Vectric Aspire makes a mess of a circle?

**Davek0974** · 03-08-2016

Doesn't really matter of course, i just like to know whats going on thats all :)

Sometimes Aspire seems to resort to making curves from many lines and these were visible in the finish, especially if feed rate override was in use.

**Clive S** · 03-08-2016

Sometimes Aspire seems to resort to making curves from many lines and these were visible in the finish, especially if feed rate override was in use.

Not sure what you are saying here. If Aspire generated code with arcs then you turned the federate up in Mach3 that could not change it into small lines.

I think there is a setting in Mach3 CV that can be ticked.

**Neale** · 03-08-2016

I'm guessing a bit here, but one reason for Aspire's 4-arc strategy might be potential problems with motion controllers. I seem to remember a gcode manual mentioning that some motion controllers could get a bit confused by full turns, so breaking it into arcs could be more reliable. If that was true once, it's probably not relevant any more with the motion controllers we use today but maybe it's just a historical thing?

There's a discussion of a possible reason here, to do with rounding errors in start/stop points in nearly-full circles. I used to use a free CAM package with LinuxCNC and it often threw up errors with these kind of arc calculations in g2/g3 moves. When I moved to vCarve all those problems went away, so maybe there's sense in it!

**Davek0974** · 03-08-2016

Interesting.

The one time i noticed it, i was doing a dummy run so had the feedrate turned up to max, it was very jerky on curves, thats what made me think.

I will need to do some more observing but at least i know now its probably just normal :)

**Ger21** · 03-08-2016

Originally Posted by Davek0974

so had the feedrate turned up to max, it was very jerky on curves, thats what made me think.

This is a known issue with Mach3 and Feedrate Override. It works fine when below 100%. but it can cause jerky movement when turned up a lot above 100%.
I don't recall if there's a safe max to use, but I would keep it below 125%.

**Davek0974** · 03-08-2016

Excellent, i like known issues :)

At least there is a reason.

Thanks

**magicniner** · 03-08-2016

I ran a couple of parts earlier this week using Mach3 at 300% without noticeable jerkiness on the curves.
Different versions have different issues, mine doesn't seem to have jerky curves above 100% feedrate, I'll check the version but it's the one most recommended for general use on the Mach3 forum,

- Nick

**Ger21** · 03-08-2016

I think that the issue is PC dependent, and doesn't affect everyone. But it is an issue, and was confirmed by Art, the author of Mach3.

The Machsupport forum is down right now, but I'll try to find some more info when it's back up.