I don't know why I keep doing this.
I mean, having ideas for an explanatory video, then going down the rabbit hole of whether
it actually works or not.
But here's z-hop, overanalyzed.
Lets go.
This video is sponsored by PCBWay.
ZHop is this.
Do you see that?
Wait...there.
Before moving from one part of a print, you retract, and zhop is the additional act of
raising the nozzle during that retract.
And I'm not gonna waste your time if you just want to know what to do about it - I am going
to convince you that it needs to be turned off in almost all situations.
Almost all.
A lot of printers have default profiles with z-hop on, but in all my testing, I do not
have a good enough argument to support that being a good idea.
If you want to leave now, go ahead, but you'll miss the fun.
I mean, maybe there's fun.
It might just be boring.
Could be a trick.
Anyway.
Let's refer to the manual and see what it's supposed to be for.
Pretty mcuh what I just said, but it goes on to give us a diagram of what I just said.
The interesting thing is, when it z hops, it literally stops.
So z-hopping is stopping the print, raising the nozzle, waiting for that, moving across,
lowering the nozzle which is another wait, you get the idea.
So....why?
Well it says it right here.
These are the official reasons for z hop existing, preventing a scar from the nozzle hitting
the print when it enters or presumably exits, oozing causing blobs, and blobs caused by
travel knocking the print over.
The reason I find this funny is because as you know if you have been printing a while,
thats the exact same list of things z hop is accused of doing.
There's a further 2 unofficial reasons, I guess unofficial, on a top surface you can
get scarring especially if you're ironing or doing monotonic infill, as the nozzle moves
it can take necessary paths around the top surface that leaves a trench in your nicely
ironed print.
The other unofficial reason is..
..noise.
Now in a huge ironic twist, those last two reasons, are the only ones I can support using
it for.
Kinda.
So let's get to the meat of the episode.
Does it work?
You'd think not, from what I just said, but it's....never that simple, is it?
I've got a series of tests to do to try to figure out whether there's any huge impact
on any of the scenarios just mentioned and this as usual turned out to be a rabbit hole.
Hop.
Rabbits.
Get it?
Firstly lets look at top surfaces.
This does depend on the slicer, back when I did a monotonic infill video some years
ago....
two years ago... the monotonic infill samples I printed were totally carved into on prusaslicer,
but less so with cura.
I've learned a lot in those two years though, and slicers have probably changed too, so
I retried it.
I have gone as far as to reproduce the original as best I can, it was the top of an XYZ cube.
There's nothing really to speak of here in terms of gouging.
I tried a lot of permutations, ironing on, ironing off, prusaslicer, cura, the best I
can show is tiny marks where you'd expect them when you have
ironing on.
So what changed?
Well, maybe nothing.
I'll come back to this in my summary later on.
But is it worth using z-hop here?
It depends.
Next let's look at the print quality argument, and we'll go back to these viaducts from the
intro.
Here's z hop off.
This is creality silk rainbow filament, and this kind of scenario really ought to be able
to replicate that curling of edges that you would expect because you have overhangs, and
silk filament which typically likes to curl upward, and yet, it's not doing it.
When the head returns to print on existing layers there's not much hitting existing parts
happening is there?
Same part but with z - hop on and set to a modest height, I think it's around a layer
high, which seems to be around the value a lot of defaults are set to.
It's certainly working, hopping is happening, but you have to question why we need to do
it?
And we appear to be winning an extra prize, all this weird fluff.
Which by the way, we will see more of, the weird fluff or fine stringing is a common
issue with z-hop.
And you can see why, I think.
Thirdly, and this would previously have been my main reason for recommending z hop in the
past, the problem of hitting existing parts and knocking them off the print bed, especially
when dealing with fine or thin and tall parts.
Z hop is largely regarded as the main setting to counter the phenomenon of the print head
flying across existing printed parts during its travel moves and catching on a part of
the print and knocking it off.
Or is it?
I printed a whole bunch of different agepbiz print in place models check out the description
for links to his work, each one once with zhop off, once on.
These normally print absolutely fine but I'm not going particularly slowly, because I was
actually trying to find a point they would fail.
Now theres a small thread of possible evidence in favour of z hop here as you can see.
But it's very tenuous.
On most models, there was very little difference in reliability, and very little difference
in how freely the parts moved.
To me, this isn't particularly statistically significant, but if you like, maybe the zhop
versions are slightly less likely to come off the bed, but you'll have to deal with
stringing, and I'd rather print two of these and have one perfect, than have two stringy
ones.
