Installing and using limit switches

Possibly off topic, but I don’t understand the limit switch thing. I have a Shapeoko and have never installed any limit switch.

It seems to me that if you design your project well, then your router/ spindle will go where you want it to go. Is there a “feeling of security” thing happening with limit switches? :thinking:

@CrookedWoodTex Tex: I agree with you that your post was off the topic that started the other post. I have moved yours here in a topic of its own. With luck, anyone who has installed switches will respond. I have not installed them. :grinning:

I got them for the long mill and don’t think I’ve ever actually ‘needed’ them. If you lose your zero for some reason other than setting a new zero, machine belt slipped or whatever, you can home and then just go to zero. Granted, you could just zero with the block, unless you started in the center.

I could see them as a convenience if you had different jigs that were always in the same spot when installed. Then you could use a different WCS for each jig and the XYZ would be saved.

So it seems that I have to grasp at straws to justify the purchase, maybe someone else can do better?

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Yes One reason is Security, but I would say there are two more.

Secondly as @_Michael said getting back to job Zero easier. Even if it was in the Center you could save the Coordinates with the Workspace Feature.

Then three as @_Michael also said repeatability/quick set up. You turn on your machine, it runs its homing cycle. Then you can use the Workspace Feature to automatically go to the Zero position of your first cut, say cutting circles out as blanks. After that you have a jig to the right of that you can insert your circles you just cut. Now you can go to your second Workspace Zero Setting for that jig, and cut.

I have not installed mine either, but am about to so I can do the above mentioned steps for a project I have coming up. If this project comes to fruition, then I want to save as much time as possible in set up as I will be needing to make hundreds of these. So with this I would only have to set my X & Y zeros once for each part. After that its just button clicks.

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I set them up a few months ago. I currently have 4 jigs set up so the workspace feature comes in real handy. I don’t think I will go back to not using them, they do save quite a bit of time.

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So you only use “limit switches” for homing? I suppose I would call those “homing” switches that, yes, are used during the homing cycle for machine XYZ origin.

So, why would your machine not come with switches to allow the homing cycle? What other use would there be for a “limit” switch?

There’s a bit of miscommunication if you think that limit switches have anything to do with the WCS. I use WCS all the time without thinking about limits.

Really. Design your project to fit the space available, and you don’t have to worry about mechanical limits. For the most part.

I think that’s the real reason for limit switches. There are times when things go wrong. In the automation and robotics industry, there are plenty of machines that will happily tear themselves apart. A relatively cheap switch is worth the security.
They’re probably not necessary on our hobby level CNCs as not much will give before the stepper torque does, and we shouldn’t be running them without being close by.
I use homing switches, but I have soft and hard limits disabled.

One situation that a more inexperienced person should watch out for (ME! :rofl: ) is moving a project from the default XY zero location to one of the WCS locations without considering whether the outer reaches of the project will encounter a physical limit of the machine.

I bought a set and installed them, but I have had so many OTHER problems with my MK2 3030 that I never hooked them up. Yesterday I removed them and probably won’t ever put them back on, so they are brand new, if anyone would like to buy them pretty cheap.

@sp5937 If you are serious about selling them, please post them for sale in the marketplace category, including an asking price.

Just got done with a project working on a post now. But without the limit switches I would have been lost.

Switching back and fourth from laser to router was a snap. (macro more then switches, but macro homes then goes to laser offset)
If you have to hit the stop bottom for any reason. You home and are back to where you need to be.
You can setup macros for different workspaces, just a push of a button and you are in an exact location. (believe handy if making same projects in different areas)
If the software bugs. ie… jogging goes full. your machine stops before running into limits.

They have been especially useful for this new guy.

Remember that there is a subtle difference in the discussion between “homing” and “limit” switches.

Homing is an absolutely necessary use for limit switches, but that is not something that happens while a program is running.

agree not while program is running.
Once you shutoff, have a running in, you stop button. You can never get an exact spot back.
but wit a limit switch you can guarantee the exact same position of your machine, after homing

I see you use workspaces. What if you are not able to use an autoprobe for x,y? You would have to guesstimate using visuals. With a limit switch, and homed machine, once you get those coordinates it is simply pushing a macro button and your there. Just usually need to set Z.

Just my thoughts

@Shipwreck I would very respectfully disagree with your assertion that without limit switches, “you can never get an exact spot back”.

