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Slic3r - Settings and Extruder Calibration

Posted at: SATurday - 03/12/2016 23:43 - post name: SuperG
Slic3r - Settings and Extruder Calibration

Slic3r - Settings and Extruder Calibration

This part developing Slic3r very quickly so this guild may be a little out of date, but hopefully may still help you get started if you are new to 3D printing, it's certainly the easiest route for an easy tool-chain to great looking prints.

Step 1 - (do not ignore this bit) Extruder Calibration - 
And as with every other 3D tool-path generator you need to have a calibrated extruder first before you can get awesome looking prints. it's really easy to do and will save you so much messing about when you attempt to compensate for poor calibration.

So as a refresher you need to set the correct steps per mm of used filament in the firmware, you can work this out by just extruding some plastic, I recommend using Printrun (Pronterface) Get it here

To do this you will need to edit, re-compile and upload firmware to your electronics, I'm going to assume you already know how to do that using the Arduino software. - (If not let me know).

So in most firmwares like Sprinter or Marlin you will find lines in the Configuration.h file that look like this -
//// Calibration variables

// X, Y, Z, E steps per unit - Metric Prusa Mendel with Wade extruder:
float axis_steps_per_unit[] = {80, 80, 3200/1.25,700};

The number at the end (700) is the number of motor steps needed to extrude 1mm of the input feedstock plastic.
Your number could already be different and may be half of this if you are using 8x microstepping (GEN6) instead of x16 (RAMPS usually uses x16).

Every hobbed bolt and filament drive / extruder gear setup is slightly different, so it's a very good idea to calibrate.

Now we need to check if this number is correct for your filament drive and the plastic you are using, you can use Pronterface  to extrude an exact amount of filament and we are going to measure the distance to check if it's correct or not -


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First check that your filament drive (Hobbed bolt) is clean and free from any plastic or debris.
Feed the filament in and make sure your hot-end is at temperature.
 
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Make sure your Extruder gears are really meshing well and there is no wobble, move your motor so you have no extra play.
 
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Set your spring compression, this does make a difference as the hobbed bolt teeth dig into the filament - 
For 3mm PLA I have the springs quite tight with only a small amount of compression remaining. 
For 3mm ABS I slacken them off just a little more.
For 1.75mm filament, I find you need less compression.
 
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Then stick some tape or make a mark on your plastic filament about 50mm up from the extruder, somewhere you can measure as accurately as possible (try to use a digital gauge if possible)
Either measure this or set your digital gauge to zero measured out to this point.
Tape makes it easy to align the edge to the digital gauge.

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Now you can extrude 30mm of plastic. You need to make sure you don't do this too fast as you do not want your motor to skip steps or the filament drive getting jammed.
So either slow down the speed to about 50mm/min and enter 30mm and hit Extrude or I tend to extrude 5mm at a time with a little pause in-between until 30mm has been extruded.
 
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Now check how far the filament marker has moved with your digital gauge - 
it should have moved around 30mm if your firmware is close to the correct number.
If it's exactly 30mm, then you already have a perfectly calibrated extruder :)
If  not then this is how to set the new number in firmware-
Our firmware in this test was set to 700 steps per mm and we extruded 30mm of plastic.
 
700 x 30 = 21000 (E motor steps for 30mm)
 
 For example if you actually measured 32.6mm then  21000/32.6 = 644 (so you need to put 644 into your firmware replacing the 700 we had before, re-compile and download and you can re-check again and your filament should now move exactly 30mm as you have just calibrated it.
 
If you measured 27.2mm then 21000/27.2 = 772 (put 772 into your firmware)
 

I recommend that you do this calibration for both PLA and ABS (the hobbed bolt teeth can sink deeper into ABS filament, so you will usually have a different Estep value for ABS) and if you have 3mm and 1.75mm extruders then check them also.
You can always add all your calibration readings into the firmware and comment them out so it's easy to change if you change plastic type or extruder.

Now you have a perfectly calibrated extruder, you are well on the way to perfect printing -

Understanding Slic3r Print Settings-  



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The first screen you see is the Print settings, for completeness I'll comment on each section, but it's mostly self explanatory.


Transform -  You don't need to change anything here, unless you want to scale the part of make multiple copies of the same object at a time. - this does the same as the Skieinforge Multiply command.


