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May 22, 2018, 01:19:14 am


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Author Topic: Disaster with a 3D profile, need some serious help  (Read 152 times)
jgmick
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« on: May 20, 2018, 18:02:21 pm »

Background:  Asked for some assistance in cutting a 3D profile.  Bubba stepped up and gave me back a .cb file that solved it.  Thank you sir for your help.

I fooled around with the file a bit trying to understand it better, decided to generate an ,NC file and just go cut some parts to see what I got.  I made a couple of minor changes (I think they are minor).  Changed "constant velocity" to "exact stop" (better accuracy but slower, good trade in my book).

What I got was a disaster.  I went back into the .cb file and did some measurements.  The file appears correct.  CamBam did NOT reproduce the part the same way.

If you look at the attached file and switch to viewing the part in the XZ plane you will see a circle that I just added to the drawing.  It has a radius of 0.375" and is tangent to the edge of the part pocket that I am trying to cut.  It is very obvious that the internal fillet in the part has the same radius.

The finished part has a MUCH smaller radius.  I didn't measure it exactly (no radius gauges) but it is about 0.150"

I had seen comments on the poor quality of the solid model and watched it as the roughing MOP was running.  I can clearly see facets in the part.  I had added a 2nd "waterline finish" MOP to the original file given me by Bubba since the one he supplied was set for "waterline roughing".   All I changed was from "waterline roughing" to "waterline finishing" in the 2nd MOP.  My thinking was that it would clean up the facets somewhat.  The tool path it produced in that MOP looked encouraging so I thought I was on the "right track" in doing that.  The finishing MOP did NOT actually do much to clear out those facets. (maybe a small cleanup.) So much for that theory.

I cut a 2nd part (raw stock is cheap, run time is about 55 minutes) but omitted (stopped short) of allowing the 2nd MOP to run.   Got the same undersized radius.  The problem is in both MOPs.

I went back and looked more closely at the tool paths generated while viewing them in the XZ plane.  I can pretty much see now that the end of the tool is following a smaller radius then the part profile.  Can't measure in that view to get exact numbers but it does appear that the tool path dives in more sharply than the part curve.  Didn't occur to me to look at that earlier. (Not sure I would have picked up on it anyway before the fact.  History is a wonderful teacher.)

At this point I am about off the end of the diving board with no life jacket.  I am enclosing the .cb file that I used for this.  If I made an error somewhere please advise.

What went wrong?


* Corner8_SAMPLE_B_Problem.cb (58.7 KB - downloaded 4 times.)
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EddyCurrent
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« Reply #1 on: May 20, 2018, 18:07:01 pm »

Try the file I posted here; http://www.cambam.co.uk/forum/index.php?topic=7355.msg59350#msg59350
called cube3.cb
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dave benson
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« Reply #2 on: Yesterday at 04:29:29 »

Hi Jim
this is an alternative way to do this job using 2.5 d with a slope profile.
because this takes some time to generate I used 1 mm increments, you can change this to suit although it looks pretty good as is.
Dave


* Slope profile for jim.PNG (121.83 KB, 640x418 - viewed 4 times.)

* Slope profile for jim2.PNG (500.31 KB, 1038x582 - viewed 5 times.)
* Alternative to 3d mop using slope profile for jim.cb (251.73 KB - downloaded 1 times.)
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EddyCurrent
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« Reply #3 on: Yesterday at 09:32:38 »

Dave,

Good alternative, I used the 3D method myself so that the same technique could be used on irregular slopes for example, but it's always best to have more than one method in hand.
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jgmick
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« Reply #4 on: Yesterday at 13:23:12 »

Eddy: 

No sale.  I downloaded the .cb file and generated the tool paths.  If I change the view to XZ plane it shows the tool path diving down more steeply than the curve in the part.  I think it's going to do the same overcut as what I had seen in my experiment.

Take a look at it in XZ and see if I'm reading that right.

Something I have been remiss on (shame on me):  I'm running (copied from Help>About):
CamBam plus [0.9] Rel 8N
Copyright © 2013 HexRay Ltd
CamBam.CAD : 0.9.4878.23990
CamBam : 0.9.4878.23992
Build Date : 5/10/2013 2:19:40 PM
Framework Version : 2.0.50727.5485

Not sure if that might be a factor.
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jgmick
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« Reply #5 on: Yesterday at 13:38:58 »

Eddy:

Ignore my last post.  Went back and looked at that again.  It does look OK.  That Z position of the tool endpoint has to appear to come down faster than the part curve.  It's cutting on the edge of the ball, the farther down it gets the closer it comes to cutting on the tip of the ball, the further up it is the more it's cutting on the flank of the ball.

