[harryn]

Hi,

A friend is helping me through an upgrade of a small cnc project. It actually didn't work when I got it and with mach 3 / windows support becoming complicated, decided to change out some items.

The motors and controller for the project are on a test board for convenience and we can now move all 3 axis with on a bench.

Before we transfer it onto the cnc, I would like to add some limit switches to reduce the risk of damage.

If possible, it would be nice to also have a way to go to a (0,0,0) position, but that is not an absolute priority right now.

Any suggestions on some limit switches ?

This is a hobby. I want it to be reliable, but don't want to spend $100 / switch either.

I prefer to not buy from ebay if possible.

Thanks for any insights.

Harry

Misc info for the curious:

- MK3/9
- software license
- MPG pendant and adapter
- 10 pin header adapter
- 16 pin header adapter
- various shielded USB cables, and wires
- 3 each of the gecko 213V stepper motor drivers
- 3 stepper motors
- 48 volt power supply, etc


In case it matters, it is a small moving gantry system.
- about 3x4 ft x ~ 4-5 inches of z
- palm size router attached
- The linear motion parts are just the hobby grade cnc router parts carriages, so not a precision setup
- nema 23 size stepper motors
- lead screw - looks like an acme thread
- single motor and drive on each axis
- 8020 type construction

Plans
- Routing some 18mm baltic birch with joints
- Drilling holes
- Possibly some plastic hole drilling
- Goal is +/- 1mm overall dimensional accuracy results on a 20 x 30 x 3/4 baltic birch ply ( ~ 500 x 700 x 18mm ply)

Not sure if that is possible or not with the linear motion components and framing or not, but will have some fun playing with it.

Harry

[maki]

I am using this ones, big robust. They are suited for smaller speed fe. <2000mm/min. For high speed machine is bertter something like this one, mounted before mechanical limit.
Sorry this is not in us but....

[machinehop5]

Multiple Limit Switch type with all in one unit are nice for Home, - Limit, + Limit
https://www.mouser.com/datasheet/2/3...2175-42899.pdf

[maki]

I personaly just don't see anny advantages of this werry werry expensiwe switches instead a few € or $ specialy because the sotware itself have special procedure for homing&ending (assuming this is a hobby cnc machine). If I would like to have more sophisticated system then I will took some of electronics ones (non touchable), both works great!

[joeavaerage]

Hi,
I use these as home switches. I personally get better that 0.02mm repeatability with them. I believe they are more useful than limit switches.
Once your machine is homed then 'Soft Limits' are adequate.

https://nz.element14.com/honeywell/b...ger/dp/1525198

If you really want limit switches the get cheap Chinese proximity switches, you ca get half a dozen for $30. Note that because they are electronic devices you can't
just hook them in series, you would be advised to have one switch per input pin. Three axes=6 switches=6 inputs PLUS 3 home switches=3 inputs for a total of 9 inputs.

Craig

[harryn]

Thank you everyone for the suggestions. I have some more reading to do now and these suggestions will definitely help.

The plan at the moment is to wire each switch individually to the MK3/9, so yes, 6 of them.

At this stage - which is mostly reading knowledge and not as much hands on - my main concern is to prevent the machine from crashing due to user errors.

Several people in the family and friends will likely be using the router, so the risk of errors becomes high for all of us, especially during the learning stages.

I will strongly consider the idea of using switches for both limit and homing.

US$20 / each is within my budget. $320 / each is more than my budget at this stage for a hobby machine.

[SeeAnnSee]

HarryN:

For a strictly hobby-use machine, why would you need anything more elaborate than a simple $2 micro switch?

Something like this:
Attachment 435968

The reliability, and the repeat ability, of these cheap switches is quite remarkable. No, they are not state-of-the-art, but they are definitely good enough for most hobby applications. At the very least, give them a try. For less than $15 you might have a solution that works well enough for your needs. If not, you could swap these out for something more sophisticated (and, yes, expensive).

- SpindleJockey

[maki]

The only thing is the size you use, "SeeAnnSee" sugesstion is perfect for small to medium size, I have more robust ones (bit bigger) quite cheap (few €/piece).
Just take care to mount them before the end fe. 3-5cm so the mowement have place to stop. This depends of adjustement in the Planetcnc software (speed up and speed down nr. defoult is 200).
Sugesting that you test how much movement is made when arming the switch. My switches are connected in series like in the info for connectin things po mb.

[Fishermanmax]

I use Schmersal which are designed to automate work operations in industrial plants and mobile work machines...

[tombaker]

I used this one Limit switch / switch Schneider Electric XCKP2145P16

[harryn]

Hi,
I use these as home switches. I personally get better that 0.02mm repeatability with them. I believe they are more useful than limit switches.
Once your machine is homed then 'Soft Limits' are adequate.

https://nz.element14.com/honeywell/b...ger/dp/1525198

If you really want limit switches the get cheap Chinese proximity switches, you ca get half a dozen for $30. Note that because they are electronic devices you can't
just hook them in series, you would be advised to have one switch per input pin. Three axes=6 switches=6 inputs PLUS 3 home switches=3 inputs for a total of 9 inputs.

Craig

I did quite a bit of searching and could not find that exact switch stocked in the US at an online electronics distributor. Instead I purchased a similar part number ( BZ-2RG18-A2 vs BZC) from online components.

They should arrive soon and hopefully next week I will get a chance to try them out.