Author Topic: DXF Import circle diameter inaccuracy  (Read 2857 times)

Offline shorton

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DXF Import circle diameter inaccuracy
« on: August 01, 2021, 22:21:26 pm »
I teach a high school robotics program and this season we started using Fusion 360 for CAD.  When I export a a DXF with a specific hole size, CamBam is seeing it as a slightly smaller hole.  The hole is designed at 0.125", CamBam shows it as "0.12499999999999994".  I use a .125 tool and so if I try to drill a .125 hole with the tool I get an error.

My first assumption was it was F360 causing the problem, and it may be still.  For what it's worth, I opened the same DXF in my old CAD software and that shows the hols as 0.125, correctly.

The problem is reproducible.  I've attached a sample export with the offending hole.

Recommendations for a fix or workaround?



Offline shorton

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Re: DXF Import circle diameter inaccuracy
« Reply #1 on: August 02, 2021, 03:30:56 am »
I looked inside the DXF.  Problem is with Fusion360, it coded the hole size wrong.  Appears to choke on imperial units, no error on metric.  Alas, my tooling is imperial.

Offline Dragonfly

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Re: DXF Import circle diameter inaccuracy
« Reply #2 on: August 02, 2021, 07:31:45 am »
With the hole diameter and tool diameter the same the only drilling method is 'canned cycle' (peck drilling). And in this case CamBam will not complain and will generate the required code.
Actually you can use a smaller or lager physical drill in the actual drilling process.

Offline EddyCurrent

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Re: DXF Import circle diameter inaccuracy
« Reply #3 on: August 02, 2021, 14:28:50 pm »
It's opening up for me at 0.125 there may be a setting in CamBam options that does it.


« Last Edit: August 02, 2021, 14:30:23 pm by EddyCurrent »
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Offline shorton

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Re: DXF Import circle diameter inaccuracy
« Reply #4 on: August 02, 2021, 14:46:57 pm »
Now THAT is interesting.  I literally looked in the DXF file (with text editor) and the dimensions there are the 9 decimal place wrong version.

I wonder why my CamBam displays all the digits in the properties column.  Is there a setting somewhere I can adjust?

My version:
CamBam plus [0.9] Rel 8P
CamBam.CAD : 0.9.5729.19316
CamBam : 0.9.5729.19317
Build Date : 9/8/2015 11:43:52 AM
Framework Version : 2.0.50727.9151


« Last Edit: August 02, 2021, 15:00:58 pm by shorton »

Offline shorton

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Re: DXF Import circle diameter inaccuracy
« Reply #5 on: August 02, 2021, 14:49:42 pm »
With the hole diameter and tool diameter the same the only drilling method is 'canned cycle' (peck drilling). And in this case CamBam will not complain and will generate the required code.
Actually you can use a smaller or lager physical drill in the actual drilling process.
Thanks, I hadn't run CamBam in a while and didn't remember that I couldn't do a normal (spiral) drill with a hole=tool.  And peck is OK with the discrepancy.  SO that's good.  But I'm really wondering why @Eddycurrent 's setup is showing differently.

Offline shorton

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Re: DXF Import circle diameter inaccuracy
« Reply #6 on: August 02, 2021, 15:24:45 pm »
Well, this morning I opened the attachment form my OP, it showed .125".  Weird.  I made another one and it had the error.  Made a 3rd and it did not have the error (Inside the DXF) so clearly F360 has some inconsistencies in rounding going on.

Oh well, I'm not going to worry about it.  I have to peck drill anyway so I'm good.  Screenshot of bad one FYI:




Offline Bubba

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Re: DXF Import circle diameter inaccuracy
« Reply #7 on: August 02, 2021, 15:25:00 pm »
Why are you using older version of CamBam?
« Last Edit: August 02, 2021, 15:26:34 pm by Bubba »
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Offline shorton

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Re: DXF Import circle diameter inaccuracy
« Reply #8 on: August 02, 2021, 15:27:58 pm »
Cause I didn't know v1 was released till a few minutes ago.  Auto-version check didn't pick up on it.  It's so f'ing rock solid stable I dare not mess with what works LOL.  One of my FAVORITE pieces of software.  Wish everyone's worked like it does.


Offline dh42

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Re: DXF Import circle diameter inaccuracy
« Reply #9 on: August 02, 2021, 15:30:05 pm »
Hello

Quote
It's opening up for me at 0.125 there may be a setting in CamBam options that does it.

Same for me on both 0.98P and 1.0 (Win versions) ... and I can't see any setting for that ...

++
David

Offline shorton

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Re: DXF Import circle diameter inaccuracy
« Reply #10 on: August 02, 2021, 15:36:51 pm »
Hello

Quote
It's opening up for me at 0.125 there may be a setting in CamBam options that does it.

Same for me on both 0.98P and 1.0 (Win versions) ... and I can't see any setting for that ...

++
David
David, try this one, I just verified it was "wrong" on my end, and CamBam shows it as wrong (not quite .125).  Just curious.

Inside the DXF is has the radius, which F360 should have made 0.0625
Code: [Select]
AcDbCircle
10
0
20
0
30
0
40
0.062499999999999986



« Last Edit: August 02, 2021, 15:45:11 pm by shorton »

Offline dh42

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Re: DXF Import circle diameter inaccuracy
« Reply #11 on: August 02, 2021, 15:43:32 pm »
Yep, I get 0.12499999999999999 in CamBam with this new file.

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David

Offline shorton

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Re: DXF Import circle diameter inaccuracy
« Reply #12 on: August 02, 2021, 15:47:21 pm »
David, thanks for checking.  Inconsistent behavior in F360.  Alas, it is not a problem.  I had forgot the peck operation wasn't fussy about the tool size mismatch, I had originally set it to spiral.