3D shapes nets printables: 3d Geometric Shapes — Nets

Lesson Worksheet:Nets of 3D Shapes

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In this worksheet, we will practice forming a three-dimensional shape from a net.

Q3:

Identify the three-dimensional figure that the given net makes.

• Aa cube
• Ba cylinder
• Ca triangular pyramid
• Da sphere
• Ea cone

Q4:

Identify the three-dimensional figure that the given net makes.

• Aa cube
• Ba cylinder
• Ca triangular prism
• Da triangular pyramid
• Ea cone

Q5:

Identify the three-dimensional figure that the given net makes.

• Aa cube
• Ba rectangular prism
• Ca triangular pyramid
• Da cylinder
• Ea triangular prism

Q6:

Identify the three-dimensional figure that the given net makes.

• Aa cube
• Ba triangular prism
• Ca rectangular prism
• Da triangular pyramid
• Ea cylinder

Q7:

Identify the three-dimensional figure that the given net makes.

• AA triangular pyramid
• BA cube
• CA sphere
• DA rectangular prism
• EA cylinder

Q8:

What 3D shape can be made from this net?

• Atriangular pyramid
• Bcylinder
• Ctriangular prism

Q9:

Which of the following is the solid that can be formed from folding the given net?

• A
• B
• C
• D

Q10:

Which of the following is the shape that can be formed from folding the following net upward?

• A
• B
• C
• D

This lesson includes 39 additional questions for subscribers.

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What’s New — Autumn 2022

Interactive Place Value Blocks Tool

Our new Place Value Blocks Tool is perfect for exploring the place value system with integers, and visualising the relative sizes of digits in different places. You can also compare numbers and explore larger numbers with the decimal blocks. This is adapted from our popular Decimal Blocks Tool.

Vectors & Quadrilaterals Worksheets

Can you work out which type of quadrilateral will be formed if you follow the sequence of vectors?

Our * free * Vectors & Quadrilaterals Worksheets, provide practise working with vectors whilst prompting thinking about whether pairs of vectors are equal in length, parallel or perpendicular, and encouraging mental visualisation.

There are easier and harder versions of this worksheet.

Curriculum and Textbooks Update

Our curriculum and textbooks are now complete for all of years 7, 8 and 9.

The textbooks chapters each contain a mixture of practice exercises, puzzle-style activities and review questions. Each concept is broken down and covered in depth and questions regularly draw on knowledge from previous chapters, providing integrated practice.

Year 7 Curriculum:

1. Place Value	Core	Support
2. Calculations	Core	Support
3. Negatives	Core	Support
4. Fractions	Core	Support
5. Indices	Core	Support
6. Introduction to Algebra	Core	Support
7. Measures	Core	Support
8. Shape, Area & Pythagoras	Core	Support
9. Fractions, Decimals & Percentages	Core	Support

Year 8 Curriculum:

1. Expressions	Core	Support
2. Angles	Core	Support
3. Formulae	Core	Support
4. Area, Volume & 3d	Core	Support
5. Forming & Solving Equations	Core	Support
6. Number Theory & Sequences	Core	Support
7. Functions, Co-ordinates & Graphs	Core	Support
8. Introduction to Statistics	Core	Support

Year 9 Curriculum:

1. Fractions, Decimals & Percentages	Higher	Foundation
2. Linear Graphs & Gradient	Higher	Foundation
3. Transformations	Higher	Foundation
4. Ratio & Proportion	Higher	Foundation
5. Angles & Similarity	Higher	Foundation
6. Pythagoras & Trigonometry	Higher	Foundation
7. Probability	Higher	Foundation
8. Maps & Constructions	Higher	Foundation
9. Percentages / Calculations	Higher	Foundation

Preparing 3D models for 3D printing in T-FLEX CAD 17

The T-FLEX CAD design system allows not only creating 3D models of any complexity, but also preparing them for 3D printing. Moreover, all the tools necessary for this are also in the Educational version of T-FLEX CAD. Starting with build 17. 0.55.0, the Polygon Mesh Export Options dialog became modeless so that you can now navigate through the model when setting export options. In addition, it became possible to display a grid of triangles before saving to grid formats and redefine the path to save the file.

