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tomaszklos

Getting started: settings, tips to nice prints

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Hello.

I'm Tom. The company I work for just got a Ultimaker 2. I volunteer to be the one operating it. I took it home and started working with it. First prints were somewhere decent. By that I mean you can tell what it is but from close they dont look as good. I updated the firmware using CURA to Merlin firmware (one of the information I took from this forum). Now some of the prints look decent and some of them look great. For example the "stackable cup" that was loaded on the SD looks great. On the other hand the "Ultimaker robot" looks decent. The worst parts are where the printer starts to print away from the print. The layers separate and at the end look distorted. I started to playing with settings on the fly ( fan speed, temp for PLA 2.85, plate temp etc) Nothing seems to help it noticably. I really need some directions what to do to get a decent looking prints in overall. I'm new to this so please go easy on me. Thanks in advance.

 

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The best way to get help is to post some images of the problem prints,

and start reading through and follow all other postings, this will give you a good idea what to look out for when getting problem prints.

best is to start basic shapes cubes and such, these are great test object to see what is going on.

 

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Hi Tom,

there are many ways to improve a print but in my opinon it boils down to these four points:

  • Model structure and orientation
    • As with any FDM printer, the inability to print mid-air restricts the model structure. This is one of the topics where you can expect most creativity from model creatores when they come up with ways to orient and support parts of a model in such a way that they will be able to print properly.

    [*]Speed

    • Printing slow (20-30mm/s) will improve print quality but will obviously increase printing time.

    [*]Temperature

    • A higher temperature will increase filament viscosity a so you will be able to print faster.

    [*]Layer height

    • This is the most important parameter. A bigger layer height (0.2mm) for example will print faster but produce a more coarse surface. Printing below 0.1 layer height is usually not necessare because it takes ages and the visible improvement is minimal.

The key combination is between layer height, speed and temperature. Sadly there are very few common rules to follow because every model is different. But that's the beauty of a rapid prototyping machine. Before you commit to a 15hr print, you could scale it down in Cura and print it in one hour or less to test for potential problems. Another thing to take care is the volume of filament you are asking the extruder to push through the hot-end and the nozzle. The Ultimaker Original and Ultimaker 2 have a nozzle with a 0.4mm diameter. In combination with layer height and speed you'd get this simple formula:


nozzle_diameter x layer_height x speed

For example: 0.4 x 0.2 x 150 = 12mm^3/s filament.

There are certain upper limits of what the printer is capable of. As a rule of thumb (I hope others will correct me if I am wrong), when you want to print something with a high visual quailty - print at 20-30mm/s with 0.1 layer height and 220° temperature (for PLA).

Also I suggest to enable the "full settings" in Cura and also open the expert settings. Usually one big question (depending on the object you are printing) is if you print with or without retraction and cooling enabled. Cooling will be helpful for small and thin features of an object where the hot nozzle would move often above the same part of the object thus not giving the plastic enough time to cool and harden a bit. Retraction is very helpful for bowden type printers where the stepper that moves the filament is not attached to the head. This allows for fast movement of the head at the cost of oozing plastic when the head travels to a new part of the object. Retraction is used to counter oozing and is often one of the factors that make a print look awful or briliant.

There are many more future of Cura to look at and overall things you'll learn from experience. I don't think it is possible to sum all of them up here.

Interestingly, that was my first and biggest gripe with 3D printing when I started. How do you know which combinations produce great prints? My idea was to create a kind of a cheat sheed for 3d printing (geared towards the Ultimaker) to help people understand basic concepts. I am not very far with this project due to lack of time, but it is still on my agenda and I am actively collecting random bits of useful information from the forums and elsewhere.

So in the end I suggest you print lots of objects. If you print at 0.2 layer height and without infill they'll finish pretty quickly. Also make sure in Cura always activate "Layers" view mode (buttom top right) and move the dial (lower right) up and down to get a preview of every layer. There you can spot many problems before printing (like top covers that are too large to be printed without infill).

