I tried setting G64 Q and P to high or low values. Low values gets worse 
squarier results of course, no value small amount gets the path followed 
even close to the previewed path.
I tried increasing acceleration and velocity to 1000 and 10000 in the .ini
I tried with and without G61.

No change. Previewed path looks good, actual path followed does not come 
close

Any other suggestions ?
Can somebody tris this program on the sim or a real machine ?

Thanks,

Bruno

On 5/31/14 8:20 AM, bruno wrote:
> Here is a much simplified test program using the values output from my 
> routines and test.
> If someone can help me figure how to make the tool follow the path 
> shown in the preview, I would very much appreciate that !
>
> I tried on the actual mill, with G61 enabled causes lots of stop and 
> go but the trajectory is still completely wrong and goes way off to 
> the side. Same as on the sim.
>
> Bruno
>
> ;;;;;;;;;;;;;;;;;;;;;;;
> ;
> #<mill_number> = 5
>
> ( some init )
> G21 (Unit in mm)
> G90 (Absolute distance mode)
> ;G64 P0.005 (Exact Path 0.001 tol.)
> G61
> G17
> G40 (Cancel diameter comp.)
> G49 (Cancel length comp.)
>
>
> G54
> G0 X0 Y0 Z0
>
> ( select endmill )
> T[#<mill_number> ] M6
> G43 ( enable tool length compensation )
> G0 Z5
>
> F300
> ;;;;;;;;;;;;;;;;;;;;;
>
> G0     X[[0.000000 - 0.000000] * 0.943750 + 0.000000] Y[[40.000000 - 
> 0.000000] * 0.943750 + 0.000000]
>  G5.2 X[[40.000000 - 0.000000] * 0.975000 + 0.000000] Y[[40.000000 - 
> 0.000000] * 0.975000 + 0.000000] P[356.124661] L3
>      X[[40.000000 - 0.000000] * 0.975000 + 0.000000] Y[[0.000000 - 
> 0.000000] * 0.975000 + 0.000000] P[356.124661]
> G5.3
>
> M2
>
>
>
>
>
> On 5/30/14 8:03 PM, [email protected] wrote:
>> ------------------------------
>>
>> Message: 2
>> Date: Fri, 30 May 2014 17:29:28 +0200
>> From: bruno<[email protected]>
>> Subject: [Emc-developers] bug with nurbs ?
>> To:[email protected]
>> Message-ID:<[email protected]>
>> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>>
>> Hello,
>>
>> I wrote a quadrangle pocketing routine in G-Code which uses nurbs
>> (G5.2). The motivation for this is that I dislike the current ngcgui
>> routine (qpocket) for a couple reason. When qpocket cuts from one quad
>> to another, "spiraling out", it actually cuts a scaled quad, then adds
>> one edge where it slowly cuts toward the next scaled quad. That cut is
>> really slow and is superfluous if the cut was really following a quad
>> spiral instead. Second, and most important for me, the cut fully digs in
>> on each corner (depending on the angle of the corner of course, but
>> generally it is pretty big).
>>
>> So the width of cut goes from the overlap set for each pass, to almost
>> the full endmill width. Maybe not important on a big mill, but I have a
>> mini-mill and I like to try to cut at full depth if possible and with
>> very small overlap, on many fast passes, it gives (I think ) better
>> finish and wears the mill more evenly. (kind of like with adaptative
>> clearing). So the way corners are cut is really a problem with qpocket.
>>
>> Here is the fruit of my experiments using nurbs, pasted below. The nurb
>> weight are scaled with an exponential as the path comes closer to the
>> final pocket shape, to (un)round the corners progressively. The function
>> is parametrable.
>>
>> The preview looks great, however, when running it, I get a path that
>> does not follow the previewed path ! And I see no reason for the massive
>> divergence from the programmed path. See a screenshot here:
>>
>> http://imagebin.ca/v/1OCw5gNzXQBF
>>
>> http://ibin.co/1OCw5gNzXQBF
>>
>> notice how the purple path has "wobbles" in some sections, which go way
>> aside the previewed path.
>>
>> I tested with the sim on linuxcnc 2.5.3
>>
>> At first sight it really seems to be a bug as the preview looks correct.
>> Could anyone test this on their setup ? Is there an explanation for 
>> this ?
>>
>> Thanks !
>> Bruno
>>
>


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