Accuracy - Layer height is very important and needs to be compatible with the Nozzle hole size. For a standard 0.5mm nozzle I always use 0.3mm layer height, you should avoid going any bigger than 0.4mm and as low as you dare, but much below 0.1mm you will struggle to see the benefit.
Leave first layer height and fill N layers set to 1.
It's a very good idea to select layer heights that divide into even numbers of steps of your Z height, having a miss-match of steps as the object builds is going to cause problems - Just to explain this - a 200 step motor using 16x micro-stepping gives you 3200 steps, an M8 threaded rod is 1.25mm per complete revolution so 3200/1.25 = 2560
So 1mm of height (Z) movement takes 2560 motor steps, a layer height of 0.3mm takes 768 motor steps.
If you set a layer height of 0.32, that needs 819.2 steps - not an even number of motor steps, so not ideal.


Skirt - This allows you to draw an outline around the perimeter of your printed object, this is a good idea as it  starts the flow of plastic in the nozzle and helps prime before the print, it will always do this first, so you can also check if your bed height is set correctly and stop the print if it looks like it's not sticking well.
6mm is fine and if you like you can build the skirt outline up more than 1 layer, this is the first thing it will do before the next layer of the object, people normally just do one skirt layer.


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Note the skirt and first layer are squashed down onto the bed (Glass in this picture)

Print Settings - Perimeter of 3 means it will draw 3 solid outlines around the edge of the object if it can, for thin elements it may only be able to draw 1 or 2. Sometimes you are better off having less outlines (Shells) and having more directional infill. But 3 Shells is a good starting point for general purpose building of parts.
Solid layers, is the number of fully filled layers built on top of each other on a flat surface, the base, tops of objects. 3 is a good number, you should never need to go much higher than 6.
Fill density, is the amount of infill to be used when filling the internal space in your object. the 0.4 shown means 40% infill. 25% is a normal and good figure to use when printing things like parts for a Prusa Printer, when printing art or organic objects you can use lower infill, hollow being 0% and you can get away with just 5% - to 10% for many objects . For some things like the Extruder or motor mounts you may want to use a higher fill (35% - 50%). it's very rare to need to go much higher and often slightly reducing layer height can make parts much stronger than just increasing fill levels.


Fill level examples - 


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Fill angle - 45 Degrees will start to draw the infill at a 45 degree angle between Y and X axis.

Fill pattern and Solid fill pattern - This is the style of infill used, normally Rectilinear is used, but here are some examples of what the others look like - they are all 37mm high and 25% infill, 3 outlines.



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Gary has a good thread going on here discussing alternative fill ideas, and check his Blog post about fill ideas

Retraction -  This section relates to your Extruder - Length is the amount of feedstock that is reversed by the extruder after completing a set of moves, just before it needs to re-position to another place for a subsequent set of moves. (extruder toggle) You will need to experiment with this number depending on what extruder hot-end and gearing setup you have. - Normally you need some level of reversal so a minimum would be around 0.5mm and a maximum needed for 3mm filament is usually 1.8mm. 1mm is a very good starting point.
For example a Mendel-Parts 3mm V5 hot-end oozes a lot and so needs 1.8mm of retraction, where as a 3mm J-Head nozzle only needs 0.9mm retraction.

If you have a Bowden extruder or are using 1.7mm filament you may need more reversal, but don't go too high - I needed 3mm reversal for a Bowden using a mendel-parts 1.75mm V5 hot-end, but with an Adrian style mini-extruder hot-end on a 1.75mm Bowden setup I only needed 1.5mm

Lift will give you the option to raise the extruder before it moves to a new point of extrusion,  EDIT - don't use this on machines with a slow Z axis (like Mendel, Prusa, Huxley) As Nophead mentions in the comments you can use lift on Machines with slow Z axis as you only need to lift a fraction (1 layer height).
Some machines like the TOM and the BFB 3000 have fast lead-screw drive Z axis and can lift nozzle away from the print before doing a fast move to new extrusion point. - EDIT So if you are building fragile tall parts that may be detached from the bed, then maybe try out the Lift setting - Otherwise usually leave this at 0.

Speed is how fast your extruder pulls back (toggles) the filament, you want this as fast as possible, but there is a limit of how fast most firmwares can do this and also how quickly the stepper can drive the filament back.
In Skeinforge and using Sprinter firmware I always used 16mm/s but after switching over to Marlin Firmware and using Slic3r then 30mm/s is possible and makes a very positive impact on quality and print speed and also (usually) allows a smaller reversal length.

