[Normsthename]

Now that I have repaired my press brake, I would like to replace the mechanical limit switches with something a little bit more modern and accurate.
What is the best switch to replace a Limit switch, the limit switch has a normally closed contact.
An electrician friend recommended that I fit a 24v DC Power supply and use a proximity switch with a solid state relay to replace the limit switch.
How accurate are proximity switches??
Is there a simple wiring diagram to show me how to wire the proximity switch?

Thanks

Andy

[Al_The_Man]

You could fit a prox, but if you use a quality switch such as Honeywell Micro switch, they are probably just as repetitive as prox, especially when using it to switch magnetic devices such as relays and solenoids, the characteristics of which have activation times that are relatively slow anyway.
The majority of brakes and shears use this type.
There is a diagram that usually comes with prox switches, the load symbol would be your relay and you can select the logic N.C./N.O. by selecting the appropriate relay contact.
If you use a SSR then you would have to select a prox with a N.C. output.
But check to see if the present switch is N.C. but held open.
Al.

[Normsthename]

Thanks AL
One of the reasons I want to change to a Proximity switch or similar is because there is no physical contact between the sensor and magnet.
On my machine the cams have worn and they have been built up with weld a couple of times.
So updating it would do away with that problem.
I also want to add a fine adjustment screw to the proximity switch or magnet so that I can finetune the bend angle
The limit switch that is currently fitted is normally closed.
What proximity switch or similar would you recommend I use for the best accuracy?

Andy

[Al_The_Man]

There are two types of proximity, magnetic reed switch and ferrous metal detection type.
The former is fairly slow and is electro/mechanical.
The latter is the best, also you do not require a magnet.
There are a great deal of makes and models to pick from. it would be an idea to browse some of the on line catalogues.
I do not know now what suppliers there are in the UK, but there are Omron, Turk, Balluff, Honeywell, etc.
I believe Keyence are in the UK also.
I would look at one of the 16mm threaded barrel type, if you get shielded, i.e. threaded right to the head end, they can be mounted flush, but have smaller sensing range.
The three wire type can switch a heavier load, if using it with a mechanical relay.
The two wire type require leakage though the load, so it can be a problem when using 2 wire with SSR's.
You can also get some universal AC/DC from 24v to 240v.
If you find a suitable one, you can post the number for it here.
Al.
Make that 12mm type.