Offset after homing sequence (router table)

[muibubbles]

When I home my machine with my proximity sensors it leaves g54 off the table. I assume there a way to change the distance the machine offsets itself once those sensors are tripped on the x and y axis. Can some point me in the right direction? I came up empty handed searching "home offset" and skimming through the manual, please let me know if I'm not searching the right term.

Thanks in advance!

[Dan M]

I don't know if anyone is going to understand what you are talking about or trying to do. What does it leaves g54 off the table mean, are you setting up the part before trying to run a job?

Why do you want the xyz axis to back off the sensors further than the software initially does? I would think that you would want the maximum amount of work envolpe that you can get. Post a picture and more info on what you're talking about. If anything I would think you may need to relocate your proximity sensors not change the homing distance.

Either way post more info so someone can help you out.

Dan

[muibubbles]

Hey Dan,

I apologize, I may not be using the right technical terms...

I am using my (3) proximity sensors when doing the homing sequence (albeit, I really don't understand the difference between home/limit switches as it seems like the same function IE my home switch also acts like a soft limit before the hard stops.)

This is a retrofit AXYZ CNC router that originally came with 2 spindles and an air drill attachment, thus the gantry is oversize allowing the carriage to over hang off the table for the other spindle/attachment to be able to reach (0,0) (Pics attached) So if I had the original set up, when I home the machine now, the air drill will be at (0,0) spindle 1 would be at (0,-3) and spindle 2 would be at (0,-6)

Since I retrofitted the machine with acorn, I am only using one spindle which leaves it at (0,-3). What I want to do is be able to press the home button, have the machine search for the proximity sensors, and once they are triggers, back off to (0,-3) Which is what I am calling "home offsets" which may not be the technical term. I am not concerned about a work envelop as the table has a work space of 6'x14'

I assume this is possible since this is what we did at my old job to locate the corner of the work bed as the rails overhung the machine (older shopbot machine)

Please let me know if there is anything else I can help clarify. I appreciate the help!

[tblough]

Edit your cncm.hom file to include a move between the move to home switch command (M91/M92), and the set axis home command (M26). Below is my cncm.hom file, yours will be different but the process is the same.

Code: Select all

M92/Z
G91 G1 G20 Z0.120 F10.0
M26/Z

M91/X
G91 G1 G20 X-0.060 F10.0
M26/X

M92/Y
G91 G1 G20 Y0.100 F10.0
M26/Y

[Gary Campbell]

This is pretty common on router tables, i.e., the switch location does not represent the physical table location. You will have to find and open the "cncm.hom" (homing) file in the C:\CNCM folder.

Here is a simplified version showing ONLY the relevant motion commands. The M91/M92 lines move the machines to the switch and backoff. The M26lines set the current location to machine home. You will need to insert X, Y and possibly Z movements in between them. Here is a "basic" example:

M92/Z L1 ;Move Z to switch
G91 G0 Z-0.1 ;Move Z desired distance off switch

M91/X L1 ;Move X to switch
G91 G0 X0.2 ; Move X required distance to table

M91/Y L1 ;Move Y to switch
G91 G0 Y0.5 ; Move Y required distance to table

M26/X ;Set Machine Zero X axis
M26/Y ;Set Machine Zero Y axis
M26/Z ;Set Machine Zero Z axis

G90 ;Return to Absolute positioning

Make sure that you save a backup copy of the CNCM.HOM file as it will be overwritten by the Wizard

[Dan M]

Now that I understand I have a question? When you edit the home distance, would you have to adjust your soft limits as well? Or will you still have the ability to have the spindle run off the table?

Example your y soft limit travel is say 100 inches and you change the back off number from 1 inch to 2 inches. Would you then have to adjust the 100 inch limit to 99 inches? If not then wouldn't the machine y zero after homing really be at 1" not zero and you would potentially trip the soft limit at the other end of the axis?

I'm just curious how this all works since my spindle hangs off the table as well. I need it to since I have my tool setter off the table. I need every square inch of work envelope I can get since I have a small table.

Thanks for any info on this as I'm still learning.

Dan

[tblough]

You will need to change your soft limits. The soft limits are distances from the home position, so if you change the home position, the soft limits will need to change as well.

That said, you really shouldn't be changing your home position or soft limits. It sounds like you just need to set your fixture offsets to 0,-3.

[cnckeith]

you can edit up the home program to back off the switches and then home out at that position if you like.
homing is setting the MACHINE coordinate system to a zero location.
then from that point travel limits (distance for each axis before crashing into the other side) figure to be the distance for each axis that is the work envelope. ....so, put another way, travel limits are measured from the home position to the point you want the machine to stop before crashing the axis. you can easily figure the travel limit number by pressing <ALT D> which switches the DRO into MACHINE coordinates and then slow jog to the point in which you want the axis to stop, read the DRO position and set that as the travel limit in the Wizard. or just use a tape measure.

once the home position and software travel limits are established during CNC control commissioning any other zero location settings should be using the WORK coordinate system (WCS). here is a good article explaining use of WCS https://www.autodesk.com/products/fusio ... made-easy/

[Dan M]

So it does function how I thought it did, so it goes back to what I originally said that you should move your proximity sensors since the distance in between becomes effectively dead space.

Or you just set up a aux button that you can push after you home the machine that jogs to g28. From what I've read it would be a simple macro to write.

Dan

[muibubbles]

Thank you guys for all your replies, such a wealth of knowledge!

After reading Keith's suggestion I think he's right and WCS is probably more appropriate for what I'm looking for. It sounds like offsetting the Machines home is a bandaid for what I want.

Now for an even more embarrassing question, can someone walk me through how to set up/use the WCS?
Is it as simple as going to Set up > Parts > WCS Table > Origin and then changing the values for each axis?

Now how do I put WCS into practice?
Let's say I set up WCS #2 (G55) to be at machine coordinates X=5 Y=5 Z=5
If I want to cut a part with the origin at G55, is this something that needs to be indicated in the code from my CAM software or input manually into the code? (I'm using vetric for CAM software)
Or do I Just command the machine to go to G55 (which will 0 out all the axis at machine coordinates X=5 Y=5 Z=5) and run from there?

Another really dumb question, is there a WCS home button? I came from mach 3 with a home button and always find myself looking for one...

T