Extra length on restart allows you to specify the feeding of more plastic before a new set of extrusion moves, I can't understand why you would ever need to do this as this effectively adds more plastic that's not needed and has no where to go apart from blobbing all over your nice print. If you ever feel the need to use this setting, something else is wrong with your printer set-up and/or calibration - Always leave at 0
Minimum travel after retraction Simply tells the extruder not to reverse (toggle) if the start of the next set of extruder moves are closer than this distance, otherwise you may end up with constant tiny extruder toggles if you were doing a highly complicated small print. 2mm is a good figure.
 

Part 2 - filament and printing

 
This is Part 2 of my getting started with Slic3r and 3D printing. 


In Part 1 we looked at Print settings and calibrating your extruder.


In this Part 2 will setup the printer, filament and print speeds and then do some printing. 


After more settings it's going to get into some level of combining Gcode and optimising print speeds, so any questions, do ask.


Lets take a look at the second Slic3r screen and settings, here are the defaults you will see.
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Printer - Nozzle diameter:  Slic3r needs to know what nozzle size you have so it can help calculate the width of each path for the selected layer height along with filament diameter (see below) it can then best work out where to place the extrusion paths to get correct infill and perimeters. Your most likely to have a 0.5mm, 0.4mm or 0.35mm nozzle.


Print Center: Your object is placed in the middle of the bed by default, so Slic3r needs to know where that is, some machines have offsets for wider carriages, for a standard Prusa mendel machine 100,100 should be correct. I have a wider X and smaller Y so I use 115, 85.


Use Relative E Distances: Some Firmwares use relative positioning, this makes the Gcode different by stating the distance to the next point from where you are now. Absolute positioning always states the end point regardless of where you are. unless you know your firmware is using Relative do not tick this box.


Z Offset: With this you can set a starting point for your Z axis, you may do this if you use a glass surface for some prints (PLA) and maybe remove the glass for ABS printing, the Z offset for PLA would be the thickness of the glass plate. - I use 0 and set-up my machine to be at the surface of whatever print bed I'm using, this gives you the maximum print height.

Filament - Diameter:  This is really important to get correct, Slic3r needs to accurately know what volume of plastic is being fed into the extruder, so you need to measure the filament really well. Be aware that it may well change from supplier and by batch, and if you are really unlucky by the meter!


Also be aware that 'normal' 3mm filament is usually around 2.75mm but it's also still quite common to get 2.9 from American suppliers and 3.0 or 3.1mm from Chinese sourced suppliers, so it's worth checking what you have and how consistent it is.


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Use a digital calliper and don't measure it at the very tip, use the bigger middle section as in the photo.


You want to be entering this value to two decimal points into Slic3r.


For good filament you are looking for a deviation of +/- 0.1mm or less along a good length of the coil or reel. You don't want it to be 2.75mm then 2.9mm at a different point as that will just mess up your prints. 


Also when you do this check that the filament is round and not oval, In my opinion badly oval filament is not worth the bother of trying to use it, reject it back to your supplier. 


I have been supplied '3mm' Chinese sourced filament as big as 3.55mm and as small as 2.6mm. Over 3.2mm could block your extruder but the 2.6mm is still usable in a 3mm extruder.


If you are using 1.75mm filament, then it's exactly the same principle as above.


Extrusion multiplier: This is another fudge value, changing it from 1 alters the value you have just entered into the filament Diameter. Some people use this to compensate for different (Soft/Hard) plastic materials sinking into the extruder hobbed bolt more or less, but really your calibrated extruder from Part 1 and the filament diameter is all you need to get correct, so leave this set to 1.


Temperature: Slic3r will add this value into the Gcode so at the start it will wait for the extruder hot-end to warm up to this value before starting the print process, you can still change this value in pronterface at any time during the print. For PLA 185 is a good value, but you may need to increase this depending on your hot-end configuration or if you are printing very fast.


Print Speed - Perimeters (mm/s):  This is the speed that outer shell of the part will be printed at, I use 65 for 'normal' printing, 80 for 'fast' printing and below 50 for 'slow'.


Small Perimeters (mm/s):  Small islands in a print or holes in a part can be have a different speed ascociated with printing their shells, usually slower than normal perimeters. - I use 55 for 'normal' printing, 65 for 'fast' printing and below 30 for 'slow'.


Infill (mm/s):  This is the speed of all the other infill of the object, you can normally go a little faster when doing this, but make sure the filament strands are not breaking apart if you go really fast - I use 80 for 'normal' printing, 130 for 'fast' printing and below 60 for 'slow'. 


Solid Infill (mm/s):  This is the speed of the any soild infill layers (apart from the very first layer) and you normally go slightly slower than the infill speed. I use 70 for 'normal' printing, 100 for 'fast' printing and below 60 for 'slow'. 


