LO2

P2: Plan the production of a CNC machined component

Resource List

The image attached is the resource list I will be using to complete the project.

All materials to be used are available on-site.

Gantt Chart

I am using a Gantt Chart to help me visually track and achieve my progress by allocating time to each task.

Flow Chart

Here I have created a flow chart to easily explain the lathing process

In summary:

Digitally design prototype
Collect resources
Cut to specification
Load into CNC machine with tools
Start cycle

P3: Produce a CNC part program utilising manual programming techniques

Manual programming:

A CNC uses G-code which stands for geometric code and refers to the movement, positioning and speed of machine tool paths such as in a lathe. The sharpness and hardness of the tool will effect the finish of the material and when used in additive manufacturing G-code can deposit material to create a shape with precision and accuracy.

G-code uses the letters G, X, Y, Z, I, J, F and these letters refer to:

G- tool movement, e.g. linear, rotational (clockwise/anti-clockwise)

X/Y/Z- x/y/z coordinate

I- x offset to centre point

J- y offset to centre point

F- feed rate which refers to the rate of tool movement

Some examples of G-codes that I have an understanding of are:

G00- moves tool from origin to coordinate without cutting at maximum feed rate which means it doesn't have an F code. Also considered a rapid tool movement

G01- this is a linear motion that has a set feed rate and cuts the material

G02- this is a clockwise rotational movement requiring an end point coordinate and centre point I to know how far to rotate. This G-code has no Z-coordinate

G03- this is the same as G02 but it is a counter-clockwise movement

G17/18/19- is the code used to select the X, Y, Z planes

G20/21- these are the G-codes for unit selection (G20=inches, G21=millimeters)

P4: Use mathematical calculations to produce accurate part programs for use within a CNC machine.

Many calculations are done to make the usage of the CNC machines as efficient as possible. This requires precision to guarantee the maximum efficiency in accuracy, time and tool damage.

𝛑 - 3.14/circular constant

n(ss) - spindle speed (RPM) (S-code)

Vf - feed (mm/min) (F-code)

Fz - Feed/tooth (mm/tooth)

Zn - Number of teeth

Variables used:

SFM - surface feet/min

MPM - meters/min

Vc - speed (m(f)/min)

D - tool diameter

Formulas I will be using are:

Cutting Speed (Vc) = (π x D x Sn) / 1000

Feed (Vf/F)=Fz x Zn x S

Feed/Tooth (Fz)=F/S x n

Spindle Speed (S/n)=Vc x 1000/D x π

Number of teeth refers to the edge of the tool that will be cutting into the material; the holes in between the the teeth are called flutes and they act like a tunnel to help the waste material to come away from the stock that we want to keep.

Teeth and flutes diagram

ISO Material Groups

Lathe machine

Since the material used was brass and is non feral the letter code used is N, this means that the speed that the spindle would be used at is high as the material is softer than others.

Using the range 90 - 100 the calculations for the upper and lower bound will use these.

First of all, lower bound is

S = 90 x 318

S = 1788.75 rpm

and then the upper bound is

S = 100 x 318

S = 1987.5 rpm

Here is the mill calculation using the lower bound I have calculated.

S/n = 90 x 318 / 20 = 1431 rpm
Vf = 0.08 x 4 x 1431 = 508.8 mm/min

M2: Produce a CNC part program using CAD/CAM software

Setup and dimensioning stock

Dimensioning the stock allows the machine to know exactly how much stock there is and will reduce the amount of material wasted.

Profile facing

I used the facing tool path to remove material from the front of the stock that the CNC machine will be cutting .

Profile roughing

Profile roughing removes larger chunks of material using vertical and horizontal cuts.

Profile finishing

Profile finishing cuts along the profile of the material.

D1: Analyse the advantages of the use of CAD/CAM software rather than manual programming techniques for a CNC machined component

CAD/CAM software allows engineers to automatically produce programming with different types of CNC codes using G-code. Using CAD/CAM software rather than using manual techniques for the production of a CNC machined component has many advantages

What is CAD/CAM software?

CAD/CAM software is computers being incorporated in the design and manufacturing process of 3D parts through the use of computer-aided software such as fusion 360. CAD software is typically used in fields such as design engineering or architecture, whereas CAM is used by manufacturing engineers such as in aerospace or automotive industries. Lean manufacturing describes a style of manufacturing that is more efficient in every way, this includes: using more economically friendly and efficient materials and maximising productivity whilst minimising waste in the manufacturing process. This process is what takes the industry towards industry 4.0. The industry 4.0 refers to the fourth industrial revolution and involves newer technology such as robotics and AI to be integrated into different industries such as design and manufacturing,

What is CNC machining?

CNC machining is the application of CAD/CAM software to manufacture 3D parts using CNC (computer numerical control) machines. CNC machines can be used both in subtractive and additive manufacturing using G-codes to accurately program the movement of the tools This is usually done using a minimum of a lathe or 3-axis machine; if a more complex part is needed, this can also be done using a 5-axis machine. There are different types of CNC machines for subtractive and additive manufacturing which use different techniques; examples of CNC machines are lathe, mill, plasma cutter and water jet. The machines will follow a tool path based on the g-code instructions to either cut from a starting shape, known as a stock, or follow the tool path and extrude material out into a build area in order to create the desired shape.

