8. Large format CNC (computer controlled Machining)¶
This week I worked on my final project idea and learnt about CNC machinig.
CNC¶
A CNC router (computer numerical control router) is a computer-controlled cutting machine which typically mounts a hand-held router as a spindle which is used for cutting various materials, such as wood, composites, metals, plastics, glass, and foams. A CNC router can be used to produce items such as door carvings, interior and exterior decorations, wood panels, sign boards, wooden frames, moldings, musical instruments, furniture.
In the Fab Lab Bahrain, we have a ShopBot CNC Router.
ShopBot¶
The Shopbot CNC router is a subtractive manufacturing machine. It operates on 3 axes and has a drill bit that takes away material as it moves forwards, backwards, side to side, and up and down around the workspace. There is a tube vacuum on the top, connecting to the drilling bot. It helps in removing dust, etc., from the cut areas, so as to clean the spaces from any dust particles.
Safety Measurments¶
Don’t wear loose clothes. Be sure to raise your sleeves and wear suitable shoes. Always wear safety goggles because dust is there due to the cutting process. Also, wear hearing protection such as soundproof buds and headphones.
Don’t cross this yellow line while the machine is working.
In case of an emergency, press this red button to stop the machine immediately. On the side of the machine, there is another button that stops the machine immediately.
Group Assignment¶
Our group assignment was to test runout, alignment, speeds, feeds, and toolpaths for our machine. Visit Ayman.abdulaziz’s website to see details about group assigment.
Individual Assignment¶
Creating a design in fusion360¶
For my CNC assignment, I wanted to design something that I could also use for my final project. So, I started looking for ideas and found this fingure joint table lamp on Pinterest and started creating it on Fusion360.
Original dxf files download link
Original fusion360 archieve file download link
Problem Encountered¶
I faced problems regarding alignment. My instructor, Abdul Ghafoor, helped me with allignment. After I was almost done with my design, I found out my joints were weak. My instructor, Abdullah, (who is an expert in Fusion360), helped me with changing the joints size and thickness and with alignment as well.
Working with CNC Router¶
The material we were going to use was MDF.
MDF (Medium-density fibreboard) is an engineered wood product made by breaking down hardwood or softwood residuals into wood fibres, often in a defibrator, combining it with wax and a resin binder, and forming it into panels by applying high temperature and pressure. MDF is generally denser than plywood. It is made up of separated fibres but can be used as a building material similar in application to plywood. It is stronger and denser than particle board.
One of my colleagues and I were going to cut our designs together, so we uploaded dfx files of our designs to VCarve Pro.
VCarve Pro provides a powerful but intuitive software solution for creating and cutting parts on a CNC Router. It is used to control the path that the machine follows while cutting. Different toolpaths can be combined to achieve the best possible finished product. For example, a “roughing” toolpath can be used first to take out the majority of material and leave a rough shape of the final product. Then, a “finishing” tool path can be used to go back over the material to clean up the surfaces and add fine details.
After making the machine settings, we chose the dog bone fillet. Because the needle cannot cut the corners, we had to use a dogbone or tbone fillet.
Dogbone fillets are used to overcut into a corner when the application of the part you are making needs to fit tightly with another. When cutting out internal corners on a CNC you are left with a round corner due to the round tool you have used, you would need to manually finish off each of these corners with a sanding file to remove the rounded corner. With dogbone fillets you can use the CNC to overcut into these corners by the radius of the tool so that any mating material will be able to slot into place . This method is great for concealed joints where it will not affect the finish of the product.
After choosing the dogbone fillet, we went to pocket toolpaths where we set the parameters, feed and speed rates.
Feed is the linear feed of the tool through the material, and speed is the rotational frequency of the spindle which turns the bit.
After that, we went to profile toolpaths, where we set the cutting depth and also set some other settings.
We also added tabs to fix the design in place.
At last, we previewed the movement of the drilling tool.
Finally, after choosing all the required settings, we started the CNC machine to cut.
After the CNC completed cutting after 30 to 40 minutes, my colleagues Islam and Sikander helped me with cleaning the pieces with sand paper and a sanding machine, and our instructor, Abdul Ghafoor, helped me with assembling the pieces (fixing the joints) using a rubber hammer.
Hero shot¶
