Start Point

Start Point

Postby BernieNUFC » Thu May 21, 2015 8:23 pm

Hi
Forgive me if not in the right place but after looking at cnczone i think my head would explode with the choices before i wrote my question :)

So, as i am new here and setup with high-z 730, my wood in place and i need the cuts to be accurate (obviously) i put the first mill in the router and set my xyz start zero point
I understand resetting the z each time i change the tool but i got to thinking, surely my xy zero must change fractionally from when i use a large clearing tool to a smaller finishing tool due to teh diameter differences, so how do i get the centre of the tool exactly at the zero point each time?

thanks
malc
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Re: Start Point

Postby Adrian » Thu May 21, 2015 8:34 pm

Everything is calculated from the centre of the tool and that stays the same regardless of the diameter so you don't need to reset the XY between tool changes only the Z.
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Re: Start Point

Postby calgrdnr » Thu May 21, 2015 8:35 pm

x 0 y 0 will not change that is the center of the tool :)
only need to rezero z as you wont put next tool in exactly as first tool .
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Re: Start Point

Postby BernieNUFC » Thu May 21, 2015 8:39 pm

Thank you for replies
so i get most of that but what i am thinking or missing is if i put a 1mm down i can visually get it bang on but if i were to put a 6mm for instance i would not be able to see the centre of the mill just the circumference of the bit and i could out with my eyes :D , am i missing something obvious here?
cheers
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Re: Start Point

Postby Adrian » Thu May 21, 2015 8:50 pm

I zero my machine using the limit switches and then it set the XY zero as a fixed offset from there which lines up with the corner of the 8x4 sheet.

When I used to do smaller work I used copper plumbing caps (wired into the Z zero plate) fitted to t-track jigs and a routine that centred the bit in those. Lots of people use a laser pointer on the Z axis with a routine to set the actual XY as an offset from there.

Basically loads of different ways to skin the cat.
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Re: Start Point

Postby BernieNUFC » Thu May 21, 2015 8:54 pm

Adrian wrote:I zero my machine using the limit switches and then it set the XY zero as a fixed offset from there which lines up with the corner of the 8x4 sheet.

Basically loads of different ways to skin the cat.


Going to figure this one a give it a try, sounds good to me
thanks
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Re: Start Point

Postby Rcnewcomb » Thu May 21, 2015 9:57 pm

Another method is to put a V bit in your router to set your X0Y0, then switch to your other bits since X0Y0 won't change

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Re: Start Point

Postby BernieNUFC » Thu May 21, 2015 10:01 pm

Hi randall

I just went out and used my v cutter as you shown and set the point and i am pleased you also showed it as i now feel confident about setting my zero'snow

thanks all
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Re: Start Point

Postby calgrdnr » Thu May 21, 2015 11:42 pm

I like Rcnewcomb use a v bit, normally the 30 degree bit and Zero all three axis's. Start the router and then I lower the "Z" 3-5 thousands to put mark in material

if I screw up (clamp loosens) or lose steps I put the v bit back in and can rezero X&Y pretty dang close to start point even if I have to remove material from original spot. move to close by rezero the Z
All my vectors start at least 0.125 normally more for clamping from the edge of the material
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Re: Start Point

Postby zeeway » Wed Jun 24, 2015 3:25 pm

One more....my process...

1. Home machine to limit switches.
2. Use laser to locate bottom left corner of material.
3. Hit laser zero button on Mach3 - this moves axis with built in offsets to the zero position.
4. Make sure that X and Y did zero in material coordinates.
5. Switch to machine coordinates and write down X and Y zero values - in case of emergency.
6. Zero Z to top of material or top of table with a piece of aluminum bar tied back into control. When grounded bit hits bar, the z zero routine stops it, and zeroes Z. There is a built in offset for the aluminum bar thickness.
7. Confirm that my toolpaths are using the same X Y and Z zero positions as the machine.

Keep in mind, that a laser position is only good to about .010 inches, so this is not a good way to reacquire zero. A v-bit with good eyes may be a tad better, but not much.

If I have to reacquire zero, I home my machine to limit switches, switch to machine coordinates. Make sure machine coordinates are the same as those written down (step 5 above), and hit the "Go To Z" button on Mach3.

While this process seems a bit fiddly... from time to time I have paid dearly for not doing it.

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Re: Start Point

Postby BernieNUFC » Thu Jun 25, 2015 7:52 am

Fiddly yes but detailed and very informative, I have found for what I am doing I was worrying unnecessary but thank you very much for time to reply
Malc
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Re: Start Point

Postby zeeway » Thu Jun 25, 2015 11:40 am

Just one more comment...if you zero to table top, in the last step above (go to z), you hit stop after the machine goes back to x/y=0, to keep the bit from driving into the material. Then you re zero z with the aluminum bar.

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Re: Start Point

Postby 4DThinker » Thu Jun 25, 2015 2:35 pm

When setting X and Y but using a large end mill in the chuck, I'll often draw a circle at 0,0 the diameter of the bit. I keep a circle template near the CNC. Easy to visually center a 1/4" bit in a 1/4" circle.
Another option is to align the edge of the bit (tip of the flute when rotated perpendicular to the direction of approach) to your 0,0 mark and set it for 1/2 the bit diameter (rather than 0), plus or minus depending on which side of the mark you are on. Do it again in the other direction. When done a move to 0,0 should have the bit perfectly centered over your 0,0 mark.

If I know the exact dimensions of my board, and 0,0 is in the center, I'll align the tip of the bit to the edges of the board and set it for 1/2 the dimension (of the board) and 1/2 the diameter of the bit. Plus or minus depending on which side of 0,0 you are on. I've seen college students mismark center more often than not.

I know LinuxCNC will let you type in any number when touching off each axis. I also know there is a SET option in the CNC Shark control software to let you do the same thing. You Mach3 users hopefully have the same ability.
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Re: Start Point

Postby BernieNUFC » Thu Jun 25, 2015 3:49 pm

4DThinker wrote:
Another option is to align the edge of the bit (tip of the flute when rotated perpendicular to the direction of approach) to your 0,0 mark and set it for 1/2 the bit diameter (rather than 0), plus or minus depending on which side of the mark you are on. Do it again in the other direction. When done a move to 0,0 should have the bit perfectly centered over your 0,0 mark.

If I know the exact dimensions of my board, and 0,0 is in the center, I'll align the tip of the bit to the edges of the board and set it for 1/2 the dimension (of the board) and 1/2 the diameter of the bit. Plus or minus depending on which side of 0,0 you are on. I've seen college students mismark center more often than not.


I like this
thank you
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Re: Start Point

Postby TReischl » Sun Jul 12, 2015 6:22 pm

4DThinker wrote:I know LinuxCNC will let you type in any number when touching off each axis. I also know there is a SET option in the CNC Shark control software to let you do the same thing. You Mach3 users hopefully have the same ability.
4D


In Mach, one can press the Zero button or type in a number.

If I have to be very accurate with my zeroing I use the following procedure:

Chuck up a .5 dowel rod
Jog near the edge to be zeroed
Set jog to step .001
Put .500 bar between dowel and work
Jog until I feel a very slight drag on the bar.
Set Zero either +/- .75 depending on which end of the workpiece I want zero. That is done by simply typing in the value on the Mach Screen.
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