Microbit Gaming Device - CAD

Computer aided design is the process of using a computer to help you design a digital model. 3D CAD (Computer Aided Design) is software that allows designer and engineers to model their designs digitally before manufacture. There can be many reasons for using 3D CAD.

Onshape is an example of 3D CAD and you can access it here www.onshape.com

Key Words:

CAD - Computer Aided Design

Sketch - A drawing

Constraints - limit or restrict

Duplicate - copy and paste

Fillet - and rounded edge

Shell - Make a shape hollow inside it

Modelling - the process of making a 3D model in real life or digitally

CAM - Computer Aided Manufacture

Spline -

Dimensions - measurements (sizes betwen lines)

Extrude - to stretch in order to make a 2D sketch become 3D

Microbit - a programmable computer chip

setting up Onshape accounts

Returning students will need to renew your subscription. Click the button to go to the Onshape Support page and follow the instructions to renew your account.

Onshape Support Page

If you are a new student then you will need to set up an Onshape account. Click the button to go to the onshape support page where there is a video that will show you how to set up your account.

Onshape Support Page

Stages of Modelling...

There are several steps required to complete the 3D model of your Microbit gaming device, follow each step carefully and in order. If you encounter a problem, ask your teacher for help.

Copy the basic file and share the file with your teacher
Add image to "Top face plane" layer
Sketch, basic shape - sketch spline. Must be smaller than the primitive not over the side.
Extrude shape top view
Extrude shape front view
Fillet shape
Shell shape to 2 mm
Add decorative details, 0.5 to 1 mm only
Add keychain detail if necessary
Split design into 2 halves and fillet 0.5
Make holes for microbit and fillet 0.5
Make microbit locator walls 1.5mm out and 'up to next the other way'
make microbit supporting walls
Make locating pins (2mm) and lugs
Make hole for cable

1. Copy the basic file and share the file with your teacher

Brainpad AR-1 Onshape file

Click the button above to access the basic file.

Make sure that the file opens in a new tab.

Allow the workspace to load and then click the "make a copy to edit" button at the top of the workspace.

Change the document name to be your class code, your name and the word Brainpad AR-1,

e.g. 7D Mrs Douglas Brainpad AR-1

then press "create copy"

Press "share" in the top right of the workspace.

Type your teachers email into the email box and click share

kdouglas@rugbyschool.ac.th

cdouglas@rugbyschool.ac.th

gjones@rugbyschool.ac.th

The correct email should appear in the box. You can then press "close"

2. Add image of your design to Top face of the primitive

To help you sketch the shapes of your design idea, it can be helpful to import an image of the design work to sketch over the top. The following steps show you how to bring in an image that has been handed in on Google Classroom. You can also use other methods to access images of your work such as email the image to yourself or airdrop.

Open a new tab in your internet browser.

2. In the new tab open the google apps pannel and select drive.

3. Open the classroom folder.

4. Find your D&T class folder. Click the 3 dots next to the image of your design and select download.

5. The image should now be in the downloads in the Finder app on the computer you are using

6. Now return to Onshape and press the 'sketch' button.

7. Select the Top Face of the primitive. In the sketch menu it should say "face of primitive"

8. Select a top view angle. This will make it easier to insert and size the image. (N)

9. Click the drop down arrow next to the DXF button and select Insert image

10. In the control menu, click import.

11. You downloaded image file should be in the downloads or the recents folder.

12. The image will upload and then appear in the control menu. You can close the upload menu by clicking the X.

Select the image file and then draw a rectangle to place it ➡️

13. click in the top left and drag to the bottom right of the screen to place your Final Design image.

14. Select the straight line tool and make a line that is the height of your design. (look at the image carefully!)

15. Select the dimension tool. Click the line. Drag the mouse to the right. Click in the space. Enter 100mm into the size box.

