Got a Gecko G540, now which limit switches and E-Stop?

[CNC Lurker]

I got a 3-axis kit which includes a Gecko G540, power supply, and Nema 23 380 oz-in stepper motors. Now I need to buy the e-stop and limit switches. I've searched and read several threads on limit switches and e-stops, but I haven't found which ones to buy or where to get them from.

I've read it is better to get the e-stop that locks close when you hit it, and you have to twist it to unlock it, but where do you buy those at?

I've googled micro-switches and limit switches, and they range from $2.50 to over $100. There are also some with a roller on the lever/arm, and some switches don't have any rollers.

I'm in the states, TX actually, where would be a good place to get limit switches?

One last thing, I know I need 2 limit switches for each axis, so that is 6 switches. I've read where some are using them for "home" also. Would I use 1 of the limit switches as a "home", or would I need to add another switch to each axis (for a total of 9 limit switches)?

[brtech]

I got my e-stop on ebay. Something like this:
Emergency Stop Mushroom N/O N/C Push Button Switch - eBay (item 300498494577 end time Dec-28-10 14:24:18 PST)

For limit switches, you get "snap action" microswitches, and Digikey is a good place to get them. There are two types: a "lever" and a "roller". Opinions vary if you need/want a roller.
A sample part number is:
Digi-Key - SW873-ND (Manufacturer - SS-5GL2T)


You usually have one limit switch on each end of each axis. 3 axis, 2 per axis, 6 switches. You can use one of the two on each axis as home. You don't wire it differently, you just configure the home switch on the same pin as the limit switches.

[Torsten]

Originally Posted by CNC Lurker I got a 3-axis kit which includes a Gecko G540, power supply, and Nema 23 380 oz-in stepper motors. Now I need to buy the e-stop and limit switches. I've searched and read several threads on limit switches and e-stops, but I haven't found which ones to buy or where to get them from. I've read it is better to get the e-stop that locks close when you hit it, and you have to twist it to unlock it, but where do you buy those at? I've googled micro-switches and limit switches, and they range from $2.50 to over $100. There are also some with a roller on the lever/arm, and some switches don't have any rollers. I'm in the states, TX actually, where would be a good place to get limit switches? One last thing, I know I need 2 limit switches for each axis, so that is 6 switches. I've read where some are using them for "home" also. Would I use 1 of the limit switches as a "home", or would I need to add another switch to each axis (for a total of 9 limit switches)?

You actually only need one limit Switch per Axes.
Just have to make sure something triggers the switch as the travel nears each end.
You will want to design the trigger mechanism in a way that allows the axes to travel past for a short distance.
The controller needs a little room to decelerate once triggered.

[brtech]

Uh, if you want to stop motion on either end of the axis, you need two switches per axis. I think what you meant is you only need one INPUT per axis, with both switches wired to the same input.

[CNC Lurker]

Originally Posted by brtech I got my e-stop on ebay. Something like this: Emergency Stop Mushroom N/O N/C Push Button Switch - eBay (item 300498494577 end time Dec-28-10 14:24:18 PST) For limit switches, you get "snap action" microswitches, and Digikey is a good place to get them. There are two types: a "lever" and a "roller". Opinions vary if you need/want a roller. A sample part number is: Digi-Key - SW873-ND (Manufacturer - SS-5GL2T) You usually have one limit switch on each end of each axis. 3 axis, 2 per axis, 6 switches. You can use one of the two on each axis as home. You don't wire it differently, you just configure the home switch on the same pin as the limit switches.

I looked at that seller fro the e-stop, from he's from Hong Kong and it would take about 10-21 days to get here. BUT you did give me the search term to look for and I found a USA seller of that exact same e-stop and I just ordered it.

For future reference, the Ebay seller's name is tree_kicker and he sells it for $7.99 with free shipping. He had it listed as "Emergency Stop Switch Push Button Mushroom PushButton".

I'll look at the Digikeys micro switches.

By the way, I see you built the FLA-300, I'm going to start a thread on the FLA-100 I'm building.

I got my 3-axis kit from FLA with the Black Friday $50 off deal : 3 Axis Electronics Kit

[JD_Mortal]

Remember, the purpose of an "emergency stop" is to kill power directly at the source. (As opposed to being an input to a digital readout, requiring the computer to act on that action. That is unsafe.)