But it's not really good enough to start throwing around conclusions.
I needed a test piece or two to really drill down into this point, or at least I thought
I did.
Meet this.
Whatever it is.
This is twice in two videos now I've made a mockery of fusion 360.
But this piece is designed to test exactly the thing z hop is supposed to fix, as the
print head goes round and round these skittles are increasingly likely to get bumped and
knocked over.
Great idea, I'll run this a few times on each of my printers with z hop on, and off, and
see what the difference is.
The problem is , as I did this and logged it , it quickly became evident that none of
my printers appear able to print this, at all, with z hop on or off, even with modest
brims.
I think I may have created an unprintable print.
I've actually shared it on printables, I'm curious to know if anyone can print it, so
go get it and see if you can, it's totally not my evil plan to get more prusameters,
but no, seriously, I think you might be able to get this to work if you use a textured
bed or glue, but see how you go and feed back to me in the comments or post makes or something,
and tell me whether you used z hop!
And while you contemplate whether it's worth doing that, let's talk about this video's
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Thank you PCBWay for sponsoring this episode.
I'm aware thanks to teaching tech's latest video that there are novel z-hop methods,
in slicers other than cura and prusaslicer.
Orcaslicer has several z hop methods, and weirdly, so does creality print.
These can be seen in action doing what they're supposed to do.
And they are cool.
But I didn't see them doing what they're really supposed to do, which is stopping these pins
falling over.
Why?
I'll save what I noticed, and why I think these pin based pieces won't print, for the
conclusion...
I want to finally talk about tree supports because this might be the last potential use
case for z hop.
Of course it's not, obviously.
Z hop doesn't even make a difference there in my tests.
At all.
We should then...consider what's going on here.
It's time for the long awaited conclusion and don't skip because this isn't a normal
conclusion, all the tips are hidden in here.
So why do these pins fail?
Let's watch the row of pins just as it fails with z hop off - see if you can spot what
happens.
It does appear that the nozzle is knocking over the pins as it flies past.
But.
I'm being disingenuous here.
If you look at the routing I have set up for the part, cura doesn't print these in left
to right order so it's hopping over ones it just printed.
It doesn't do this if you have this setting switched on, and this is the buried lede in
the video, avoid printed parts is more useful than z hop.
If you turn on this option, the pin isn't knocked over by the head flying past because
it simply doesn't.
It still is knocked over though, it's always knocked over.
That's the thing.
This is with z hop on.
You can see the hopping, and you can see all the stringing caused by it.
Here comes the failure....the failure that is supposed to be avoided by z hop.
There we go.
That's what I was expecting.
You see, filament is viscous, and this viscosity is a pretty sizeable force.
You can see on this half failed piece just how large the viscous force is.
In the results I saw this failure almost every time, the sticky nature of the molten filament
is what's pulling the part over.
Not, the nozzle passing in or out.
So there's a logical assumption here, if you can make the filament less sticky, it will
fail less?
Actually...yes.
You make filament less viscous by heating it to a higher temperature and believe it
or not it actually works.
This print very, very nearly finished with the print temperature at 240C on PLA.
So, avoiding printed parts and raising the print temperature, perhaps not that high though,
I don't recommend that, are two potentially more reliable ways to prevent failure than
turning on z-hop.
In terms of the scarring on top layers?
I think you can decide for yourself if zhop's downsides are worth the minimal gains, I would
say _generally_ no, but with caveats.
You might want a flawless top layer and have unavoidable travel moves which necessitates
z hop, and I'd advise looking at the preview because it will quite literally tell you where
those marks will be.
In prusaslicer and presumably its derivatives you also have z-hop only over a certain height.
Which I would also advise using, if possible.
so it seems the ultimate answer is always some version of an instead, instead of using
z hop, do something else.
Use different settings to achieve the same thing, or maybe try to design better for FDM
meaning not creating weak parts in the first place, or tune your machine or print at the
right speed, or maybe tune your flow correctly or temperature or maybe buy better filament.
Almost every use case for z-hop seems to point towards some version of something else being
a better solution.
Z hop can make quality worse, and it can slow down your print.
Z-hop, in all likelihood, won't help you.
What do you think?
Do you have a situation where you're convinced z hop did help and I'm full of gyroid infill?
Let me know in the comments about your experiences.
Also go try that test model, no cheating, it should print, it's not even got any huge
overhangs, I'm obviously just doing it wrong.
Anyway, I will see you next time.
Thank you for watching.