Messages

301

General Mach Discussion / Re: Cutter Compensation

« on: October 23, 2008, 11:37:23 AM »

Ok guys. Give me some time to absorb this. I'm still perplexed by the actions of Gerry's code.

Any further thoughts on why Mach is screwing up on my code as described and posted a couple of messages back?(Sage_comp2).

I can learn more about what I should and should not do by understanding why something doesn't work i.e. my code.

Maybe I'm wrong?

Sage

302

General Mach Discussion / Re: Cutter Compensation

« on: October 23, 2008, 06:40:52 AM »

Graham:

Reply / additional options / attach    is how I attached the file. What I don't know how to do is attach a screen shot. My problem was getting the print screen into a jpg (or the many other acceptable forms listed) to attach. I don't see a tool to insert a screen shot. The usual Paste didn't work after doing a shift-prntscrn.
Please enlighten me.
Sage

303

General Mach Discussion / Re: Cutter Compensation

« on: October 22, 2008, 10:43:36 PM »

ger21:

Thanks for that. I see it's a lot more complicated than I thought and that a lot of planning went into your code. This perplexes me quite a bit because, being that I'm just learning, I'm reading a lot of different books, and so far, I gathered that the tool compensation is something that is used to quickly make changes to a program to accommodate, for, say the fact that you may only have a 3/8 cutter instead of a 1/4 cutter or maybe something as small as a worn tool. I imply from this that cutter compensation should work (with obvious limits) on almost anything. Far cry from the tedious planning you have applied in making a complete program around tool compensation.
 I can see that the compensation works on your program but what of the real life situation such as mine where I take an otherwise properly functioning program and add cutter compensation for a perfectly good reason i.e. to add some roughing cuts to the path??
This is why I am more interested in figuring what is wrong with my simple program rather than generating something new that actually works.

BTW
Using your ideas and to see what could be done with my code, I added some simple code to take the tool on a little tour well outside the part and back again. I added only .020 compensation to tool #1 and I can see that it goes around the touring lines with the offset visible just fine. SO there is something in your "rule" about moving more than the cutter diameter. Lesson learned there.
BUT the path is still screwed up in the bottom left corner where it does not seem to go far enough in -X to clear the original path. This screwup is far remote from any of the lead in/out code. I can't figure out why it messes that up.

Still perplexed about the usability of the cutter compensation function for what (I thought) it was intended.

I've attached the modified file. Try it with 0.0 and then .020 tool #1 compensation. Look in the bottom left corner, left side and top left corner.
I'm sure I'm getting poor old Mach confused somehow. I'd like to know where.
(not sure how to attach a screen shot).

Thanks for you help in getting me to understand this.

Sage

304

General Mach Discussion / Re: Cutter Compensation

« on: October 22, 2008, 08:54:17 PM »

ger21:

Thanks for that. It's pretty cool. I'll have to analyze it though because I see that you have drawn "horns" on the corner of the part but they aren't even used in the resulting tool path. So I'm a bit confused how the tool path was created unless the compensation function created it's own path based on whatever it saw fit. Then I have to ask why did you make the "horns" with 45's on them when straight lines out from the corner - your suggested two cutter diameters or so  - would have sufficed.

I get your point though about the lead in/out needs to be bigger. My little attempt at that was an after thought just to stop the divot that was giving me trouble. I didn't know it was going to be a problem with the tool offset - also an after thought.
You'll notice that my little lead out is a relative move away from the part and I expected it to always be the proper amount since it was relative. I guess it was just to small.

Let me look it over and analyze what going on bit more.

Thanks

Sage.
 

305

General Mach Discussion / Re: Cutter Compensation

« on: October 22, 2008, 06:22:19 PM »

Graham:

The best I can do is give you a DXF of the original drawing (attached). But it's been through a lot to get where it is (posted previously)
The process I followed (with great pain) is as follows:

I used LazyCam to create an outside offset so I could cut the profile with a 1/8 cutter.
I used LazyCam parameters to make it take multiple .020 passes. To .380 depth,
That's basically what you see if you don't add any cutter compensation to what I posted.

After each pass it stops and plunges another 20thou but that left a divot on the side of the finished part so I manually added the little 45 angle to the side to get away from the part a bit to plunge and then return.
It had to be run pretty slowly otherwise the cutter would get in trouble when cutting at depth (.380).
I decided I could speed it up if I used a 1/8 hogging mill to get most of the metal out and then use a standard mill to do the finish cut.
Rather than go back to LazyCam and create another offset for the rough cut I figured I would just use the cutter compensation to make the rough passes and call the subroutine again without the compensation to do the finish pass(es).

