On Mon, 2011-06-13 at 13:47 -0700, Peter Loron wrote: > Hello, folks. Can anybody comment on using hall effect switches on a 3 > axis mill for limit / home switches? Seems like they would have some > possible advantages over physical contact switches. > > Thanks. > > -Pete
My Hardinge lathe uses Hall limit and home sensors. The Z axis target magnet is small and mounted such that there is minor protection from chips. There is a small gap between the magnet and sensors when aligned. If chips are in the magnet area, they get wiped off, but not too small such that small chips don't bind in the gap. the magnets are weak enough to have largesh chips fall off. The trip location accuracy only needs to be within about 2 or 3mm because, in my case, the home sensor is used in conjunction with the screw encoder index, which should be accurate to .002mm or better. What I like about Hall sensors is that they are machining fluid proof and will practically never wear out or change the trip point or behavior over time. I tend to think using mechanical micro-switches is silly, but a lot people use them to good effect. The Hardinge Z axis uses a Hall sensor with magnet in a micro-switch housing: http://sensing.honeywell.com/index.cfm?ci_id=154286&la_id=1&Ne=7&sid=1308EB555700&ci_id=154286&N=3591+4294966517&la_id=1 Short URL: http://alturl.com/v2jzu These are mounted in a location well protected from chips, but the area is not sealed from coolant, which is fine because the sensors don't mind fluids. The Z sensors are in an aluminum threaded barrel similar to this one: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=480-3256-ND Short URL: http://alturl.com/netsd They tend to be expensive, but it should not be too difficult to machine a barrel and pot an IC sensor with leads into it. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ EditLive Enterprise is the world's most technically advanced content authoring tool. Experience the power of Track Changes, Inline Image Editing and ensure content is compliant with Accessibility Checking. http://p.sf.net/sfu/ephox-dev2dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
