Models for printing on a 3D printer

Accuracy

Accuracy in the XY axes depends on the backlash, structural rigidity, belts, in general, on the mechanics of the printer. And is approximately 0.3mm for hobby printers.
The Z-axis accuracy is determined by the layer height (0.1-0.4 mm). Hence, the height of the model will be a multiple of the layer height.
It should also be borne in mind that after cooling, the material shrinks, and along with this, the geometry of the object changes.
There is also the software side of the problem. not every slicer processes the internal dimensions correctly, so it is better to increase the hole diameter by 0.1-0.2 mm.

Wall thickness

The walls should be equal to or thicker than the nozzle diameter. Otherwise, the printer simply will not be able to print them. The wall thickness depends on how many perimeters will be printed. So with 3 perimeters and a nozzle of 0.5mm, the wall thickness should be from 0.5, 1, 1.5, 2, 2.5, 3mm, and over can be any. That is, the wall thickness should be a multiple of the nozzle diameter if it is less than Nd, where N is the number of perimeters, d is the nozzle diameter.

Large Models

When modeling, it is necessary to take into account the maximum possible print dimensions. If the model is larger than these dimensions, then it must be cut to print in parts. And since these parts will stick together, it would be nice to immediately provide for connections, for example, “dovetail”.

models, printing, printer

Location on the desktop

The strength of the model depends on how to position the model on the desktop.
The load should be distributed across the print layers, not along. Otherwise, the layers may separate. adhesion between layers is not 100%.
To make it clear, let’s take a look at two L-shaped models. Lines show print layers.

The strength of the printed part depends on how the force is applied relative to the layers. In this case, a small force will be enough for the right “G” to break it.

Flat base

This is a desirable but not required rule. A flat base will help the model to better stay on the printer table. If the model peels off (this process is called delamination), then the geometry of the base of the model will be violated, and this can lead to a shift in the XY coordinates, which is even worse.

If the model does not have a flat base or the base area is small, then it is printed on a raft. a printed substrate. Raft spoils the surface of the model it touches. Therefore, if possible, it is better to do without it.

10 rules for preparing a model for 3D printing

I downloaded the model, printed it out, use it. what could be simpler !? But, if we talk about FDM 3D printers, then not every model can be printed, and almost every model (not prepared for 3D printing) has to be prepared, and for this it is necessary to imagine how this 3D printing goes. First, a couple of definitions:
Slicer is a program for translating a 3D model into a control code for a 3D printer. (There is plenty to choose from: Kisslacer, Slic3r, Skineforge, etc.). It is necessary because the printer will not be able to immediately eat the 3D model (at least not the printer in question).
Slicing (slicing). the process of translating a 3D model into a control code.

The model is cut (sliced) in layers. Each layer consists of a perimeter and / or fill. The model can have a different percentage of filling with fill, also there can be no filling (hollow model).
Each layer moves along the XY axes with the deposition of plastic melt. After printing one layer, the Z axis moves one layer higher, the next layer is printed, and so on.

Minimum overhanging elements

For each overhanging element, a supporting structure is required. support. The fewer overhanging elements, the less supports are needed, the less material and printing time you need to spend on them, and the cheaper the printing will be.
In addition, the support spoils the surface in contact with it.
It is allowed to print without wall supports, which have an angle of inclination of no more than 70 degrees.

Narrow places

Bottlenecks are very difficult to handle. If possible, it is necessary to avoid such places requiring processing, to which it is impossible to get close with sandpaper or micro drill. Of course, you can process the surface in a bath with a solvent, but then small elements will melt.

Moving long open distances

As we already said, the web appears when the extruder moves to a new position, and the plastic at this time flows out through the nozzle. How significant this kind of leak can be has a lot to do with the distance the printhead moves. Short distances are covered quickly enough that the plastic simply does not have time to seep. But if the distances are significant, the probability of the appearance of a web is much higher. Many 3D printing programs have an extremely useful feature that allows you to minimize the distance the nozzle travels over void. This is done due to the fact that the trajectory changes from a straight and shortest, to a longer and more winding. but above the surface. In most cases, you can generally choose a trajectory that will never turn out to be a “bridge”. That is, there simply will not be opportunities for the emergence of a web, because the nozzle will always be above something. Such an option lives somewhere in Advanced and can be called, for example, Avoid crossing outline for travel movement, i.e. “Avoid going beyond the boundaries of the contour when moving”.

