment.

Fockele and Schwarze's LMS rapid prototyping equipment. Light sculpting equipment.

Two-beam laser device.

<b>2 .2 .2 . Cubic form. </b>

With the exception of powdered materials, rapid prototyping systems with block base materials involve all forms of ceramic block materials of all forms: wire, roll, laminated and pellet. The following are some rapid prototyping methods that symbolize this method:

Helisys LOM Thin-Layer Forming Equipment. Stratasys FDM Multilayer Spraying Equipment.

Hot stamping equipment using KiRa's SAHP coupling agent. Kinergy Rapid Prototyping Equipment.

3D System Thermojet Multi-Nozzle Prototyping Equipment. IBM RPS Rapid Prototyping System.

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Sanders Prototype MM-6B prototyping equipment. Sparx AB's Hot Plot Rapid Prototyping Equipment.

Scale Model Unlimited's CAMM Laser Prototyping Equipment.

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<b>2 .2 .3 . Powder form. </b>

In limited capacity, the powder state form is still considered the block state form. However, it was created on the intention of being a type of device that does not depend on the base block state material rapid prototyping equipment system. The following are some rapid prototyping methods that symbolize this method :

DTM's SLS Laser Sintering Equipment.

Soligen's DSPC Direct Thin Shell Molding Equipment. Fraunhofer's MJS multi-stage rigification device. EOS EOSINT Devices System.

Inkjet equipment, also known as BPM Technology's BPM . MIT's 3DP holographic printing device.

Z-Corp. Z-Printer rapid prototyping equipment.

To do that, people use laser scanning technology to recapture the shape of the object, then use CAD / CAM software to design and process to recreate the shape of the product and finally use color to make the object look similar to the sample .

<b>2 .3 . FDM 3D Printing Method Analysis (Fused Deposition Manufacturing). 2 .3 .1 . Reasons to choose FDM. </b>

FDM machines have advantages including using a variety of materials, easy to change materials, simple structure, low cost compared to machines using Stereolithography and Sinterin Lazer method, easy to repair, capable of producing thin parts and large size, No laser sources, lots of materials, and no toxic materials . To produce rapid prototyping without spending a lot of money on prototyping, FDM rapid prototyping may provide the best choice. Compared to the Stereolithography and Lazer Sintering methods, the FDM method is clearly feasible to build a low-cost rapid prototyping machine that is still sufficient for rapid prototyping.

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<b>2 .3 .2 . Principle of operation. </b>

Instead of lasers and materials, FDM builds by stretching molten plastic and solidifying layer by layer to create a dense part structure. The material builds in the structure of a slender solid fiber, which is directed from a roll to the moving head controlled by a stepper motor. When this fiber reaches the probe, it is melted by temperature, which is then ejected through the nozzle onto the part plane .

When molten material is ejected, it is leveled by nozzles in the same way that a welder or painter uses the tip of a pipe to spread the material. The width of the spread can vary between 0.193mm and 0.965mm and is determined by the size of the nozzle. The nozzle cannot be changed during prototyping, so model analysis must be selected in advance.

When the molten material is leveled evenly, it cools quickly by about 1/10(s) and solidifies. When a coated layer is complete, the support plane moves downwards to a conventional thin layer of 0.178mm to 0.356mm and the process is repeated.

As well as streolithography and laser sintering, the FDM system reads STL files according to the standard input of all rapid prototyping methods. The STL file consists of a closed triangular mesh generated from the plane of the CAD model. The software in the FDM system cuts the STL file into a series of cross sections, which are mapped by the material nozzle.

To create accurate parting, it controls the critical temperature of the chamber and the part forming process. The temperature of the chamber must be kept lower than the melting point of the material, so only a small amount of heat is enough to melt the ejected hair and form a part that does not sink or deform. The part must be kept cold enough for the molten material to solidify and bond together .

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<b>2 .3 .3 . Support. </b>

Protrusions or isolated parts of FDM parts require intermediate assistance during construction. FDM machines use a second nozzle next to the basic nozzle to spray the required auxiliary material. (Stratasys) offers 2 types of auxiliary materials. Wax type material for machines with low price and water soluble material type with machine are more expensive. Auxiliary wax can be damaged from the part but it is difficult to remove from internal grooves or small details. Water-soluble auxiliary material can be dissolved in an agitated tank. Other auxiliaries are removed, FDM details do not need post-processing.

<b>2 .3 .4 . Surface accuracy and quality. </b>

Stratasys' FDM system with a precision grade is in the ±0.005 inc (± 0.127 mm) range. The surface roughness of FDM parts is not as good as those made by the Stereolithography method but higher than those manufactured by Sintering Lazer. But on the contrary, the details using the projection method have a smooth texture. The FDM detail appears ribbed because both the transverse layers and the displacement line appear repetitive.

