What Limit Switches?

[Chaz]

So looking for both homing and limit switches.

This is for Thor which will have movement speed of at least 10m/min. Mechanical or Proxy? Will possibly using Index homing once sorted but I need to be able to stop a servo run away, so looking for something that will work and reliably.

[audioandy]

So looking for both homing and limit switches.

This is for Thor which will have movement speed of at least 10m/min. Mechanical or Proxy? Will possibly using Index homing once sorted but I need to be able to stop a servo run away, so looking for something that will work and reliably.

Mechanical limit switches us the normally closed contacts.

Proxy for home switches.

That's how we do it at work anyway.

Andy

[cropwell]

It took me a second or two to realise that proxy in this case did not mean one acting on behalf of another.
If you are using proximity switches mount them where they will not get covered in metal swarf.

Rob

[Boyan Silyavski]

I always overdo but probably anyone will need only 4 switches, where 2 go on both side of long axis / If a router/ . At the end i mounted only 7 on my machine/ though bought 12 of them. But as Soft limits work, servo has its own limits, probably the board has its own software limits...maybe 4 will be enough.

I use Proximity, NC of course.

Another aspect which i overlooked is that they activate at 4mm, so basically to Home now i have to do it slowly so i will not overshoot, luckily the Chinese controller i use does up to 5 times homing, so if first time overshoots second time its precise.

What i am saying is i just found out that there are 8mm versions which may be better, so you could home faster, not that i am in a hurry. I think its worth checking and finding longer distance limit switches.



I start to think mechanical could be better idea, but they must be enclosed in solid case and avoid bending plate type. There should be clearly defined push axis and mount them respectively.



I was also mistaken to think that perpendicular to plate measured mounting will give me better precision. means i can hit the switch face and crush it if machine does not stop. / ok not so i i have hard stops, but you get the idea/. So if i am to do it again it will be side mounting where no interference will happen and switch will be better hidden on the machine, not bluntly visible.

[cropwell]

I learnt the hard way that end-on proximity switches are vulnerable.

As far as homing accuracy is concerned Mach3 wallops up to the switch until it is triggered and then backs off until the switch is un-triggered, so I would imagine if you approach at warp speed, it would still maintain accuracy and consistency of the home position.

Rob

[A_Camera]

So looking for both homing and limit switches.

This is for Thor which will have movement speed of at least 10m/min. Mechanical or Proxy? Will possibly using Index homing once sorted but I need to be able to stop a servo run away, so looking for something that will work and reliably.

I definitely vote for mechanical NC limit switches. The reason is that if something goes wrong with them the machine stops, you look for the error and eventually will find it. If you use proximity switches this may not always be the case, regardless if you use NC or NO type. Of course, for limit switches, nothing else but normally closed (NC) should be used, they guarantee broken wire detection also, which you can't have if you use normally open connection.

For home switches... well, I think mechanical is best but accurate mechanical switches are very expensive. I don't use any home switches, but have heard that proximity switches are accurate too. I guess it depends on the accuracy you need and the method of homing. Some software are better than others.

[komatias]

Depends on the controller actually.

Mechanicals are fine for both limit and home but have you thought of maybe using the home on index function offered by some controllers? I have this on my GSK and I know that some of the CSMio's have this function too.

It would be the case of hitting a switch that initiates the slow movement and then does one full rotation of the screw until a flag is tripped or similar.

[Chaz]

It took me a second or two to realise that proxy in this case did not mean one acting on behalf of another.
If you are using proximity switches mount them where they will not get covered in metal swarf.

Rob

Sorry, its an 'old' term we used to use as Electricians in South Africa.

[Chaz]

So based on all of this, I am 'leaning' towards this type of limit switch. There is no 'end' sensor so if it runs part, it just pushes the arm.

Something like this -

[Chaz]

Any reason this will not be suitable?

This will be used to trigger into a CS Labs IP-A unit.

http://uk.rs-online.com/web/p/safety...tches/6211515/