Having trouble with touch off

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23 May 2012 19:04 #20308 by andypugh
Chipmunk wrote:

I then invoked G53 again and all off the axi's went to the home position.

There is no need to use G53 at all, my machine is permanently in G54.

I then was greeted with another error message (Linear move on line 5 would exceed joint's positive limit.)

You should see a red box in the preview, does your preview plot go outside of it?
Maybe T1 is very long? Have a look in the tool table. (though with no G53 that probably doesn't matter). You can see the tool offsets in a little box at the bottom of the screen.

Normally I think it tells you which program line the axis limit is exceeded in.

The more I think about it, the more I think this is a tool length offset problem.

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23 May 2012 19:24 #20309 by BigJohnT
For readability I don't put tool changes on the preamble line.

Also note that you did not load the tool length offset.

I would structure my program similar to the following and note that I didn't use the % and prefer to use M2 to end the program for some unknown reason:

G17 G20 G40 G49 G54
M6 T1 G43
M7
...
M2

When you touched off the tool to the material did you take into account the tool radius along with your feeler gauge?

Have you read my tutorial on setting up material in your mill?

John

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24 May 2012 07:06 - 24 May 2012 07:49 #20315 by cncbasher
which post processor are you using with cut2d ?
and after homing are you setting the z axis to the top surface of the work and setting to work z0 touch off etc ?
if not then that is the reason for the exceeds limits error
Last edit: 24 May 2012 07:49 by cncbasher.

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25 May 2012 02:42 #20362 by jmelson
OK, the move exceeds limit mans the machine is not properly set up. Do you have home switches?
If not, you really should set up one of the methods of homing the machine to limit switches.
Once you have the machine homing to a repeatable position, then move the machine to
the limits of mechanical travel and observe the coordinates in the machine coordinate system
(G53 or I think pressing the @ will display that coord system.) You will apparently have to
expand the limits in the .ini file where you have MIN_LIMIT and MAX_LIMIT in the axis
that is hitting the limit (Z is the first one, but you may have others when you clear this one
up.) Once you know the limits of travel, then use these values in the .ini file for
MIN_LIMIT and MAX_LIMIT. Then, as long as your workpiece and program fit in
these limits, you should not get these messages anymore. The great thing about
setting all this up is that when you load a part, touch off and then load the program,
you will get a message if the program would exceed the limits before you even hit run!
You then can reposition the part before starting so there will be no problem.

Jon

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25 May 2012 03:09 #20363 by Chipmunk
Hello

cnbasher I am using EMC2 Arcs (inch) * ngc for my post processor.

Jmelson You are correct in saying that my move is outside my machine coordinates. It was not the setup of the machine it was a bad entry in the Cut2D material size. I inadvertently put in a to large value in G0Z0 .7854 this value was outside of the box and gave me the error message. I reduced this value to .125 and the program started running quite happily. The reason I did not have a problem when I was cutting air was because I did not do a touch off from my vise which is about 4 inches above the table. Given that I only have 5.75 inches of Z travel, it made my upper limit very close to the top of the work area box. I need to purchase a vise that does not take up as much room.

BigJohnT Also I did not take into consideration half the diameter of my tool bit when setting my touch off. I re read the article on touching off, it is surprising how much comes to light during subsequent readings.

In summary I made my first part this evening and it worked out very well. Thank You Folks for all of your help without it I would still be struggling.

From a Happy Chipmunk who finally made some chips.

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25 May 2012 10:01 #20378 by andypugh
Chipmunk wrote:

this value was outside of the box and gave me the error message.

Gosh! An error message reporting an actual error, there's a shock.

I need to purchase a vise that does not take up as much room.

There are alternative hold down methods that might help:
www.ebay.co.uk/itm/2-Piece-Milling-Vice-6-/290704086009 (we only spell "vice" one way in the UK)
www.wdsltd.co.uk/products/Standard-Parts...DS-218-Edge-Clamp-9/
www.wdsltd.co.uk/products/Standard-Parts...mp-Mitee-Bite--1364/
In fact, you can double or triple your investment in your machine with fixtures and clamps. With all of those you might want to put a layer of board or card under the work piece to cut in to, instead of the machine bed.

From a Happy Chipmunk who finally made some chips.

And very glad we are to hear it.

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25 May 2012 11:42 #20385 by BigJohnT
Chipmunk wrote:

From a Happy Chipmunk who finally made some chips.


I love it when a plan comes together.

John

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26 May 2012 00:00 #20403 by Chipmunk
I must say that I didn't get an actual error message, what I noticed was a box outside of the work area and was outlined in red with the .7854 number in it. This made me do some searching to find out where the number came from. I eventually found it in the material sizing criteria of CUT2D ,it was listed along with the home positions for X and Y which were both at zero and Z which was at .7854. I reduced this value to .125 in order to match the safe clearance which was also at .125. I tried to set Z at zero but the program complained so out of expediency I set it at .125.

We have an outlet called Busy Bee, they sell a vise which is about the right size for my mill, It has a jaw opening of 3 inches, and a width of 2 inches,
I have a have a much larger version of the vise on a manual knee mill and I am very happy with it. It is made out of solid steel and sells for $79.00.

I will check out the links you sent me to see what they have to offer. I also want to make a fixture mounting plate instead of using the t slots in the table.

Yes it is always nice when things come together and one can move on to other areas.

Thanks Again

Chipmunk

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