The menu of the Simplify3D slicer is used as an example. Menu items, their names and locations in your software may differ.

Overheating of plastic

The plastic that comes out of the extruder has a temperature in the range 190-240 ° C. Because the plastic is hot, it is soft and easy to shape. But when it cools down, it quickly becomes hard, and its shape cannot be easily changed. You want to balance temperature and cooling so that the plastic can flow freely through the nozzle but harden quickly, ensuring the 3D part is printed accurately. If there is no such balance, problems with print quality may arise, when, for example, the external dimensions of the object do not turn out to be what you planned. As you can see in the photo, the filament that was extruded onto the top of the pyramid was unable to solidify quickly enough to maintain its shape. Here are some common causes of overheating and how to fix them.

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Too high layer height

Most 3D printers have a nozzle diameter of 0.3-0.5mm. The plastic is pushed through this tiny hole so that very small parts can be printed as a result. But these small sizes of the nozzle also impose certain restrictions on what the height (or, if you prefer, the thickness) of the layer can be. When you print one layer of plastic on top of another, you want the top layer to be pressed against the bottom so that they stick together. The iron rule is this: the layer height you choose should be 20% less than the nozzle diameter. For example, if you have a 0.4mm nozzle, you cannot deviate too much from the 0.32mm layer height. otherwise the plastic layers will not adhere properly to each other. Therefore, if you notice that your print is flaking, the layers are not sticking, the first thing to check is the ratio of the layer height to the diameter of the nozzle hole. Try lowering the layer height and see if the cohesion of the layers improves. This can be done in the Edit Process Settings menu, in the Layer tab.

Select where to start printing

If minor defects still remain, it is possible to tell the printer where it is permissible to leave such dots. This can be done in the Edit Process Settings menu, in the Layer tab. In most cases, the print start location is chosen to optimize speed. You can also randomize this starting point, randomize it, or specify a specific position. For example, if you are printing a statue, you can instruct the print to always start from the back of the figure, so that nothing will be visible from the front. To do this, enable the Choose start point that is closest to specific location option, and printing will start as close as possible to the specified point, the coordinates of which must be specified.

The menu of the Simplify3D slicer is used as an example. Menu items, their names and locations in your software may differ.

Bad filling

The filling of your 3D model plays a very important role in its durability. It is responsible for holding together the outer skin of a 3D object and maintaining those planes that are printed on top of it. If the infill is weak or “hairy”, you should change a few settings in the print management software to give extra strength to this part of your object.

Print head moves too fast

If you are printing at a very high speed, your 3D printer’s motors may have trouble keeping it up. If you are trying to get the printer to print faster than the motors can handle, you may hear a distinctive clicking sound when the drive fails to reach the target position. When this happens, the rest of the printable object will be offset from what was printed below. If you think the print head is moving too fast, try reducing the speed by 50% and see what happens. To do this, there is the Other tab in the Edit Process Settings menu. Adjust Default Printing Speed ​​and X / Y Axis Movement Speed. The first parameter determines the speed of any movement when the extruder is actively pushing through the plastic, the second determines the speed of rapid movements when no extrusion occurs. If the value of one of these parameters is too high, it can lead to displacement of the layers. If you are not embarrassed when changing the advanced settings, you can also try decreasing the acceleration value in the firmware settings of your printer so that the speed increases and decreases less dramatically.

Layers separate and split

3D printing is designed in such a way that at one particular moment one specific layer of an object is printed. Each subsequent layer is printed on top of the previous one, and in the end a given 3D model is obtained. But in order for the resulting object to be strong and reliable enough, you need to make sure that each layer is properly connected to the one below it. If the layers are not bonded together well enough, the resulting object may crack and fall apart. Here are some typical reasons for this and suggestions on how to fix everything.

