Onefinity Home / Limit Sensors - Limit Theory

[Ziggy]

Hello

I am still learning and building my CNC. I am grateful to all of the help here.

I have a Onefinity Woodworker CNC. https://www.onefinitycnc.com/product-pa ... odworker-1

It has a 32” x 32” cutting area. It uses stepper motors rather than servo and it has two steppers for the Y axis; one for each side.

My machine came with a Buildbotics controller. It used stall homing.

Since I am now setting up an Acorn board and stall homing isn't an option with my current motors, I am looking into the options for limit/homing sensors.

I see sensors listed in the “DIY Gear We Use” section of the website. I was wondering how other Onefinity users mounted their sensors since our machines weren’t originally designed for them.

I have some ideas and I am pretty sure I can make it work. But it would be nice not to have to re-invent the wheel if someone else has had some better ideas.



Also… I have been reading the CNC Axis Paring and Squaring manual. I hope someone can tell me if I am on the right track design/theory wise.

Originally I thought I would need 6 limit sensors: Two for the Master and Slave Y axis, two for each end of the X axis and one for the far positive end of the Y axis.

After reading, it appears as if I can get away with 4. Three NC sensors connected in series for XYZ homing and one wired to the Y slave (to trigger first) for auto-squaring.

Once this is done, soft limits can be set up to keep the gantry from slamming into end-stops in the event of user “cranial/rectal” inversion….as sometimes happens when I am the user.

Do I understand this right? If this is the case, it will save me a lot of hassle and wiring if I don’t have to have those last two limit sensors. Can I really trust the soft limits? Honestly, I don’t see how a speeding gantry can stop in time even if it does trip a limit sensor. The design of slowing down when it gets near the end is really nifty. (I am old… I use the word “nifty.”)

Thanks again!

[ShawnM]

Yes, you are correct, 4 switches total is all you need at a minimum. Soft limits work perfectly, I can drive my router at 650 IPM at the soft limits and it stop every time. My plasma table was running at 1200 IPM until I slowed it to 800 IPM and it stopped every time. You can trust the soft limits and it’ll save you lots of extra wiring and inputs.

Good luck with the build.

[Ziggy]

Great! Thanks for the reply!

Just for my own knowledge...

As I understand it, when the machine homes it goes Z then X and finally Y.

If the X, Y and Z switches are NC and in series and all connected to the same input, how does the Acorn board know when the X or Y is triggered when the Z has already been tripped. It seems that once the series circit is opened the second sensors wouldn't do anything.

I must be missing something.

[ShawnM]

Yes Ziggy, you are missing something.

When the Z axis homes first it moves towards the switch and trips the switch.......then it backs off the switch until it closes again and sets that as the Z home position. Now all the switches are closed again and it moves on to the next axis doing the same thing. Make sense?

You can set the homing order sequence to be whatever you like but Z should home first so it's up and out of the way. Then you can home X or Y. I operate a large 6x12 router that homes in the order you stated, Z first then X and then Y. And yes the Y slave trips first then Y master.

[Ziggy]

Ahh!!! Thanks! I knew I was missing something!

Now that I think about it, even when my original controller used stall homing, once it reached the end it moved back a little!

This is great! I apppreciate it!

[Ziggy]

https://www.amazon.com/Twidec-Inductive ... ss_tl&th=1

From the image, it doesn't appear that the cable is shielded.

I have used IGUS Flex cable (Expensive!!!) for my spindle and stepper motors. (Braiding tied to earth ground)

I have clad any AC lines that run near my control cables with copper braid, also tied to ground.

Should the proximity sensor cables be shielded as well?

Thanks!

[Ziggy]

Sorry to resurrect an old post of mine...

I am almost ready to try out my Home sensors for the first time. I think I understand things correctly but I just wanted to check in and see if I have misunderstood.

I am working through the install manual and the pairing and squaring manual.

In the install manual on page 88 they show a graphic indicating that the software travel limits should trigger before the limit switches. At first I thought that these would be the switches used for homing and squaring. However, on page 16 of the Homing and Squaring manual it appears as if the limit switches are separate from the homing switches and are just used as a backup in case something goes wrong with the software travel limits.

So far so good?

So last weekend I was working my way through the install manual. I set steps per inch, lash, squaring, etc. The next step in the manual was software travel limits. Having not understood the above point I went ahead and set them up even though I have not set up the software for the home switches yet.

I decided that I wanted about .1" space between the gantry and the end stops. So I moved the gantry (Y axis) .1" away from the beginning end stop and set the software travel limit to the remaining distance minus another .1". I then clicked reset home and it now showed the machine home to be 0,0,0, at my desired point. This seemed to work perfectly as I could not drive the gantry into the end stops. The software stopped it perfectly.