<b>2 .3 .5 . Material. </b>

Over the years, Stratasys has developed a number of plastic powder materials for FDM systems. One type for producing high -quality parts is ABS. Other materials include wax for molds around parts, polycarbonate for durable parts, and polyphenyl sulfones for heat-resistant applications. FDM parts, made from molten and solidified materials, exhibit closed physical properties compared to parts made from similar materials but by different methods.

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<b>2 .3 .6 . Speed. </b>

Because FDM systems create parts by narrowly stretching material particles, wide, blocky or thick-walled parts take a long time to complete. Small or thin -walled details can be created fairly quickly. The time required to fabricate the part depends on the solidification rate of the FDM system (determined by the size of the nozzle), the height of the part (the number of layers), the horizontal dimension of the part (the time required to solidify each layer), the quantity and complexity of the required additives (additives for each layer form a separate step) .

<b>2 .3 .7 . Choice of use. </b>

FDM parts are stiffer and more durable than those manufactured by stereolithography but they have poor surface quality and are not sharp. ASB, polycarbonate, polyphenyl sulfone materials are thermal, mechanical, and moisture resistant, so FDM parts can be used for a wide limit of specialized samples, depending on the application. FDM details are not pitted and do not need to absorb me a second time. Unlike stereolithography or laser sintering, FDM machines can be used in office environments and FDM materials do not require much special handling. Many FDM systems are cheaper than stereolithography and laser sintering. For companies that want to produce durable and accurate models for the company. FDM can be a good choice.

Auxiliary removal: There is plenty of room in the detail where the auxiliary

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and layer thickness increases the speed but is recommended for a part .

<b>2 .4 . Delta parallel robot structure applied in the topic . 2 .4 .1 . General introduction of Delta parallel robots. </b>

Stemming from the needs and flexibility in production, robot mechanisms are increasingly developing very diverse and rich. In recent decades, parallel structure robots were studied by Gough and Whitehall in 1962 and attention to the application of parallel structure robots was started by Stewart in 1965. He was the creator of an airplane training chamber based on a parallel mechanism. Currently, parallel structures are widely used in many fields .

The typical type of parallel robot consists of a dynamic machine table connected to a fixed rack, driven in many parallel branches, also known as the number of pins. Usually the number of pins is equal to the number of degrees of freedom, controlled by the drive source located on a fixed stand or directly on the foot. It is for this reason that parallel robots are sometimes called pedestal robots. The actuators control the external load, so the parallel actuator usually has a large load capacity.

Due to the superiority of parallel robots, it is attracting more and more research scientists, and is also applied more and more widely in many fields:

Physics: Microscope holders, precision measuring equipment holders. Mechanical Engineering: Precision mechanical processing machines,

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The choice of parallel robots to build 3D printers brings many advantages over conventional 3-axis robots, such as faster travel speed than conventional printers, z-axis is not limited by the low speed of threaded rods. It uses a highly linear motion system (thanks to the mobility of the sliding ball bearings), and minimizes the mass of movement. This means we can tackle a large volume with multiple printheads, and do it quickly. With a parallel structure, the error depends only on the axial error of the individual leg mechanism assemblies, and the errors are not accumulated like serial robots.

<b>2 .4 .3 . Some advantages and disadvantages of parallel robots . </b>

<b>- Advantage: </b>

High load capacity: The structural components are smaller, so the mass of the components is also smaller.

High rigidity due to their geometric structure:

• All simultaneous impact forces are shared for all pins.

• The special kinematic structure of the linking joints allows all applied forces to be converted into tensile/compressive forces of the pins .

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Can perform complex operations and operate with high precision . Can design in different sizes.

Simplify machine mechanisms and reduce the number of elements due to the pre-designed pins and couplings into standard assemblies.

Provides high mobility during work due to its compact mass and size . The actuators can be positioned on the panel.

The range of parallel mechanism robots is very wide from assembling extremely small parts to movements that perform complex functions, requiring high precision such as: milling, drilling, turning, welding, assembling...

Parallel robots work without platforms and can move anywhere in the production environment. They can work even when on a boat and hang from the ceiling, walls...

The cost of parallel robots applied in mechanical processing is less than CNC machines with equivalent features.

<b>- Disadvantage: </b>

However, parallel robots also have certain disadvantages when compared to chain robots such as::

The workspace is small and difficult to design.

The solving of complex kinetic and dynamical problems ... There are many decays (singularities) in the workspace.

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