Relationship between nozzle size, layer/nozzle height, print quality, print speed

Anything goes! Cheap or expensive, FDM or SLA, DIY or Commercial.
User avatar
ido
Posts: 40
Joined: Wed Jul 12, 2017 10:09 pm
Location: Rotterdam - The Netherlands

Relationship between nozzle size, layer/nozzle height, print quality, print speed

Post by ido » Thu Jul 13, 2017 9:07 pm

Hi,

I must admit, I am new to 3d printing, but you probably got that from reading the topic title. Been reading and watching youtube's for several weeks now, and I recently build my prusa mk2s printer, even got a few good prints from it.

I am however still learning about all the various print settings and I cant get my head around the relationship between nozzle size, nozzle height, layer height, print quality and print speed.

I understand there's X/Y resolution and Z resolution (= layer height)
If slicer applications talk about 200 or 100 microns, this is layer height, right? So what defines the X/Y resolution?

And nozzle size, 0.4 is commonly used, but you can print higher resolutions with a 0.4 nozzle, how does that work?

And if you use a print quality of 200 micron, does this mean the height and the x&y is 200 micron? And the ideal nozzle height (from the bed) would be 200 micron?

And print speed, I can imagine the faster you go, the thinner the plastic coming from the extruder? Or is thickness + speed something the printer takes care off?

I hope Tom will do a video on this :) Or perhaps he already did, couldn't find it though. Or if someone else on the forum can enlighten me, that would also make my day :)

Ido

User avatar
lowfat
Posts: 30
Joined: Thu Jun 15, 2017 3:36 am

Re: Relationship between nozzle size, layer/nozzle height, print quality, print speed

Post by lowfat » Thu Jul 13, 2017 10:31 pm

Nozzle size affects the size of the line/extrusion width of the print. This is what you would call x/y resolution. With a 0.4mm nozzle you'll use a line width of 0.4mm to about 0.6mm. Obviously the thicker the lines the quicker of the print. Thicker line width also increases strength of the print. Line width doesn't have much impact on print quality, except for the fact that if a part of the print is thinner than the line width it won't be able to print that part.

With a 0.4mm nozzle you can print to about 0.35mm as the max layer height. Layer height affects print strength, but not to the degree of line width. It mostly affects visible print quality and time to print. Larger nozzles can still print w/ smaller layer heights.

Print speed affects quality mostly due to vibrations from the printer frame/chassis as well as heavy X gantry / moving heated beds. A very rigid printer (CoreXY, etc) can print print much faster because there is less vibrations.

chumm
Posts: 176
Joined: Thu Jun 15, 2017 11:24 am

Re: Relationship between nozzle size, layer/nozzle height, print quality, print speed

Post by chumm » Thu Jul 13, 2017 11:54 pm

It's important to reorient your thinking regarding "resolution". Z is the closet thing we have to, say, a computer's concept of resolution, because the entire layer is printed, then Z is stepped up, and the next layer is printed. On X and Y, your resolution is imperceptibly small because instead of printing line by line like a computer display, lines are drawn continuously, more like a vector display. For example, on my printer my X and Y steps per mm are 160 (pretty standard). So the printer can move to within 1/160 of a mm, or 6.25 microns. This has some slight error, +- 3 microns, let's say, due to microstepping. There's also not really a concept of X and Y as independent axes, because they move at the same time. So where on a computer you'd have a diagonal line that would look jagged up close, on your printer the line can be perfectly straight in any direction.

In computer graphics a circle is one of the simplest tests of whether or not you can see resolution, but when you print a circle on a 3d printer it essentially looks perfect. A good test print to demonstrate this is a dome or hemisphere. When you print a dome, each layer will basically be a perfect circle if the model is sufficiently detailed, but the whole dome will have obvious layer lines and therefore Z is a MUCH smaller "resolution" in the traditional sense.

