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Author Topic: making parts to size on customer prints  (Read 6713 times)

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Offline Hood

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Re: making parts to size on customer prints
« Reply #10 on: November 25, 2008, 05:13:01 AM »
I think Brian is about to do a major reworking of cutter comp but this could take a while as I would imagine its not an easy part of Mach to mess with.
Hood

Offline RICH

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Re: making parts to size on customer prints
« Reply #11 on: November 26, 2008, 11:20:37 PM »
Jimpinder,
Wanted to try out cutter compensation using my mill along with MACH & the SS so here are some screen shots.
The code contours a 1" x 2" rectangle and was generated with an .3" arc entry and exit and .2" dia mill.
I added the G40 & G41 as shown below. The tool paths were drawn onto paper using my tacer pen ( picture attached) while attached to the mill. By just adding a P value after the G41, ie; .001, .050, .1 you will get the different compensations.They are all plotted in attached picture.
RICH

Offline jimpinder

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Re: making parts to size on customer prints
« Reply #12 on: November 27, 2008, 03:15:07 AM »
Rich - yes - that is what I anticipated I would get, but, as I say, I kept getting the original without the comp. I notice you are using  a Px.********* command after the G41/42. Does G41/42 not pick up the cutter diameter from the tool table, or do we have to add this each time.

I was trying to use the tool table.
Not me driving the engine - I'm better looking.

Offline RICH

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Re: making parts to size on customer prints
« Reply #13 on: November 27, 2008, 06:34:01 AM »
Never used the tool table, but will try it out. Currently have V3.042.015 installed and been meaning to upgrade
it to the lockdown. So will try with both. First wanted confirm the Gxx Pxx worked. Will repost tomorrow as no time to fool around today.
RICH

BTW: With no tool changer it would seem just as easy to add or change the P value.
« Last Edit: November 27, 2008, 06:47:54 AM by RICH »

Offline ger21

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Re: making parts to size on customer prints
« Reply #14 on: November 27, 2008, 08:56:04 AM »
# different ways to use comp:

G42 by itself uses the diameter in the tool table of the current tool

G42 Dx use the diameter in the tool table of tool #x

G42 Px.xx where x.xx is the tool diameter.

It looks like in Rich's example code above it calls Tool #0, so I don't think you'd get any comp with tool #0 being the current tool. Unless you used the D or P option.
Gerry

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Offline ger21

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Re: making parts to size on customer prints
« Reply #15 on: November 27, 2008, 09:00:08 AM »
i am also under the impression that the wear offsets don't work.  is this correct?

No, the wear offsets in the tool table don't do anything.
Gerry

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Offline ger21

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Re: making parts to size on customer prints
« Reply #16 on: November 27, 2008, 09:33:14 AM »
in mach when starting cutter comp is it necessary to have both an x and y move?  or will just one of them suffice set cutter comp? 

Just one should be fine, but make sure the lead-in move is at least as long as the tool radius, and preferably in a location where the comp can be easily applied.

Here's how I'd code a simple arc with comp.

G40
G20
M3
G0 Z0.1250
G0 X0.0000 Y0.0000 Z0.1250
G1 X0.0000 Y0.0000 Z-0.2500 F50
G42P0.125
G1 X0.0000 Y0.3750 Z-0.2500 F150
G2 X3.0000 Y0.3750 Z-0.2500 I1.5000 J-1.8670
G40
G1 X3.0000 Y0.0000 Z-0.2500
G0 X3.0000 Y0.0000 Z0.1250
G0 X0 Y0
M5
M30

Just a note. Mach's comp has been constantly evolving over the past few years. In it's current incarnation, it can behave differently in different situations. Notice in the pic and code that I posted, how comp is applied. The tool moves along the programmed path, until it's diameter is tangent to the arc. At this point, comp is applied. Then, notice that comp is turned off when the tool's diameter is tangent to the lead out move. At one point, comp was applied the same way it is turned off in this example. The tool would move from the programmed start point, to a point where it was tangent to both the lead-in move and the first comped move.

Now, I did a little testing. Basically the same code, but without the arc. Notice now, the the way comp is applied and removed is exactly the opposite of the way it is with the arc. Now, comp is applied during the lead in move, moving to a point where the tool is tangent to the lead-in and the first comped move. But during the lead out move , the tool actually travels along the programmed path. Here' the code:

G40
G20
M3
G0 Z0.1250
G0 X0.0000 Y0.0000 Z0.1250
G1 X0.0000 Y0.0000 Z-0.2500 F50
G42P0.125
G1 X0.0000 Y1.1045 Z-0.2500 F150
G1 X3.0000 Y1.1045 Z-0.2500
G40
G1 X3.0000 Y0.5698 Z-0.2500
G0 X3.0000 Y0.5698 Z0.1250
G0 X0 Y0
M5
M30

Now, the last pic is a drawing I did showing how comp used to work, and how I hope it works again at some point. I believe that the comp should be applied during the lead-in move, and removed during the lead-out move, as shown in the pic. And hopefully it works the same whether the first comped move is a straight line or an arc, NOT diffeent as it apparently does now.
Gerry

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Offline RICH

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Re: making parts to size on customer prints
« Reply #17 on: November 27, 2008, 05:50:40 PM »
Gerry,
So i quess the best thing to do is take a look in a dry run as to how the compensation is applied by MACH.
OR     Is there a simple way to remember it all.
RICH

Offline ger21

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Re: making parts to size on customer prints
« Reply #18 on: November 28, 2008, 07:53:28 AM »
   Is there a simple way to remember it all.
RICH

For right now, I'd say just be sure to program the lead-in the same all the time. If you need to lead in to an arc, just you two lead in lines and two lead out lines. That should get you consistent results.

We'll see what happens when Brian changes the comp code. :)
Gerry

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JointCAM Dovetail and Box Joint software
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Re: making parts to size on customer prints
« Reply #19 on: November 29, 2008, 11:01:56 PM »
i have to run a few sample part by the end of the week so i will see how close i can get to the prints with the tolerances and the current mach setup.