That said, I’m not disputing the benefits of limit switches. However, I do not have them installed and I can get an exact spot back any time that I want. I’ve done it numerous times.

On my table, I have secured a block of hardwood, which I ensured was square to both the X and Y axis by screwing a block down and cutting it on the Long Mill. The block is in the front left corner of the table. I can use the original touch plate on that block to set XY0. I can set that position in workspace 55, for example. Then, no matter what I do after that, I can always get back to the exact position.

Now, obviously, I lose that position when I shut down the machine for the night. But I can get back to it the next day by simply using the touch plate on the hardwood block to set XY0 again. I have to do the same thing if a project goes south or there is a power failure.

I want to emphasize that I am not suggesting that my method is as simple as hitting the homing button and letting the switches do their job. It’s simply another method to set a repeatable origin without what I read to be the sometime frustrating experiences people are having with switches.

Finally, I must admit that I don’t use the block/touch plate process very often. If I am doing multiples of a piece, I simply screw down a right-angle into which set the corner of each successive piece. That is my XY0 for each piece and it is precisely in the same spot every time.

Have fun. :grinning:

I can see where a hardwood block could get you extremely close. I would disagree about how exact especially overtime. Wish i could find those particular sensors to see level of accuracy.

Touch plate relies on touching. You plate, just putting it on will cause friction with the wood. The magnet will not always be as strong. Wood itself can dry and swell with humidity/heat. Slight imperfection on chosen bit. Touch plate perfect to 15mm? Different tips of bits will have magnetic differences.(just speculative that it could cause a deviation.

Software is computing location based on factors that can change or imperfections introduced.

I agree that even an induction sensor has limits on accuracy. Couldnt find for this model. Maybe someone has the number.

Over time touch plate location is going to change.
Overtime an induction sensor, short of failing will have more longevity in accuracy.
I perfer to set and keep my machine as accurate as possible, i know not perfect, but any outside action will help.

There are probably other reasons as well. I mean i have yet to see a 3d printer without them. CNC is just the next evolution for some of us.

Just my opinion.

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I’m confused by your statements, @Shipwreck.

What “limit switch” do you have and use that isn’t involved in “homing” your machine?

Why is homing and then setting XYZ zero as accurate as the machine can get for hobby use?

sorry if I confused you. I don’t see where I said limit switch is not involved in homing.

Limit switch allows you to get as close to absolute coordinates as possible(think most are .001 to .0001 accuracy) These coordinates allow repeatability for a variety of situations. Power outage, jogging issues (where it just keeps going), ect…
as well as
protects your machine from your original question a bad project design or even just software error.

For Hobby use its all preference. I’m just extremely picking and want it as close as I can with limited outside factors.

Again just sharing my preference and opinion. Very well could be flawed and there are different ways perfect for others take @gwilki solution.

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@Shipwreck I’m certainly not suggesting that your position is flawed.

I simply wonder if .0001 accuracy is really achievable on a repetitive basis, switches or not.

Using switches, the Mill jogs over to a corner and automatically sets XY0 at the same place every time. I believe that is not up for dispute. However, then the operator jogs the Mill to wherever he wants XY0 to be on the work piece. Now, if that location is precisely the same as the XY0 position set by the switches, then I believe we can assume that the level of accuracy is still the same.

However, for the sake of this discussion, let’s assume that the material is placed somewhere else on the spoil board. The operator jogs the Mill to wherever they want the XY0 to be and sets it using the touch plate or a manual method. Are we to believe that, in the event of a power failure, let’s say, he can find that exact spot again? I concede that he can find the “limit switch” XY0 again. But, I believe that it is a stretch to believe that he can get back to the precise coordinate from which he started his project.

That exact spot is the critical one, after all. If that one is off, the project cannot continue. If that spot is off on a two sided project, for example, the project will fail.

Maybe this is where my thinking is wrong. I have never considered the idea that, using switches and relying on their precise repetitive accuracy means that I must always place the front left corner of my material precisely where the switches determined XY0 to be. Any deviation from that position introduces the potential for an “error” what would kill the ability to get back to the precise starting point again.

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switches don’t automatically set you zero position.
In essence the switches allow the machine to find its position.

If I lose power and re-home, my zero is still set to the project area. Hit go to zero XYZ and its on the corner of your piece, no matter where it was at on the mill. No re-probing needed.

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