Bridges (mm/s):  This is the speed when you a 'bridge' or span filaments across a gap in free-air. It needs testing as temperature, nozzle, and Plastic material makes a big difference to the ability to 'span' gaps.
I use between 35 and 70 here.


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An example of some quite extreme bridging of filament, a slight bow-down but after 3 layers it's flat.
 
Other speed settings - Travel (mm/s):  This is the speed that the machine will accelerate upto when positioning itself before printing and also any in-air moves to a new point before extrusion again.
The maximum speed of your machine will depend on weight of each axis and how much torque the motor can deliver, what bearings you have and how your acceleration speeds have been setup in firmware.
With a low weight print bed and a Bowden extruder machines can run at 300mm/sec
For a Linear bearing Prusa with normal Nema17 Extruder and a heated PCB print bed you can run at 200mm/sec (I use 195mm/sec all the time)
If you have a big metal heated bed on your Y axis or are using PLA bushings then stick to travel speeds lower than 150mm/sec.
 
Bottom layer speed ratio:  This allows you to slow down the very first layer by a factor to help make it stick to the print bed and get a good clean start before part building goes higher.
For my 'normal' speed settings detailed above I use a bottom layer speed ratio of 0.35, this makes things 35% of the speeds you have specified in Perimeter, infill and solid infill for this first print layer.
 
But how do I know if my print is stuck down well to the print bed?
 
It depends on what surface you are printing on, I can highly recommend heated Glass as the very best surface I have used for PLA printing and heated Kapton or PET for ABS printing
 
Top Tip - I use 4mm temperature resistant glass, you can get sheets 200mm x200mm with nice ground rounded edges sold in the many 'home shops' up and down the country, they glass trivets to stand hot pans on and are sold for £1-2 each and withstand 200+ degrees C, perfect for our use and they fit very well on a Prusa heated PCB. Some people use plain window glass, but that can shatter or crack easily when hot.
 
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(Old Photo) Temperature resistant glass plate 200mm x 200mm
 
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The rounded corners on the glass allow a Prusa heated PCB to be screwed down flat and you can fix the glass in place by using bulldog clips or I use PET tape at the corners.
 
Top Tips for glass printing - 
 
  • Allow your glass to expand, most people use clips or tape the glass down.
  • If you can try to keep the glass fixed to the heated bed, you should not need to remove it.
  • Keep your Glass finger print free. - try not to touch the glass, ever.
  • I use supermarket brand nail polish remover, just a quick wipe while it's warm keeps it clean.
  • Other people use window cleaner or acetone.
  • If you don't let the parts or bed to cool and try to lever them off they will bend.
  • If you let the parts cool after printing they will pop off the glass all by themselves.

 
Getting your first layer to stick - 
Below are some examples of what the bottom layer of a print should look like, and what to look for when getting the first layer height stuck correctly down to the print bed - 
 
First make sure your bed is level and at 90 degrees to your X carriage bars so things build up straight and true.
 
I'm currently making the transition to not using springs on my heated bed, even with really hard and tight springs I still believe they are not a good idea for perfect printing quality - More on this in a future post.
 
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An example of a very over-squashed first layer, this will stick really well but will give you a pronounced ridge on the bottom of your printed object.
 
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Still slightly over-squashed, but fine and a lot of people like this look.
 
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This is hardly stock down at all and popped off the print bed half way into the print.
 
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same print just on an angle so you can see the poor adhesion
 
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This print is a about perfect for first layer adhesion and minimal distortion.
 
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And another print that I would consider to be perfect adhesion and no bottom layer distortion, this also matches a lot more like all the other sides of the object when printed.
 
Wow! we got there, all those settings. Now lets take a quick look at Start/End Gcode and then do some printing - 
 
Here is the Start Gcode I use - (Suitable for a Prusa with heated bed)

G28                 ; home all axes
G92 E0 ;reset extruder
G1 E3 F1200 ;Prime extruder 3mm
G1 E2 F1200 ;retract extruder 1mm
G92 E0 ;reset extruder

And my End Gcode - 

G1 X12.0 F4000       ; home (almost) x - stops extruder crashing into frame if at very top of Z height
G1 Y170 F4000        ; move the print to the front.
M104 S0                   ; make sure the extuder is turned off.
M140 S0                   ; make sure the bed is turned off.
M84                          ; shut down motors.