16. Now move the image to fit within the primitive shape in the workspace.

17. In this 3D view we can see that the top view of the design is within the primitive border, not overlapping.

18. Now right click on the "Sketch 1" and select "rename"

19. Rename the sketch final design drawing.

3. Sketch, basic shape using the spline or Line tool * It Must be smaller than the primitive - not over the sides!

Select the sketch button to create a new sketch layer.

click the plane called 'Top face plane' in the features menu and begin sketching with sketch tools that suit your design, such as the spline and straight line tools.

In the 3D view, your outline sketch should look like this but based on your own design.

ERRORS TO AVOID

Zoom in and out to double check that you have sketched a closed shape - A closed shape is a shape where all lines meet and there are no gaps.

Tangling or knotting the line can happen when you adjust or distort your shape, especially when using the spline tool. Knotted lines will create many problems later so try not to do this or look out for them later.

You can use the Scissor tool to delete knotted lines or tails of left over lines. Choose the scissor tool and select parts of the line you want to delete or rebuild.

CORRECT LINE

After using the scissor tool and deleted the parts that are causeing the errors, it should look like this.

4 Extrude shape top view

Select the Extrude tool from the top menu bar.

Select the outer part of your sketch - the part you want to cut away. Once you select it successfully, it will highlight yellow but be sure to choose the option Remove from the side menu so that you actually remove the shape instead of adding a new 3D shape.

Check all angles so see that it has removed/extruded properly. There is nothing wrong with extruding/removing more than once if you have an unusual design with multiple parts.

5 Extrude shape using the "front view shaping" sketch

Find the front view shaping sketch and unhide it.

Select Extrude feature

Select the options shown in the menu.

the depth should be 100mm or similar so that the extrude cuts through the whole model.

Make sure you tick the symmetric option.

6 Fillet shape

Select the fillet tool from the top menu bar.

In the fillet option box under the tab Edge, you will see Entities to fillet. In this section you will select all the edges of you design - mainly the top and bottom faces so that you have smooth rounded edges.

Be careful to only select the edge line and not the face or surface of the model. Once you select the edge, the fillet setting will round and smooth the edge. Adjust the setting so that the fillet edge is rounded to the size you want.

In this view you can see that the top edge on the top surface has already been filleted and the edge is now rounded and smooth. The next step will be to do the same on the bottom surface in the same way.

Error 1 might affect your proportions and the template. Make sure your design sketch and fillet edge are on the outside of the dotted template lines. In this example above you can see that the rectangular dotted line is not affected by the fillet edge or sketch because there is enough space but the round circular template shape on the right is half in and half out. this will cause a problem so you will need to adjust your original sketch design but opening your first sketch and moving the control points to edit the shape.

Error 2 could be red lines showing when you are creating your fillet. this could be because your fillet it to large (reduce it to fix this problem) or that you original sketch lines have an error such as a double /parralel line, a knot or entangled line or a small gap. To fix this you will need to re open your original sketch and check your lines and use the scissor tool to delete any error lines.

7 Shell shape to 2 mm and how to check it worked

To Shell your shape basically means to hollow you model. We need a hollow model because we will be inserting a MicroBit inside side. It also helps to cut down unnecessary or wasted material.

Select the Shell tool from the top menu bar, tick the Hollow option and under Parts to hollow, select Part one from you side menu on the lower left (or click the 3D model).

You should now edit the Shell thickness to be 2mm. If you have an error showing in red then you may reduce the thickness to something between 1mm-2mm (such as 1.7mm).

To check the shell

Click the small cube icon on the right of the worspace. In the dropdown menu select the section view option

In the section view menu click the front plane from the features menu to create a section view. That will show if the inside of your model in hollow. Once you have checked, press the red X to close the section view

7 Add decorative details, 0.5 to 1 mm only

This step allows you to add details, designs, grips and textures to the top surface.

Step 1. Create a new sketch and sketch on the top surface - this will be called Face of Primitive. It is suggested to sketch your design as an extended shape where the lines and edges extend out passed your actual design. This will ensure that control points and sketch entities are not locked together. Make sure that you sketch closed shapes.

Step 2. Once your sketch design is complete you can extrude up.

Remember that you can extrude down with the remove tool because the thickness is now just 2mm thick after you you used the Shell tool.

