Computer Controlled Machining
Assignment
The assignment this week was to create something "big" using the CNC cutting machine.
The CNC Router Machine- Shopbot- PRSalpha 96-48
Machine with a tool-holding head whose movements are controlled by a computer. Laser cutters, water jets, and CNC routers are all CNC machines.
The machine we have at fablab CEPT is the ShopBot Alpha with a bed size of 96"*48" which allows us to go upto the depth of 6".
It can go maximum upto 24000 RPM using a 3rpm colombo spindle.
Types of CNC Bits
Below are the types of CNC Bits available and you can use one accoring to the end result you wish to achieve. The red line shows the section of the cut you will get using that tool.
Types of CNC Machining
2D CNC Machining
If all we have is a flat outline of something we want to cut out, that would be considered 2D cutting.
2.5D CNC Machining
If we then added straight up and down movements of the cutter into and out of the material, we might now consider the project as 2.5D,cut features like grooves or flat pockets,where you are pocketing areas (e.g. around letters in a sign)All such cutting can be done in one or more different cutting planes after plunging to a cutting dept, V-carving as a 2.5D design process.
3D CNC Machining
This capability is technically described as 3-axis interpolation, which means that moves are made smoothly in 3D space using diagonals and curves. In 3D, your CNC cutter tip follows paths at 3D angles or in 3D curves in order to mill or carve complex shapes into the material.
Limitations of CNC
- The biggest limitation of CNC is that it cannot carve in undercuts at shown below. Thus ther are wide range of manufacturing that cannot be done using CNC.
- Also, since the drillbit used in CNC has a certain diameter, there is no problem in outcuts line shown but for incuts, there is a part of material that the tool cannot remove. Hence, we add *dogbones* when making press-fit kits in CNC.
Designing the Tolerance Test File
We were supposed to characterize the CNC machine this week. Thus we designed the test file for it.
Parameter that we wanted to test were : 1. Check Difference In Dimensionin In-Cut and Out-Cut also difference in Pocket Depth 2. Difference in dimension with material and shape of cut part.
The file was designed in autocad and screecnshot from process is given above.
Path-works and Machining Parameters
Parameters : Attempt 1
We used parameters as below for machining at the first time with 3mm Endmill.
.png)
The above parameters didn't work well. You can see the output of the same below.
Interdum et malesuada fames ac ante ipsum primis in faucibus. Pellentesque venenatis dolor imperdiet dolor mattis sagittis. Praesent rutrum sem diam, vitae egestas enim auctor sit amet. Pellentesque leo mauris, consectetur id ipsum sit amet, fersapien risus, commodo eget turpis at, elementum convallis elit. Pellentesque enim turpis, hendrerit tristique lorem ipsum dolor.
Output
Attempt 2
Parameters
The above parameters worked Well. You can see output of the same as below.
Output
Test Result
The difference between dimension and the analysis of dimension is as given below.