The only other tab is the Advanced section in here you can specify a Width over Height ratio, but if this is 0 then Slic3r calculates it (very well) for you. So lets' not mess with that.

Remember to save and load your configurations and call them some helpful names, I have a 'draft' (very Quick, little infill) 'normal' ( fast and solid), 'fine' (Lower layer and slower) and a setting for 'hollow pots'
During this test process I have also now another configuration called 'lift' I'll explain that a little more later.

Let's Print !
I'm not going to use any normal calibration objects like the hollow pyramid as some of them show up an issue with Slic3r and the fact it does not yet have a minimum layer time (yet) - I'll explain below - 
 
With just my calibration done and speed settings to 65mm/sec perimeter and 80mm/sec infill, prints of most things come out very well,- 
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 This is a Prusa Z motor bracket at 0.3mm layer height, nice and smooth.
 
You should now be able to start using Slic3r, everything below here goes a little deeper into printing and optimising printing.
 
I have selected a few parts that we can analyse how best to print and also this is where we can look at some of the present limitations with Slic3r and how we can get around them, and I hope a few tricks here and there.
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One nice object to try printing is this simple poly cup by WickedAndy, it will help you check you have good layer alignment and it's a nice big but hollow object, quick to slice and print, very satisfying.
These were printed with two perimeters, 25% infill, concentric fill pattern and 0.3mm layer height.
Perimeter speed was 65mm/sec and infill was 80mm/sec.
 
Another nice and easy to slice object is the little stone house by Whistler this is quite a small but detailed building.
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Perimeter at 65mm/sec and infill at 80mm/sec - 0.2mm layer height (0.5mm nozzle)
All the normal settings are the same, just the layer height was changed to 0.2mm.


This matt grey PLA is great for seeing defects, it shows every indent and casts a shadow with every bump, any PLA that's shiny or semi-transparent tends to hide defects.
 
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The infill is 10% and as you can see I'm printing it a little too fast so a few infill filaments are breaking.
I'm also using 3 perimeters, two would have been just fine.
 
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Close-up on the left front window it's (only about 7mm wide) - with a smaller nozzle size the edges of the window will be less curved and have more horizontal detail.


 


Little video of the house printing - Watch is in Hi-Def Here
 
Now I'm going to jump straight into a little problem with Slic3r on the next part to print.
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The very nice  http://www.thingiverse.com/thing:10330  is one of my favourite objects to print, I'm currently printing one in every colour I have.
 
My links are scales up to 1.75x the size of normal on thingiverse. I print one set of links at a time at 80mm/sec with Skeinforge. This is still very fast for such a small object,  but Skeinforge automatically reduces the time to print per layer so it always takes a minimum of 12 seconds to do layers (that's quite slow with such a small part). So it prints the link 'body' very quickly doing 65mm/sec perimeter and 80mm/sec infill, then as it moves up the part and it has less to print so layers slow down and you still get a nice print, by the time it gets to the top it's doing both the perimeter and infill slowly.
 
Slicer can have a slower 'small perimeter' setting, but it will still do the infill as fast as you set it. When you try to print this object with Slic3r at 80mm/sec it does the body fine but as it moves onto the 'prongs' of the link it's just a total mess of hot plastic being placed much too quickly the object ends up unusable.
 
Solutions - 
You can just slow the whole print down to 20mm/sec, but I don't like waiting for parts especially when I know they can be printed faster with no loss of quality.
 
So we take advantage of the fact that Slic3r can produce Gcode in just 2.2 seconds for this link and we slice it with different speeds and then combine the gcode at different layer points to get a mixed-gcode-speed printed object. - Don't worry I'll explain how to do that in the next example.
 
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The basic idea is to end up with Gcode at different speeds for the different layers that is compatible with the object you are printing.
In the picture I print the base at 80mm/sec and then the middle at 40mm/sec and the 'prongs' at just 20mm/sec, this produces a very nice print and much faster than if we had printed the whole thing at 20mm/sec.
 
This method of combining Gcode from Slic3r becomes really important when trying to print other things like the Tardis! below - 
 
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For the Parametric Tardis by Gossamer we have a similar problem, but also we can see other things that would benefit from completely different Gcode as the model changes in height.
 
