I have found the problem. It was not the firmware, but my settings. As a test, I had set the jerk for the frequency measurement to 0. Now everything works again

I have found the problem. It was not the firmware, but my settings. As a test, I had set the jerk for the frequency measurement to 0. Now everything works again

Hi,
I wanted to test input sahping and had to update my firmware for this to 3.4.5. Before that I had a version running below 3.3. I'm not sure anymore, something with 2.x.
Since the upgrade, I now have a problem printing circles and arcs. Whether the radius is very large or very small, the printer starts to hum extremely, as if it stops for a millisecond between each segment. The print result looks accordingly. Input shaping is not activated.
Is it possible that this is due to the new firmware? Is there perhaps some function that recognizes curves and can lead to such problems?

Unfortunately the link is no more active. Neither to the V6 clone nor to the cyclops clone or the NF hotend.
But most tests were made with the V6 clone.
I already ordered a coated heatbreak from mapa refining here in Germany and a new bowden. I think the heatsink has no effect as long as the heatbreak and the nozzle are good. And I have a lot of nozzles here.

I printed PLA at temperatures down to non extrusion.

I have a hotend from aliexpress. There was no B Value mentioned.
For the calibration I removed the filament and the bowden. Then I put the temperature sensor of my multimeter from the top into the nozzle. In the nozzle was some molten filament left, so there was a very good thermal connection to the nozzle. Then I set 230 °C and tweaked the value until the printer and the multimeter showed exactly the same value. I assume, that I eliminated any thermal transitions and tolerances this way, as I measured the temperature of the molten filament and not the heatblock or so.

Thank you for that clue! You were right! I had to calibrate P1 and landet at B3980. The hotend was more than 20C to hot (at 230C)! But since I tested a lot of different temperatures, this didn't help for my problem

Finally I found the time to change the board and it did not help. Same blobs with Marlin. So it has nothing to do with the Duet or RepRap Firmware which means it must be a mechanical issue. I am kind of happy about that, because I love everything about the Duet. But now I have no idea how to solve the problem.

@danl said in Blobs at every start and end of line:

Could it be a bowden related mechanical issue, e.g. the curvature or a slight kink or dent of the tube, a loose tube/end fitting connection, slight play in the tube-to-extruder fitting......?

I assumed something like that, too. The bowden is about 50 cm long, which is longer, than I'm used to. That's why I try made a test with a very short bowden, allowing me only to print on one corner of the print area. Again no difference.
Watching the tube-to-extruder fitting while printing didn't bring the enlightment, too.

@dc42 said in Blobs at every start and end of line:

Blobs at the end of a line are typically caused by lack of pressure advance or insufficient retraction. Blobs at the start of a line are not normal. Are you sure that you don't have a positive "extra restart distance" or similar configured in your slicer?

Makes sense. But I even set ...

@jorge said in Blobs at every start and end of line:

... a negative restart distance until I got a fatal underextrusion at the beginning of a line but though I have a blob. So first a blob and then underextrusion for a few mm. This confuses me a lot.

@dc42 said in Blobs at every start and end of line:

But did you also set the jerk policy to 1 ?

Yes, no visible difference

I did not find the time to change the board yet but I did some coasting and restart distance tests. I set a high coasting distance and a negative restart distance until I got a fatal underextrusion at the beginning of a line but though I have a blob. So first a blob and then underextrusion for a few mm. This confuses me a lot.

I updated the firmware but unfortunately it makes no difference.
Next I will test it with a simple 8 bit board with Marlin. I hope it makes no difference because I really like the duet and the Dibond housing is milled for it...