Creation and printing of chess pieces on a 3D printer

“Creation and printing of chess pieces on a 3D printer”

1.2. Choosing a program for 3D modeling. 6

1.3. Selecting the print environment for models, slicers. 9

1.4. The choice of plastic for printing models. ten

Chapter 2. Creation of 3D models on the example of chess. eleven

2.1. Modeling a pawn figure by extruding a circle. eleven

2.2. Modeling the shape of an elephant using point extrusion of faces along the coordinate axes. 12

2.3. Modeling the figure of a horse from the background image. thirteen

Chapter 3. Printing models on a 3D printer. 14

3.1. Export of the created models into a form suitable for 3D printing. 14

3.2. Comparative study of the quality of the resulting models with different settings of the printing environment. 14

3.3. Choosing the optimal environment and printer settings for the fastest and most accurate printing. 17

Relevance : This work will focus on a new technology for creating objects and objects. a 3D printer. The basic principles and technologies of the device operation are indicated. 3D printing is becoming more and more affordable and opens up many possibilities. I am exploring the possibilities of using 3D printing for the example of creating and printing chess pieces. In everyday life, 3D came to us at the beginning of the new millennium. We naturally associate this definition with cinematography or animation. But this technology covers much more spectrum of our life. So, what is a 3D printer, and what is printing on such a device??

The purpose of the research work: Learn how a 3D printer works, create real models and print them, get optimal settings for further work with the printer.

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Find information about the operation of a 3D printer installed in a school 3D modeling laboratory. 2. To study the principle of operation of this device. 3. Select a program for modeling and, on its basis, create models of chess pieces. 4. Print the created models on a printer. 5. Analyze the results.

Hypothesis: The capabilities of a 3D printer are very large at the moment, so in the future it will probably be in great demand in various fields. At first glance, the technology seems very complicated, but it seems to me that any schoolchild can master it.

Research methods : Studying 3D modeling in the process of creating a model of chess pieces in the Blender program and printing on a school 3D printer, observation, comparison.

Object of study : 3D printer, Cura printing environment. modeling in Blender.

Subject of study: 3D printer capabilities.

Relevance research is that 3D modeling plays an important role in the life of modern society. Today it is widely used in marketing, architectural design, medicine and cinematography, not to mention industry. 3D modeling allows you to create a prototype of a future structure, a commercial product in a volumetric format. 3D modeling plays an important role in the presentation and demonstration of any product or service.

Practical significance: In the modern world, 3D technology allows printing real houses, human organs, food and steel parts.

Chapter 1. Research of 3D technologies

The Arduino mega 2560 3D printer is not a complex design (Figure 1): motors moving the x, y and z axes, a heated table, a power supply, an extruder and a controller. T

Picture 1 Arduino mega 2560 printer schematic

The technology of printing on a 3D printer Arduino mega 2560 assumes that an object is created on the basis of a virtual model by layer-by-layer application of thermoplastic. The extruder, that is, the print head of the Arduino mega 2560 3d printer, heats the material to the required temperature and distributes it in the required proportions along the coordinate points specified in the virtual model. This happens by extruding the thermoplastic by the extruder (Figure 2).

Figure 2. Extruder working principle

1.2. Choosing a program for 3D modeling

3D modeling is a very popular, developing and multitasking direction in the computer industry today. The creation of virtual models of something has become an integral part of modern production. It seems that the release of media products is no longer possible without the use of computer graphics and animation. Of course, specific programs are provided for various tasks in this industry.

When choosing an environment for three-dimensional modeling, first of all, you should determine the range of tasks for which it is suitable.