That is why emergency switches are so expensive. They usually connect directly to the power, or a power-breaker, which has to handle high voltages and amps directly, and keep the operator safe from disconnect shocks. (When you abruptly stop power, the amps continue to flow, like momentum, and try to jump connections. Thus, the elaborate internal setups for industrial emergency switches. This often includes dual-line breaks, and a physical separation arc-gap wall between contacts. Possibly also some quick-snap springs to pull contacts to a non-arc distance.)

For these tiny devices, we don't need super-industrial, OSHA required emergency stop buttons. We simply need something that will handle 240vac @ 30a for most uses. It should be 4x your consumption. Though, you may want to get dual-contacts, and break the live-wire of the motor drivers/power and the spindle/power separately. Though, if they are all plugged into one location, like a power-bar or a rail, killing the rail is fine. (But you can get feedback from the spindle, pumped into your sensitive electronics.)

You do not, and should not, have to kill the computer. Just the power to the moving devices.

I got my hand crushed in a 6-on-6 web printing-press, hurt like a b***h because the one place that I was located, didn't have an emergency stop button. Every other location had one, except that one. So the conveyor grabbed hold of my rag, and pulled my hand inside the conveyor-belt, slowly... My hand wrapped backwards, popping and crunching, around a metal roller that was as wide as a beer bottle... Luckily, it was just tendons and knuckles popping. No permanent damage. It stopped when the circuit-breaker popped. No-one could hear me screaming.

You don't want to accidentally lean over, and your hoodie-tie gets grabbed by the 10,000 RPM spindle... Or accidentally "think" that it is safe to clear some debris, and the spindle decides its next move is up, and into your finger... and not have a stop-button handy for you to reach.

Sorry, got a little side-tracked... what was the question?

Oh yea... switches...

You can use one micro-switch for each axis, if you mount it in the moving mount. The switch, for example, would be in the center near the nut, and a pole extending off the walls would break the NC connection. That works for both the STOP and the LIMIT switches, which you should have both. However, I think it is better to have two LIMIT switches, so you can freely move them to the work-area-edges. That keeps the tools from having to travel all over, and gives you more options for mounting your material in any location.

EG... like this... (--- = rod) (# = switch) (=== = rail) ( [] = spindle)

|---     [  #  ]     ---|
|========[_____]========|

does this...

|-[--#  ]            ---|
|=[_____]===============|

and this...

|---            [  #--]-|
|===============[_____]=|

The STOPS should immediately stop the motors, as that is the crash border. Having enough room to decelerate is a thing to remember. The LIMITS should be prior to the STOPS, eg, hit first by the moving platform. They should be set to reverse the motors, or throw them into slow-mode, or some other corrective action. (You would/could also use those for your HOME switches.)

You don't need them both, but it makes it better and safer if you do have both STOPS and LIMITS.

[Fastest1]

Where in Texas? If Houston, try EPO or Ace Electronics. A latching Estop is safer but as long as it cuts the power til reset either style works.

[CNC Lurker]

Originally Posted by JD_Mortal Remember, the purpose of an "emergency stop" is to kill power directly at the source. (As opposed to being an input to a digital readout, requiring the computer to act on that action. That is unsafe.) That is why emergency switches are so expensive. They usually connect directly to the power, or a power-breaker, which has to handle high voltages and amps directly, and keep the operator safe from disconnect shocks. (When you abruptly stop power, the amps continue to flow, like momentum, and try to jump connections. Thus, the elaborate internal setups for industrial emergency switches. This often includes dual-line breaks, and a physical separation arc-gap wall between contacts. Possibly also some quick-snap springs to pull contacts to a non-arc distance.) For these tiny devices, we don't need super-industrial, OSHA required emergency stop buttons. We simply need something that will handle 240vac @ 30a for most uses. It should be 4x your consumption. Though, you may want to get dual-contacts, and break the live-wire of the motor drivers/power and the spindle/power separately. Though, if they are all plugged into one location, like a power-bar or a rail, killing the rail is fine. (But you can get feedback from the spindle, pumped into your sensitive electronics.) You do not, and should not, have to kill the computer. Just the power to the moving devices. I got my hand crushed in a 6-on-6 web printing-press, hurt like a b***h because the one place that I was located, didn't have an emergency stop button. Every other location had one, except that one. So the conveyor grabbed hold of my rag, and pulled my hand inside the conveyor-belt, slowly... My hand wrapped backwards, popping and crunching, around a metal roller that was as wide as a beer bottle... Luckily, it was just tendons and knuckles popping. No permanent damage. It stopped when the circuit-breaker popped. No-one could hear me screaming. You don't want to accidentally lean over, and your hoodie-tie gets grabbed by the 10,000 RPM spindle... Or accidentally "think" that it is safe to clear some debris, and the spindle decides its next move is up, and into your finger... and not have a stop-button handy for you to reach.

