Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: nicubila on December 23, 2012, 03:22:42 PM

Title: homming with Ethernet SS problem
Post by: nicubila on December 23, 2012, 03:22:42 PM

Hi all


I have a very strange problem with homing my axis. I have 4 axis, A slave to Y, all 4 axes with magnetic home switches (reed).

Before installing the ESS, it happen a few times that when homing the gantry came all the way to hit the switches and ruin my square. Didn't know what it was.

Figured out that is safer to use a physical stop - and good I did, as once every 20 homings the gantry tries to hit the limits, but no more chances now!!!. Now it just hits the bolt I put - over and over again, until I stop the router. But I saw that there are 2 situations when the gantry doesn't stop in the magnetic limits: (i) mach3 says limit switch triggered, and (ii) other when mach3 says nothing. But in both cases the Y and A readings in mach3 stop, so mach does not send any more impulses - or at least this is what I imply.

Still, that should be fine unless other issues gives me a very hard time: repetability of the homing is bad. I mean 0.3mm. I measure a distance between gantry and the fixed table, and get random variations.
I saw it indeed more since I installed the ESS. If I do holes in the table, when restarting the mach3 and the router, do homing and redo the holes, no more repetability.
To be mentioned that if I do NOT make a homing, I can run the router for an hour and get very good repetability - 0.02mm or so.

I read that magnetic switches are very accurate. Cannot figure out where the problems comes from. Any idea?

Marius

Title: Re: homming with Ethernet SS problem
Post by: rrc1962 on December 23, 2012, 06:08:37 PM

Between magnetic, mechanical snap action and optical, magnetic switches are probably the least accurate.

Title: Re: homming with Ethernet SS problem
Post by: nicubila on December 25, 2012, 01:58:02 AM

are these better?
http://www.ebay.co.uk/itm/90-250V-Inductive-Proximity-Sensor-Detection-Switch-/160646476557?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item256746b30d

or same thing?

Marius

Title: Re: homming with Ethernet SS problem
Post by: rrc1962 on December 25, 2012, 12:54:32 PM

The trigger point of any non-contact switch can be effected by outside conditions.  That's not a big deal if you're just detecting an open door, but when you need exact repeatability, a snap action limit switch works best. 

http://www.automationdirect.com/adc/Shopping/Catalog/Sensors_-z-_Encoders/Limit_Switches/Compact_Limit_Switches_%28AEM2G_Series%29/Lever_with_Roller_Actuator/AEM2G42Z11-3 

Title: Re: homming with Ethernet SS problem
Post by: hilux on December 28, 2012, 08:28:26 AM

Hi Marius,
Have a look at these http://www.ebay.com.au/itm/130566462673?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649#ht_2578wt_907 (http://www.ebay.com.au/itm/130566462673?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649#ht_2578wt_907)
This is what i use
Cheers