1) The most popular representative of 3D-modelers remains Autodesk 3ds Max (Figure 3) Is the most powerful, functional and versatile 3D graphics application. 3D Max is a standard for which many additional plug-ins have been released, ready-made 3D models have been developed, gigabytes of copyright courses and video tutorials have been filmed. It is best to start learning computer graphics with this program.

modeling environment Autodesk 3ds Max

This system can be used in all industries, from architecture and interior design to the creation of cartoons and animated videos. Autodesk 3ds Max is ideal for static graphics. With the help of it, realistic pictures of interiors, exteriors, and individual objects are quickly and technologically created. Most of the developed 3D models are created in the 3ds Max format, which confirms the product’s reference and is its biggest plus.

Some disadvantage of the program is that it is copyrighted and paid, as well as very difficult to learn and manage.

2) For the purposes of construction, engineering and industrial design, the most popular drawing package is used. AutoCAD (Figure 4) from Autodesk. This program has the most powerful functionality for two-dimensional drawing, as well as the design of three-dimensional parts of varying complexity and purpose.

Having learned to work in AutoCAD, the user will be able to design complex surfaces, structures and other products of the material world and draw up working drawings for them. On the user side. a Russian-language menu, help and a system of prompts for all operations.

This lack of support for a large number of 3D model formats, Blender boasts over the same 3ds Max more advanced animation toolkit. The program should not be used for beautiful renderings. Element of Autocad. working drawings and detailed model development.

3) Free Blender program (Drawing 5) is a very powerful and multifunctional tool for working with 3D graphics. In terms of the number of its functions, it is practically equal to the large and expensive 3ds Max and Cinema 4D. This system is quite suitable both for creating 3D models and for developing videos and cartoons. Despite some instability of work and

Blender modeling environment

Blender can be difficult to learn, as it has a complex interface, unusual logic of work and non-Russianized menus. But thanks to an open license, it can be successfully used in everyday life and for commercial purposes.

We will choose the Blender program and will use it in our work.

What are slicers and why are they needed??

Slicer is originally a utility that can cut parallel planes from a surface array and translate the information received into G-code. After all, the extruder heads work exactly in this way, building an object by sequential build-up of surface “cuts” in parallel planes. Today, all powerful simulators have built-in capabilities to compile their models to an stl file.

The programs used to work with a 3d printer are mostly free. Only a few of them have paid versions or extensions. All free programs provided for 3d printers by developers are still supported and updated on a free basis. Many of them are open source.

Cura. one of the most convenient and intuitive applications from the Ultimaker 3D printer manufacturer. Got the most widespread. this is the most popular slicer for a 3D printer. In addition to editing tools, material settings, printing options, a number of convenient functions are included for calculating the amount of material and its cost, product weight. Has open source. Completely free, updatable utility, which I will use

Fused deposition technology has many advantages, including the relative simplicity of the design of the printers and the affordability of both devices and consumables. Typically, thermoplastics are used for printing, but there are exceptions. composite materials containing various additives, but based, again, on thermoplastics.

In modern industry, a large number of various thermoplastics are used, each of which is produced for specific purposes, respectively, they all have different physical and mathematical characteristics. Some plastics are hard and durable, others are soft and can only withstand light impact; there is non-toxic plastic for making food packaging; plastic varies in color; on the impact on it of external and other factors.

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ABS is made on the basis of a thermoplastic resin by copolymerizing acrylic, nitrile and styrene butadiene. The properties of ABS plastic can
vary slightly depending on the ratio of the proportions of substances in its composition. ABS is a high impact thermoplastic. Very popular due to its physical and mechanical properties. It handles beautifully. skins, drills, saws. Well suited for functional prints. But unfortunately he is very capricious to the environmental conditions during printing, with a draft, the model may delaminate, it can give strong shrinkage when it cools.

PLA. it is an aliatic polyester composed of organic substances such as potato starch or cellulose.
PLA has low shrinkage, that is, loss of volume during cooling, which helps prevent deformation of future models, is not capricious and easy to use.
The cost of PLA is relatively low, which adds to the popularity of this material.

Chapter 2. Creating 3D models using the example of chess

2.1. Modeling a pawn shape by extruding a circle

To create the model, I decided to use the Blender program. One of the main pieces of the chessboard is a pawn, with which I decided to start modeling.

