Tangential Saw shaving 4th axis

[David]

Hi SkyMoBot

Glad you like the gear, even if it is just an old washer the cuts do seem pretty good.
I ran the program twice on the same blank with different things checked  as Art and I were looking at a particular issue
Feeds speeds were deliberately slow, X clearance generous; guessing if ran all three parameters together (rooting, root wall and toothing) it would have been about 2 hours.
I have produced the code for a 96 tooth mod 0.6 gear which I will try soon. Because of the smaller teeth each one will take a lot less time (about 90% lines of code per tooth) to cut, but a finer depth of cut might be better for small teeth so I guess around 3 hours. According to the software and my calculations a 0.6 mod can still be cut with a 0.015" saw but I will purchase some 0.2mm and some 0.3mm on Ebay and try those in the future.
Hope that helps
David

[David]

Hi JohnS

I had wondered about using supporting washers for the finer saws, thanks for the information and confirming the improvement it gives.
I will give that a try before I settle on actually producing mandrel and blanks for real the clock gears
Regards
David

[ArtF]

Hi:

  I use the supporting washers trick on my table saw for its blades on hardwood, it is a good way to
stop deflection. A a word about time... if you select a higher depth per pass you may ind it much faster,
in theory the saw should be able to take a fair amount due to its sinusoidal width in the direction of cut.
Secondly, I default to 10 segments , JohnS proved quite well that 8 seems optimal for time vs quality
and can save you two passes per tooth.

  Hopefully, this year we can have our simulator, Im still reading and researching the topic..

Art

 

[JustinO]

Nice gears considering the frugal cutters. You might improve the finish by lightly sliding the saws on a diamond hone to remove the most extremely "set" teeth.

Art, do you have a shaving option for cycloidal toothed gears?

--Justin

[ArtF]

Justin:


  You can do cycloidals, no special code is needed, G2 uses the tooth shape from the dxf as the shape to tangentally shave.
How well it works may vary, but the program wont complain if you do a cycloidal. The new algorithm is a generlize one, meant to work
as well as it can on any tooth shape...

Art

[David]

Hi Art

Tried a 96 tooth 0.6 module gear today with less success.
Saw width I appreciate is a little wide at 0.016" with a maximum suggested of 0.0175" so it should be OK as a trial, no too large warnings in gearotic.
Two problems occurred, on the first tooth shaving cut the tooth is all but machined away, the last 2 shaves cut air.
The dreaded 90 degree A rotation is back along with the full depth Y plunge just about clears but fouling the mill spindle is worryingly close.
Not sure if these smaller gears are the area you felt might need more work, I am happy to wait if that is the case,.
I still have a traction engine to finish and a clock to start  ;D
Attached a first part of the code
Regards
David

[ArtF]

David:

I see what you mean, The lines at line 92 take a terrible jump.

Can you'll post a snapshot of the screen that created it.

Im thinking it may be an overflow. The problem is the math that determines
the max diameter isnt exact, its a bit heuristic, so if its wrong, the saw may be a touch too large,
which may cause a nasty math error. But thats really good, if I can figure out exactly how to reproduce this
code, I think I can fin ally nip it, its an obvious overreaction to something in there..

  It seems after the 90 things go back to normal for the next tooth. This does seem reminisent of a bit
being too large. I often enter 0 as the diameter to see the toolpath, ( which usually looks good, ) and then
increase slowly, as you get larger youll see the toothing passes move away from the flank, when the path
on each side crosses over the other side, the bit is too large.

  Its a hard one to explain, but when you see it it gets more obvious. SO if you can , post a snap, and
Ill dig into it, and if your playing, set a zero and slowly increase to saw size to see if it looks as if its too
large  a bit.. I highly suspect its got something to do with small numbers of some sort..

Art



Art

[David]

Hi Art

First screen shot is the 96 tooth 0.6 module  with 0.015" saw as requested. I regenerated the code and still got the A 90 degree and deep Y plunge.
Second screen shot is same but with 0.001" saw, code generated also has the A 90 Degree and deep Y plunge.
Hope this information is helpful
David

[ArtF]

David:

Nope, all I get is good paths, no 90's.. Can you post the project file, maybe theres something weird in it..

Art

[David]

Hi Art

Just had a thought, as a Mac user I design either on the Mac or on a virtual PC, I wonder if that is the problem.
Not sure why you would get a different result on a mathematical process.
Before we do anything else I will take the project file into the workshop and generate the code on the PC that drives Mach 3 and the mill
Will post results later

David

[ArtF]

David:

  Thx, Im sure we can narrow it down. Im thinking its the root wall routines failing.. so turning them off by unchecking RootWall may make the 90's go away.. but I find it strange I cant duplicate it.. Ill bet its one  of those "Whoda think that" moments when I find it.. :)

Art

[David]

Hi Art

Some of the issue must be virtual machines in my case both VMware and Virtualbox both on Macs.
I have zipped files up for you to see.
The gth file name ending in macVM was produced on my Mac, the tap and screen shot  on the win7 PC I use with Mach3
The files ending in win produced solely on the win7 Mach3 PC
You can see the A90,s in the macVM files, but those gth file created using the same gear parameters on the win7 PC are fine.
Never seen difference between VM,s and PC before. I use 2 different Macs each running a different VM both produce the A90 problem.
As I store files on a NAS I was not really aware were I had created them until I found no difference reducing saw width and you finding no problem when you used the same settings. 
I think I have unwittingly caused you a lot of work, sorry. Perhaps you could ask if anyone else has tried running Gearotic on a VM and had problems?

David

[ArtF]

David:

  Not at all. I have just uploaded a fix to correct it. I dont know why the gear tooth form created by mac's were slightly different
than windows, but they just crossed under the zero line by about .00001 units and that was enough to create a bug.
Try the new version, the toolpath should look much better...

Art

[David]

Hi Art

You certainly work quickly
Tried latest version in both Mac virtual machines, looks good (see attached screen shot) and no A 90 degrees.
Its gone midnight here so will try a test gear over the weekend.
I am sure you have had enough of me, but do you know if anyone has tried to use your program to produce say a four lobed relieved involute gear cutter?
I am thinking using a standard size endmill to give the cutter profile and cnc motion to give relief. For the larger gears it would be easy enough to find the correct endmill size.
I wondered if a blank was gashed quite widely producing 4 lobes then when correctly aligned it should not be too difficult for the cutter to be correctly relieved.
Please feel free to ignore those thoughts you must have plenty to do!
David

[ArtF]

David:

  Ahh, that looks much better.

  Im not aware of anyone doing a cutter that way.. I have been asked and have promised to make the program
put out code to make cutters, so its something Ill have to look into eventually..

Art