Limit swtich newbie question

[mealman]

Hello everyone, I am completely new to CNC electronics.

My recent project requires me to build the electrical part of a 3 axix cnc milling machine.

I have purchased the stepper motors, breakout board, gecko drives and power supply. What I need to do is to find suitable limit switches with good price.

Do I need 6 limit switches for 3 axis?

What are the limit switches you guys are using? I have been looking on the internet, there are roller, or leveler limit switches, what are the exact difference between them?

I want to keep my budget as low as possible. Thanks in advance to answer my stupid questions. Have a nice, fun and happy day.

[Bubba]

mealman,
OK, how many switches do you need, is a good question. On my mill drill,I use 1 switch for the X and Y axis respectively (2 switches) and on the Z, I use two switches.

On the X and Y, I used mini din switches from Automation direct (about $12 ea) on on the Z axis, I used micro switches (dumpster dive $0).

The X and Y switches are "coolant resistant" and well worth the money. The Z switches are out of the path of coolant and swarf so micro lever operated switches work just fine.

Repeatibility on all of the switches is good and I am happy.

[project5k]

just how important is repeatability on your home switches? i guess if you were using a true fixture and running several copies of a part over the course of several start up cycles, then maby.. but for the average home user, just being able to home the machine within a few thou would would seem to be good enough for me.. cause i'm gonna manually jog over to my work anyway and re-zero there...

[mealman]

[QUOTE=Bubba;344867]mealman,
OK, how many switches do you need, is a good question. On my mill drill,I use 1 switch for the X and Y axis respectively (2 switches) and on the Z, I use two switches. QUOTE]

Hi Bubba, I don't understand why you only need 1 switch for X and Y respectively. Coz X and Y axis travel both horizontally right? so don't you need 2 switches for X and Y respectively (that's four in total)?

[Greolt]

What Bubba means is the switch is mounted on the moving part and whatever actuates it is at either end of the travel.

That makes one switch per axis instead of two.

Greg

[project5k]

i know mach will accept having the same input for the home and -- limit, but will it allso accept the ++ limit on the same input as well?

[Greolt]

Yes

[Bubba]

to clarify, I have the X and Y switches mounted on the non movable portion of the base and saddle respectively. There are contact points that will hit the switch lever from either direction. Here is a lousy picture of my X limit that I happen to have on file.

[mealman]

Thx Bubba for your explanation. But it is still a bit confusing to me, I still dont get it why only 1 limit switch is needed for each axix. I will search a bit more on the internet

[Bubba]

If you look just to the left of the limit switch, you see the piece of angle with the bolt sticking out of it? It is bolted to the dovetail and moves with the X axis.
There is a lever on the switch and when the table moves (in this case to the right), it will contact the lever on the switch and trip it. There is a similar bracket bolted to the table on the right hand side.

Attached is the first two pages of the specs on the limit switch from Automation Direct.

I tried to put the whole thing up, but it is to big.

[mealman]

Thank you very much, Bubba. I finally got it now. ~

Thanks for your data sheet and pictures