Going to hack on it some to rotate it and fix some other stuff.  I need that corner in the lower left looking at it in XY.  Also have to sort out the inch/mm stuff.  Got an error message about tool library not found.  Not a surprise, I don't use a tool library,   If I can sort that out I'll try it.

Not going to be quick, I have to go see some folks about getting some eye repairs.
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jgmick
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« Reply #6 on: Yesterday at 13:59:43 »

Hacking away, got the part rotated and located correctly, scaling changed to inches, changed the rates, stepover, depth, etc. to what suits me.

Get 2 error messages when opening the file.

  Tool library "Mine-mm" not found (Q: Where is that library being invoked)
  Tool Index (35) not found  (Q: Where is that tool being called out)

I had changed the tool number to (0)

How/where do I change something to dump those messages?
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lloydsp
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« Reply #7 on: Yesterday at 15:41:52 »

Tool #0 is a 'special' tool number, which says, "Use the last tool explicitly called-out".

You need to give it something other than 0.

Your various 'libraries' are called in the system tab, Tool Libraries.  Styles are under system tab, CAM Styles.

Lloyd
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EddyCurrent
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« Reply #8 on: Yesterday at 17:25:02 »

I usually set the Tool number to 99 when posting cb files, I must have overlooked it this time.

Attached image shows where the tools are defined;

Manual - http://www.cambam.info/doc/plus/cam/ToolLibrary.htm

In the file you have modified a near tool size would be 1/4" ball nose



* Image3.jpg (237.74 KB, 800x1494 - viewed 1 times.)
« Last Edit: Yesterday at 17:27:02 by EddyCurrent » Logged
jgmick
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« Reply #9 on: Yesterday at 18:40:17 »

Now it's time to take one step back and think. (Good idea, I don't do it often enough.)

First, it finally dawned on me that the file you put up was your solid model, not mine.  What I actually gained from that is that you nailed the cutter path perfectly. That is actually all that I can get from it and also what I needed to know. (I.E. you can get there from here.)  Making that specific part would be useless.

Now comes the rub.  For the past week or so I have been trying to "reverse engineer" how you folks are crafting the tool path and extracting the pocket from the overall solid.  I haven't been able to do that and I don't think reverse engineering at that detail level CAN be done.  Part of this whole effort has been (at least on my part) in learning generically HOW to do the process.  Unfortunately there isn't enough depth in the CamBam HELP files, the tutorials, or the examples to get there from here.
I cannot use this forum as a subcontractor to do the work for me, I have to know how to do it.

About 15 minutes ago I took the scrap I made yesterday, went thru it with an 0.750 ball end mill on a full size mill and cut out 2 corners.  They look fine except that the XY axis radius is wrong.  How wrong is it?  It doesn't meet the design requirement.  Time to re-visit that particular design requirement.

This little science project is done.  Lessons learned: Don't try any more 3D profiling with CamBam until I have learned how to do it.

If there is some study material somewhere that you can suggest to allow me to learn it better (meaning that I can do this stuff) please point me to it.  In the meantime, I'm moving on.

General comment: I have been using CamBam for about 5 years.  I have made roughly 1000+ parts, mostly internal/external profiles, some pocketing, some engraving (great way to make simple printed circuit cards), a few drill ops.  It is working extremely well. A few warts, learned the work-arounds, stuff is getting done.  This is a really seriously "good bang for the buck" package.  I am a happy customer.

I profoundly thank all of you gentlemen who have offered assistance for this experiment.
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EddyCurrent
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« Reply #10 on: Yesterday at 19:07:53 »

Too many words for me  Wink

Here's my work flow.

1. create required 3D object in CAD software, Rhino3D in my case, save as stl file.
2. import stl into CamBam ( the stl created is the surface model included in my cb file )
3. apply 3D MOps using the most appropriate settings for the job in hand.
4. CamBam then does the work of creating all toolpaths.

No need to make it any harder than that.
« Last Edit: Yesterday at 19:12:33 by EddyCurrent » Logged
Bubba
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« Reply #11 on: Yesterday at 19:31:53 »

Too many words for me  Wink

Here's my work flow.

1. create required 3D object in CAD software, Rhino3D in my case, save as stl file.
2. import stl into CamBam ( the stl created is the surface model included in my cb file )
3. apply 3D MOps using the most appropriate settings for the job in hand.
4. CamBam then does the work of creating all toolpaths.

No need to make it any harder than that.

That's exactly how I go about things, except I use ViaCAD, or purchase 3D model.
Occasionally for 4th axis work, CB created code is wrapped Wink
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