DXF export issues

[Locolima]

Hi,

Brand new here...just downloaded and bought the software today.

I made simple gear for a test and when I export to dxf I get an odd result, the line is made up of many short segments. I want to cut this on a cnc, either a proto trak BP or a small machine I retroed and is running mach3. I can't dimension it, it wont pick up any of the radii with the file like this...

I searched the forum some but don't see an obvious answer to this.

I am attaching my dxf.

Thanks for any help for the newbie guy :)

Paul

[ArtF]

Hi Paul:

  The DXF IS made up of small lines, this is normal, a gear is made of involute curves
that are created as segemented line contours. Mach3 doest load DXF's natively, what are you using to make
the toolpath for Mach3. ( You can use Gearotic, but youd want to put out the code as Gcode, not DXF..)

I may be misunderstanding your issue , can you explain what your doing and how the DXF is affecting you?

Thx
Arty

[Locolima]

Art,

Thanks for the reply! When I import the dxf into Acad Inventor I can't dimension any of it as it all just little tiny line segments(hundreds of them). I import dxf's into IV all the time and its not usually like this.

Ideally I would just pull enough dimensions in IV for one tooth, then input that info into my proto trak and rotate it.

Second choice would be to use Onecnc and run it on my little machine with Mach3. The size of some of the gears is pushing it for my little one.

Thanks,

Paul

I attached a close up snip of what I am seeing.

[ArtF]

Hi Paul:

  Im still not understanding the issue, but then I dont use inventor at all. Any DXF which approximates
a formulaic arc (involutes in this case)  has to either use line segments or arc segments for that curve, Gearotic used line segments as they are more universal than arc segements for most users and pretty much all DXF importers
will accept line segment. What are you expecting  ( or hoping :) ) to see? Beziers or Arc segementation?

  Im unsure why one would try to approximate a tooth or copy one to create a toolpath? why not just
ask Gearotic to put out the Gcode for the gear itself.. or just select the line segements that make up a tooth
and rotate it? If you can explain the issue I may be able to show a work around..

Thx
Art

[Locolima]

Art,

First I sincerely appreciate the help here...

I guess I am just unfamiliar with the issues and maybe there isn't a problem!

So if I use the g-code output the tool paths with be all straight lines moves? The cutter diam will "smooth out" the transitions then I guess.

I'll give it a go and report back!

Paul

[ArtF]

Paul:

  Yes, the number of segments is far above that necessary to make the gear face quite smooth. I can make it smoother with more points , but over
time the right number of points seems to be about what is set, weve had complaints of too many and too few.. which adjusted the total, but there havent been any complaints of segmentation number for over 2 years now so I think we're just about right. .

In 4th axis we typically cut about 8 segements per tooth with no problem,
in 2.5D the segments youll get is up around 50 or so, way above the point at which youd notice. In the end, "smooth" is defined by not the absence
of line segments, but the greatest number of them. ( A perfect arc is infinite line segments really..).

  The problem in such things is always where you draw the line. If I increase the segmentation to huge numbers, the program would slow
considerably with no real improvement in the gear you make.. but then, all things are relative and some people may need much higher
levels of smoothness for whatever reason, shoudl that happen let me know and I can probably make it so for you.

  Take note too that noncircular gears are special in that they are built using digital subtraction techniuques so can be rough edges in the root moreso than anywhere else, this too can be made smoother by special request if one need it, so far noone has requested such a fix.. but you never know.. could happen. :)

Art

[Locolima]

OK I cheated! I was planning to cnc these but I noticed that little stl thing on the screen :)

So I exported that, sent to Shapeways and had my gears in hand in 7 days for a lot less than it would have cost me to make them!

I probably dont need to add they came out perfectly!

One question...how do I find the shaft center distance dimensions?

Thanks for the help!

Paul

[ArtF]

Paul:

Just hold down ctrl and click on each in the tree. When two gears are selected, the screen data will show center distance.

Glad to hear the gears are good.. :)

ARt