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Old Jan 17, 2010, 09:39 AM
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X,Y,Z co-ordinate set up.

Hi Guys,
congratulations on getting the new CNC forum going. Yesterday I finally managed to get my home built Rockcliff machine routing out a pair of foam cutting templates.

I use Profili Pro for the template/wing rib designing, and use it's built in G-code export facility to generate the G-codes for Mach 3. This gave me a major headache as, initially, I could not get the Z-axis to work correctly. Before I manually editted the code the Z-axis would drive down to the start position and then when it should have raised up out of the workpiece it lowered again. At the next lowering command it drove down again and down again when it should have moved up. Fortunately, the soft limits that I set up prevented damage.

I currently have the Z-axis zero point at the raised (safe/home) position and it drives negatively to lower and start cutting. Is this the accepted norm? Or should I set the top of the workpiece as zero or perhaps the lowest point in the Z-axis as zero?

Can any of you experts enlighten me as to how the zero points are set? I am thinking that it really ought to match the XYZ origins of a 3D drawing.

Please help,
Martin.
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Old Jan 18, 2010, 05:56 AM
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Okay, so no replies as yet! Let me rephrase the question somewhat.

Where is the zero point for the Z-axis normally positioned?

Is it a) On the cutting table surface with the safe (non cutting) position +Z

b) Raised just above the workpiece (cutting is -Z and safe is +Z)

c) Somewhere else?

Can anyone comment?
Martin.
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Old Jan 18, 2010, 07:57 AM
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Hello Martian,
Congratulations on your new build!
I am not sure how the Profil software outputs your post process code, but I can say that for our machines and for most standard mills. You would jog the z to the top of the material being cut and zero out your work orgin. You have to remember that there is also a machine origin in Mach as well that has to be zeroed to your machine zero. Which in your case maybe the limits of the machine. Usually on a gantry style machine it is in the left/front most position if standing in front of the machine. The machine coordinates can be a little confusing and once set in mach will ask you if you want to save the fixture when you exit. Whn you pick yes they will be set for the next session and from that point on you only have to set the start origin of your work piece.
We have set up a mach3 screenset for Mach that makes this a little easier to do. One thing you may want to look into is finding someone that uses a Rockcliff machine with Mach3 and ask them to send you their MachMill.xml file. You copy this to your Mach3 Dir and you are set up if they are set up right.
Hope this helps
Mark
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Old Jan 18, 2010, 08:17 PM
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I'm not sure about the routers,But as Kram mentioned, using the highest point of the work piece is Z Zero, if there is an M28, (home) capability, starting at home, then the first code line is
(GO TO G54 x,y,zero)then
(Z 3. ) as a safety location, using single step, then verifying Z as safe to continue, move forward from there.
regardless of the code, this sequence will keep you safe.
Johnny
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Old Jan 19, 2010, 12:52 AM
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Old Jan 19, 2010, 12:52 PM
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Thanks for the replies Guys.

Mark - you said, "Usually on a gantry style machine it is in the left/front most position if standing in front of the machine." This would explain why the X and Y axes looked to be the wrong way round on the drawings!! Doh! It also explains why my cutting area appears to be in portrait mode and not landscape. Now that someone has mentioned this to me I understand it. Must be a newbie thing!! Oh well! I can just unplug the X and Y motors and swap them around and reset the soft limits in Mach 3.

Johnny - thanks for code. I use a designated drive direction to a home switch on each axis and not M28 (yet). Can you explain the setup of the M28 in Mach 3, I think it would be useful for a lot of people.

Paul - I have just upgraded for free to Profili 2.24c Pro - it even has an output for 4-Axis foam cutting. My original Pro version was only 30 euros and great value for money in my opinion.

Regards,
Martin.
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Old Jan 19, 2010, 09:26 PM
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Heli Bee!
here is a couple shots of Haas G and M codes. even though it's more detailed than what you'd be running ( more like engraving) It would give you a few ideas of staying in the safety zone.. the best setups I've seen is the basic mold locations, which are all set at the center of the part. now, to explain (hopefully) easily, thinking of a map of the U.S.,
New York is in X+ Y+ location, Florida is in X+ Y- Location.
California is in X- Y- Location and Washington state in X- Y+ location. NOW
------
Regardless of your machine's home position, the G 54, which is the work origin, will be designated by you in the machine (set-up).
suppose your home position is Washington State, and your work center is in Kansas,
with X+ and Y- from your home position will be G 54. now as long as there is table travel enough from that point without 'crashing' into your limits, lock that location in as your G54. You have not executed any Z (danger) zones. now the next phase of set up is your tooling. you will want the shortest length able to complete the job. Now there are at least 6 ways to go about this, But let's say the "default for today" is that you tool touches the highest point on the part at Z- from home (machine Zero)Z point. write a stop point at 1" above this touch point. (now leaving this +1", you can Prove the path safely, without scrapping material) this is a safety, which 99 percent of machinist's use, so that when in single block, and slow motion, you should maintain safe positioning. from there, you will rapid down to your R plane, which would be the (Return) plane for drilling cycles. If your workpiece is flat, I have seen some directional moves at the return plane, but it is scary at least, compared to a 1 or (3") move. then Rock On!
Haas has their Code available online, just looks up CNC Codes you need
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Old Jan 20, 2010, 07:13 AM
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Well said Captain C!
This is good information and I like the analogy you used of the map
Thank you
Mark
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Old Jan 20, 2010, 07:47 AM
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Thanks Mark! Now I just need to get some riches in my pocket! I wonder what for??
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Old Jan 22, 2010, 03:13 AM
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Johnny - thanks for the reply (post #7), it all makes more sense to me now. I have levelled the cutting table by using the machine to router the top surface off it. I have noticed a small amount of movement in the Z-axis which will need to be addressed before I do any 3D cutting - but it is fine at this time for all the 2D work that I have planned!!

Regards,
Martin.
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Old Jan 22, 2010, 08:17 AM
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Originally Posted by Captain Canardly View Post
Thanks Mark! Now I just need to get some riches in my pocket! I wonder what for??
That would be AWESOME
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