Limit switches or not?

I am definitely sold on using them. I’m new to machining of any kind, so I’m making every effort not to develop any bad habits.

So the shielded wiring sounds like a good idea even if I’m upgrading my controller. But I’m really not looking forward to having to thread everything through the drag chains again. Is there some trick that might make that easier?

+1000!

It IS worth your time to wire the switches and learn how to use them, it will have a dramatic impact on your carving experience.

I bought my switches with the machine but didn’t install for the first 2 months, and I did all of the positioning \ zeroing by eye and was constantly terrified that the power would go out, or I’d lose steps or have to hit the E-Stop because I did something stupid and ruin my cut.

Once I added a bump stop, and the limit switches, I’m no longer concerned about stopping the cuts mid-carve, because I know I can issue $H and G28 and pick right back up where I left off. It really IS that simple… a few dollars in switches and a few dollars in shielded cable really makes this a no-brainer, and considering that you’ve already demonstrated you’re capable of building the machine from parts, and you’ve gotten this far, it would really be a pity if you didn’t finish the machine properly.

Make sure to watch @PhilJohnson’s youtube video above as many times as it takes to answer all your questions about the necessity of limit switches, and make sure to ASK if anything is unclear. IMHO the switches change the machine from a CNC to an Ultra-Precise CNC…

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Running an extra wire, or a piece of string, when you first install cables in the cable chain is handy. This can be used to pull any extra wires you want to add later. Sorry, not that helpful if you’ve already run your wires.

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You can also use one of the wires that is currently in the drag chain as a pull wire. Just hook two (or more) together and pull one of the existing wires out with the new wires attached.

That’s a great point. I’ve already got the unshielded limit switch wires in the drag chain. I’ll use them to pull the replacements in.

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Just to add a little more to this thread…I switched out my mechanical switches for magnetic hall effect sensors. 2 on the X and Y axis and 1 at the top of the Z-Axis. I am NOT using shielded wire, I simply twisted three wires together and ran them from the sensor to the controller…no false triggers yet. Homing and limit switches are turned on in GRBL. The switches will stop the gantry moving 200 inches per minute without a collision (I tried this a few times…on purpose :slight_smile: ).

I bought my sensors here:

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This is the setup I’d be willing to try sometime in the future (and what I wish the machine had come with).

@ErikJenkins - I assume you’re using one for homing and the other for hard limits on X and Y?

Correct, I home to the front/left/top using those switches, but all the switches are also hard limits.

Thanks!

And at the risk of asking a question already asked (I searched but can’t find) - when you add hard limits you simply just add another switch inline for that axis and then enable a $ setting in GRBL to turn hard limits on, right?

If that’s the case (I’m assuming yes) - how does that work if you’re using NC switches? or does it?

Do the hall effect switches even support NC?

There is another setting in GRBL to use normally closed. $5 setting.

$5=0 - normally open
$5=1 - normally closed

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thanks @ErikJenkins and @PhilJohnson - I knew about $5 for NC, I guess for some reason I was thinking that series wouldn’t work for NC … not sure why, apparently it’s time for more caffeine.

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Phil,
I watched your video… very helpful. Just wanting to make sure I’m clear. When you are talking about a bump stop, you mean the “L” shaped piece of wood you have attached to your machine, and not something that your machine bumps into to go to a position, correct?

This overall discussion is convincing me that I need to build some physical protections for my switches and get them mounted and use them. It is somewhat sad that I have ALL the wiring completed except for connecting the switches. Unfortunately, I’m tied up this weekend and all next week so won’t be able to try it out for a couple weeks.

–Rick

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Great thread. Nice to see the exchange of ideas/opinions/facts without people getting ugly, which I have witnessed on other sites. One reason I like this site!

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I did long time ago, just one simple hole and thread. No possibility to break Z switch again.

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I drilled and tapped a hole for a bolt in my Z axis plate to protect the switch after the first one effectively vaporized in a crash, I think I’ve shared it before. Got the idea from someone else though…

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I installed a second limit switch on my ‘Z’ axis slightly behind the ‘homing’ switch. This is wired inline with my emergency stop button. If the ‘Z’ homing fales the power is cut off.

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I ordered and installed limit switches with my x-carve, but quickly found I had no use for them. I never did break any, but I discovered that so long as I was properly zero-ing my X/Y/Z at the start of every project, the limit switches served no function from my perspective. I ended up disconnecting them and haven’t used them since.

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This is great. It reminds me of: manual vs automatic, Beta vs VHS, Vinyl vs CD, film vs digital and on and on.

Bottom line is there is no right or wrong here. What works for you is the best way to go.

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You could always go cheap and just stand over the XCarve whenever it’s running with your hand poised over the E-Stop like you’re a contestant on Family Feud…

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