Need recommendation for limit switches

[Jackal66]

I need a recommendation for GOOD limit switches. Maybe something like Omron, Honeywell, etc.

The proximity type on my Hurco now are enclosed. The type I want are just plain NC preferably with a roller tip.

Something like this:



I know that a lot of people are using these:



I just don't care for those micro switches.

While some of the good switches are $300 new, there are a lot of them on E-bay new-old-stock, that are reasonable.

Thanks in advance,

JAckal

[Al_The_Man]

I use the hermetically sealed Honeywell 914CE series.
New Product Search
They come in many types of actuator, and the roller option can be 0° or 90° to the body, they also have a hermetically sealed cord attached.
They have an internal micro switch so the repeatability is very good.
They are not cheap, but ebay is a good source.
Al.

[Jackal66]

Thanks Al,

Here's a brew to you


JAckal

[Bubba]

Back when I set my machine up, I used the AAP series miniature DIN limit switches from Automation Direct. As I remember, they were about $13 a piece then. The units are sealed, and I used some small tubing that I RTV'd into the conduit connection and ran the wiring in that back to the control box. Haven't had a problem in about 10 years with that setup.

Edit: Just checked and the price is increased to $14.25 www.automationdirect.com

[wildwestpat]

You need to be clear that the choice of axis limit switch is a bit different from the requirements of the axis home switch. (Home switch requires a degree of precision the limit switch is there to stop the travel and does not necessarily have to be so accurate.)

You might like to rule out any that use optical or magnetic sensing as these will eventually suffer from erratic action due to swarf or dust. You might get away with magnetic sensing on a wood only machine or optical on a metal working where rudimentary protection from swarf and coolant is easy to arrange.

That leaves a choice between mechanical switches and those that use the inductance shift in a tuned coil. The choice between the two technologies is about number of operations in the life of the switch and the mechanical configuration and sealing.

The mechanical switches tend to be larger than the frequency shift inductive type.

You have posted typical examples of the sealed micro-switch - the actuator arm is required to provide over travel assuming the table does not stop the instant the switch changes state and this increases the size of the switch.

The frequency shift inductive proximity switch is available as either block mount or as a bolt type. I have used types LFM11 and LM22 the LFM11 is approximately 12 mm x 18 mm x 35 and the LM22 is a threaded M22 and is 60 mm long. Both switches incorporate LED lamps to indicate their state which helps in setting up but is otherwise not needed. The price is lower than the mechanical switch and the operating life longer which is a nice surprise. I paid around £4 for the last batch I bought and the stability has been satisfactory under normal work shop temperature rises. If these sensors are of interest use eBay or Google for the type numbers.

Hope this helps - Regards - Pat

PS On a really large table I have used a switch of last resort consisting of a glass fuse in a suitable sealed plastic mount arranged to smash the fuse rather than subject the axis to the full force of the drive motor which in this case was hydraulic. The Fuse link being in series with the valve directing the axis on to end stop. This passed the testing OK but conventional (reusable !) limit switch was used for normal operation. Also with some motion control software there are soft limits when set correctly will stop excess axis excursion so that you would not experience operation of the limit switches. That said if you have faith in the software why fit limit switches - pessimist or optimist - that is the question that only you can answer.

[Jackal66]

Thanks for the info guys.
The switches will be mechanical NC type. My plan is to run each axis on a separate input and assign the same pin #'s to the switches for homing.



Thanks,
JAckal

[wildwestpat]

Plan is OK but the travel to hit the home switch is the full axis traverse. This is why some people feel the need to have a separate homing switch. Also the homing switch repeatability has to be good if the reference is to hold steady. The various designs of actuator have different characteristics with respect to sensitivity - repeatability - over travel.

Regards - Pat

[underthetire]

Sorry, you can't beat the yamatake honneywell SL1A. Very common, been in use for years, and available through all world machinery for about 22 bucks each.

[Al_The_Man]

Originally Posted by underthetire Sorry, you can't beat the yamatake honneywell SL1A. Very common, been in use for years, and available through all world machinery for about 22 bucks each.

My Honeywell price list shows these at $86.00!!
The 914CE series are less than that and come with a sealed cable.
Al.

[underthetire]

I know, the price list is high. All world is super cheap. I prefer not to have the sealed cable, I like the seal tight on the SL1A, that way when it fails, you don't have to re-string it through the machine.

[Jackal66]

I looked for All World and found them on E-bay. They only have (2) switches listed.

Yamatake Limit Switch SL1-A | eBay

Someone e-mailed me the other night about these:

Honeywell - SZL-VL-H - Switches - Sensors, Switches & Relays - Allied Electronics

The price isn't bad, but there might not be enough room on the X axis. They look like a black metal housing, with the blue part being plastic.

I need something that really is, oil, chip, & coolant resistant.

JAckal

[underthetire]

Just call all world direct. They usually have 100+ in stock.