So then I got to the Pairing and Squaring manual and found out about the limit vs homing switches.

So how does this work with homing and squaring switches? If I want the .1" gap (Let's say on the Y axis with paired motors) should I set my master limit switch to where it trips at .1" and the slave switch to where it trips at .1" plus the Master Axis Squaring/Alignment Distance amount? (So the Slave triggers first.) If this is the case, is it then just the matter of setting the software travel limit so the movement is limited to stop before hitting the end stops on the far end?

This seems logical but I wanted to make sure.

Also... I know this must be a stupid question but... Is there a home button of some sort? I found the park button but I haven't found a homing button.

Thanks again.... Maybe if I have these questions someone else my have similar questions and this thread may help them.

[Ziggy]

Ok... I finally reached the weekend and was able to play around with this.

My assumption was correct: The soft limits start from where the axis back off after homing.

Also, the Home All button homes the machine.

--

I did run into a setup issue that I was hoping someone could help me with.

The manual states that the Master Axis Squaring/Alignment distance should be about 2/3 of the distance it takes for one side of a paired axis to "drag the other axis along."

I wasn't sure how to measure this but here is what I did: I set up two plunge type dial indicators. I set one on each end of the paired axis. I zeroed one side and then slowly turned the ballscrew on that side. The dial indicator on the other side would immediately move but when it finally "jumped" I figured that was the point in which the other side was being "dragged" along.

I did this 5 times clockwise and 5 times counter-clockwise - resetting to zero each time - for each side of of the paired axis. In other words, each side had 5 movements forward and five back. I then threw out the highest and lowest number and averaged the rest. Finally I multiplied that number by 2/3 and came up with .029".

So when setting up, I set the Gantry to where I wanted "0" to be and then moved the "flag" to trip the master "switch." Then I moved the flag for the slave switch .029" further so that it would trip first.

Everything seemed to work... But here is the issue:

Sometimes when I was homing, the master and slave for the paired axis would trip at the same time. The software also indicated that they tripped at the same time. This only happened sometimes. I slowed the speed to 15 ipm and the last couple of times it worked as it seemed it should.... but it doesn't give me the warm fuzzies.

I did confirm that the axis were square before setup. I did not have time to check the square after the automatic squaring process.

Should I increase the distance the Slave switch trips first? (Software and physically) I don't like the idea of pulling my gantry that far out of square on purpose.

Any suggestions are welcomed. I can go out and take pictures later if needed. But it is about 100F in my garage right now and I am about cooked.

Plus... that stinking Contour Shuttle is really giving me the blues.... That's another thread though.

[Gadget01]

Should the proximity sensor cables be shielded as well?

Thanks!

From what I understand of best practices, yes. Any cable carrying a low voltage input to the controller is susceptible to EMI. Grounding the cable's shielding mitigates this.

[cnckeith]

Ok... I finally reached the weekend and was able to play around with this.

My assumption was correct: The soft limits start from where the axis back off after homing.

Also, the Home All button homes the machine.

--

I did run into a setup issue that I was hoping someone could help me with.

The manual states that the Master Axis Squaring/Alignment distance should be about 2/3 of the distance it takes for one side of a paired axis to "drag the other axis along."

I wasn't sure how to measure this but here is what I did: I set up two plunge type dial indicators. I set one on each end of the paired axis. I zeroed one side and then slowly turned the ballscrew on that side. The dial indicator on the other side would immediately move but when it finally "jumped" I figured that was the point in which the other side was being "dragged" along.

I did this 5 times clockwise and 5 times counter-clockwise - resetting to zero each time - for each side of of the paired axis. In other words, each side had 5 movements forward and five back. I then threw out the highest and lowest number and averaged the rest. Finally I multiplied that number by 2/3 and came up with .029".

So when setting up, I set the Gantry to where I wanted "0" to be and then moved the "flag" to trip the master "switch." Then I moved the flag for the slave switch .029" further so that it would trip first.

Everything seemed to work... But here is the issue:

Sometimes when I was homing, the master and slave for the paired axis would trip at the same time. The software also indicated that they tripped at the same time. This only happened sometimes. I slowed the speed to 15 ipm and the last couple of times it worked as it seemed it should.... but it doesn't give me the warm fuzzies.

I did confirm that the axis were square before setup. I did not have time to check the square after the automatic squaring process.

Should I increase the distance the Slave switch trips first? (Software and physically) I don't like the idea of pulling my gantry that far out of square on purpose.

Any suggestions are welcomed. I can go out and take pictures later if needed. But it is about 100F in my garage right now and I am about cooked.

Plus... that stinking Contour Shuttle is really giving me the blues.... That's another thread though.

yes increase the distance so you don't get the trip before / wrong time message.

how are switches mounted and tripped? photos please