3. Large format CNC¶
Note: Here I will put week 5 work which is the large CNC design instead of week 3 (Computer controlled cutting) as we were assigned this task this week.
This week I will be designing a model and then construct it using CNC machining, to begin with, a table is designed using Fusion 360 which is then extruded as dxf files to be translated to the motor directions to guide the CNC machine. After that, a test to validate and check the variation in the feed rate, rotational speed and depth is done to check the operating conditions for the CNC machine on a wooden plate. Finally, the dxf files were transferred to the CNC programs which are then treated to yield the satisfactory design into existence by following the CNC program guide to build the demonstrated design. Before dealing with the CNC machine there was a safety session to have a background about the machine and how it might harm the users if not used in a proper way without any precautions.
Fusion 360 design¶
Fusion 360 software was used to design a 3D table to be fabricated using CNC. First of all, the design consists of 5 parts, the head of the table, two stands that hold the table and two supports to ensure the table stability as seen: First of all, after choosing to do a new project, the following site will appear:
The design was started by the designing the head of 100x60 cm, with a thickness of 11 mm. a rectangular shape was used to design this part, from the sketch. Then, it is extruded by 11 mm to put the thickness.
After that, the handle was designed to yield approximately 45 cm height to the table with a shape like the one showed below:
This part was done by connecting lines from the exterior of the handle, 45 cm inclined line from both sides and a 100 cm line in between, and then the interior was connected to complete the design with the required dimensions to have the same specified angle of 77. The width of the handle was set to 6 cm. After finishing the handle design it was extruded like the previous part.
A 30, 39 mm safety distance was used while putting the handle below the head of the table so that when we make the joints it is more convenient from down and left respectively as seen in the photo. Also, the dimensions of the pocket were set to 50 mm length and 10.65 mm width, having a tolerance of 0.35 mm for the joint to fit later on:
Six pockets were adjusted to ensure the fitting of the table, four at the corners and two at the middle of the table, this was conducted by constructing one pocket and then mirroring it to all designated spotted by the usage of a mirror plane:
All six pockets were generated by putting 3 mirror planes, two halving the head and another halving the halve to mirror it to the middle as seen in the picture (the yellow lines):
These pockets were constructed as new bodies as this made is easier for me to construct the joints. These joints were designed on the handles rather than the table to just extrude it upwards to get the required pocket size with the required depth. This will generate the holes in the table as they will cut through them. Later on the height of the Joints was set to be 7.5 mm and the combine command (joint) was used to make these parts as one part. Also, the joint was made to be 11 mm in width rather than 10.65mm using the extrude command, extruding it 0.175 mm from both sides. Making the joint 50,11,5.5 in length, width and height respectively. Also, a fillet of 35 mm and 125 mm was done for the handle inner corners and the table corners respectively using the fillet command. Finally, the supports were designed 36 cm length and 6 cm width and the same thickness, same procedure for the joints was followed for the supports to that of the handles. Only one handle and one support were designed, the second ones were mirrored across the previously illustrated mirror plane. These are the steps followed to design the table and below are the pictures of the stated things done in this paragraph.
CNC machining¶
Safety precautions:¶
Before entering the CNC room, several precautions should be taken into consideration and implemented. When you enter the room, you should know the places of the emergency shut down so that whenever an emergency happens or things get out of control, you can immediately shut down the system. There are 3 ways to shut down the system: two red buttons one on a control panel and the other is on the CNC machine itself, and the last way is to move the mouse on the laptop as this would cause the system to stop. Below are the three methods.
Safety goggles should be worn at all times when inside the room and a sufficient space from the machine should be taken to avoid any accidents.
There should be devices to clean the dust of the cuts done on the wooden sheet, the following two pictures show the devices used for this purpose as to ensure there is no dust going off:
The wooden sheet should be adjusted to the sacrifice sheet with an offset on the edges for the screws, this is done so that it does not effect the design and the machine would not be damaged:
Testing the settings of the CNC machine:¶
Group assignment.
Link: Group assignment
Constructing the table by CNC machine and the set up of the programs required:¶
First of all, after completing the design, the design was exported as an dxf file to be translated so that the motor of the CNC machine understands it, the three main parts (Head of the table, handle and the support) were all exported as a dxf files through making a sketch on each of the stated parts and then exporting them:
After that, they are transferred to the laptop connected to the CNC machine to begin the procedure of cutting the pieces. This is the home screen of the program when you launch it:
Select new and then the following page will appear where you can put the dimensions of the wooden sheet used:
After clicking OK, the following page will appear where you can use various commands too adjust the design, on the top left you can click file and then import, where it will show the files to select which of them to import:
Here in the following picture, an illustration for the offset command, where you can define the distance to be offset and the type pf offset, this is used to ensure that there is enough space left to put the screws to fix the wooden sheet to the sacrifice sheet and that the CNC machine does not cut there where the screws are present:
These pictures illustrate the join vector command which ensures having each part as a whole and not separate vectors:
If the dimensions were to be scaled up, you can use this command to scale up or down. For example, if you want to scale from mm to cm put 1000%.
Here the following pictures show the place were you can change the joint type, here it was chosen to be a T- bone fillet. These fillets were used because the machine (CNC) cannot go a 90 degrees path in an inner corner and therefore the fillet allows to achieve the required design.
This command is used to choose every body present in the board:
This is what happens after using the command where, it will reassemble the parts at the best way possible:
Here you can switch to the tool path:
The following command permits various adjustments to the tool path , like the feed rate, rotational speed and other different parameters related to the operation as shown bellow
Here, you can put taps, these tabs are used as placements that are not cut along the toolpath to ensure the stability of the part while cutting it to get the best precision possible, and you can adjust the settings (dimensions) of the tabs as well:
This photo shows the warning that will show, as the thickness put for cutting is above the thickness of the wooden sheet to ensure the cut process to be successful. We can ignore it as there is a sacrifice sheet which would protect the machine:
This is the control panel that would show on the laptop connected to the machine:
Firstly, we will adjust the Z axis to set the origin point afterwards by putting both X and Y equal to zero, then we will use a metal conducter and a metal plate to adjust the drill bit to be above the wooden sheet in a sufficient range for cutting:
When everything is prepared this we should proceed with this:
Here we can see on the tool list that there are profile and pockets, pockets are recommended to be done first as the profiles to be cut are still intact which would give the wooden sheet more stability:
Here is shown the command used to start the CNC machine and the final warning shown before exterminating the procedure:
Here, you can monitor the CNC machine and if any emergency happens you can move on the laptop to stop the process:
The Final designs¶
After finishing cutting the parts, they were put together to form the designated table. The following pictures show the head of the table, support and handle respectively:
The table needed to be hit several times by the hammer to ensure its put intact:
The final table looks like the following:
