How to set machine and use offsets?

CNC USB Controller Software

How to set machine and use offsets?

Postby Andrej » 03 Feb 2012, 09:14

And not only offsets. To fully exploit potential many different things need to be set. Everything works together.

I'm assuming machine is router or mill type and standard axes X, Z and Z are used.
Machine needs to be equipped with limit switches, fixed tool sensor and movable tool sensor.
Machine should already have StepsPerUnit correctly set and should already be working.


First thing that we need, is define machine size. For this we will use limit switches.
We want that machine stops when limit switch is hit so make sure “Settings/Axes 3/Limits/Limit Switch” is checked for X-, X+, Y-, Y+ and Z+. Uncheck others checkboxes.
Also uncheck all “Settings/Axes 3/Limits/Soft Limit” checkboxes. We will set soft limits this later.

Lower machine jogging speed with speed override slider (bottom left corner of main screen).
We will hit limit switch and we don't want to do this too fast.

Start jogging to negative X side (you can trigger limit switch with hand just to make sure machine really stops). Jog all the way until limit switch is hit and machine stops. Machine should now be at absolute negative X position.

Before we continue we must do some other things.
Make sure “Machine/Set Position/Enable” is checked. We will use set position to change machine absolute position and these commands need to be enabled.
Execute “Machine/Offset/Zero” to zero working offset.
Execute “Machine/Tools/Zero tool offset” to zero tool offset.

Now we can continue.
Execute “Machine/Set Position/Zero Axes/X” to zero X position. X coordinate will now have value zero. Now jog machine to other side (positive X) until limit switch is hit. Write down coordinate X. This is your machine X size.

Repeat procedure for Y axis.

Now you know machine size in X and Y direction. In next step we'll define Z. This is little different.

I hope you understand my writing. Any questions?
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Re: How to set machine and use offsets?

Postby m_thread » 03 Feb 2012, 09:19

Excellent guide. Will try it out later today.

/F
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Re: How to set machine and use offsets?

Postby Kristof » 03 Feb 2012, 14:05

Great job Andrej. Tonight is my big night to mount the limit switches. Hopefully I'll not crash it :mrgreen:
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Re: How to set machine and use offsets?

Postby Andrej » 03 Feb 2012, 23:29

We need to measure Z now.
Z is different. We only have one limit switch Z+.

Mount your favorite tool into spindle. Then slowly lower Z axis so that tool just touches tool table. You can use "step" jogging (set step to low value). Be careful not to crush tool into table. If you need to practice "step" jogging then do the at safe height first.

I put a piece of paper between tool and table. Tool will press paper to table and when I can no longer move paper then I know I'm low enough.

Now that we have tool at tool table height position we execute “Machine/Set Position/Zero Axes/Z” to zero Z position (don't worry, I also use Z0 at top of material – we'll do this later).

Now jog up until Z+ switch is hit (you can trigger limit switch with hand just to make sure machine really stops). When machine hits Z+ and stops, jog back a little so that limit switch is released. Write down Z coordinate. This is your machine Z size.
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Re: How to set machine and use offsets?

Postby Andrej » 04 Feb 2012, 00:02

Now that we have measured machine X, Y and Z size we can define machine absolute coordinate system.

Jog machine to position where you normally start cutting. Usually this is somewhere near X-, Y- corner. Just short distance away from X- and Y- limit switch. Of course you can also go somewhere else. Table center is also quite common. Z is not important.

Execute “Machine/Set Position/Zero Axes/X” to zero X position.
Execute “Machine/Set Position/Zero Axes/Y” to zero Y position.

Jog to X- until switch is hit. Jog some distance back so that switch is released. Write down X position.
Jog to X+ until switch is hit. Jog some distance back so that switch is released. Write down X position.
Jog to Y- until switch is hit. Jog some distance back so that switch is released. Write down Y position.
Jog to Y+ until switch is hit. Jog some distance back so that switch is released. Write down Y position.

Now you have defined your working area limits.