Of course, as lowfat noted, the extrusion width is the limiting factor. Basically you can create any shape to a ludicrously small resolution, but only if you can draw the outline of that shape with, in my case, .45mm wide lines. And the ends of those lines are always round, so for example you couldn't really print a knife-sharp exterior edge (though you can print sharp indents in negative space). Your settings for number of perimeters lines, etc. will also limit the possibility of fine detail, but as long as there is a bit of room to store your lines, you can print incredibly detailed models. This stuff gets to be important when designing small models to print. I like to think of it like "if I scaled this up a bunch, could I draw this layer with a tube of toothpaste?"

Regarding speed + thickness, yeah that's calculated when you slice the model, so if you speed up or slow down during the print the extruder will scale accordingly.

slippyr4
Posts: 224
Joined: Thu Jun 15, 2017 10:24 am

Re: Relationship between nozzle size, layer/nozzle height, print quality, print speed

Post by slippyr4 » Fri Jul 14, 2017 9:11 am

Actually, speed and thickness is a response nsibility shared between slicer and the firmware.

The slicer breaks down the model layer by layer, but ultimately down in to moves for the extruder. They are either travel moves (where there is no extrusion, I.e the print head just needs to get to a different location) or extrusion moves, where extrusion must happen.

The slicer has settings for layer height and extrusion width and so on, and with a bit of maths what that actually boils down to is that for a given travel move (from a particular point to another point) the slicer knows the exact volume of plastic that should be extruded. And since it also knows your filament diameter, that can be converted in to a length of filament to extrude.

And that is the basis of the majority of the GCODE commands when you are printing. For example,

G1 X150 Y100 E5

Will cause the printer to move from where it currently is, to the location 150,100 whilst extruding 5mm of filament. It does this at the same rate in each axis such that when it's half way there it's extruded half the total amount of plastic etc.

Another parameter on the GCODE can set the feedrate, or speed, for the move. The printer will try and move at that speed, if it can - but it might not get that fast due to the fact that it needs to accelerate and decelerate. But the firmware in the printer handles the acceleration and the extrusion so that the plastic is extruded perfectly in sync with the travel move.
Self-built Prusa i3 MK2 clone
My things: https://www.thingiverse.com/slippyr4/designs
My Prusa firmware port for ramps & MKS : https://github.com/slippyr4/Prusa-Firmware

User avatar
Moorviper
Posts: 232
Joined: Wed May 24, 2017 1:19 pm
Location: Hessen/Rhön - Germany
Contact:

Re: Relationship between nozzle size, layer/nozzle height, print quality, print speed

Post by Moorviper » Tue Jul 18, 2017 3:50 am

I am actually printing a big benchy (300% scale).
Which has a layershift :-/
4 hours with 0.4 layer height and a 0.8 nozzle.


Image
Image
Image
Image

I_am_me
Posts: 8
Joined: Thu Jun 15, 2017 4:11 pm

Re: Relationship between nozzle size, layer/nozzle height, print quality, print speed

Post by I_am_me » Tue Jul 18, 2017 2:31 pm

As chumm stated Z is the closest thing we have to resolution and X/Y resolution is practically irrelevant.

When the slicer talks about 0.1/0.2/0.3mm this is indeed your layer height. Again, as chumm explained X/Y resolution depends on the micro-stepping and is theoretically too small to take into account.

A 0.4mm nozzle can print at 0.1mm or 0.2mm layer height because the layers are squished by the extruder, the slicer will adjust flow so that the squished line matches the line width and layer height.

There is a strong relation between nozzle size, layer height and line width. A bigger nozzle will be able to print with larger line width and higher layer heights because it is able to output more plastic than a smaller nozzle. Of course this comes at the cost of print quality because a 0.8mm nozzle will not be able to print details smaller than 0.8mm. All of this also relates to print time, higher layer heights means less layers and quicker prints.

When printing at 0.2mm you don't want a 0.2mm nozzle because then you couldn't squish the plastic and the layer adhesion would be really poor. Typically your maximum layer height is 80% of your nozzle size.

Concerning print speed, yes the faster you go, the smaller (more stretched) the line but your slicer will adjust flow-rate depending on the speed to ensure a consistent line width.

