Time Attack/Circuit Racer Mitsubishi Evo V

[mike@af]

I think the valve cover is not only the most difficult part I have machined to date, but one of the most frustrating parts as well. 65 hours, 2 broken tools, and 372 swear words later I have a valve cover. Let's walk through the process.

As usual, started with a piece of 7075 Aluminum. I almost always do the drilling operations first, because they are the most likely operations to break a tool and damage the part beyond repair. The drilling operation used 3 drills, a .012" (0.30mm), .0197" (0.50mm), and a .0313" (0.70mm) for the camshaft trays, valve cover bolts, and spark plug holes respectively.

One quick note, the design of the valve cover- it is slightly different than most valve covers around and is more similar to high boost formula motors. Instead of the valve cover covering the camshaft trays/caps, they are integrated into the valve cover itself for added rigidity.


Drilling operations completed.


Next step was to move on to the roughing using a .125" (3.0mm) end mill. I have been experimenting with optimizing my tool paths for the CNC mill lately to help reduce cycle time. Using a special sequence of algorithms to apply a consistent chipload on the tool I was able to take a heavier cut at 3 times the typical speed, which cut the cycle time for roughing by 75%.


After the main shape was roughed out, I moved on to the inside of the valve cover where the camshafts would reside.


Using various long end mills ranging from .020mm" (0.50mm) to .065" (1.65mm) I continued to rough out the inside.


Once most of the material had been removed, I removed the rest of the material using a .020" (0.50mm) long reach ball mill. This is the step that I broke one of my tools, and the long reach ball mills are not only fragile, but very expensive.

Note: One of the reasons this part took an excessive amount of time is that the inside walls of each of the clearance pockets for the camshaft lobes are tapered by 2° for added rigidity if this were a real part. To be completely honest, even I will admit that was over the top. After several hours of machining the taper walls I was wishing I hadn't made them tapered, especially since they will never be seen. But I am happy with the overall result.

Moving on!


To finish clearing out the pocket for the timing pulleys, I used a .065" (1.65mm) long reach end mill, followed by progressively small ball mills to create a smooth finish.


The inside of the valve cover is now completed. Typical process of removing the excess material as mentioned with previous parts. Camshaft journals will milled using a .062" (1.60mm) ball mill.


The top of the valve cover is what I was most excited about. The roughing process is just the same as on the bottom side.


After roughing, it was time to start adding the details using a .020" (0.50mm) long reach end mill.

...broke one of those too. Damn.


Finally, the valve cover was starting to take shape! Using a .0313" (0.70mm) ball mill I started the first stage of finishing by scalloping the part.


After the first stage of finish was completed, I refined the detailed with a .020" (0.50mm) ball mill.


The last setup involved machining the front face of the valve cover. I could have machined it from the top side, but it was less than optimal. As I am constantly mentioned, precision is key. Since I had to use the vise to hold the valve cover to machine the front face, I qualified my vise with a dial indicator. While this can be a time consuming process, it is extremely worth while to ensure the results are within tolerance. I qualified the vise to within .0002" over 2" parallelism.


The last machining step was the machine some detail into the front face of the valve cover, specifically the area that covers the pulleys. This was done using a .0313" (0.70mm) corner rounding end mill with a .010" (0.25mm) radius.


Finally the part has been completed. A few little details to add later, but for now it is complete. I am very happy with the result. it was well worth the frustration. I thought for sure this part was going to make me crazy.












Thanks for looking! By the way, if I am posting to much detail for each of the steps or too many photos, please let me know! Cheers!

[88Porsche944]

Mike,
Your work is just incredible.

Trevor

[MidMazar]

Originally Posted by mike@af

I) if I am posting to much detail for each of the steps or too many photos, please let me know!

No we need more photos and more details. Very informative, thanks for sharing. How much do these bits cost a piece, if you don't mind me asking?

It's crazy how one side was done and then flipped and the other was milled. Still can't put my head on that. Keep us posted!!

[John18d]

Mike
I've said this before - You are INSANE - in a good way
I'm am just in awe at what you can do with a lump of aluminum alloy
Simply in AWE
John

[slowhonda5]

This is an amazing build Mike, Dirk sent me the link to it. I remember years ago on another site when you were building that 1/12th street rod. The machine work your doing on this motor that small is unreal.

[mike@af]

Thanks guys! I appreciate the motivation! Unfortunately, there wont be much progress in the coming weeks. This weekend I will be attending a model show in South Carolina, next weekend I will be heading to Daytona Beach, Florida for the Rolex 24 Hours of Daytona.

Originally Posted by MidMazar

No we need more photos and more details. Very informative, thanks for sharing. How much do these bits cost a piece, if you don't mind me asking?

The ones that were broken were $47/each.

[nugundam93]

always a pleasure to see an update from you.

[Decs0105]

Originally Posted by mike@af

This weekend I will be attending a model show in South Carolina, next weekend I will be heading to Daytona Beach, Florida for the Rolex 24 Hours of Daytona.

Have fun, I am watching the 24h on TV

[RobertJablonski]

Awesome job! I can't stop watch! You have such a small man who it will go? If not, then you will have to do

[Greg23]

I've done some milling and this is amazing work you are doing.

[scrappyj1]

Originally Posted by scorpiopab

Wow this is freakin' awesome.

I lost my jaw somewhere on the floor, and can't Find it anymore.

This is one of THE most beautiful builds i have ever seen.

It is even more impressive in person, with an optivisor. I can't wait to see the transaxle done.

You are one talented young man, Mike!!!

[white97ex]

Looking good Mike! Glad to see you still working on this little masterpiece. I've been trying to get motivated to dig out my 1/12th Camaro and get back to work on it.