Problem with involute gear generation

[Scott Pancheau]

Hello,
I am having trouble with involute gear - code generation in fourth axis method. I have tried to machine three different gears and have same problem each time. The code roughs out the first two half teeth fine. Then the a axis rotates and the z axis moves down even further than it was at the bottom the first cut and plows back through the blank in x, then z heads down again even deeper. I can send the generated code but I don't know how to attach to this post.

Thanks,
Scott

[BobL]

Hi Scott;

Have you viewed the 4th Axis Milling Tangential Shaving and CAM features of Gearotic on Youtube?  Perhaps this may help to shed some light... 

http://www.youtube.com/watch?v=UndFcWc38Wk


Cheers
Bob

[Scott Pancheau]

Bob,
Thanks for your reply. Yes, I have viewed the video. As I stated the first cuts at A 0 position are just what you would expect. Here is the code sequence. The last line of code at A 0 position is g1x-40 y0 z-.32 A0.
The very next line of code is go x-.4 y-.150 z-.4429 A7.3279. The next line of code is x+.40. This does just what you would think, it takes a full depth of cut deeper than the last correct cut and wipes out the blank at a position just outside of the last proper cut. I would expect z to return to the clearance plane before A rotates to the next machining position. I cannot see how this could be a proper code generation.

Thanks again
Scott

[Mooselake]

Scott, to attach a gcode file you'll need to zip it first.  When you reply click on the additional options below the reply window, scroll down if necessary, then use the Browse button next to "Attach:".  You can attach any of the files with extensions listed after "allowed file types" without zipping them first.

Art might like to see the gth project file, so you should attach that also.

Kirk

[Scott Pancheau]

Thanks Kirk
I think I have the code attached. Thanks for your help.
Scott

[ArtF]

Hi Guys:

Sorry for the delay, I wasnt getting notifications lately.. Ill check this out and reply back. ( Are you sure the A is goign correct direction, thats usually
the issue.. but Ill analyse and check..

Art

[ArtF]

Scott:

  These are notoriously hard to troubleshoot form the numbers, it does look correct to me though... but if your
A axis is rotating backwards, you'd see the symptom your seeing.. Can you tell me what direction it rotates when you rotate
it ++ when viewed from X++ looking down towards x--?
  While the numbers look correct I cant verify it as yet. Im assuming its the old rotation issue. Make sure your 4th axis position is
selected correctly and the A axis rotates counter clockwise ( when chuck faces X++, and is viewed from X++ looking down X-- direction)
when it turns in a ++ direction....

Within a week or so I hope to have the new version out which will show a simulation of the toolpath as you generate it.
So at least soon you'll be able to see exactly what you SHOULD see on your machine..

Art

[Scott Pancheau]

Art,
I did not even think of that as a possibility. If I am correctly understanding your description then I think my rotary is turning the wrong way. I will swap it around tonight and then get back. Thank you so much for your help. On that vein - this is a home made gantry and I have it set up such that the X axis moves toward the rotary when moving in + direction. Is that correct for the way code is written ?

Thank you
Scott

[ArtF]

Scott:

  The default code is written for the chuck being in the X-- direction.. But in the options you can select the direction you face.

Its not unusual for the rotary to be backwards, few peopel follow the spec for that and youd only really notice on gear cutting. :)

Art

[danmauch]

Why don't you just reverse the direction of the motor in Mach3?
Dan

Art,
I did not even think of that as a possibility. If I am correctly understanding your description then I think my rotary is turning the wrong way. I will swap it around tonight and then get back. Thank you so much for your help. On that vein - this is a home made gantry and I have it set up such that the X axis moves toward the rotary when moving in + direction. Is that correct for the way code is written ?

Thank you
Scott

[Scott Pancheau]

I did reverse the rotary direction but it did not solve the problem. It still cuts wrong at the first rotary movement. I will double check that it is moving 360 degrees on the corresponding command and double check my gear blank sizing.

Thanks for your help.
Scott

[ArtF]

Scott:

  Try one step at a time, turn off tangental and just turn on rooting.. does that cut properly ( though teeth have raggen edges? )

Lets see if we can g=figure out what step its screwing up on..

Art

  Generally, when cutting involutes, if the Tool moves to one side of the blank, then the rotation thats next or mixed with that move will rotate the blank towards
that same side.. Does it seem reversed to that? In other words it always with the top moving towards the side the toolbiot has moved to..

Art


Art

[Scott Pancheau]

I will try this out over the weekend and see what I can learn. Thanks for your patience and help.
Scorr

[ArtF]

Scott:

  The new version isnt ready yet, but here s a short video from it showing how the cutting "should" look when your looking into the 4th axis..

https://www.youtube.com/watch?v=TpbjYPV ... e=youtu.be

  The pauses are the tool sweep back, then forward on the tooth surface.. but this shows at least the order of motion vs revolution ..

While this is the new code, the old code is similar...though during this development I have found an error in the old code that coudl badly affect small tooth count gears,
the new module will correct that..

Art

[Scott Pancheau]

Art,
I viewed the video and see how it should look. That is not what I am getting. The first move for the A axis rotates a little beyond the profiling area and makes a full depth of cut pass that wipes out that side of the tooth profile alltogether. I did as you suggetsted and ran the roughing cut only and that worked just as it should roughing out all the teeth. It is the shaving that is messed up. I even tried reversing my Y axis thinking it may be the problem I ran the rotary in both directions with Y set one way and both with Y set the other. All ways wipe out the profile as soon as A starts its rotation process. This is a small count gear at 11 teeth. I will try a larger tooth count to see if that works? On another subject, can the involute settings be changed to match a cutter for a smaller tooth involute set ? If so is there a tutorial that addresses this as I cannot find anywhere to change from the one that comes with gearotic.

Thanks,
Scott