Greetings,

I have been using 5-24V Omron photoelectric switches to home my axises on a small CNC machine. They are currently plugged in to the Konnect extension board.

I am wondering if I would be better off plugging them directly into some of the KFlop inputs. Are there any latency issues with the Konnect that would give me better repeatability if I go direct? I am currently jogging very slowly into the switches to try to avoid this and it seems to be working well.

Thanks,

Scott

Don't know about the Konnect, but this is the way we home fairly quickly: move at high speed toward the switch, then reverse at low speed and stop when off the limit switch. The low speed search is over a fairly repeatable small distance, so it doesn't really make much difference to the overall timing. 90% of the time will be in the initial traverse. This also adds a bit of "slack" between the soft limit (the point at which the axis stops) and the limit switch position, by taking advantage of the switch hysteresis interval.

Regards,

SJH

On Fri, Jul 24, 2015 at 8:16 AM, cnc_machines@... [DynoMotion] <DynoMotion@yahoogroups.com> wrote:

Greetings,

I have been using 5-24V Omron photoelectric switches to home my axises on a small CNC machine. They are currently plugged in to the Konnect extension board.

I am wondering if I would be better off plugging them directly into some of the KFlop inputs. Are there any latency issues with the Konnect that would give me better repeatability if I go direct? I am currently jogging very slowly into the switches to try to avoid this and it seems to be working well.

Thanks,

Scott

There should be no significant delay using a Konnect input, as they're read every 180uS (IIRC - it's been a while since I looked at one in detail!), so you'd have to be going quite fast for it to make much difference.

If my quick maths is right, even moving at 10m/s that 180uS is only a difference of 0.03mm.

However, I would recommend the homing method SJH describes.

Moray

On Fri, Jul 24, 2015 at 4:51 PM, Hardy Family hardy.woodland.cypress@... [DynoMotion] <DynoMotion@yahoogroups.com> wrote:

Don't know about the Konnect, but this is the way we home fairly quickly: move at high speed toward the switch, then reverse at low speed and stop when off the limit switch. The low speed search is over a fairly repeatable small distance, so it doesn't really make much difference to the overall timing. 90% of the time will be in the initial traverse. This also adds a bit of "slack" between the soft limit (the point at which the axis stops) and the limit switch position, by taking advantage of the switch hysteresis interval.

Regards,
SJH

On Fri, Jul 24, 2015 at 8:16 AM, cnc_machines@... [DynoMotion] <DynoMotion@yahoogroups.com> wrote:

Greetings,

I have been using 5-24V Omron photoelectric switches to home my axises on a small CNC machine. They are currently plugged in to the Konnect extension board.

I am wondering if I would be better off plugging them directly into some of the KFlop inputs. Are there any latency issues with the Konnect that would give me better repeatability if I go direct? I am currently jogging very slowly into the switches to try to avoid this and it seems to be working well.

Thanks,

Scott

Hi Moray,

Thanks for contributing. But I think you meant to say 10 m/min (~400ipm) - which is still pretty fast and should be repeatable to +/- 15um :)

Regards

Group: DynoMotion	Message: 11977	From: Moray Cuthill	Date: 7/26/2015
Subject: Re: Homing Switches

I'm glad somebody is around to check my numbers!

But at least it shows the switch is most likely going to be the weaker link, given I doubt any typically used homing switch is going to be that accurate.

Moray

On Sun, Jul 26, 2015 at 2:57 AM, Tom Kerekes tk@... [DynoMotion] <DynoMotion@yahoogroups.com> wrote:

Hi Moray,

Thanks for contributing. But I think you meant to say 10 m/min (~400ipm) - which is still pretty fast and should be repeatable to +/- 15um :)

Regards
TK

Group: DynoMotion Message: 11995 From: az@aimele.com Date: 7/27/2015

Subject: Re: Homing Switches

I think the latency of the photo electric switch would be an important spec to know. I've used a number of photo electrics and I've found that I needed to test the components with a scope to see the actual response time. I've had no trouble with latency with Sick optic laser sensors but they are pretty pricey.

AZ

------- Original Message -------
From : Tom Kerekes tk@... [DynoMotion][mailto:DynoMotion@yahoogroups.com]
Sent : 7/25/2015 8:57:40 PM
To : DynoMotion@yahoogroups.com
Cc :
Subject : RE: Re: [DynoMotion] Homing Switches

Hi Moray,

Thanks for contributing. But I think you meant to say 10 m/min (~400ipm) - which is still pretty fast and should be repeatable to +/- 15um :)

Regards
TK

Group: DynoMotion	Message: 11960	From: cnc_machines	Date: 7/24/2015
Subject: Homing Switches

Group: DynoMotion	Message: 11961	From: Hardy Family	Date: 7/24/2015
Subject: Re: Homing Switches

Group: DynoMotion	Message: 11975	From: Tom Kerekes	Date: 7/25/2015
Subject: Re: Homing Switches

Group: DynoMotion	Message: 11967	From: Moray Cuthill	Date: 7/25/2015
Subject: Re: Homing Switches