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> Fixtures with DXF files.
rtp_burnsville
post Jun 3 2009, 10:16 PM
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Hi Guys,

Here is a new issue for all to ponder. Yes, I have more than my fair share of these!

Today's adventure involves doing a 2D contour of an object imported via a DXF file. Being the part needed to be fixtured I thought it would be a good time to learn a bit more about the fixture feature in SC.

I created a fixture as a DXF file much like I do for some of the contouring things I do. Everything went as planned until I ran the simulation of my part with fixtures placed as they would be in the mill. Well, much to my surprise the 2D contour plowed right through the fixtures just as if they did not exist.

After much messing around I thought I would cut some air on the mill just to check my sanity. The G-code did not lie and proceeded to cut where the fixtures were to have been placed. Good thing I simulated the part and checked the G-code before actually cutting metal as I have done in the past.

My question is; Has anyone tried to create 2D fixtures using a DXF file and then perform a machining operation with success??

I have used a 3D (iges format I believe) fixture in the past and it worked as expected. I thought I would check to see if someone else has tried a 2d fixture before reporting this to SC.

Currently using SC version 5.51. I will attach my files a bit later.

Thanks,
Robert
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Sprut_UK
post Jun 4 2009, 05:43 AM
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You don't say whether the collision is with 'rapid' or 'feed' moves?
Currently, SprutCAM does not modify 'Rapid' moves to avoid a fixture only 'Feed' moves. Normally you would always set the 'Safe plane' height to be above everything else i.e. Part - Fixtures etc. and you would never get a collision.
When extruding 2D fixtures it's good practice to make sure that the geometry being used is closed (joined).

If you've checked all of the above and are stuill having a problem, post up you files and I'll take a look.

Dave


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rtp_burnsville
post Jun 4 2009, 09:19 PM
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Hi Dave,

Thanks for the response, I believe what you mention is being done correctly: Feed moves, safe plane should be set, and the elements should be closed.

That is good info to know that fixtures are ignored on rapid moves...

I will attach my project file..... Thanks as always for your assistance.

Robert
Attached File(s)
Attached File  Kplate_Final.stc ( 51.24K ) Number of downloads: 4
 
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Sprut_UK
post Jun 5 2009, 07:54 AM
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Robert, I've taken a look at your project, and I could see that you had added two curves to the fixture list, but these will not work as fixtures like this. What you must do is extrude the two curves to the required height / depth. You will see the two fixtures displayed as solids once you do this.
I also noted that on the second operation (2D Contouring) you have the Job Assignment curves set to Offset output AND Compensation.......this could cause problems unless you are using a postprocessor which doesn't have the cutter radius compensation feature (G40/G41/G42) enabled.......?

Dave


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rtp_burnsville
post Jun 5 2009, 01:23 PM
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Hi Dave,

Thanks for taking a look at my project......

So if I understand correctly; To have an item become a useable fixture it must be a true 3d item and not just a 2d curve representing the fixture. I will guess that the height of the fixture just needs to be something greater than 0 as would be in the case of a 2d drawing. It would also make sense then to have the safe area to be greater than the height of the fixture. The later would prevent a rapid move from hitting the fixture.

Note taken on the offset and compensation as well...

So many things to remember but I am making good progress through all the unknowns.

Thanks Again,
Robert
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