CnC question - B axis tilt

[cboggs]

Larry, Richard, or whoever else might know, ..

How much B axis tilt do you use to port conventional big block
chevy heads, .. small block Ford, .. etc?????

What heads need to most B axis tilt and how much?????

I've been told by several people you need at least 30 degrees and
a few said 32 degrees of B axis.

based on a good lollipop cutter and a 1/2" tapered shank or at least
enough shank to avoid serious tool deflection.

Curtis

[larrycoyle]

Curtis,

A lot depends on how much the cutter is tapered. I don't know how anyone can make a blanket statement that you have to have xx° tilt on the B axis because my machine works on a totally different concept that the one you are using. For instance, I am working on a Track I file right now and it tilts to -37° maximum in the B axis. The way it works though the C axis is rotated and it kind of sweeps in the direction of cut. I will look up a BBC file and let you know what it reads but I don't think it is anywhere that extreme. Quick question... do you use some type of G Code editor? Depending on which one you use they are very handy for telling you the max and min numbers on all of the axis you are using. What I like best is that you can "backplot" your program and if you make any changes you can actually overlay one on top of the other one to see what it looks like. Another thing I had to do is have some cutters made with a different taper on them. I am actually trying to get away from the lollipop cutters because of the cost involved, coatings and the time it takes to get what I want. I have actually used three different vendors to date and I notice in the current PRI mag there is another vendor offering a diamond graphite coating which I like but they cost $200. One thing I have noticed about these vendors is then you ask about what to use for cast iron they just have that far away look in their eyes. Another tip regarding deflection is the actual cutter speed and the depth of cut. I have found that when I run the tool at least 10,000 RPM my machine seems to cut better.

Maybe we should talk on the phone a little more in depth tomorrow. I have to be somewhere early am but I will be back in the shop before noon.


Larry

[cboggs]

Larry,

Thanks for the comments, ..

just to be sure, .. my A axis rotates around the X axis, ..
and my B tilts side to side , .. .. X ( side to side), Y ( front to back ) Z ( up & down ).
I posted this cause I think you have a horizontal machine?, .. or your axis might be
different then mine, .. .. but it's the side to side tilt of the head I'm talking about.

Total B axis tilt on the Centroid is 24.9 degrees each way of center
and at the current formation will not get the area behind the push rod pinch of
a big block head. We are working on it, .. Centroid and I, .. but as always
I ask the people with more experience then I.

Yes the lolipop cutters are a pain in the cylinder head.
They need at least a 1/2 shank with as little taper as you can get away with, ..
and they still can't take being "leaned" on very hard.
Now, .. take a 7" long 1/2" ball end mill and rough out and SB2.2 or DRCE port, ..
that's something cool to see!

Larry, on a 1/2" lollipop with 3 flutes are you running that at 10,000 rpm?
I've been running it at 3,000 and it seems happy????

Thanks,

Curtis

[larrycoyle]

My B axis will tilt almost any way possible plus or minus 110° in either the X or Y axis. My C axis rotates around the Z axis plus or minus 365° which is how the B axis gets its ability to tilt either X or Y. I also have a rotary table for a sixth axis that rotates around the X axis. I will call you tomorrow.

Larry

[larrycoyle]

I forgot to say that mine is a Vertical CNC not horizontal.

[headman]

I expect Larry has a vertical machine with an articulate spindle that accomplishes the B axis motion.
If the cutter can be positioned at the origin of rotation on the B axis, some compounding errors in positioning could be avoided.
I always viewed machines like the Boston Digital or the Sunstrand as ideally suited for head porting.
Yet, a horizontal machine with an axis built into the table, and a rotary fixture on the table, seems like a good solution. And the range of motion in the 4th and 5th axis would not be limited.