draft

[dustinwassner]

can anyone explain to me how to machine draft into molds? i can see how this would be simple with a 4 or 5 axis machine since the table could rotate the amount of degrees desired, but if that is not available, would one typicaly use a tapered end mill? thanks

[HuFlungDung]

Yes, tapered endmills can be the solution if the mold has simple contours. Internal corners can be problematic if the designer is not aware of the limitations of a tapered tool, because a tapered tool lends itself to cutting corners with a variable radius.


Other times, you may have to use ballnose endmills and simulate the taper by going round and round with very shallow changes in depth between passes.

[dustinwassner]

is using a 4 or 5 axis a common way also? or not really

[HuFlungDung]

Sure, 5 axis would probably be a great way to handle it, not that I've done it.

[mc_n_g]

The long way is a lot of paths with a ball mill.

[adam_gtm]

Most 2 and 1/2 axis cad programs can do this. If you use an edm to create your pocket it makes a natural draft from the carbon particles being flushed out. It's only good for .3 deep any more than that and you have to cut the draft into your electrodes.

[Boots]

Use a ball tool and program using profiled or sloped sides input your angle and your step over and you will have it.

[roninB4]

Don't know about others but for large core/cavity work we almost always used a cutter with the draft angle ground on it. You'd make 1 or 2 passes and you're done, sending the cutter off to the tool crib to be reground. Sure seemed faster than a ball mill and step over for large surfaces. Less work for the polisher too. I'm not saying this is better, just consider the cost and pick what works better.

[3D Accuracy]

Hi Dustin,

Depending on what exactly you are trying to cut, if you don't have CNC capabilities available you could always tip the block or tip the head on the milling machine.

As HuFlungDung mentioned, corners can be a problem. If you can't have a tapered radii in the corners then you can always cut them close using one of the two options above and then edm the corners after you've cut your drafted walls.

Of course the other option is outsource it to someone who can cut it for you.

Good luck and have a terrific weekend!
Robert
3D Accuracy