1) In the working window of the program, I added a mesh circle with 32 faces. (Figure 6)

2) Using the extrude, extrude, and shrink / stretch tools of my meshes, and I converted the circle to the base for the pawn. ( Figure 7 )

Extruding a circle.

3) To create the head part of the pawn, I used the addition of a polygonal icosphere, placing it on the base obtained earlier. (Figure 8)

Adding a polygonal icosphere.

2.2. Modeling the shape of an elephant using point extrusion of faces along the coordinate axes

The creation of the bishop piece is very similar to the creation of the pawn, but we distinguish that we model the pommel of the bishop ourselves, in contrast to the pawn. I used the point extrusion of the faces and their displacement along the coordinate axes. (Figure 9)

Point extrusion of faces

2.3. Modeling a horse figure from a background image

1) To model the Horse figurine, I used a background image, which I placed on the coordinate axis. (Figure 10)

2) In the process of creating the figure of the horse, I used extrusion up, shift and shift along the coordinate axes. To draw the ears, I extruded and tilted two edges. ( Figure 11 )

The process of extruding a horse from a background image

3) I used the smoothing modifier to give the horse beautiful baked shapes. surface. (Figure 12)

3.1. Export of the created models into a form suitable for 3D printing

In order for the slicer program to recognize the model I created and prepare it for printing, it is necessary to export the created models in stl format. To do this, I used Blender’s built-in 3D printing addon. (Figure 12)

3.2. Comparative study of the quality of the resulting models with different settings of the cura printing environment

To print the resulting models of chess pieces, I opened all three models in the Cura program (Figure 13)

Displaying models in the Cura environment

I set up the Cura environment according to the settings recommended by the printer manufacturer. Filament diameter 1.75mm, nozzle diameter 0.4, printing temperature from 180-250, layer height 0.1mm, PLA plastic was used.

At the first start, the model did not stick to the table, I connected the table heating to 70 degrees.

When restarted with the recommended settings at a low speed, the model was printed quite high quality: the polygons of the cap are visible, but the excess plastic on the leg sticks out, this is due to the lack of cooling during the printing process. (Figure 14)

The result of printing at the recommended settings without airflow.

I tried to solve the cooling problem by printing a model with plastic blowing (cooling) implemented by connecting a cooler in the Cura program. To shorten the printing time, I tried to print three pawns at the same time. The printer did a good job. And the quality of the resulting models is not bad in the end due to the gradual cooling of the layers during the transition of the printer from model to model. (Figure 15)

Having increased the speed from 50 to 100, in order to save printing time, I received a model with exfoliated layers, the printer did not have time to fix the plastic filament properly. (Figure 16)

Printing the printer at high speed.

In order to save plastic, I tried to change the parameters of the filling density and wall thickness. With a filling density of 25%, excess plastic appears in the narrow places of the finished model. When filling 20 percent, this problem does not occur I also tried to reduce the wall thickness from 0.8mm-0.4mm, as a result, with a smaller thickness, the model turned out to be not strong enough and easily deformed when pressed.

Printing at 20% and 25% coverage and different wall thicknesses.

3.3. Choosing the optimal environment and printer settings for the fastest and most accurate printing

For a convenient comparison of the print results, I have combined the results obtained in a table. (Table 1)

Table 1. Summary table of print performance.

To print in high quality, you need to stock up on time. The printing speed must be lowered to the minimum, otherwise the small parts of the chessboard overheat and extra plastic tails appear, the shape of the polygons at the pawn is lost. Working airflow is very important, without it a high-quality top did not work.
Printing in normal quality, with less investment in time, did not work out very badly when printing three models at the same time. Due to the alternate printing of layers on several models, the plastic has time to cool down and the next layer lays down smoother.

The most optimal filling turned out to be 20%; with a larger filling, excess plastic accumulates and climbs out. (Figure 18)

The optimal layer thickness is 0.8 millimeters, with less, the model turned out to be soft and not very strong. Fast print mode produced poor quality and poor stacking. Low quality will be used for “rough” layout.

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