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My scaled Tardis model is 69mm High, if I print with a 25% infill it takes 1 hour 30mins to print and makes a mess of the top because it's printing too fast, the light on top is no where to be seen. - 
 
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This is the same model but successful printed with the same layer height in just 45 mins print time.
This was done by combining Gcode and doing the following - 
 
  • The base section (5mm) needs infill to support the middle section and give support for the slope, if you print this part hollow the base will look very poor.
  • The middle section (45mm) can be hollow with no infill at all, just 2 perimeters, this makes if very fast to print and the main reason that this print is half the print time.
  • The top part again needs to be printed slower than the body or base and needs infill (25%) to make the top look good and help support the final light on top
  • The light needs to be printed very slowly or it will not build.
The point of showing you how to do this is that even when Slic3r does have a minimum time per layer setting you may well still want to combine Gcode for different reasons, like having sections of hollow and solid layers in the same object.
 
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You can 'measure' a model very easily using the basic free version of Netfabb - 
This will tell you at what height the parts of the model you are interested in begin (the base line here is showing  5.31mm)
 
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The middle section has already been hollowed out but still has quite an area that would be filled if we sliced it with 25% of infill that we need on the base. It works perfectly well with just a hollow perimeter outline.
 
With the different 'sets' of Gcode you have generated, you just need to open them up in an editor (I use Textpad) and search for the change in layers - G1 Z
 
The start of the Gcode is a handy reminder as to the settings you used - 
 
 
; generated by Slic3r 0.5.7 on 2012-00-08 at 12:09:38
; layer_height = 0.2
; perimeters = 3
; solid_layers = 3
; fill_density = 0.10
; nozzle_diameter = 0.5
; filament_diameter = 2.79
; perimeter_speed = 65
; infill_speed = 80
; travel_speed = 195
; extrusion_width_ratio = 0
; scale = 1
 
If you search in the Gcode for G1 Z5 

 
you will get to a section of Gcode like this - 
 
 
G1 F1800.000 E6.50116
G92 E0
G1 Z5.000 F11700.000
G1 X84.707 Y81.055
G1 F1800.000 E1.00000
 
Everything above the  G1 Z5.000  is the object up to 5mm in height, everything below is the rest of the object.
 
If you replace the Gcode below the G1 Z5.000 with the same objects Gcode but sliced at a different speed or infill then your object will print the original Gcode to 5mm and then the alternative Gcode after that.
You can combine Gcode however you like but for starters I recommend doing it by layer.
 
In Part 3 of this guide we will combine Gcode with different layer heights, this is another very handy thing when you start to print with very low layers, as you can print the first few at a 'normal height' (0.3mm) to help get a good bond to the bed and level our the surface then switch over to lower height Gcode for the rest of the object. Skeinforge has a setting in 'Skin' to do a similar job of ignoring skin on the first X layers. 

 
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Maybe you would not go to this effort for printing one thing, but the next time you think your printing too fast, check if you can selectively slow down some layers or vary the infill of layers to both minimise print time and also maximise print quality.
 
So hopefully you get the idea, it's good to know more about Gcode, you can find more commands on the Reprap Wiki pages here - 
 
I just wanted to show one more printed object and say how it was printed, as it's a brand new test and technique for me and so far has produced some of the best results I have ever made. 
 
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Some of my favourite things on thingiverse are the MakAlot pots and objects, but they are actually quite hard to print, especially if you print them small, you need a well calibrated machine and if you want to print them fast you run the risk of making a mess of your print or it becoming detached from the bed.
 
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I had two prints fail by getting knocked off the bed due to a very tiny surface area (1mm) on the first layer.
they were also a little bumpy (red one on the left)
 
I tried to print the MakeAlot Link bracelet quite fast and both times it got knocked off the bed about 1/3 into the print, the quality was a little poor and I was about to slow-down the print when I thought this would be a perfect object to test the Z axis 'Lift' setting in Slic3r, I had not tried this before believing that the Prusa mendel Z axis would be too slow and may end up adding extra 'artefacts 'of plastic to the print, I also have my Z axis limited to 4.1mm/sec in Firmware so I was expecting worse results using 'lift'... I was so wrong.
 
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Just using my normal settings for a standard 0.3mm layer height but also a 0.3mm 'lift' on the Z axis.
The print came off the printer as smooth as glass, I'm really impressed with the 'lift' setting, do try it!
 
I think that I may now be able to print this object the size of a ring, maybe a smaller nozzle would also help.
 
Thanks to Nophead for pointing out that the Mendel Z axis is fast enough to 'toggle' and use the 'Lift' setting. What I didn't think was that it would help produce such amazing prints, I'm going to try some more of the really complicated MakeAlot pots...
 
 
I hope this was useful and if you do nothing else, experiment with a glass bed and the 'lift' setting.
 