Open settings.
Set position which was at X- to “Settings/Axes 3/Limits/Limit-/X”
Set position which was at X+ to “Settings/Axes 3/Limits/Limit+/X”
Set position which was at Y- to “Settings/Axes 3/Limits/Limit-/Y”
Set position which was at Y+ to “Settings/Axes 3/Limits/Limit+/Y”
Set “Settings/Axes 3/Limits/Limit-/Z” to value 0.
Set “Settings/Axes 3/Limits/Limit+/Z” to value which was measured as Z size.

On 3D display your machine working area will be displayed as orange cube.
You can try to enable “Settings/Axes 3/Limits/Soft Limits” and check if they are working. Be careful in Z- direction. You can crash tool into table. But if everything is correct tool will hard stop exactly at table top. Z- is only direction where soft limit makes hard stop. In all other directions there is deceleration.

Be careful not to loose steps. You're now using machine absolute coordinate system and if you change it your position is lost and you must repeat this step from beginning.
You should NOT use any of "Set Position" commands. They change absolute coordinate system. It is best if you disable them by unchecking "Machine/Set Position/Enable".

If limit switch is hit before soft limit stops machine then your working area is too big and you should adjust its limit value.

Next topic will be homing.
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Re: How to set machine and use offsets?

Postby Andrej » 04 Feb 2012, 14:44

If previous step was done correctly than you have orange box representing machine working area. In this space machine can move freely. If "Soft Limits" are enabled then moving outside this box will cause motors to decelerate to stop.

Image001.png
Image001.png (66.4 KiB) Viewed 21072 times

Here you can see my working area. Yellow cone representing tool is at X0 Y0. This is location where I usually start cutting.

In previous post I warned that lost motor steps or any of "Set Position" commands will change absolute coordinates. That basically means, that controller does not know correct position of machine. Soft limits, fixed tool sensor, tool change positions,... are all useless because controller does not know where they are.

Maintaining correct absolute position is essential. That is why I added option to disable "Set Position" commands.

But how can we set correct absolute position? This is where homing comes in. Homing procedure is method to determine machine absolute position. Just like we did it manually in previous steps this is now done automatically. I'll explain how.
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Re: How to set machine and use offsets?

Postby craigthefabricator » 11 Feb 2012, 03:40

This information is very helpful... Will you be continuing the discussion on homing in this thread or will you begin a specific thread for the next section?

I look forward to seeing the next part of this process properly described and sequenced so I can figure out how to set my machine and control systems up in an effective manner.

Thanks again.

-Craig
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Re: How to set machine and use offsets?

Postby Andrej » 14 Feb 2012, 07:22

Now we know how to manually set machine absolute coordinates. You also know, that you should NOT use any of "Set Position" commands.

But what to do if my X0 Y0 is not where I want to start cutting? And I want my Z0 to be at top surface of material.

Place material somewhere on machine table. Jog to position where you want to start cutting. Usually this is corner or center of material but it can be anywhere. Click "Offset - Current XY" or execute "Machine/Offset/Current XY".
You will notice that coordinates are changed to X0 Y0 and that "W" is enabled and checked. Enabled "W" means that working offset is active. Checked "W" means that offset is applied to coordinate display. If you uncheck "W" offset will still be active. It is just coordinate display that don't show it.

To clear offset click "Offset - Zero" or execute "Machine/Offset/Zero".

Now set your XY offset. Then slowly jog down (you can use step jogging) until tool just touches material. Click "Offset - Current Z" or execute "Machine/Offset/Current Z". You've set your Z0 working offset. If your Z0 is not on material top surface then you need to set it to somewhere else but procedure is the same.

Now that your working offset is set for X, Y and Z you can load G-code and start cutting.

I recommend you practice this. Put different pieces on machine table and set working offset. This should become routine.

You don't really need to set absolute coordinates to use working offset. But you will need absolute coordinates for next steps.
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Re: How to set machine and use offsets?

Postby Kristof » 18 Feb 2012, 20:19

Andrej will you continue on the homing procedure?
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Re: How to set machine and use offsets?

Postby Kristof » 21 Feb 2012, 13:27

I want to use my limit switches as home position. How do I set it up?
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Re: How to set machine and use offsets?

Postby Andrej » 21 Feb 2012, 13:53

We will continue with homing soon.
You should be familiar with limit switches and with working offset by now.
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Re: How to set machine and use offsets?

