I am intermittently getting a Probing Error that says "2nd Probe, no Surface!". It is not always on the same probing operation. Any hints for what to look for? Is there debounce timing in the probe interface, minimum length of the probe active signal pulse width, or other such things to be aware of?
Bill
2nd Probe, no Surface!
- charisbill
- Posts: 8
- Joined: Fri Jan 24, 2014 7:16 am
Re: 2nd Probe, no Surface!
Additional Info: I am using the "One Signal" interface for all the touch plates and the probe.
Re: 2nd Probe, no Surface!
Hi,
What are your probe fast and slow feed rates set to?
The #1 cause of this symptom is the probe feed rate being too low.
Yes, I did say to low .... It's counter intuitive but slow probe operations cause any contact bounce in the probe to cause a "surface not found" situation (for tech details of what happens see section 8.11.1.1 in the mill manual).
Many people set up the probe for a single probe operation and get things working. Then they add the 2nd probe operation by setting the slow feed rate to a non-zero value. Of course the slow feed rate is now the lowest probing speed - and in fact the real feed rate may be much lower than the actual setting for the slow feed rate (if you use a short back off distance, the 2nd probe has little distance to accelerate so it''s actual velocity may be much lower than the set feed rate when the probe makes the 2nd contact).
Try raising the slow feed rate - if the problem goes away you have strong clue about what is happening.
BTW, This can happen after things have been working for a some time .... the low cost probes do not run enough current through the probes to keep the contacts clean and so they tend to oxidize over time. The oxidation changes the contact resistance and that alters the switch bounce characteristics.
Dave
What are your probe fast and slow feed rates set to?
The #1 cause of this symptom is the probe feed rate being too low.
Yes, I did say to low .... It's counter intuitive but slow probe operations cause any contact bounce in the probe to cause a "surface not found" situation (for tech details of what happens see section 8.11.1.1 in the mill manual).
Many people set up the probe for a single probe operation and get things working. Then they add the 2nd probe operation by setting the slow feed rate to a non-zero value. Of course the slow feed rate is now the lowest probing speed - and in fact the real feed rate may be much lower than the actual setting for the slow feed rate (if you use a short back off distance, the 2nd probe has little distance to accelerate so it''s actual velocity may be much lower than the set feed rate when the probe makes the 2nd contact).
Try raising the slow feed rate - if the problem goes away you have strong clue about what is happening.
BTW, This can happen after things have been working for a some time .... the low cost probes do not run enough current through the probes to keep the contacts clean and so they tend to oxidize over time. The oxidation changes the contact resistance and that alters the switch bounce characteristics.
Dave
Productivity Software for Personal CNC Machinists
http://www.CalypsoVentures.com
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- charisbill
- Posts: 8
- Joined: Fri Jan 24, 2014 7:16 am
Re: 2nd Probe, no Surface!
That seems to be the issue. At a slow rate of 10 I don't seem to have problems. At a slow rate of 5 I occasionally have a problem and at a slow rate of 2 I get the error about 50% of the time.
I'll play around with the speeds and I'll give myself some debounce as well (the debounce was set to 0, so I'll use 25 to give me a millisecond of debounce).
I've got some electrical engineering background as well, so maybe I'll think about a hardware debounce or minimum pulse with trigger or ....... If anyone has some tried and true hardware I'd be interested in seeing it.
Bill
I'll play around with the speeds and I'll give myself some debounce as well (the debounce was set to 0, so I'll use 25 to give me a millisecond of debounce).
I've got some electrical engineering background as well, so maybe I'll think about a hardware debounce or minimum pulse with trigger or ....... If anyone has some tried and true hardware I'd be interested in seeing it.
Bill