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Messages - Kingjamez

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1
LazyTurn / Re: School me on tip radius.
« on: January 23, 2011, 03:17:05 PM »
Hi Rich,
Thanks for the exceptionally complete reply. I'm known to be dense to please bear with me.

It seems that your are making the argument in the PDF that the final pass is offset correctly in regard to the tip radius. I 100% agree. The point I was making in my first part of post #2 is that when I touch off on my work piece, that is NOT the zero point (as it is on a Mill). If I touch my tool to the work piece in the X direction, and I'm using a tip radius of 0.0156", then my tool center is actually at a point 0.0156" from the radius of the stock.

 Example: I have a 1" bar. I touch my tool in the X direction to the stock, the actual location of the center of the tool is 0.5156". At least that is what I got from the manual (and your well made pdf). That works for me and I'm getting accuracies of about 0.0005" in finished diameter.

I believe that we are in agreement on the issue above.

Now to the issue I wrote of in post #2. Attached is my .dxf and .tap. I'm in radius mode. Note that the first cut is at X=0.475" when (from my understanding) it should be at 0.475+0.0156=0.4906 for a true 0.025" first cut.

When I run a program like this, my mill (lathe mode) nearly comes apart because the first cut is so deep. All subsequent cuts are smooth.

I'm quite certain that I'm just not getting it...

-Jim

2
LazyTurn / Re: School me on tip radius.
« on: January 23, 2011, 12:04:48 PM »
Hi  Rich, thanks for the help. I'm now able to get accurate diameters by offsetting the tool the radius of the tip.

Another issue has come up though. It seems as if LT compensates for tip radius on the final cuts, but not on the first pass.
To demonstrate, here is how to duplicate my issue:
Import a straight line that will result in a .5" diameter cylinder. Now set the stock size to 1" and use a tool with a 1/64" radius. Then set a roughing tool path with  0.025" per pass. The first roughing pass will be at X0.475 which would be correct with a 0 radius tool, but not correct with a 0.0156 radius tool that ends up making a first cut pass depth of 0.0406" in reality because of the offset of the tool radius.

My work around is to specify a diameter of my stock larger than it actually is by 2 radii of the cutter. That seems a little kludgy.

So now that you see what I've done, what am I doing wrong in my set up?

3
LazyTurn / School me on tip radius.
« on: January 12, 2011, 07:38:11 PM »
I'm making some parts now with LT. I love free CAM!!! However, I'm having a little problem with tip radius and how to use it. My parts are coming out to big. The radius of the parts are always the correct diameter of the part plus the tip radius.

Perhaps I'm zeroing the tool incorrectly. I'm zeroing the tool so that the tip of the tool touches the stock. I measure the stock and put the radius of the stock as the position that the tool is on the X axis.

I'm new to CNC turning so if I'm missing something obvious, please be gentle.

-Jim

4
LazyTurn / Re: Inscribed circle, what am I missing?
« on: December 16, 2010, 09:18:16 AM »
I'm sorry , that last post was not intended to berate Rich. I was just frustrated that he continued to say the manual was correct as written despite all my efforts to say otherwise. So I over reacted as is so easy on the interweb.

I do sincerely appreciate all of Rich's contributions. I have read many many of his posts while learning LT and they have been exceptionally valuable. The manual is well written, and provided all the info I needed to get turning.

-Jim

5
LazyTurn / Re: Inscribed circle, what am I missing?
« on: December 15, 2010, 08:19:07 PM »
Thanks for the clarification Art,
So noted in my manual ........page 16

RICH

As I have been saying for this ENTIRE thread, rev 8 of the manual DOES NOT say that!!!!! The manual says over and over the EXACT OPPOSITE of the definition given by Art above. I don't know how I can say that any more clearly so that you'll get it.

-Jim

6
LazyTurn / Re: Inscribed circle, what am I missing?
« on: December 02, 2010, 09:58:36 PM »
Yep, I agree completely. The tolerance should absolutely be accounted for. In my case I'm using a diamond profile insert so, yep, as long as the angle, and tip radius is correct I should be good to go.

Square cutters at 0 degrees (and perhaps trigon) would need to be accurately defined.

Let me know what you find. When I use 0.379 on a 35 degree diamond as the inscribed circle as per one of the figures in the manual, the tool generated by LT is well over 2" long.

-Jim

7
LazyTurn / Re: Inscribed circle, what am I missing?
« on: December 02, 2010, 07:58:08 PM »
Hi Rich, I'm reading from rev 8 as well and I quoted it in the third post in this thread. Does that quote match the current wording? To me rev 8 goes out of it's way to very clearly state that the external circle is the correct measurement. Your right that the figures posted in the thread linked to by Overloaded are exactly the ones used in the manual. Art says right underneath that the figure is incorrect. in the manual I have the text says the red circle is the circle used by LT. From my use of it so far, and from Arts post, I don't believe it is. 

Unless of course I am being dense and don't understand the manual and have very clearly read the completely wrong thing.
-Jim

8
LazyTurn / Re: Inscribed circle, what am I missing?
« on: December 02, 2010, 06:21:11 PM »
Hi Rich,

Quote
"The definition is as stated and shown in the link by Overloaded in the manual."

I guess I'm confused now. The definition in the manual, is very different than the post linked to by Overloaded. The manual says the EXTERNAL circle radius is used. However the most recent version of LT clearly uses the INTERNAL circle radius.  See the graphic I attached in the first post for proof.

-Jim

9
LazyTurn / Re: Inscribed circle, what am I missing?
« on: December 02, 2010, 01:26:34 PM »
Excellent. Thanks for finding that Overlord!


10
LazyTurn / Re: Inscribed circle, what am I missing?
« on: December 02, 2010, 12:52:16 PM »
Hi Dan,
Thanks for the help. When I read page 16 of the manual, it's pretty clear that LT's definition of inscribed circle is not the same as the standard definition for inserts. The verbage straight from the manual says:

"2. Inscribed Circle - Defines a circle, which when drawn about the center of the tool insert, will include the entire tool insert."

However, the actual behavior of the program is working as you describe, a circle that fits completely within the insert.

-Jim

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