In this regard, we decided to tell you in detail how to take advantage of all the possibilities of exporting T-FLEX CAD 17 to grid formats in order to prepare your model for 3D printing as efficiently as possible.

In order to obtain a high-quality printed model, it is necessary to prevent all possible defects at the design stage. There are also a number of modeling features, which depend on the selected printing technology. These features should be familiarized with in more detail before starting the modeling process. Their diversity is so extensive that familiarization with them deserves a separate article.

We will consider the procedure for preparing for 3D printing using the example of a real object — a steam gun, the model of which was developed by the Center for Prototyping and Design of the Moscow State Technical University «MAMI» by order of VDAshop. Figure 1 shows a render of a 3D model created in T-FLEX CAD.

Fig. 1. Steam gun model render

Checking models in T-FLEX CAD

The finished model must be checked before exporting. You can do this using the Model Check command, which is located on the Analysis tab. This command is intended for diagnosing the selected body for errors in its geometry, which can lead to defects when exporting to the required format and, as a result, 3D printing. Such errors can appear even during the creation of a 3D model, since only local verification is performed automatically. A full check, depending on the complexity of the model, may take some time.

Rice. 2. Checking the steam gun model

2 shows that the team found an error in the operation. Without fixing it, it is not recommended to continue exporting the model.

When exporting to mesh geometry, the following types of errors may occur:

• gaps are the most common mistake. They arise when neighboring triangles do not have two common vertices, as a result of which some of them may disappear in the grid (Fig. 3). Often such errors appear due to the inaccuracy of creating a 3D model: uncut surfaces remain, surfaces are not stitched or Boolean operations are performed. If this error is not corrected, the model will not print correctly. Imagine that the model needs to be lowered into the water. So: the model can be sent for printing only if the water does not seep from its surface inside.

Fig. Fig. 3. Gaps arising between the triangles of the grid

• intersection of triangles occurs when two surfaces overlap or intersect each other (Fig. 4). Such an error can be recognized by the zigzag shape on the surface of the model. The intersection of triangles can lead to uncontrolled application of material in the problem area, as well as clogging of the nozzle or other application tool (print head, nozzle).

Fig. 4. An error in the mesh geometry caused by the intersection of triangles

• inverted normals. Each triangle has a normal vector that points towards the outer surface of the model. It is used to indicate to the printer the direction in which to add material. If the normal is directed in the opposite direction, then this can lead to an error in the printer, as it will not be able to recognize the internal and external surfaces of the model.

Triangle degeneration is another reason why printing errors can occur. Such triangles do not have a normal due to violations in the construction of the shape. There are two main types of triangle degeneration.

• geometric degeneracy occurs when all sides are collinear and the vertices are distinct (Fig. 5). Such triangles contain implicit topological information about the connection of surfaces, but if there is no normal, the printer may not recognize it correctly.

Fig. Fig. 5. Geometric degeneracy of grid cells

• To Pological degeneracy occurs when two or more triangle vertices coincide (Fig. 6). It does not affect other triangles, but it must also be corrected before printing, as this may cause the print program to crash.

Fig. 6. Topological degeneracy of grid cells

Special tools of the T-FLEX CAD Surfaces tab will help you correct the model (Fig. 7)

Rice. 7. A group of tools for working with surfaces

Often errors occur when importing 3D models from other CAD formats due to inaccurate creation of source files or violation of 3D modeling rules. To prevent such errors, there is a special option Treatment of the model, which will check and treat the geometry during the import process (Fig. 8). In the Educational version of T-FLEX CAD, it is possible to import models in STEP format; treatment will be performed by default, without the need to set a special flag.

Rice. Fig. 8. Dialog for importing models from other formats

Now let’s take another model and also try to check the model (Fig. 9).

Fig. 9. Checking the model without errors

The team found no errors, this part can be exported to STL and other meshes without additional corrections.

T-FLEX CAD allows you to export 3D models to all required file formats (Fig. 10).

Fig.10. T-FLEX CAD Export Dialog Box

Recall that the free Educational version allows you to export to mesh formats (STL, VRML, OBJ, PLY, 3D PDF, X3D, U3D). The most common format for 3D printing is STL.

When preparing a model for printing, it is more convenient and faster to use the special Print 3D command, which will automatically save the file in STL format (Fig. 11).

