February 5, 2010 at 7:01 am #2259
I just ordered everything tonight! What i didn’t see on the list was any kind of limit switches. Does your cnc have them installed? Where do you advise getting them?February 5, 2010 at 3:58 pm #3356
@DIYengineer, the plans currently do not include limit switches, but they are easy enough to set up. We ran a few tests but left them out of the plans for simplicity’s sake.
We had good luck with these switches from Jameco. In a nutshell, the switch ties in with the 5V line from the driver board, then terminates in the appropriate pin. Here’s a blurb from the HobbyCNC instructions about how to set it up:
EMC2 can accommodate either normally open (NO) or normally closed (NC) switches, and the instructions above are right that normally closed switches are better since they fail safe. Check here for info about how to set up the signal controls once you get the wiring done.February 6, 2010 at 8:32 pm #3357
How many would I need? Im guessing 6 right? 2 for each axis? What is a home switch? Are they just speaking of the same thing, or is that another that needs its own switch. I will order them up when I hear back from you, thanks for your help.February 6, 2010 at 10:31 pm #3358
There are a couple terms at work here. Hard limits are the physical limitations of the rig – hit those and the machine will mechanically lock up and potentially damage itself. Limit switches should be placed where they will arrest machine movement before it can reach hard limits. You can program the machine to instantly stop whenever one of the limit switches is tripped (due to careless jogging/manual movement or a toolpath that accidentally runs the machine to a hard limit).
Home switches are used to run the mill back to a default starting location. When you run the same kind of job over and over, you might benefit from an additional set of home switches (if you used 1/2″ material exclusively, for example). You can also use the hard limits as home switches, where you effectively tell the computer to run all three axes until the homes are tripped. We usually just jog the device by hand with a careful eye and reset the axes for each job as material thickness and positioning changes.
You’re right about the number – you need 2 switches to limit each axis.February 7, 2010 at 12:56 am #3359
You explained that extremely well, thank you. If I wanted to incorporate home switches how many more switches would I need? 3, one for each axis? So tonight if I order 9 of the above switches I should be set correct? Will the controller accept that many switches?February 7, 2010 at 6:54 pm #3360
9 is exactly how many you need (assuming you don’t plan on making any mistakes ;)). Check the HobbyCNC documentation to check on whether the board can handle that number of switches. I imagine it can, but I’m not sure.February 8, 2010 at 12:13 am #3361
One more point, if you construct the limit switches in series as mentioned above in the HobbyCNC instructions, you’ll only end up needing one board input for each axis, leaving you with one to spare.February 9, 2010 at 4:53 am #3362
Ok! 9+1 switches ordered! (One extra just in case i need a backup laying around, just as you suggested, not a bad idea!). Hobby CNC said the pro board will handle all 9 as well with ease.
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