Hope that helps

User avatar
ido
Posts: 40
Joined: Wed Jul 12, 2017 10:09 pm
Location: Rotterdam - The Netherlands

Re: Relationship between nozzle size, layer/nozzle height, print quality, print speed

Post by ido » Sat Jul 22, 2017 4:29 pm

First of all, thank you all for your replies, things are becoming more clear.

So to summarize
- 3D printer resolution ≠ 2D printer resolution. When advertising a 3D printer, they talk about 100 micron, this is layer height
- X/Y resolution is defined by X and Y steps per mm where the width is defined by nozzle size
- A printer can place a line very accurately in the 2D space, but line thickness will be 0.4 (when using a 0.4 nozzle), height can vary, to max of 80% of the nozzle size
- Z resolution is defined by layer height
- A printed line doesn't have the same width all round, common sizes are 0.4 width x 0.2 height

Am I correct by saying this.

Now I also understand why the slicing algorithm is really important. Printing is a complex thing, where a lot of components need to be tuned and work together. Pretty amazing we can actually print stuff :)
Last edited by ido on Mon Jul 24, 2017 6:16 am, edited 1 time in total.

slippyr4
Posts: 224
Joined: Thu Jun 15, 2017 10:24 am

Re: Relationship between nozzle size, layer/nozzle height, print quality, print speed

Post by slippyr4 » Sun Jul 23, 2017 8:55 am

Yes you are right, but you can have an extrusion width greater than the nozzle width; imagine what happens when you squeeze your toothpaste onto your brush when the tube is close to the brush - it spreads out sideways. It's just a volume calculation for the slicer. There is a practical limit to how wide you can go though, in the region of 25% to 40% wider.
Self-built Prusa i3 MK2 clone
My things: https://www.thingiverse.com/slippyr4/designs
My Prusa firmware port for ramps & MKS : https://github.com/slippyr4/Prusa-Firmware

User avatar
ido
Posts: 40
Joined: Wed Jul 12, 2017 10:09 pm
Location: Rotterdam - The Netherlands

Re: Relationship between nozzle size, layer/nozzle height, print quality, print speed

Post by ido » Sun Jul 23, 2017 9:09 am

Oh wait, I think i mixed up the 80% thing, it should be layer height. So a nozzle size of 0.4 can have a max layer height of 0.32 (80%)

mmm, how does that work, when the width is wider, say 25% more, so 0.5mm, will the height still be 0.2 (when selecting this in the slicer) ? or is this something the slicer takes care off, to make sure the width is 0.5 and height is 0.2.

And I also heard single wall thickness should always be a multiple of the nozzle size, so with a 0.4 nozzle, walls should be 0.4, 0.8, 1.2 etc
But how this explain the width thing, you can have any wall thickness...
Last edited by ido on Sun Jul 23, 2017 9:56 pm, edited 1 time in total.

I_am_me
Posts: 8
Joined: Thu Jun 15, 2017 4:11 pm

Re: Relationship between nozzle size, layer/nozzle height, print quality, print speed

Post by I_am_me » Sun Jul 23, 2017 11:01 am

You're right about layer height.

Yes the height will still be 0.2 because it is how hight the nozzle is, the slicer will take care of adjusting your extrusion width based on your nozzle size and extrusion multiplier (the more material you push through, the wider the line).

Wall thickness should be a multiple of your nozzle size, making a 1mm wall with a 0.4 nozzle (extrusion width) will leave gaps or introduce artifacts. So 0.8, 1.2, 1.6, ... are good wall thicknesses because they are multiples of your nozzle size (extrusion width) and ensure solid walls.

Some slicers will ask how many perimeters you want while others will ask for wall thickness (2 perimeters = 0.8mm wall thickness, 3 perimeters = 1.2mm wall thickness, ...)

Yes you can have any wall thickness but usually models designed for 3D printing will have wall thicknesses optimized for 0.4 nozzles (things like 2.4mm or 3.2 mm) if your wall thickness is not a multiple of your nozzle size the slicer will add infill between the perimeters.

Post Reply

Who is online

Users browsing this forum: No registered users and 5 guests