Should CAM software generate circular interpolation?

[M30]

Apologies for posting this problem again, but I was not getting much response in the Mastercam forum. I want to open this question up in a general sense.

Basically, I am using Mastercam and it is generating a bunch of tiny linear moves to resolve arcs. I think this is messing up the finish on my parts because my TM-1 shakes around theses "linear equivalents" to arcs and the effective feedrate goes way down (while the control says it is the same).

It seems to me that the post should be generating circular interpolation commands. But I don't know for sure - I don't have enough experience in CNC/CAM.

Is this G-Code output consisting of only linear moves and the resulting machine behavior normal?

Thanks.


Btw, in these photos the pockets did have a finishing pass while the corner profile did not.

[Geof]

If you go to the Haas website www.Haascnc.com you will find a link to the CNC Magazine put out by Haas. Some time around 1 or 2 years ago one of the articles, maybe a series of articles describing CAM and how to optimize the code.

It mentions about the many linear moves and how you can control the size of the straight line move and it also mentions tool path filtering which can help regenerate circular moves.

[tobyaxis]

Mastercam should be generating Arcs for these not Line Segments. I think your Post Processor needs some modifications.

Also, with my short stint with MCV9 and MCX I found that MC takes Arc Geometry that is Imported and turns them into Splines.

I forgot what was done to fix this issue, Sorry

[dertsap]

if you use the mpfan post it should give you arcs
mastercam will normally post line segments on arcs when ramping but on a normal path it shouldn t, well , from my minimal exp anyhow

it almost looks to me like chatter or the feeds too high ,or the speeds too slow ,there appears to be the same marks on the side of the flang across the flat ,it usually becomes more ponounced when cornering

[M30]

The flat along the outer edge there (pic 3) is just an optical illusion, it's actually quite smooth as it was face milled.

My chip per tooth was .0083 and my feeds and speed were as high as I could get on this mill. This is just machinable wax, I was using a 4 flute 1/2" carbide around those outer 3/8 radius corners.

I'm reading through all the haas cnc mags... Haven't found anything yet, but have read other interesting stuff.

[Geof]

This is the one I was thinking of:

http://www.haascnc.com/CNCMag/PDF/v10i34.pdf

[One of Many]

If these are G2 and G3 moves then I'd guess it is interpolated. There may also be a setting in MC or the machines parameters that tells the machine to use constant velocity around corners.

DC

[M30]

Thanks Geof, good stuff. I will play around with the cut tolerance and the filtering.

It definitely was not using G2/G3. You could see it running through many lines of XY coords around the corner of the profile.

[Frankenfab]

You should be getting g2's and g3's in your post. if the settings or the post is the issue, then I can't help.

If it's the drawing, and you know the radii, you can erase one line segment or curve at a time and redraw it from the endpoints left after erasing the segment. This will give you lines that mastercam can work with. i have had to do this with imported files.

I always use HSS 2 flutes at max spindle speed on aluminum, or softer materials. It's cheaper, and you actually get a better finish most of the time. With a 4 flute the chips can get caught up in the flutes and ground back into the part.

[tobyaxis]

Originally Posted by Frankenfab I always use HSS 2 flutes at max spindle speed on aluminum, or softer materials. It's cheaper, and you actually get a better finish most of the time. With a 4 flute the chips can get caught up in the flutes and ground back into the part.

Frankenfab,

This is what I keep telling an individual at work about 4 Flute Emills in Alm but he doesn't listen. He would be better off with 3 Flutes 60 degree Helix.

BTW, Cool Handle, now all you need is an Avatar to go with it.

M30,

Have you gotten any closer to resolving your line segment issue? I remember now that Frankenfab mentioned it. You will have to import the Wire Frame Geometry into Mastercam as a DXF File to get Arcs from the G-Code. If you use Iges, Step or ant other it will Post Line Segments.



Cheers!!!!!!!!

[Geof]

Are you planning on making one or many? If it is many and the many is hundreds you should consider hand coding it. To make it simple you would need to do a minor redesign of the angle fillet between the boss and the flange; make this is radius fillet and then you can run around the boss with a big ball end.

A hand coded program will run faster than a CAM program and much smoother.

[tobyaxis]

Originally Posted by Geof Are you planning on making one or many? If it is many and the many is hundreds you should consider hand coding it. To make it simple you would need to do a minor redesign of the angle fillet between the boss and the flange; make this is radius fillet and then you can run around the boss with a big ball end. A hand coded program will run faster than a CAM program and much smoother.

Your always throwing out those better methods of doing things LOL . This is true in many respects, but if he is trying to learn how to use a CAD/CAM it kind of defeats the purpose of his question LOL

The choice is ultimately his though.

Smile it's Saturday