Total Newbie question here

[redbaron]

I am new to CNC machining and was wondering how a 2-sided relief is completed. Do you mill one side and then flip it? How do you keep the accuracy. Also if the design cuts through the stock completely, what holds the piece in place for the final cuts?

THanks for your time

[castguy2003]

There are as many ways to hold parts for two sided machining as there are part designs. Experience will help here. Until you develop your own methods. try posting sketches or e-mailing drawings or photos.

[Rekd]

Depends on the part, the machine etc.. I use 4 axis machines with a tombstone type fixture.. with which I can do a 6 sided part with only 2 holds. Machine a top face, and the sides... flip to the next hold, machine the bottom face and 2 ends. Very effecient.

Your work holding will determine your accuracy. Generally, you would use a precision machine vise, like Kurt or Dapra or Chic. You can hold tolerances to 4 places with the right setup.

Holding parts gets really tricky. You need a good imagination and a lot of common sense. Some times you can cut jaws to the shape of the part, so you can easily hold/orient it in a vise. Or use a fixture designed specifically for that part. Way too many options here, it will all depend on the part and the machine you're running it on.

Machining is a black art. It will take you a lifetime to learn. The rewards are fantastic. I have parts in space, on planes, in super computers, in radio communications, and in missles/rockets.

99% of everything ever produced in the last 50+ years has something to do with machining. Be it the object itself, the machine that makes it, or the equipment that handles it. Almost everything is related to machining in some way.

Job security? You bet. There's prolly not a state in the country that I coudn't get a job within a month and make enough money to at least eat and sleep under a roof.

The very best part about it; I love doing it. I get paid to do it. It just doesn't get any better than that.


'Rekd

[HuFlungDung]

Hi Redbaron,

Assuming you are really "green" at this, you can often use an edgefinder or a spindle mounted dial indicator to locate a couple of features on the part when you flip it.

Another good way is to machine the piece with tabs on it, in which you would drill/ bore /ream locating holes. In some parts you could even allow permanent locating holes in order to facilitate ever setting it up again to do something to it.

One way to machine all around a part is to write your programs to deal with only one half at a time. Then, you can move your clamps to finish the second half.

Like the other guys have said, let your imagination run.

[redbaron]

I guess it is common sense and an art. I didn't even think about milling one side then clamping the other, then doing the same for the back face. The 4th axis idea sounds cool and maybe a purchase option.

From a simple hobbiest view, I can get dragged down with the specifics of the machine I want to buy, without focusing on the general design skill and art. It looks like I will be running through a bit-o stock to learn how to use the machine correctly.

Thanks mucho guys!