Problem with 4th axis toolpath

[Greolt]

As a new user I am reluctant to call this a bug.  More likely user error.

When cutting a 50 tooth 2.5 module spur gear with a 2mm ballnose cutter, the tool moves 28mm each side in the Y, as it cuts the final pass on the involute face.

However the tool never goes lower than the depth of the tooth at top dead centre.  This means it is cutting air on that last pass.  It needs to go lower in the Z.

I made a diagram to hopefully show this more clearly.

Can someone set me straight?

Greg

EDIT:  Forgot to say 20 degree pressure angle.

[Greolt]

Ahh yes....I see now.  :D

Missed the fact that the first cut is at 16 degrees.

So I gather that the earlier cuts (at less degrees) are not necessary.

OK I will go ahead and cut one of these tomorrow.

Greg

EDIT:  I plotted it out and can see why the cuts at less than 16 degrees are not doing anything effective.

And I guess that 16 degrees will vary with pressure angle and number of teeth.

[Greolt]

Tried everything I can think of.  Even another computer. Still same version.

Have to go to work now.  :'(

Greg

EDIT:  OK I have tried everything I can.

Refreshed browser.  Google searched on refreshing proxies.  Installed on another computer.  Still getting 1.64.0

Is there somewhere else I can download it from?

[Greolt]

Ok this morning I tried the download again and now it is Ver 1.64.2.  Go figure.   ;)

Unfortunately when I compare the old and new version's output of my Mod 5, 300 tooth gear, there is only a very small difference.

As shown in the two pics.

Just to make clear,   I have no need nor ability to make a gear of this size.

I saw a problem with a much smaller gear that I cut and used this large example gear to demonstrate.  To make the error easily seen.

Or I should say, the error I believe is there.  I could be wrong.  ::)

Greg

[Greolt]

Art

The A axis positions now look correct.  

The next problem I see is the amount we are asking the tool to cut on the first flank cut.

Cutting prior to this point would not cut proper involutes, ( if it cut anything at all), only cuts made after the initial 16 degrees should have any involution to them, which is why I eliminated them in this case.)

Because you are now skipping moves until meeting tangency of the root or lower part of the involute, this means the first cut is aggressive and may be too much for the tool in some cases.

Approximately 50% of the remaining material is taken with this first cut and the remaining 50% shared amongst the next ten cuts (in this case).

Greg