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Author Topic: How to zero "machine coordinates" of cnc with no switches of any kind using Mach  (Read 18427 times)

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Good morning to everyone from Europe :)

I received the other day my first cnc machine. That fulfilled me with happiness until the moment when I decided to ask the device to cut a rectangular with the maximum dimensions of X (400mm) and Y (600mm) on table with size 480mmx800mm. The first problem that occurred was: the machine went off the physical zero that I set manually and started cutting let say about 150mms off the zeroed Y and 50mms off the zeroed X. After quick check I've noticed that the art-cam file (converted to G code) when loaded in Mach3 went to the top of the table display and not from bottom left as it should be! I spent hours of reading and watching video tutorials on youtube and found out that the problem is caused by the fact the "Machine Coordinates" are not= to zero when the machine is manually moved to bottom left corner (X/Y)
I can't figure out how to zero this numbers! everyone talks about some sort of switches that allows the device to understand when the axis have reached the end of the table, switches that are not included in the configuration of my device (I still can't explain to myself why Mach3 does not support in the settings screen function where the user can set the machine coordinates to zero according to the position of the axis without getting into the trouble of spending hours of configuration for something that shouldn't be so complicated)

Could someone help me set up my machine because I did restore all the settings of Mach3 and now the position of all the axis is physically located on the bottom left corner and the software after the restore shows +0.000 for all the axis for both machine coordinates and the starting coordinates. The problem that occurred after the restore is a message: "Limit switch triggered" which does not allow the axis motors to move in any direction. What am I doing wrong? could someone list all the steps that have to be done in order the device to be zeroed and the G codes that I load to go to the right position on the table plan. In simple words how to make it work properly? I am sure that there are many people facing the same issue as most of the budget cnc machines do not have homing and/or limit switches....

Thank you for your time reading my post!

Offline Tweakie.CNC

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Hi Bugatti,

Welcome to the forum.

If I understand your question correctly (and I often get this part wrong) I think you need to set the Origin (X & Y zero) within ArtCam at the bottom left hand corner of your stock.
Then, when the stock is placed on your machine table, jog your axes until the cutter is positioned to the bottom left hand corner of the stock (Origin) then Zero the X and Y axes DRO’s. Presumably your Z axis zero is the top surface of the stock so you need to jog your Z axis until the cutter touches the surface of the stock then Zero your Z axis DRO. Now jog the Z axis until the cutter is clear of the stock surface and you should now be ready to Run.
However, it is always worth checking the Program Limits in the Toolpath screen to make sure that the X, Y & Z ranges are within the dimensions of your stock before you begin.

I don’t know if this helps but this is the way I work, totally ignoring machine coordinates, homing routines, etc.

Thank you for your quick reply Tweakie.

I've tried what you suggested but unfortunately Mach still tries to cut beyond the physical dimensions of the device.

Let me try to explain what I want to achieve and tell me if is wrong...

I want to dig a hole with size of 400x600x-5mms into MDF that I am going to place on top of the aluminium working surface that has size of 800x480mms in order to be able always to place other pieces of MDF with measures of 400x600x18mms to the same position always which will let me optimize the process of cutting my models. However this seems to be impossible due to the missing end switches on my cnc.
How I can set up limits in mach3 for the axis and stop them of moving beyond certain coordinates so they don't hit always the machine when reach the end of their way? Is there such a set up for users that do not have end stopping switches?

Offline RICH

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There is more to CNC machining than just plug in the machine and play. So loading a file without reading the manual to see it run is
like being blind folded and deciding to take a trip down the race track in a car and hope you get to the end.

There are machine, part, program coordinates and there are machines with, without limit switches and also soft limit switches. Then you also have offsets, tool compensation , and a number of other things to consider, etc. You configure Mach according to the machine and how you are going to work.
You also set up the machine before running a program.

Now also understand that depending on how a part is defined in say CAD, then the CAM, then processed, and how Mach is configured all have an affect on what the axis movements are relative to the piece.

That all said, we'll keep it super simple .............for no tool offsets, no switches, no soft limits, siingle piece to be done, etc........
Wherever 0,0,0 (origin) is in the programs code that is where you want to set the tool, so you just move to that point and once the cutter is set at the
location, you simply click ref all home button and now the XYZ Dro's will be 0. So machine, program, part and tool are all set to the same spot.
Hopefully your piece is positioned on the table such that any axis travels are within the table travels.

What happens after starting the program depends on what instructions the code gives to Mach.  Dry run the program with no tool and clear of the material to be assured all is well.


Offline RICH

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Go to members docs and you will find how a write up on how to home a machine without switches.
If your machine is accurate you can have the code go to or end at some point.Simply place the material in the same spot and now move the XYZ to
the origin and start again.