the line segments will give a more accurate following of the area under the curve of your cam profile. if it is an engine cam .014 could make a dramatic difference in functionality. i would want to know if you can adjust the parameters of sheet cam to out put segments at .001 resolution to get a most accurate rendition of your camshaft profile. i know nothing of sheetcam , this is a simple adjustment to mastercam resolution parameters however. the other concern is one that has been being discussed in the developers list, that is one of linuxcnc lack of infinite look ahead and jerky motion. programming by line segment allows very accurate following of nurbs splines but generates a lot of code that the controller must be able to process in a smooth manner to achieve best results. it is my understanding that lcnc has some issues with this , although i have not done much profiling in mastercam on my mill so i cannot speak from authority on this subject only to state that it is a present topic that others have an interest in seeing developed. I for one would love to see infinite look ahead and smooth motion to be able to take maximum advantage of mastercams high speed toolpath and nurbs functions. the lack of these 2 functions may well cause some undesirable tool gouge should you be requiring highly precise camshaft contours. in the production coding world programming of g2, g3 arc segments is becoming largely antiquated due to the great advancements in cad cam packages and machine accuracy . in short the cad cam packages are now so good as to be able to make accurate repeatable segments of .001 all day long allowing nearly perfect recreation of your model from cad space. Now i have the disclaimer that all of the above is not been tested by me on an lcnc machine but again has been subject to much discussion on this and the developers list . without smooth motion there is a brief stop at the end of every segment that can cause the aforementioned tool gouge . so in this case if a perfect rendition of your cam is not necessary it will be at your best advantage to program using g2 , g3 but if strict adherence to profile is necessary you will have to see how well you can get the line segment resolution and see the affect of tool gouge , if you have gouge you may even be able to reduce the resolution to get a better surface on your part . lastly what are you using to check the profile of your cam with and what type of camshaft is it?
On Thu, May 30, 2013 at 5:57 AM, Marshland Engineering < marshl...@marshland.co.nz> wrote: > I did an interesting exercise today. I received a DXF from the cam grinder > with 360 line segments. I imported into SheetCam and then exported it to > GCode. > > I looked at the GCode and couldn't believe my eyes. It was only 7 arcs > long. > SheetCam must have joined the lines together and created arcs. > > So I plotted the arcs against the original DXF. Most of the arcs were very > similar to the original and the greatest error was 15 thou. (this is on a > 3 > " disk) Most sections were under 1 thou out. I reckon it would be almost > perfect with 14 or so arcs. I have posted a similar question on SheetCams > forum but does anyone have a DXF line to arc converter where I can enter > the > maximum error acceptable and it comes out with closest arcs? > > Surly the grinding head would be a lot happier and smoother with 14 or so > arcs instead of 360 line segments. > > Cheers Wallace > > > > ------------------------------------------------------------------------------ > Introducing AppDynamics Lite, a free troubleshooting tool for Java/.NET > Get 100% visibility into your production application - at no cost. > Code-level diagnostics for performance bottlenecks with <2% overhead > Download for free and get started troubleshooting in minutes. > http://p.sf.net/sfu/appdyn_d2d_ap1 > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- We conclude that the Second Amendment protects an individual right to keep and bear arms. That right existed prior to the formation of the new government under the Constitution and was premised on the private use of arms for activities such as hunting and self-defense, the latter being understood as resistance to either private lawlessness or the depredations of a tyrannical government." - U.S. Court of Appeals, D.C. Circuit, March 9, 2007 jeremy youngs ------------------------------------------------------------------------------ Introducing AppDynamics Lite, a free troubleshooting tool for Java/.NET Get 100% visibility into your production application - at no cost. Code-level diagnostics for performance bottlenecks with <2% overhead Download for free and get started troubleshooting in minutes. http://p.sf.net/sfu/appdyn_d2d_ap1 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
