GearHeads Corner

Hi Art and All,
Been a while since I hung out here so I'm probably way behind.
Back then the program didn't/wouldn't even try to 4th axis cut an XL timing pulley. Apparently that has changed. Someone please drag me up to date. Are the Radii at the top and bottom of the profile being shaved? What is the bit profile; rounded, ball, flat?
Thanks,
Ozzie

Hi Ozzie:

  The 4th axis was updated to control itself based on the tooth profile instead of the
math involutes. This means it will attempt to do any shape. It cant do a perfect timing pulley,
but it does tend to do well enough. Several people have shown results that work fine
just using the same straight mill that you'd use for spurs. This works well for the GT's it sems
as well as the T series. Basically you get what you get, but that often works. Same for sprockets,
can leave an imperfect grind that needs cleaning, but it basically will do as well as it can
on any shape.  Id advise you watch the simulation of it as it goes to see if you can picture just
how well that'd work out..

Art

The sim looks like it works. The needed bit is tiny; good job for a spindle-hung-router. I don't see where to specify my own mill bit size.

found it !!! ::)

I had some time to play with simulating cutting an XL with 4th axis. Trying the tangential path, the tool goes far below the root of the pulley. What am I doing wrong?

Ozzie:

  Just tried it here to be sure. Seems OK on tangental on an XL. The path is created from the solids shape, so it shouldnt go into the root to deep. ( mine doesnt go all the way down..). What size tool is it?

Art

Attachment

I see what you mean. I cant seem to make that happen here, can you post the project
file here so I can try to reproduce it. Its definitely going too low..

Art

I've seen  that same effect when I was shaving gears it has to do with the indexing of the work piece when getting into position while
the cutter is off to the side, the indexer & cutter axis are moving to the opposite side of the tooth openings next pass.  

The spindle in Z depth remain the same as the indexer rolls over and the cutter shifts over to the opposite openings side

I just had to make sure the cutter was good and clear.

Guess I'd call it the roll over effect.

So what parameter should I change to make it work?
I tried putting a clearance in and then it says the tool is too big???????

Art,
Project file? Where, how?

I don't think you need anymore than to make sure your passes are longer than the width of the blank, the diameter of the cutter, plus a little extra for what your heart can take when you see the action in process. Freaked me out the first time I saw it in action. You just need to be assured that the tool holder and shank wont hit when shifting. It is a feed move so the positional relationship is represented in the graphics.

I understand. I'm looking at it in 2D, I'll try to get a good 3D view. Thanks. Ozzie

Ozzie,

Yeah, its probably positioning moves while the tool is off to the side.
Do a simulation and see if it actually seems to cut into the root.

YaNvrNo has cut quite a few, now that he mentions it , it makes sense..

Art

Okay, I confirm they are moves outside the part/pulley.
I'm not sure I see the wall being cut, even at the slowest speed it is hard to see. I have tangential and rooting turned on.
I see it cut to the root, but then it looks like it goes to cutting/shaving the tiny radius at the upper edge.
If I turn on root wall it makes a straight up and down cut, no angle.
It would help if there were a step by step animation, or a slower visualization.