Choosing Limit Switch? How to? Please advice

[cjchands]

Choosing Limit Switch? How to? Please advice

I have been listening to couple post in regard to choosing limit switch that will be use with mini mill X2, obviously I got different opinions how you would pick either NC or NO. But what I don't see in the discussion is how what brand or where people recommend to get for the limit switch.
I have seen many types of limit sw: BUTTON, LEVER, ROLLER and they come into different price and spec.
I am a total newbie here, and would like recommendation of where and what type (NC) that experience users are using.
Doesn't have to be super precise, but don't want crappy one either.
Thank you very much.
Appreciate it.
JEff

[pastera]

Normally closed is the "safer" route - if a wire gets pulled it actiivates the limit.

Roller allows the axis to overtravel without crushing the limit switch or bending brackets.

Get a switch that is specified as a limit switch - they have well defined actuation displacements and are repeatable. A switch that activates in different spots every time is of no use, so spend a little extra.

If you're on a budget, look at optical interrupters (slot switch). With a little effort they can be very accurate.

Aaron

[Bubba]

CJCHANDS
To answer your question on brands etc, I use the AAP2T51Z11 mini switches from Automation Direct. www.automationdirect.com
As I remember, I paid on the order of US$12 each for the ones I used and according to the lit. are rated at and accuracy of "0.01mm on the operating points at 1 million operations"
I have been a happy customer etc.

[cjchands]

Bubba, $12 for each limit, I guess you get for what you pays for.
In the post that read, a lot use something below $3-5, so I suppose those are not good quality wises.
Also, I guess 'garage door' limit switch is also out of question?
What about RADIO SHACK one that a lot of people use? (...I haven't seen one in the store and can't find it on their online store either).
Any comment? Thank you
Jeff

[Bubba]

Jeff,
The first set of switches that I built for the X and Y axis were of the micro switch variety and even though I "attempted" to protect them from swarf and coolant (I use flood), they soon became corroded and loaded and failed to work. So the change to the ones listed was a good move for me. In addition to changing out to these switches, I ran the wiring through pvc tubing that was sealed on the switch end. To me, this was money well spent a couple of years ago as they have given me no problems.

[Walt@SGS.Inc]

I was going to recommend Square D from Grainger but then I looked at the money that was being talked about and decided to forget it.
Regards Walt..
But it don't cost too much to look. Limit Switches and roller arms.

[lerman]

For a limit switch, it doesn't really matter if the actuation point varies by 50 or 100 thousandths.

You want a home switch to be dead on if you are going to want to be able to hit the same location from one homing operation to another.

Ken

[Bubba]

Ken,
The above switches are listed at a repeatability of .01mm (0.000393") and doing some testing some time back, that is pretty darn close to what I remember getting. I also have an optical on my Z axis that is used for tool length offset and it has shown a repeatabily of 0.000142"

This is well withing my equipment and my talent abilitys for the work I do:})

[cjchands]

Thanks for a lot of comment guys...
I see why you rather choose to go with AAP2T51Z11 mini switches from Automation Direct.
This will be my first project, so I am not looking at cutting any hard metal or using any flood or a lot of coolant. Therefore, budget does come into play here, but again, I do not want to get any crappy limit switch that doesn't work.
So a low budget switch that would do the work, would satisfy my first project.

http://cgi.ebay.com/ws/eBayISAPI.dll...MakeTrack=true

I found this one on e-bay, any good with this???
Thanks again guys.

[cjchands]

Or I found another one next to it:
http://cgi.ebay.com/10-BURGESS-Micro...QQcmdZViewItem