Postby Kristof » 21 Feb 2012, 14:26

Yes I'm. But here is the other question. Each time I move the machine to X- switch, Y- switch and reset the coordinance to 0 and then move away and come back, the coordinance is no more 0. It's always negative something.
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Re: How to set machine and use offsets?

Postby Andrej » 22 Feb 2012, 13:38

Better late than never :-)

By now you should be familiar with working offset. You should also know how to use soft limits (Mk2, Mk2/4) and have functional limit switches.

Now it is time to set homing. Remember, I'm using millimeters!
First check “Machine/Set Position/Enable”. We will need these commands.
Uncheck “Machine/Soft Limits”. We will need to jog past soft limits.
Clear working offset with “Machine/Offset/Zero”.
Clear tool offset with “Machine/Tools/Zero Tool Offset”.

First thing we need to to is measure “Return Distance”. What is this?
If you have mechanical limit switch trigger one with hand. Then release it. Now do this really slowly. You will notice, that when switch releases little later. There is short distance between.
Slowly jog machine until limit switch is hit and machine stops. Make sure it does stop before you hit end. When machine is stopped, position display is red. That indicates limit switch is triggered.
Now zero axis using “Machine/Set Position/Zero”. Very slowly (I use step jogging with distance 0.1mm) move back until position display is no longer red. Position display now shows how much we need to return for switch to release. This value is usually between 0 and 5mm.
Write down this number and repeat procedure for all other switches.

Now you should have these switch values for all axes. Take largest value, apply at least *2 safety factor and round it. Now you have your “Return Distance” setting. For example, if largest value is 1.4mm then use 3mm for “Return Distance”. I don't recommend value smaller than 1mm.
Set “Settings/Axes 3/Homing/Return Distance” value.

This might seem complicated when you read but it is simple with real machine.

Now jog to position, where you want to have “home”. Usually this is at X0 Y0.
Zero all axes using “Machine/Set Position/Zero”.
Now jog up, to safe height. Roughly measure distance between tool and table top with ruler or tape meter. Round this number and use “Machine/Set Position/User ...” to set Z value. I use Z100 on my machine so position display now reads X0 Y0 Z100, tool is at safe height.
Uncheck “Machine/Set Position/Enable”. You don't want to change absolute coordinates any more.
Set “Settings/Axes 3/Homing/Go To” to this position (X0 Y0 Z100 in my example).

You don't want to hit limit switch too fast.
Set this with “Settings/Axes 3/Homing/Speed”

Usually you want to home Z first, then X and Y together.
Set this with “Settings/Axes 3/Homing/Sequence” Z to 1, X and Y to 2.

You can home to positive or to negative side (Z is usually always positive).
Set this with “Settings/Axes 3/Homing/Direction”.

I use X and Y negative and Z positive in this example.

Now jog to X- until limit switch is hit. Read position display and add “Return distance”. For example, if your display reads X-85 and your “Return Distance” is 3 then -82mm is your value.
Set this with “Settings/Axes 3/Homing/Set Position/X” (X-82 in my example)

Now jog to Y- until limit switch is hit. Read position display and add “Return distance”. For example, if your display reads Y-50 and your “Return Distance” is 3 then -47mm is your value.
Set this with “Settings/Axes 3/Homing/Set Position/Y” (Y-47 in my example)

Now jog to Z+ until limit switch is hit. Read position display and add “Return distance”. For example, if your display reads Z120 and your “Return Distance” is 3 then 117mm is your value.
Set this with “Settings/Axes 3/Homing/Set Position/Z” (Z117 in my example)

Idea behind this is, that machine moves until switch is triggered. Then it moves back by “Return distance” so that switch is released. This position is then used to set absolute coordinate position to “Set Position” value. Machines then moves to “Go To” position.

Enable homing with “Settings/Axes 3/Homing/Enable”.

Now try homing with “Machine/Home”. Keep one hand on e-stop in case you did something wrong.

You will probably need to set machine limits again using these new values. Use slightly smaller limits because soft limits need to decelerate machine to stop before limit switch is hit.
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Re: How to set machine and use offsets?

Postby Kristof » 22 Feb 2012, 14:58

Andrej thank you very much for the follow up with homing. Finally I can start working :D
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Re: How to set machine and use offsets?

