LO3

P5: Set-up and operate a CNC machine to produce components.

M3: Prove the accuracy by checking a final result against specification.

D2: Evaluate the effectiveness of the Computer Aided Manufacturing (CAM) process used and make recommendations for possible improvements.

This is the control panel that is used to manully control the lathe

This is the chuck, the material is tighly put in here so it can be spun without slipping

The coolant is not aimed at the stock because it is not needed for this material

This is the lathe machines tool carousel where the tools are stored and ready to swap out when the GCODE tells it too.

Here the center drill creates a hole to guide the main drill

The tool is changed

The main drill creates the hole

Table of measurments

Brass Part Measurments

Here is the table of values for the 3 parts that I measured. I used a vernier calliper for this as it has a very high resolution so that there is less uncertainty when I measure the small parts, it also allowed me ot measure the hole depth which would have been impossible with a ruler.

From the table I can see that the biggest uncertaity was caused by the center hole, this was caused by the tool that I used in the lathe - the tip was pointed when it should have been straight. This could be fixed by changing the tool tip out for a flat one so I added up the percentage uncertaity with this excluded so I could find the total uncertainty when I use a flat bottomed tool bit when I remake the part

Drawing comparison

As shown on the left there are noticeable differences between the part we made in fusion 360 and the part that was made by the lathe. some of these differences include, the diameter difference between the hole diameter and the lip diameter is noticeably greater in the drawing of the part, this could cause issues such as the part not being able to fit inside its casing or the lenses not having enough space so needs to must be improved for this part to be effective, this was caused by the drill bit that the lathe was equipped with not being the right size (it was 10mm when we needed 11.3mm), to improve this I ordered a 11 mm drill bit - I explained about this in greater detail below.

The drill also caused an issue with the hole not having a flat shape, instead it has a concave shape with the centre hole being 1.58mm deeper than the outside hole. furthermore, both of the measurements taken about the depth of the hole had the greatest absolute percentage uncertainty, this issue will also be solved by the flat bottomed drill bit.

Additionally, because I used a right hand turning tool some of the material got shaved off that wasn't supposed to, this could cause the part to not sit right in its holder which could cause it to shake unintentionally. The way I intend on fixing this is by getting a new turning tool with a much steeper angle so that it can reach further into the corner without shaving off the corner as much, this wont completely solve the issue as there will still be a small amount of material that the lathe cant reach without shaving off a bit but this shouldn't be an issue as it will be too small to make much of a difference.

Tool bit

Here I found and ordered a flat bottom drilled tool bit from a trusted site to be used to cut the hole with more accuracy. I ordered a carbide coated tool bit because a regular flat bottomed drill bit would lose its sharpness quicky so I went for the more expensive option because it will last longer and not only save money in the long run but it will also stay accurate for longer. There where no cheap ways to order a tool bit with exactly a 11.3mm diameter so I opted for using a 11mm drill as it will only be off by 2.65% which is a smaller than most of the other uncertainties. There was a longer option but I deemed it as an unnecessary expense.

I also ordered a right hand turning tool woth a sharper tip, this is so that the tool can reach further into the into the the crevice so that it doesn't leave as much material and will be able to fit its holder better.

Evaluate the effectiveness of the Computer Aided Manufacturing (CAM) process used and make recommendations for possible improvements.

Burring

This is a picture taken by an electron microscope with a 180x zoom, as seen in the picture there is little bits of metal and dirt left by the machining process and other things. It is caused by physical impact and when heat is generated, more heat is generated if the tool is blunt or worn down which would cause more burring which could damage the parts efficiency. This makes the surface finish rough and gives it an undesirable look. This can be fixed by using a poleshing wheel to clean off all the burrs and give the surface a smooth and shiny finish.

Ridges

Each ridge is a tool running over the surface of the part - it shown the tool path - this means that the slower the spindle is spinning the more prominent this feature would be which would increase friction when putting in the part. A solution to this problem is to spin the part faster but doing so comes with a drawback, the faster the part spins the quicker the tool tip will ware down faster which would mean it would need to be replaced sooner making it more expencive which is not worth it for this part becuase the effect this has on the surface finish wont make the part any less effective

Micro fracture

Imperfections in the material such as areas of impalance or bumps in the surface which casues the tool to get caugt and causes microscopic tears and cracking. The microfracture in this image is only 160µm and these will be scattered along the surface this wont have a great effect on the strength of the part but could cause extra friction when inserting the part. This could be solved by improving te surface finish by sanding down the surface and poleshing it.

Improvements

Clean the machine - by cleaning the machine before use, the amount of dirt and debris left after machining would be reduced which would decrase the amount of further machining.

Tighten the chuck - this will ensure that the object doesn't slip when being spun, this will make is safer for the operators and will possibly decrease the uncertainty if the material slipped the first time that I machined the part then that would explain some of the uncertainty. furthermore, when if the material came loose it could get flung out by the high spin speed and damage the machine, this could mean the machine would need to be repaired or worse, replaced which would be very costly and time consuming.

Replace the tool with the a flat bottomed drill that is carbide coated, this will allow the drill to clear out all the material that the pointed tool could not reach, this is important as the part I was intending to make needs to have flat space for the lenses to fit properly. Replacing the turning tool with one with an angle closer to 90 decrease with a pointer tip would allow the tool to get into the corners which will define the shape better and allow it to fit into the other parts like it was initially designed. A 3 axis machine could be used so that the tool can reach further into the crevasse but this should not be necessary because the lathe is suitable if any worn down tools are replaced.

I am going to use the same spindle speed. Using a higher spindle speed will make the ridges smaller, making the surface finish better as soon as the part is done machining, but this comes at the cost of the tools' durability. The tool will wear down a lot faster at a high spindle speed, meaning that the tool will lose its sharp edge, which will cause more burring and increase the chance of microfractures. This would mean that the tool would have to be replaced sooner, which would reduce the amount of profit made on each part. I think the cons of increasing the spindle speed outweigh the pros, which is why I will continue to use a spindle speed of 500 revolutions per minute.

Use a sander to remove improve the surface finish and remove the ridges that where caused by the machining, it can also be used to increase the hole diameter from 11mm to 11.4mm. To remove the burring I could use a polishing wheel. By doing both of these things I will be left with a smooth part that easily fit.

With these changes the part will have a much lower absolute percentage uncertainty and will be much closer to the part that I intended to make

www.cutwel.co.uk. (n.d.). Engineering Cutting Tool Supplier | Cutwel Ltd. [online] Available at: https://www.cutwel.co.uk/.

Page updated

Report abuse