Fig.11. Command Print 3D

The system will prompt you to save the file in the selected format, after which the export parameters window will open and dynamic viewing of the 3D model mesh will be enabled (Fig. 12).

Fig.12. Mesh adjustment process before export

Let’s take a closer look at the options in the export dialog box.

Pack in archive. Reduces the size of the received file and allows you to store all the necessary data in one file. For example, you can transfer unloaded parts and assembly units as an archive for printing.

Separate file for each body.

A separate mesh file will be created for each body in the assembly. Otherwise, the model, even if it consists of several parts and assembly units, will be saved to a common file.

13 shows an STL model with a common mesh for all elements in the model. In the same example, you can see the rough execution of the grid.

Fig.13. Steam gun model exported with coarse mesh

File type:

• 
  binary (with color support) is a binary format with color support. The bodies are stored as one large grid. In this case, the grid consists of many shells. To separate bodies into independent shells, you will need special tools in the software for working with faceted geometry. Binary files are also small and support color.
• ASCII (multibody) is a text format with no color support. The bodies are divided into separate meshes. For further work with faceted geometry, special tools are not required — therefore, simplified versions of the software can be used.

Color support. You can choose from two standard formats: VisCAM and SolidView Format or Materialize Magics Format. You can also select No Color.

Mesh quality. Sets the image quality of the exported model. The higher the quality, the more accurate the part or assembly will be when 3D printed, and the larger the file size will be saved.

The original coordinate system. Allows you to select the LCS that will determine the initial orientation of the model when opening the exported file.

Open file. The option allows to open the file after export in the program with which this format is associated in Windows.

It became possible to navigate through the model in the T-FLEX CAD export parameters dialog.

By default, the mesh quality will be set to Current, which corresponds to the image quality of the 3D model at the current moment. The default is Standard quality. The user can set the required values ​​and immediately check the export result. It is also possible to control the quality of the mesh using the sliders. To do this, in the mesh quality settings, select User (Fig. 14).

Fig.14. T-FLEX CAD mesh quality dialog box

Let’s compare different mesh settings. To do this, take one of the parts of the body of the steam gun.

On the left is a standard grid created by default. The grid on the right is obtained by moving the adjustment sliders almost to the maximum values. The settings must be applied so that the changes are reflected in the model (Fig. 15).

Fig.15. Comparison of meshes of different quality

The number of polygons has increased and the quality of the mesh has improved significantly. Thus, it became possible to adjust the parameters based on the specific requirements for the quality of the part.

Elements hidden in the 3D model will not be exported to STL and other meshes will not be exported. This is very convenient when there is no need to print all the details of the assembly. You should select a part that is not needed for export, suppress it, and then repeat the steps described above to export to STL.

For example, let’s hide the bolts that are not required for printing (Fig. 16).

Fig. 16. The process of hiding model details from the scene

Fig.17. Model mesh built with hidden elements in mind

On fig. Figure 17 shows that the resulting STL does not contain any bolts, although they have not been removed from the assembly.

You can use the same method if you need to export only one part. Instead of Suppress, select Show Only Selected.

This function is necessary if the assembly contains parts that differ significantly in size. The mesh settings are great for, for example, a large part, while small parts will noticeably decrease in quality due to an insufficient number of triangles. Therefore, the parts of such assemblies must be exported separately with different settings.

Often, novice users encounter a problem when exporting threads. The fact is that the thread in the T-FLEX CAD model is cosmetic — it serves to visualize it and create drawings. On fig. 18 shows a bolt with a cosmetic thread and a mesh obtained from such a model.

Fig.18. Bolt net with cosmetic thread

As can be seen from fig. 18 thread was not exported. You can fix this with physical threading, which can be found in the default documents menu.

A metric shaft thread GOST 9150 is selected. It is inserted according to the rules for inserting 3D fragments. The thread contains connectors that allow using the T-FLEX CAD library of standard products (bolts, screws, nuts, bearings, etc.) to automatically read the diameter and thread pitch from a standard product. It remains to set only the length of the threaded section. In the dialog box, shaft diameter, thread pitch and thread length can be set manually. It is important that the diameter of the thread is equal to the diameter of the cylindrical section of the part on which it is applied automatically; the maximum step value is set (large step, if available for the selected performance), which can be replaced with a smaller one (Fig. 19).