Having said all of that I hope you understand what I'm doing. I have no doubt that you can write a whole new program.

BUT

I have to ask. The program I posted is pretty simple and it works fine without the compensation. Rather than spend your valuable time creating something that is completely different. It may be more beneficial to the understanding of the problem to figure out what's wrong with my program. There must be some aspect of it that Mach does not like and it might point to a problem that needs to be fixed in Mach (or not). Or that will help me understand the programming pitfalls.

Suit youself, you know a lot more about this than I do.

Thanks


BTW this is only a simplified version of the real part I need. Reduced to the simplest version that exhibits the problem.
Sage

306

General Mach Discussion / Re: Cutter Compensation

« on: October 22, 2008, 12:34:40 PM »

The path is fine sharp corners and all until you apply the compensation. Have a look at the path generated by my code. In the bottom left corner the compensation dissapears all together which sets it up for the next corner to be cut off as described.
I put a G61 in the program and also set "stop CV on angles > 45" in general config and no difference.

Sage

307

General Mach Discussion / Re: Cutter Compensation

« on: October 22, 2008, 11:01:51 AM »

I think I have another example of the problem with cutter compensation. My program isn't the most elegant to begin with so I'd appreciate it if someone would see if it's my problem or Machs.

Load the attached Gcode.
Be sure to set tool 1 in the tool table to have 00.00 compensation so you can see what the basic pass should look like.
Zoom in at the top of the profile and you'll see I have a very small diagonal tool path to get the tool away from the part so the plunge does not leave a mark.
If you run the program you'll see the path is fine and the tool goes off the part, plunges, and comes back in and goes on its way. You can watch it runs this path several times fine going off part on each pass ok.

Stop it, Set the toll offset for tool 1 to say .020. Save. Regenerate the tool path and run again.

This time the tool still goes off the part ok on a diagonal but when it comes around for the second pass it follows a different diagonal to get to the end of the leadin line and exits on the old path (effectively missing milling some of the part). The bigger the tool offset the larger the angle in and out of the diagonal (and the more of the part that's missed).
  If you pan left over to where the tool changes direction from coming up the left side to where it comes across the top, you can see it does that corner on a diagonal instead of square. This chops off the corner of the finished part.

My problem?

Sage

308

General Mach Discussion / Re: Abnormal Condition warning

« on: October 19, 2008, 10:11:47 AM »

Great work guys. Being a rookie I do all kinds of sins starting and stopping not so good Gcode in order to perfect my programs. I've seen some strange things happen. I usually just restart everthing to get out of the situation. SOmetimes it works , sometimes it doesn't fully help.
It looks like this macro should make things more predictable. I'll give it a try.

Keep the improvements coming. I'm learning all the time.

Thanks

Sage

309

General Mach Discussion / Re: Abnormal Condition warning

« on: October 18, 2008, 12:53:11 PM »

Chip:

Between what you and Rich wrote the light suddenly went on. When troubleshooting the program I quite often stop it right in the middle and go to edit code then go back to try again. I can see now that doing that can be a problem. I think I usually have some pre-amble code at the beginning as I usually adopt code from LazyCam which does generate some. This time (and becasue I'm actually leaning a bit) I just used LazyCam to get the geometry and wrote the rest myself.
 From now on I'll pay better attention to the pre-amble code. Thanks.

 This begs another comment though. I would have thought that Mach should clear everything back to some pre-set configuration parameters when you clear the  G-code and reload a new program,  OR at the minimum when you clear the code and specifically push the reset button or something like that. This does not appear to be the case. I tried all that.
 So unless you have endless pre-amble code to cover every possible setting that could have been manipulated by another program, how do you ever return to a fresh start condition? I'm not even sure re-starting Mach clears some stuff. Maybe I missed something in the configuration.

Sage

310

General Mach Discussion / Re: Abnormal Condition warning

« on: October 18, 2008, 10:13:29 AM »

Ok I'll do some reading. RTFM as they say.  Since you say it saves the previous state this may explain why it could load fine sometimes and complains at other times (for me anyway) after runnning some other program in between. But it doesn't really (I don't think) explain why loading it multiple times in a row it can load once bad an the next time fine.
 I posted the code  at the beginning of this thread. Would you have any specific suggestion what should be set up to ensure proper loading?

It's a simple program. I can't see any possibly confusing parts.

Sage