Re: Bug report - NaN

["Matt Shaver" <mshaver-at-erols.com>]

> From: Ray Henry <rehenry-at-up.net>
> Ian sent me some flashcut nc code that he was running on EMC and said it
> killed TkBackplot.  What it does is kill EMC. 
> 
> For my machine it caused a runaway that the soft limits don't see.  Only
> metal on metal, or quitting emc, or an external e-stop power down, halts
> this sucker.
> 
> ---------------------------------------
> G01 X 5.0000 Y 0.0000 
> G02 X 5.0000 Y 0.0000 I-5.0000 J 0.0000         ########## Here Backplot
> flips and takes off at high speed! #### 
> ---------------------------------------
>
> My guess is that giving an I and J for an ending position that is the same
> as the current position causes a divide by zero.  This happened in two
> places in Ian's nc program.  I have no explanation why flashcut would allow
> or use code like this but Ian is checking into it.

My guess is that Flashcut is attempting to arc the cutter around a sharp
outside corner with a radius equal to the cutter radius which is typical
behavior for a CAM program unless you override this feature. If Ian had the
tool diameter set to 0 (like for engraving) Flashcut might generate this
peculiar code, rather than simply leaving it out and proceeding to the next
linear move. The CAM system I use won't allow a tool diameter of 0.
 
> I presume that what we need to do is trap this problem in the interpreter.
> (verify does not find it)  I think that we also need to add some kind of
> orderly shutdown of the motion stuff somewhere in EMC whenever a NaN
> occurrs.  

Yep, it's still a bug. This is why I like having lots of testers!

> I'll be out for a few days.

Have fun! I think Fred's in Florida this week, but I'm sure he'll see this
when he gets back.

Matt