Postby Darko » 26 Mar 2012, 09:20

Hello everyone,
Last few days I worked intensively on my first CNC and instructions in this topic are very useful. Yesterday I did first mechanical tests and everything seem to run fine, limit switches are functional. I was able to set up the "working area" of the machine, learned how to work with offset and made first cuting - successfully.
There are but couple of things that I noticed in instructions and I cannot solve them:
- soft limit boxes are always inactive (cannot be checked or unchecked). How do I activate the soft limit?
- when limit switch is triggered the corresponding axis display becomes red, machine stops. However any joging in any direction is now disabled. This seem logical to me, but instructions say that I should jog to the oposite end of the axis to measure the machine size. To measure the machine size I had to manually turn the motor (by force) to release the limit switch and continue. I had to do it for all axes. Is this only in my case or someone had similar problem?

BR
D
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Re: How to set machine and use offsets?

Postby Andrej » 26 Mar 2012, 14:33

- Soft limits are not available on Mk1.
- Check if positive and negative switches are swapped. Switch on negative side shows red color when triggered, switch on positive side shows purple color.
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Re: How to set machine and use offsets?

Postby Darko » 26 Mar 2012, 17:50

Thank you for prompt reply!
I have checked switches and they are not swapped. However all switches on all axis produce the same color on + and - side. I will have to check the connection to MK1 board.
BRD
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Re: How to set machine and use offsets?

Postby jonmessenger » 26 Mar 2012, 23:45

I have an unusual problem, I removed the probotix board when the software update kept losing my usb connection in the middle of a cut, so it has been a couple of months. I have the board installed, and the homing and limit switches set up, the machine homes fine, and resets the machine ccordinates. but when I load up some g-code, I get some pretty crazy info in the program info screen. The program limits are way out of whack. I have a sreen shot here all the program was to do is go up and down 4" on the z axis, and after the mahine thinks it finally reaches the start point, it does just that. Howerver it thinks it is -426.984 inches away from that start point, and well look at the screen shot. I have "homed" the machine following your procedures, zeroed the offset, and the software is set to read inches not mm. I have even removed the g20 line with no change, I am sure that I am missing something simple here but I don't see it. Help!!
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Re: How to set machine and use offsets?

Postby Andrej » 27 Mar 2012, 13:47

This seems like USB problems. Can you try with another computer?
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Re: How to set machine and use offsets?

Postby jonmessenger » 27 Mar 2012, 18:13

Went back to software version 20120131 and it works fine. Might have a bug here. I went back to 108, no problem then 121, no problem then 131, no problems.

What do ya think?
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Re: How to set machine and use offsets?

Postby jonmessenger » 28 Mar 2012, 02:45

I backed up a version and everything is working, Actually i started wityh 108, then kept checking until I got to the last version, 210 still works but after that it gets whacky. for some reason the that saves positions to the file is what isn't working, I copy the previous executable into the folder and it goes whacky. Does that make sense, it has been a long day.
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Re: How to set machine and use offsets?

Postby Andrej » 28 Mar 2012, 13:09

Mk1 firmware 108 is (almost) same as 210. There were no significant changes made. Only one minor fix.
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Re: How to set machine and use offsets?

Postby craigthefabricator » 17 Apr 2012, 22:48

Andrej,

From looking at posts in this thread and others, it seems there are numerous capabilities that are not available on the Mk1 board (or, more specifically in my case, the Probotix version of the board).

Is there any way you can break down what features described in this particular tutorial are NOT going to function at all (or have some limitation)? You may recall a thread I started showing a CNC controller (yellow acrylic) with a number of buttons intended to map to a lot of the functions and workflows described in this thread. If some of the functions are simply incompatible with my probotix version of your board, I'd like to know before I complete the wiring and before I button everything up so that I may design and engrave a new top plate containing the images and text sandwiched under the clear acrylic top plate.

Thanks!

-craig
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Re: How to set machine and use offsets?

Postby Andrej » 18 Apr 2012, 12:41

Except for soft limits all other features described in this topic are available on Mk1.
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Re: How to set machine and use offsets?

Postby Andrej » 14 Jan 2013, 19:34

Here is French translation made by Denis.
Attachments
Decalage machine.zip
(112.89 KiB) Downloaded 411 times
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