A transient anomaly I don't think I've ever seen before.

[lloydsp]

I was running a job today in 3/8" 6061 aluminum, cutting small 'sandwich' adapters to fit two tiny ratchet wrenches that are used as part of the incremental motions of a machine I'm refurbishing for a customer.

Everything was perfect until when I went to the very last MOp - cutting out the individual halves of each sandwich - then two of the four were perfect.  The other two (in the same MOp) began lifting ABOVE the clearance plane the same distance they should have gone below the stock surface AFTER beginning to cut the triangular holding tabs.  It didn't occur until the very tops of the tabs had been reached.

I immediately thought my mill had lost its mind.  But when I reviewed the g-code, it was doing exactly as commanded.

Understand, please, that these were not simply absent minus-signs:  It wasn't the distance above the stock surface it should have been below it -- it was above the clearance plane by the amount it should have been below the stock surface.

I did NOT change the CAM at all.  I simply regenerated the g-code, and the next time, the code was correct (reviewed before running!).

What?

Lloyd

[dh42]

Hello

And the toolpath display do not reflect the default ?

There is a know bug that appears sometimes when the cut start point is on a tab, but the display show the problem when in perspective mode. (and the problem do not go away until the start point has been moved on another position)

++
David

[lloydsp]

I viewed the toolpath, but did not view in perspective mode.  I just reviewed the start point, after reading this.

It wasn't exactly on the peak of a holding tab, but it was very near it.  I've never encountered that bug before.

Darn!  Why?  There's no reason.  If it will generate a bug like that, the toolpath generator should not send it to the top of a tab to start!

That's one more thing I must make notes for, and 'mentally' avoid during generation of toolpaths.  I guess I can establish the holding tabs first, then try to adjust them to avoid such a start point.  But the software already 'knows' where the tabs are.

Lloyd

[dh42]

Re

The bug I talked about

https://cambamcnc.com/forum/index.php?topic=8689

Not sure it has something to do with yours ...

++
David

[lloydsp]

The symptoms are identical.  I updated that thread to say that it can happen on polylines, as well.

Lloyd

[lloydsp]

And, confirmed with a whole different setup today.
L

[pixelmaker]

There are always problems with holding tabs and lead in / lead out strategies. If the lead-in is in the same place as a holding tab, errors occur. Since I discovered the error back then, I make sure that no starting point is located in the same area of a holding tab. CB does display the errors.  (image 1)

During a spiral lead-out with an angle of 0, holding tabs are cut through.
This is also an error that should be noted. (Image 2)
However, the errors are displayed in CB and in the toolpath filter.

[lloydsp]

Ralf,
I did not have any lead-outs.  The bad paths showed up in the toolpath display and g-code, but CB never issued any error messages.

I guess I've just been 'lucky', because in the tens of thousands of designs I've machined using CamBam (most having holding tabs), I've never encountered that problem before the other day.

Lloyd

[pixelmaker]

It's exactly the same for me. I never set the starting point on a tab, as that doesn't make any sense.

But I often use lead outs, otherwise you can immediately see the end of a milling path when milling acrylic glass. So, whenever I need polished edges, I use a lead out. This is often a spiral. The mistake of cutting off tabs is something that happens to me quite often.

[Bob La Londe]

That's a good catch.  I haven't used tabs in years because I tend to go for more creative work holding that eliminates the need for them, but there are a couple of jobs coming up where I might consider using tabs batching out insert plates. 

[dh42]

Hello,

Maybe I'm a maniac  .. or I have time to kill, but I always check my toolpaths visually and in perspective, I also always use the "toolpath view filter" to see how they link together ... and finally I do one (some !!) simulations with CutViewer ... belt and suspenders (not sure that this expression has a meaning in English lol)

++
David

[JG]

[...] simulations with CutViewer ... belt and suspenders (not sure that this expression has a meaning in English lol)
++
David

We would say "Belt & Braces"     essentially meaning that trousers are held up with a belt AND a pair of braces rather than one or the other - which would be the 'norm'.

[Bob La Londe]

I do look at 99% of jobs in CAMotics.  Sometimes several times before taking them to machine. 

Belt and suspenders is an older common English phrase.  Braces as suspenders is not a common English term in my small part of the world.  I've only heard a few times and only recently. 

[JG]

[...]Belt and suspenders is an older common English phrase.  Braces as suspenders is not a common English term in my small part of the world.  I've only heard a few times and only recently.

'Suspenders' are what women use to hold up their stockings - via a 'Suspender Belt'.

'Braces' attach to trousers at the top front, left & right sides, and go over the mans sholders attaching to the back in the centre.

I've also heard the term suspenders referring to small straps used to hold up mens socks - but only by those from the other side of the 'pond'

[Dragonfly]

'garter' is the word I know for 'suspender' and there is "Order of the Garter' as very distinguished award.
And I think it originates from French.