You make extrude each shape or part of this decorative design but should do it separately which will mean you need to extrude more than one if you have multiple parts.

Step 3. make sure that when you extrude up you only extrude to a maximum height of 1mm. If you need more than this then speak to your teacher.

Step 4. You will now need to fillet each new edge to the new parts and surfaces that you have just extruded.

The examples above shows what the filleted edges will look like but as you can see, not all edges have been finished yet in this example.

8 Add keychain detail if necessary

Select sketch

choose the "split plane"

Make sure you use the "Use" sketch tool to copy the shape of the microbit body

Draw your keychain hole shape

Here are some of the drawing tools that you may find useful to draw your keychain hole.

The elipse tool is in the menu under the circle tool

Once the sketch is complete, press extrude

copy the options in the extrude menu. Make sure you tick the symmetric option

9 Split design into 2 halves and fillet 0.5

First you will need to turn on the Split Plane from the side menu (scroll up and down to find it and turn it on by clicking the eyeball)

Second choose the Split tool from the top menu.

You now have 2 things to enter to the Split options box. Under Parts, surfaces, or curves to split you should add Part 1

Under the Entity to split with option, you should select Split Plane from the side menu or by clicking on the Split Plane on the model.

The Splite Plane appears right in the middle of the model and creates a line all the way round indicating where the split is situated.

To confirm that the Split worked, you should now be able to see that on your parts menu on the lower left side menu, you now have Part 1 and Part 2. You can turn these on and off with the eyeball option. Turning on and off allows you to see each part seperately and you will now be able to see that your shape is hollow.

The lower part (Part 2) should look like this.

The upper part (Part 2) should look like this.

If you made a mistake with your original sketch and didnt sketch lines to avoid the inner template details you will spot problems like this where the circles are half in/half out of the design. You need to adjust these.

You cannot move the templet circles or template structures so you will need to adjust your own design sketch. Double click to open your original Sketch 1 and adjust/move your control points to allow for more space. Green tick to save and the updates will take effect.

On both Part 1 and Part 2 you will fillet the outer edge of the Split surface.

The fillet you choose for Part 1 and Part 2 should measure 0.5mm.

The outcome should look like this where a smooth edges join in the split surfaces can be seen

10 Make holes for microbit and fillet 0.5mm

You will need to select the 3 squares (window holes). Select these from the upper /top part but from the underside surface.

Extrude all 3 window shapes using the Remove option to cut out the square holes.

After you have Extruded the 3 window you will need to Fillet each edge at 0.5mm

11 Make microbit locator walls 1.5mm out and 'up to next the other way'

Turn on the Locator Wall layer.

Select the rectangular shapes and extrude up to the top surface. Extrude 1.5mm

Always double check that the 1.5mm extrusion is the correct hight according to your design. Adjust if needed.

11 make microbit supporting walls

Turn on the "Microbit Chip Support Walls" layer and select the 3 right angled corner shapes. If you can't select the shapes, then it might be because theres another layer on top blocking you from selecting it - you will need to turn off/hide these other layers first.

Extrude the corner shapes down to the base. If you have arched or shapes the base of your model, you may see that the extrusions stick out of the bottom. You will need to extrude-remove this section again as shown in the following photo.

Select the shape you used to arch or model the base and extrude-remove again to cut off any of the supporting walls that stick out below the surface.

12 Make locating pins (2mm) and lugs (up to next)

Both the lug and the pin body to meet at the center split line. the same split lineplane you used to cut split the part.

Lugs will looks like this and be extruded up to the top layer.

Extrude the cylinder up as a whole shape - no hole. The select the small circle in the middle to extrude further.

Pins will look like this and be extruded down to the bottom layer. You will need to extrude twice - first for the main body of the pin and second for the smaller head that goes into the lug hole.

13 Make hole for cable

Find the cable hole sketch and turn it on. then select it

Select extrude

in the extrude control menu, select remove. make sure cable hole is selected as the Faces and sketch regions to extrude and make sure you select the top part of your model in merge scope.