I was thinking about that actually. If I hit the e-stop, it stops the steppers, but the router is still running. I was wondering if I needed a stop for the Porter Cable 690 router I will be using, something like this one from Rockler: Safety Power Tool Switch

I'm using an E-stop because in one of the builds someone posted, the z depth was set wrong and it kept on going down into the table.

I do plan on keeping all body parts out of the way. In a former life, I was a sheetmetal fabricator, and I've seen a few fingers crushed in slip roles, brake presses, and punch presses. I don't fear the machines, but respect them.

Sorry, got a little side-tracked... what was the question? Oh yea... switches... You can use one micro-switch for each axis, if you mount it in the moving mount. The switch, for example, would be in the center near the nut, and a pole extending off the walls would break the NC connection. That works for both the STOP and the LIMIT switches, which you should have both. However, I think it is better to have two LIMIT switches, so you can freely move them to the work-area-edges. That keeps the tools from having to travel all over, and gives you more options for mounting your material in any location. EG... like this... (--- = rod) (# = switch) (=== = rail) ( [] = spindle) |--- [ # ] ---| |========[_____]========| does this... |-[--# ] ---| |=[_____]===============| and this... |--- [ #--]-| |===============[_____]=| The STOPS should immediately stop the motors, as that is the crash border. Having enough room to decelerate is a thing to remember. The LIMITS should be prior to the STOPS, eg, hit first by the moving platform. They should be set to reverse the motors, or throw them into slow-mode, or some other corrective action. (You would/could also use those for your HOME switches.) You don't need them both, but it makes it better and safer if you do have both STOPS and LIMITS.

That's kind of what Torsten was stating earlier:

Originally Posted by Torsten Just have to make sure something triggers the switch as the travel nears each end. You will want to design the trigger mechanism in a way that allows the axes to travel past for a short distance. The controller needs a little room to decelerate once triggered.

I've read that there are hard switches (micro switches) and soft switches (in Mach3) and I believe having it slow down before it hits hard switches can be done in Mach3. I'll do some more reading on that.

I haven't bought Mach 3 yet, but I did get my Gecko and steppers yesterday, but I haven't hooked them up and tested anything yet. I'll have to read and see if they can move without an e-stop/fault error.

[CNC Lurker]

Originally Posted by Fastest1 Where in Texas? If Houston, try EPO or Ace Electronics. A latching Estop is safer but as long as it cuts the power til reset either style works.

I'm in Rockwall, TX.

I did stop at a Radio Shack on the way home and I found these there (see attachment).

If rollers are not necessary, then I'll just pick these up.

[JD_Mortal]

Almost any type of switch will work, depending how you setup the contact point. The voltages/amps are low, and you will not be hitting them over 10,000 times under normal situations...

The only thing you have to worry about is "contact corrosion" (Get nickle-plated or gold plated if you are going for broke.)

As for impact ratings, and g-forces... Those can be issues depending on how much your machine vibrates and how you setup the contact of the switches. The roller is good because it allows you to use a spring-ramp and the roller itself is also on a leaf-spring arm. Thus, impact is nearly zero. (As opposed to a toggle-switch or a micro-switch which would require you to manufacture some form of leaf-spring to depress the contact.)

Secure it well and if possible, within a sealed enclosure with the switch-arm poking out through a slit that is cut in a piece of rubber or thin plastic. That will keep salty-humidity and dust away from the contacts inside. (The cheap ones at RS tend to have holes and poor push-clip seals which allow contaminants to enter the shell.)

[RomanLini]

These might look a little scary at first, but they are actually simple to work with as they just have 3 wires; +5v, ground and the output wire;
http://www.cnczone.com/forums/open_s...made_easy.html

Thye have no moving parts to fail (like microswitches) and they are much more accurate, mine tested as good as 0.01mm repeatability.

[ger21]

I was thinking about that actually. If I hit the e-stop, it stops the steppers, but the router is still running.

Here's what I'm going to do. my Motor power supply and router are both fed by the same 110V line. Putting an estop switch in that line will stop motion by killing power to the drives, and will shut off the router. Depending on the power supply, it may keep moving for a second or two though.