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### Author Topic: How to use Home offset under mach configuration  (Read 2216 times)

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#### avengine

• 23
##### How to use Home offset under mach configuration
« on: October 13, 2017, 05:54:31 PM »
I have the mach4 setup to run all the basic stuff, so far so good, but I want to learn how to use the Home offset and key in either positive or negative number do not see any effect at all. I would like to know what is this setting design for and how to make use of it. Is there any manual detail explain all this detail setting in mach4?
I did look into the user manual but no luck in finding the detail.

what I want to do is that I have a laser point beside the spindle, if the spindle is 0,0, this laser say it is 2,2. I want to use this laser point as a guide to find my target then use the offset so that the spindle will always start in the right spot.
Thanks.

#### Steve Stallings

• 447
##### Re: How to use Home offset under mach configuration
« Reply #1 on: October 13, 2017, 06:40:22 PM »
Home Offset is used in conjunction with homing operations like the Ref All Home
button to the left of the digital readouts.

It does not cause any motion, rather it assigns a location value, in machine co-ordinates,
to the location where homing stops. For example if you want the machine co-ordinate
of the left end of your table to be -20.000 you should put 20.000 (positive number)
into the offset value so that the machine co-ordinates zero point will be offset 20.000
positive from where the homing leaves the axis.

Then when you are homing in the negative direction and have a home switch at the
left end of your table, the homing action will cause the table to move to the left
to find the home sensor and then come to rest. Once this has happened, the current
position is set to -20.000 in machine co-ordinates for the X axis.

Steve Stallings
www.PMDX.com

#### joeaverage

• 7,316
##### Re: How to use Home offset under mach configuration
« Reply #2 on: October 13, 2017, 06:55:44 PM »
Hi,
that screen shot is of the Homing and Limits page. It is used to reference your machine usually at the beginning of the session. Note that it
sets MACHINE co-ordinates. When you hit <Ref All> the axes will in turn drive in the nominated direction at the nominated speed until a home
switch event for that axis is detected. It will stop and back up a fraction until the switch clears and then zero the MACHINE co-ordinate for that axis.
You will have noted that there is a setting for Home Offset. I don't use it so I could be in error but the upshot is that this setting allows you to say
'my home switch is 2 inches from the end of the axis and I wish my machine to be referenced to the end of the axis'

If you use your laser pointer to reference the machine you could do this.

I suspect what you want to do and is very commonly done is to use your laser pointer to indicate the start point on your work piece. When you hit
a button the WORK co-ordinates are set to 0,0 accommodating the offset of your laser from the spindle. Does that sound like the procedure you want?
There is a section of the forum dedicated to that subject; Video Probing. It is not a thing I have done so I can't really be definitive about it. On the Offsets
page there are a number of possibilities to offset your work 0,0 from the current location. It might be a cheat but how about assigning the radius of your
edge finder to 2 inches. When you hit the Set X button it will set the WORK X to zero but allowing for the fact that your 'edge finder' is two inches away.
That's just one work-around I can see. Check out what others do, there's bound to be better ways.

Craig
My wife left with my best friend...
and I miss him!

#### avengine

• 23
##### Re: How to use Home offset under mach configuration
« Reply #3 on: October 13, 2017, 10:06:16 PM »
"I suspect what you want to do and is very commonly done is to use your laser pointer to indicate the start point on your work piece. When you hit
a button the WORK co-ordinates are set to 0,0 accommodating the offset of your laser from the spindle. Does that sound like the procedure you want?"

this is exactly what i want to try. I want to start with laser pointer to proof my idea is work then go step up and get the 6 LED Waterproof Micro USB Borescope Inspection Endoscope Tube Camera about \$15-20 to pin point the dot position for exact toolpath to cut on the object that has image on it already. Then I want to cut around it nice and good following the toolpath from the dxf file but also contour cut around the edge of the pre-print image.
With your experience, and also all the nice people in this forum, I am sure you and someone will point me to the right direction how to achieve this idea.
thanks.

#### joeaverage

• 7,316
##### Re: How to use Home offset under mach configuration
« Reply #4 on: October 13, 2017, 10:41:20 PM »
Hi,
good stuff in fact GREAT STUFF, a man with BIG TESTICLES and FORTITUDE!!!! LOL

Jokes aside what you have described is what many are working to achieve as we speak. You really need to spend some hours if not days reading
in the Video Probing board.

In some respects I see the motion control part probably the easy bit. Mach is fairly mature and capable and could be induced to follow an automatically
generated toolplath. The real trick will be the visual processing software that can detect the required outline.

Craig
My wife left with my best friend...
and I miss him!

#### avengine

• 23
##### Re: How to use Home offset under mach configuration
« Reply #5 on: October 14, 2017, 11:25:58 AM »
Here I draw a diagram of the idea how I want it to work, correct me if there is a better way to do this.
I will use the laser pointer to find the origin 0,0 first
then move to point 2, compare this number to the actual drawing,
then go to point 3, if this 3 number match to one another, that mean the size of the print to the actual thing that put in the job table match, if not then I will modify the toolpath to match the measuremnt from the router table,
once this is done, it should be ok to do the cut.
is this logic sound right to you.
thanks.

#### joeaverage

• 7,316
##### Re: How to use Home offset under mach configuration
« Reply #6 on: October 14, 2017, 01:11:42 PM »
Hi,
are points 1, 2 an 3 the maximum extent of your machine? The checking that you are doing is to ensure that the cut part is within the
machine boundaries?

Craig
My wife left with my best friend...
and I miss him!

#### joeaverage

• 7,316
##### Re: How to use Home offset under mach configuration
« Reply #7 on: October 14, 2017, 04:23:09 PM »
Hi,
if you are doing this just to ensure that the part is within the boundaries you are making very very hard work of something which is

If you reference your machine then soft limits become sensible. On the toolpath view the softlimits can be displayed and whether the part is within
the softlimit boundaries can be told at a glance. In addition on the Toolpath tab the current extents of the loaded Gcode program are detailed.
This information is repeated on the Program Extents tab of the DRO block on Machs main Program Run tab.

If the part is not within the boundaries you can manually jog until it is then <Zero X>, <Zero Y>, <Zero Z> and then <Regen Toolpath> and review
whether you shifted enuf and in the right direction. Easy!

What it relies on is that you can REFERENCE or HOME your machine. This requires good home switches at a minimum. Once upon a time it was the norm
to make limit switches double duty as home switches. With external motion controllers now having plenty of inputs to spare there is no need to do that
anymore. Three home switches, three inputs. Easy!

If you don't want to put home switches on your machine or think you cant afford them, I was exactly that way for quite a while, the go away
and use your machine. Once you've crashed it half a dozen or more times and broken all sorts of parts and thrown away wrecked jobs
left, right and centre then you will realise that good home switches are cheap.

Craig
My wife left with my best friend...
and I miss him!