Why is using CAD/CAM more advantageous compared to using manual techniques:

Mathematical accuracy is far greater

Using CAD/CAM rather than using manual techniques improves the mathematical accuracy of components as it allows designers to input precise values that apply to specifications; inputting these values using CAD/CAM means that values can be changed and scaled if need be. This is better than using manual techniques as it is much more efficient and accurate to input values using CAD/CAM software rather than having to figure out the remaining values of a component if it needs changing at any point during the design process. Additionally, doing all calculations manually would be more difficult and would take a lot longer than an automated computer which could do calculations in a fraction of a second which also reduces error throughout the design process.

When moving into 5 axis programming the mathematical processes become increasingly complex as the programmer will not only have to calculate and map out complex g-code for the positioning, feeds/speeds and manufacturing instructions for the toolpath, they will also have to do all of these for the movement of the stock in order to provide the other two axes. Not only does this increase the demand on the programmer for the amount of mathematical calculation needed, but also the difficulty as the cutting/extruding tool will need to move with synchronisation with the movement of the fixture/stock.

Complexity of toolpaths - 3 axis compared with 5 axis

Being able to use complex tool paths when making a CNC machined component automates the process and optimises complicated geometries available to make finished components more accurate and dependable through unvaried results. The more axes available, the more the user will be able to control and the more they can plan, therefore the more clarity they have of what is happening during the process.

Time saving

Using CAD/CAM software is much faster than using manual techniques as it can generate accurate G-Code. Doing this reduces the need for checking errors, which this software also has the programs to do. This gives engineers more time to focus on other tasks whilst the software creates the programs which reduces overall production time significantly. Additionally, this reduces cost as efficiency is increased it means less people need to be working and less power needs to be used. Another reason CAD/CAM software is time saving is because you don’t have to leave the program to run different tests and everything you need which moves towards lean manufacturing meaning less downtime as there is a direct workflow therefore, productivity is not interrupted. An example of using manual techniques taking more time is when I manually programmed a CNC machined part. This proved to be more meticulous because I had to repeatedly check which codes to use, this added a lot of time onto the programming process.

Compatibility

CAD/CAM software is preferred by engineers rather than manual techniques because files can be exported easily due to the compatibility of file types such as STL; these files exported from CAD/CAM software complies with industry standards. This is a huge advantage to using this software as it means files can easily be exported to machining software where prototypes can be created, editing can be done and post-process finishing touches can be done. This is a much quicker alternative to manual techniques and saves a lot of time and money.

Simulation properties

Using CAD/CAM software provides engineers with a clearer understanding of parts made as using simulation properties can show engineers different views of parts which wouldn’t be available otherwise. Some simulation tools available in CAD/CAM software include: error checking, machine kinematics, viewing the part at any point in the machining process and altering transparency levels. These simulations provide benefits such as being in more control over and during the machining process, fewer machine errors (breaking machine or parts, incorrect calculations, etc.), less time making faulty parts (saving materials, time and money). This is more advantageous than using manual techniques as it is more clear and concise. Additionally, it uses less time and money, allowing engineers to focus on progress in other areas rather than spending time on something the software can do in seconds without errors.

Using simulation properties allow engineers to simulate the entire manufacturing process including possible errors that may occur. By doing this they can understand where collisions may occur and prevent them from happening which stops tool heads or the machine becoming damaged and breaking which can be a very expensive issue to fix. Simulating tool paths using CAD/CAM software allows engineers to see how long each operation will take, what materials are used and gives them a full understanding of what is happening at each stage. This can be presented visually through the software which makes it easier to understand, making it also easier to teach to people who are newer to the industry. It is important that complex operations such as simulations can be more easily understood because it makes it easier for younger engineers to join the industry and add to it with a new perspective and ideas. Furthermore, some more examples of simulations available in CAD/CAM software also include dynamic stress testing, thermal testing and injection molding and dynamic stress which are useful to have as they allow people to see exactly what would happen to parts under different conditions which would be much more difficult to do manually. For example, when injection moulding you wouldn't be able to see what is happening in the mold which could lead to air pockets due to filament not properly reaching spots; this can be fixed with simulations as it allows engineers to manipulate it and alter directions and avoids multiple prototypes being made which additionally saves more time, materials and reruns to get the parts right.

CAM is widely used in different manufacturing industries, however, more younger workers are still needed to diversify the average age range of industry workers to integrate into modern manufacturing for industry 4.0. Industry 4.0 is the expansion of technology and manufacturing becoming more and more advanced; this is needed to create upgrades in the world whilst reducing waste and emissions and involves smart factories.
Users understanding of this technology is improving as software usability is improving making it easier for new users to learn and use the software easily.

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