Started working on work piece

This week we already started to work on our work piece. According to what Mr Tay told us, we were supposed to practice on a rough work piece first before working on the semester project work piece but due to the home based learning week, we had already short of one week, so we were going to start directly on our semester project. I was shocked to hear this. It is still alright if make mistake on the rough work piece, but now we cannot bear to make any mistake because the semester project are going to be grade.

Mr Tay demostrated every single step and explained all the precautious that required attentions. He showed the procedures for facing and side cutting all over again as he knew that after one whole month ''holiday'' we had definitely forgotten all the steps. He also told us that there are two ways for finishing. One is the method he told us the week before study week, that is reduce the feedrate which can be applied to both facing and side cutting. Another method is cut the surface by only o.o5mm without changing the feedrate. The second method is faster compared to the first one. However, it can only be applied to facing.

After all the demostrations and explainations, we started to work on our work piece. Luckily, this week none of us made serious mistake and the lesson progressed smoothly.

At the end of the lesson, we were required to clean our own machine. And this was the part that Fade me impatient. It took me about 25 minutes to make my machine dry and clean. finally, Mr Tay recapped all the procedures and precautions again before he dismissed us.

Photo showed below is the turning machine.

Home-based learning exercise

Due to H1N1, this week we do not need to go to campus but instead we study at home using the Heucampus to communicate with our tutors. Also, the lab or practical lesson is canceled.

Study weeks

Week 9 and week 10 are study weeks so no lessons.

Turning machine

Although my goal is only aimed for the grinding machine but my this blog will touch on the turning machine as the lesson of the grinding machine had ended.

This week we learned the structures and the functions of turning machine which was teached by Mr Tay. As other people told me, once started the lesson, he introduced many formulae. First was the cutting speed(v), which depends on the material of the work piece and the cutting tool being used. If the material of the work piece was soft, for example, plastic, and the cutting tool was diamond, which is the hardest substance in the world, the cutting speed need to be increased and vice versa.

Next was the spindle speed(n). Spindle is the wheel that clamps the work piece while cutting. Its formula is
n=(1000v)/(π x d)
where v =cutting speed
d=diameter of the work piece
There are differences in calculating the diameter for different process although the work pieces may are of the same dimensions.
For facing,
d=d' x(2/3)
For side cutting,
d=d'
where d'=original of the diameter of the work piece

And finally was the feedrate, which is the speed of x-axis and z-axis moving when they are set into automatic mode. These two axes can be moved manually or automatically. To determine this feedrate, we need to refer to the turning machine manual which lists all the feedrates for different work pieces and tools or sometimes to save time, Mr Tay will tell us. The speed of the feedrate can affect the surface of the workpiece. The slower the feedrate, the flatter the finishing of the work piece's surface.

These were all told by Mr Tay this week and the week after common test, we will have to start to use the turning machine on our own.

Final week

This week was really a critical week.

We learned a new technique of grinding, that is punching. We placed the thicker side of the work piece against the stopper on the magnetic table. According to what Mr Teng said, this was important due to safety reason. It prevents accident from occurring. It was because if we ground the thinner side first, there might be some students forgot to move the grinding wheel forward and after turn the work piece over to the thicker side, they just move the work piece inside, then the grinding wheel will hit the work piece and it might fly out due to huge impact. Punching is a technique that moves the y-axis slowly, 10 mm at a time. It was different from what we had done last time. Last time, we either moved the y-axis continuously or did not move it at all. But now is move y-axis gradually.

Also, we learned to grind the vertical surfaces of the 'U' shape. To do this, we could just grind them using the back side of the grindning wheel. There is a step at its back side in order to grind such vertical surfaces.

Luckily, in this final week I did not make mistake.

And next week, I am going to learn turning machine, which many people said it is really hard as there are many formulae involved. Hope that I can cope with it and no accidents occur.

Mistake again

I think I already have phobia in grinding due to last week mistake. So this week. I amde mistake again!

When zero sets the work piece, which means bring the grinding wheel juzt touches the work piece before starting grinding, I turned the wheel that control the z-axis too fast, so it results in cutting too deep on the work piece and a burn mark can be seen clearly on my work piece. Because of this, the grinding wheel also being affected, so I need to dress the wheel once more. Again, Mr Teng was so kind. He did not scold me. He just said that next time must be more careful and do not make the same mistake again. Then, I proceed to grind other surfaces with extra care. Therefore, I did not mistake again.

This week i was able to complete all surface and square grinding.

At the end of the lesson, Mr Teng told us nest week would be the final and most critical week for grinding. This made me feel worry. I was afraid that I would make mistake again.

New work piece

This week we got a new work piece as shown in the photo above.

Similarly, we grind the parallel surfaces first. But this week I made a big mistake! I was supposed to grind 0.12mm, which 120 microns on each of the parallel surfaces to a dimension of 16.55mm and to reach the total width of 36mm and also to achieve symmetry. However, after I ground the first surface and took out the work piece and checked its dimension, I forgot which side I had ground and which had not. I just simply place the ground side on top thinking that if was not ground yet. Then, when I took the measurement again, I only realised that I ground the same side! Now, one side is 16.44mm which was out of dimension already! And I could not grind the other side to the same dimension. It was because if I did so, the total width of 36mm will be affected. Luckily, Mr Teng did not scold me but just said, "Never mind. Now, what you need to do is grind the other surface to keep the total dimension of the width, just ignore the symmetry." So, I did what he told me but still felt very sad because of my silly mistake.