Hollow printing

 
Like many who print with natural PLA hollow objects start to look like good fun, they can be a little tricky to print but here are a few things I have printed so far and a few tips that worked for me -

I printed a few things with the 'Fill' module turned off in Skeinforge, this is ok, but you only get one (fragile) shell 'outline' and no base or lid on your model, for me this seems to be a problem with 0.25mm layers, the material seems to collapse on itself. So I experimented slowing down the print but really I wanted to have extra material both to make the hollow object stronger and help it stay up during a normal speed print. If you leave the 'fill' module enabled but set the infill density to 0 you get a hollow model and you can select multiple outlines and also get a nice base on your model, this seems to work really well if you are trying to print large things without a heated bed.

Here are some results printed at exactly the same speed I would print a solid model - (straight off the printer).

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Firstly thanks to Sublime for the fixed model of the Pink Panther woman, here is the progress printing a 95mm high and a full height 150mm version -
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Solid base on the legs gives it a really good grip on the bed.

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Don't you love the way the light catches her............. curves.

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That was the tallest thing I had printed until the twister below.
 
The full sized one is 600 layers @ 0.25mm each.
 
You can see from the edge that the visible banding is not a change in layer position and the object is almost completely smooth to the touch so the only thing I can think is that the slight change in heater temperature (bang-bang control) produces the banding effect? if anyone can confirm this or provide a better reason I would be interested in any feedback.
The camera also seems to extenuate it so something optical may also be going on.
 
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The next object (twister) below was printed with two shells and a base, and full sized it's quite big.
I expect that I could have made it single walled if I slowed down the speed, but I would rather have a stronger object for the same print time.

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This is the very Awesome Ultimaker Twister by Martijn
 
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I have about 140mm more on my Z axis, so maybe I need to print something really tall next time.
 
I'm almost certain this is completely watertight, and as it has a sealed bottom of 3 layers I could use it as a vase.

Thanks for looking, and if you try printing hollow things let me know how they turn out for you.

Rich.

**************** EDIT ************ UPDATE ********** 27th June ***************

Thanks to Sublime for working out why Skeinforge still adds infill even with a hollow print causing the banding of infilled areas seen above in my prints - 
So you need to turn off 'Infill in direction of bridge' in the Carve tab of Skeinforge for some models if you want a nice clean hollow print, but make sure you have your extruding temperature correct for the filament you are using, as you will suffer bridging issues if it's not spot-on, without this 'infill-support' you will be spanning free space.


When you slice this is what you may see with 'Infill in direction of bridge' enabled or disabled - 
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Skeinforge sees extreme over-hangs in the model which forces it to create the infill.
 
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'Infill in direction of bridge' in the Carve tab of Skeinforge 'ENABLED'

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'Infill in direction of bridge' in the Carve tab of Skeinforge 'DISABLED'


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**************** EDIT ************ UPDATE ********** 27th June ***************

Thanks again Sublime, I'll try a few more hollow things now.

Rich.
 

Thursday, 9 June 2011

Skeinforge Version 41

 
I have been using Skeinforge for just over 1 week now and I'm starting to get a grip on this most fantastic program.
After initial machine setup and printing with Reprap Java Host I always wanted to move over to Skeinforge, but it has a bewildering array of settings and control, quite daunting when you first start.
- But well worth the effort - 
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This image shows my best possible print quality I managed from Java Host to generate Gcode (on the left) and one of my very first Skeinforge prints with initial 'good' settings, and it's still getting better and better all the time I learn more about Skeinforge.


Some excelent information and advice from long-term Skeinforge users for the new Version 40/41 can be found on the Reprap forum here - http://forums.reprap.org/read.php?154,75635
And also on the Mendel-parts forum here - http://www.mendel-parts.com/new_forum/phpBB3/viewtopic.php?f=37&t=256

Many thanks to everyone as I would have wasted a lot of time if not for this head-start.
 


The Skeinforge manual and settings descriptions are also found here - http://fabmetheus.crsndoo.com/wiki/index.php/Skeinforge
 

My setup is not typical of a Mendel or other Reprap, so your exact settings will be different, but the following information, notes and advice may help you get going if you are new to Skeinforge and are not sure where to start.
 
One of the first problems I had was the fact I didn't know how well my machine would print so it was quite hard to judge when I actually had it calibrated to a good standard.
Other than looking at other people's prints on thingiverse it's hard to say how good your machine should be?
 