Fig.19. The process of constructing a physical thread in T-FLEX CAD 17

Be sure to explicitly specify the body on which the thread is applied and complete the operation.

The carving is ready! Now the resulting bolt model can be exported to STL (Fig. 20).

Fig.20. Bolt mesh with physical thread

A mesh has formed on the thread, which means that such a part is suitable for 3D printing. In addition, a physical thread may be required to perform, for example, a strength analysis and determine the exact mass of the part.

Now the resulting file can be loaded into the installed software for working with meshes (slicers or professional programs) (Fig. 21).

Fig.21. STL file placed in the software for 3D printing

And here is how the model from our example was printed on the PICASO 3D Designer PRO 250 printer. (Fig. 22).

Fig.22. STL file placed in the software for 3D printing

You can learn more about the algorithm for preparing a 3D model for 3D printing using our video tutorial:

Preparing files for 3D printing in Blender

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Look for open edges

If your 3D model consists of several objects or polygon meshes, the first thing you need to do is make sure that the edges of each part are closed, in other words, waterproof. To do this, you need to enter edit mode by pressing A (once to select any faces, twice to deselect), then you need to press the key combination ctrl-alt-shift-M (on Mac computers — ctrl-opt-shift- M).

After you press this key combination, all open faces will be selected. Often, to fix this error, you need to create a new surface with 3-4 faces (F key). Sometimes there are wandering edges that are either not attached to anything, or connected to only one edge vertex. Often they can be safely removed, unless they were specially made. For example, these faces can be used to shape the model using the Subsurf modifier. In this case, you will need to apply this modifier first, and only then remove the unnecessary edges. In addition, do not forget about those open faces that are part of the intersecting surfaces.

If your model has 3-4 attached polygons that the software thinks are open but says that a surface has been created, you need to delete that surface and try to recreate it. Moreover, inspect the edges of all those faces that were marked as open. Perhaps some of them are wrong: they do not belong to the polygon mesh or they are created in the wrong direction. In this case, you will have to delete this block and recreate it manually.

Tip: Hide the geometry to focus on the uncovered areas So, you can select not only open faces, but also the areas around them. Next press shift-H to hide the other faces. In this way, the closed parts of the model will be hidden, and it will be much easier for you to eliminate all the flaws.

Cleanup: Merge meshes using Booleans.

Once all the meshes are closed, make sure that each one represents a separate object. You cannot apply boolean variables to polygon meshes that refer to the same object. At the same time, it is possible to split the meshes by selecting all its faces and pressing P. Next, select one vertex, then, holding ctrl, select all the others. To detach all polygon meshes of one object, press P and select the «All Loose Parts» option.

Once you’ve separated all the meshes into objects and made sure they’re closed, save the project and save a copy of the blender file to create a printable version of it.

Open a copy of the file and select each object one at a time. In object mode, apply any modifiers you want. Next, go into edit mode by pressing the A key once or twice to select all the faces. Then press ctrl-T to triangulate all surfaces. It is not clear what this is connected with, but Blender works better with booleans if the meshes have been triangulated.

Return to object mode again, select 2 mutually intersecting meshes and press w. Then select the Union option, after which the meshes will be merged (this action does not delete the sources). The merging process may take some time. Once it completes, select the 2 original objects that were merged and either move them to another layer or delete them altogether.

Select the new merged object, switch to edit mode, deselect the edges (press the A key 1-2 times), then select the unclosed areas — ctrl-alt-shift-M. Fix these errors in edit mode, it will be pretty easy. Often, combining polygon meshes solves the problem of open areas, but not always. Therefore, we recommend that you still check your model. Otherwise, when further merging meshes that have open areas, you may have problems. Check it EVERY TIME. Then select all meshes and triangulate again. As a result, you will get a single mesh with closed faces that has been triangulated. Such a mesh is completely ready for further merging, if necessary.

If you have 2 meshes with incommensurable face density, such as when a rounded mesh is merged with a cube that has 8 vertices, subdivide the part with the fewest vertices. The mesh is then triangulated. For some reason Blender doesn’t handle this kind of joins well. The process can take several hours, and it is not always possible to obtain the desired result.