installing compound angled holes on 3 axis machines

[krustykrab]

I moved this question to this forum, perhaps I had it in the wrong one, got no response.


I've been running 3-axis machines for quite a long time.

However I never really gave much more thought to putting in bushings holes in a fixture on a compound angle, other than to use 2 sine plates.

A long time ago I was party to installing similar holes using a picker head. But don't really recall the proper method.

Has anyone done this, and if so what is the best method to achieve accurate results in positioning. Within <.001" tolerance?

[timf]

i have made fixtures that locate parts on compound angles by 3-d machining the proper angles on my fixture with the machine i plan to use and then using a tooling ball for future reference pick up.
depending on the shape and size of the part this has worked well in the past.

tricky using fixture agian, so set up good references to align and pick up fixture for next time. ( edges to tram straight and hole or ball to pick up)

the more effort i put into a set up the better the job goes.

[Montana]

Place an extra hole in for a tooling ball or you can make a fixture similar to a jig bore edge finder to allow the use of a phantom tooling ball.

[krustykrab]

I am replying to a recent hit on this (sorry.....forgotten about) thread.

I have been able to install holes/pockets in a checking fixture using a manual picker head (aka universal head).

Of course I have to helibore the holes out, and they are somewhat oblong, however, once the bushing is installed..........great results.

It saves me all kinds of time with multiple sine plate setups!

Anyone else do this? I am talking with a 3 axis machine, not 3+ any!

[Andre' B]

Assuming you are talking a universal angle head like these http://www.pibomulti-na.com/ah/uc.htm in effect you are adding manual 4th and 5th axes to the machine.

Why are the resulting holes oblong?

[krustykrab]

they are oblong just due to the machine error.

I haven't been on a machine that didn't helibore a hole oblong.

of course we are only talking about .001" per side.

[Jim Estes]

Helibore. That's a new word for me, is that the same as spiral boring?

I used to work for a company that bought a brand new machine, and they claimed that the machine would not machine a round hole right so they always left stock and then went to the bridgeport and finish bored the holes on that.

After calling the dealer and a Mastercam tech support, I figured out that the machine required a R value for G02/G03 and not the I and J values, once I modified that post processor, then machine would machine perfectly round holes all day long.

Jim

[krustykrab]

That sound interesting about the I and J. I will definitely look into that for my 2d heli-bores.

But, when you are installing the hole on a compound angle with a pickerhead, the only data is in xyz. Irregardless as to whether the hole is slightly oblong, it appears that the hole locatons are right on.

The other option I have found is to just drill and/or ream the hole, however pickup is an issue, because you need to pick up the center of the tool to get your xyz location for each tool you use. I thought of checking into ball nosed drills and reamers, but not even sure if they exist.

[Jim Estes]

One trick that I use a lot for drilling cam pin holes on an angle is to take a ball endmill and peck drill with it down to 1/2 the diameter. When I move the cam up on angle I can indicate the "dimple" and since the center of the "ball" is at the top surface and in any angle, then I know I am centered on the hole.

One problem with this is that you have to start the bore with an endmill because a drill will hit one side of the tilted "dimple" and will tend to drift to the low side.

Jim