First Step - Measuring E-steps/mm for the new Dimension changes in V40/41
 
I'm using a Bowden extruder setup that has some extra issues ascociated with controling filament hysterisis but the following is required for any extruder in any configuration.
My extruder being belt driven is also different from a Wades or Adrian's geared version, but in principle operates in the same manner, but with different gear ratio etc.
 
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I setup my Extruder on a stepper motor test jig I had made to test Pololu modules, it's just providing a simple button to full-step the stepper motor.
 
I'm using 1.75mm Feedstock and now Dimension requires you to set 1mm of INPUT feedstock. 
Before the firmware required 1mm of Extruder Feedstock, this is an important change and makes a big difference for making nozzle size changes easy and generally everything else easier.
 
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I marked the filament with tape on the extruder output and then counted how many full-steps (button presses) were needed to extrude 10mm of feedstock.
I did this again in the reverse direction to make sure of my count. Take as accurate measurement as you can for this.
 
10mm of driven feedstock = 348 full steps
I am really running my Extruder at 4 x microstepping, so 348 x 4 = 1536
 
And in the Firmware you need to provide a value for 1mm of feedstock so that would be 1536/10 = 153.6
So I used 153, recompile and download.
 
Then you need to accuratly measure your feedstock, I measured with a digital micrometer 10 random section of the coil and the average was 1.792mm
 
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These settings need to be entered into the 'Dimension' tab in Skeinforge.



Many of the sections in Skeinforge do not need messing with, the ones you will need to play around with are 'speed' 'raft' and 'fill'

After setting your input filament perameters Feed and Flow under 'speed' are the most infulentual settings to play with along with 'infill width over thickness (ratio) in 'fill'


The next bit of advice is to make your machine Go Slow for initial test and calibration of flow/feed, I wasted quite a lot of time trying to run my machine too fast before I had these settings correct, you can easily speed it back up afterwards.
So set the 'speed' for the machine to 20 or 30mm / sec
 
Set your flow/fill speed -


Set the extruder speed Feed and Flow the same value, I started at 16mm/sec and went up and down from there.

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This picture shows the effect of Flow/Fill on my machine (0.25 layer height) 160 layer 40mm tall 10mm cube.

I decided to turn off 'Limit' as I have acceleration in my Firmware, but you may want to enable it to help protect your machine from over-speeding especially on the Z axis.

If you are not using a heated bed (or even if you are) you may want to make the first layer go slower than the rest to help it stick to the bed.
Raft can do this, although you don;t actually need to make a raft just use it for slowing down the first build layer outline and initial fill.
See the Above links to Reprap forum and Mendel-parts for more on this and all the other sections.


Then tune your solid fill rate - 
Some of the guides talk about setting 'infill width over thickness (ratio)' to 1.7 from the standard default of 1.5. I found that my solid layers had too little plastic at 1.7 and 1.5 so my setting is 1.4, this gives me a perfectly filled solid layer without any 'spare' plastic, if your nozzle is pushing about plastic on subsequent layers of a solid fill (object base) then raise this number. if it's too sparce and you have tiny gaps between filament make this number smaller.

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This solid base was with it set to 1.5, I settled on 1.4 in the end.

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These are the different tool-paths for 1.0, 1.5 and 1.7 infill width over thickness (ratio) settings
 
Correct Filament Reversal length -
* Very important with a Bowden extruder *
 
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I did get lucky with my first guess at required Filament reversal length, but the above image show the effect of not having enough reversal (lots of strings)
On the left is a 1mm reversal, middle is 2mm and printing on the right is a 3mm filament reversal. I may be able to get away with 2.5, but for now I'll stick to 3mm.
 
 
 
It's easy to fool yourself into thinking you have ok settings using a standard test cube, I have found that this model (below) is an excelent peice for machine calibration and it's quick to print so you can try out settings quickly.
It's a hollow pyramid by (3dprinterbot) found on Thingiverse -.http://www.thingiverse.com/thing:8757
 

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This was still early on in the Skeinforge tweaking, but even so a great improvement over Java host.
 
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No Strings !
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Java host generated on the left, and Skeinforge V41 on the right. (With strings, but in the right places)
 
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This was my most recent print, with super-refined settings. 
This proved to be a good test of filament spanning, you can see the solid layers at the top, under this is hollow, and then a solid base at the print bed.
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I stopped the print as I have hit a problem with Gcode generation on Hollow objects. 
I'm going to need some help on sorting that.
 
Anyone like to guess on what this object is? 
When I get it all printed out you can see if you were correct.
 
If you are new to Skeinforge, I hope that some of this may help you or at least show you that it's worth learning how to use it.​
 
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