Probing speed with analog piezo sensor

dc42

@tekkydave said in Probing speed with analog piezo sensor:

It works but the 6mm/s requested results in an actual 2mm/s which is painfully slow.

That's because with analog probes, RRF slows down probing to 1/3 speed when the reading gets close to the threshold, exactly as you said. What's the reason for not using it in digital mode?

tekkydave

Only the convenience of having the trigger level adjustment in the Duet rather than the fiddly pots on the pcb.

matt3o

Is the 1/3 slowdown something specific of RRF3? I can't say I'm experiencing it on RRF2 but could be wrong

deckingman

@matt3o said in Probing speed with analog piezo sensor:

Is the 1/3 slowdown something specific of RRF3? I can't say I'm experiencing it on RRF2 but could be wrong

It's been around for an awfully long time - at least 2 years.

tekkydave

I can see the sense in the slowdown for other analog sensors but not for piezos. The analog output is constant until the nozzle makes contact with the bed.
Can I suggest 2 possible solutions:

A way of specifying the amount of slowdown for analog sensors in M558
A separate M558 probe type for piezo probes with no slowdown applied.

rkrammes

I'm guessing there has been no movement on this issue. I just ordered a new universal piezo since I wore out the pots on my older version and I was excited to see that the pots could be avoided. However, if the probe speed is locked with this 1/3 speed modifier it seems like this feature of the new universal piezo is pretty useless. They even mention that this feature is compatible with Duet hardware in the documentation.

dc42

Have you tried increasing the trigger threshold in the G31 command? The slowdown only occurs when the output is close to the threshold.

tekkydave

@dc42 I've tried that but it then moves the threshold above what the probe actually generates. Then it doesn't trigger at all and crashes the bed.
The analogue piezo probe has no concept of how far away from the bed it is unlike a traditional analogue sensor. I hope it can be catered for at some point but I realise on the scale of current developments it will be low priority.

dc42

@tekkydave, it's likely that in a future version of RRF3 I will remove the automatic slowdown and replace it with 2 configurable feedrates in the M558 command: a fast feedrate for initial probing, and a slower feedrate for the second and subsequent probes, for those types of sensor that benefit from slow probing.

tekkydave

@dc42 That would be a good solution. Cheers

tekkydave

Is it still planned to make any changes to the M558 command in RRF 3.x?

Phaedrux

I'll move this to the firmware wishlist.

tekkydave

RRF3.3beta2 has resolved this issue. G30 now probes at full speed due to changes in M558 F parameter.