Unexplained speed increase on fine detail test

[JBird]

I have a Prusa i3 MK2 using the profile provided by Prusa. I'm printing the Make Fine Positive Detail test. Things to downhill near the end of the test and a big mess of blobs is made at the tips. I have narrowed the problem down to speed increase at the peaks.

As you can see things are going along at 1.6 mm/s about 3/4 of the way up when it shifts to 40 mm/s(the default printing speed) at the end. I makes sense to me that there is a shift from green at the base to blue as it goes towards the peak. But I don't understand why it then goes to maximum speed.

I have been able to override the speed by breaking the print up in to two processes and lowering the default speed of the second process. But I would love understand better the root cause. I am new to 3D printing and I would greatly appreciate any insights you can provide.

Make Fine Positive Detail Test

[CompoundCarl]

That looks like it's either coasting or wiping, not actual extrusion. You can see that the actual extrusions are still slowing down and getting darker and darker.

I doubt that the print will look very good if you are using coasting and wiping with such small features, so I would try disabling those on the Extruders tab.

[JBird]

That looks like it's either coasting or wiping, not actual extrusion.

You were right. When I turned off wipe it gave me a smooth decreasing speed all the way to the tip. I had both wipe and coast turned on. I did some reading up here and it's not clear to me if in a general sense there is benifit for having these both on, or should I choose only one. If the are both turned on how does S3D decide which to use?

Using my workaround to print much slower using a second process at the tip printed great even with wipe enabled. I take this to mean that wipe is happening at the full default printing speed. I couldn't find any setting for wipe speed independently that might address this without disabling it.

[CompoundCarl]

If the are both turned on how does S3D decide which to use?

Coast and wipe do different things, so you can use them both at the same time if you want. Personally, I'm usually able to get good results just from adjusting the retract/extra restart alone with no coasting or wipe, but in some occasions a little bit of coasting can do a lot. Of course, the results with your printer/filament could be different.