 

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Hi Tom, lots of great points Nicolinux. I will just add that this technology is not plug and play and if you want to get consistently great prints then you have to put effort in. It is a learning process with highs and lows. Take the time to try various combinations of the major parameters noted above. If you can afford it, buy decent filament. If you are in Europe, Colourfabb and Faberdashery supply good quality filament (there will be others).

One thing I had never considered before I started was how do you orient your model for getting the best printing results? At the simple end, if you are going to print a cylinder, do you lay it flat or print it vertically? There are pros and cons. Do you print it as one piece or several pieces then glued together.

If you do your own design then design for the way the printer works. Eg. if you build a house, how thick do you design your house walls? The printer has a 0.4mm nozzles so make your house wall thickness a multiple of 0.4mm and select the number of walls/perimeters needed. If you are struggling to get clean right angled corners, try designing with chamfers.

 

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Ok. So lets start simple. I created a simple 25mm cube in google sketch. Then exported it into gcode file. Using Cura I saved it on the sd card. Did the factory reset of the Ultimaker (just to start fresh) leveled the buildplate and here we go...

Specs:

Ultimaker 2

Version: 14.01.2

Jan 10 2014 13:20:34

 

Material: PLA 2.85 Ultimate Blue

 

 

Retraction settings:

Retract lenght: 4.50mm

Retract Speed: 25mm/sec

 

Motion Settings:

Acceleration: 5000mm/sec^2

X/Y Jerk: 20mm/sec

Max Speed X: 300mm/sec

Max Speed Y: 300mm/sec

Max Speed Z: 40mm/sec

 

 

Cura - 14.01

 

Basic:

 

Quality:

 

Layer height: 0.1mm

Shell thickness: 0.8mm

Enable retraction: Yes

 

Fill:

 

Bottom/Top thickness: 0.6mm

Fill density: 15%

 

Speed and Temperature:

 

Print speed: 50mm/s

 

Support:

 

Support type: None

Platform adhesion type: Brim

 

Advanced:

 

Machine:

 

Nozzle size: 0.4mm

 

Quality:

 

Initial layer thicknes: 0.1mm

Cut off object bottom: 0.0mm

Dual extrusion overlap: 0.15mm

 

Speed:

 

Travel speed: 40.0mm/s

Bottom layer speed: 40.0mm/s

Infill speed: 0.0mm/s

 

Cool:

 

Minimal layer time: 5sec

Enable cooling fan: Yes

 

Plugins:

 

Pause at height

 

 

Ultimaker 2 Tune settings:

 

Speed: 100%

Temperature: 210 C

Buildplate temperature: 75 C

Fan speed: Slow increase during the process...

Material flow: 100%

Retraction: 4.50mm @ 25mm/sec

 

 

 

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Hi Tom, welcome to the Forum! Nicolinux covered pretty much all the important points, but a couple more things to think about.

Firstly, are you using glue on your glass plate? I recommend that you put a thin layer of glue stick on the bed, and then use a piece of folded, wet paper towel to spread all the glue until there are no visible lumps anywhere. As the bed heats, it will dry, leaving a very thin layer of glue that will hold the print well, without damaging the bottom surface of the print. I also recommend increasing your print temperature to 230, and reducing the bed temperature to 60.

I also recommend increasing your retraction distance to 5.5mm, and the speed to 35mm/s.

With those settings, you should be able to do most anything; you can worry about tweaking it later on a print-by-print basis, once you get a feel for things.

Looking at your photos, one thing I see is that the brim around your shape doesn't seem to actually connect up to the shape - and so that rather defeats the point of a brim - which is to help hold down the print by providing a larger surface area stuck to the bed. I suspect it printed the brim from the inside to the outside, and at first the head wasn't properly primed, so that it didn't actually extrude any plastic at first. That can happen, especially if the head sits hot for a while. What you might do before your print is to preheat the bed, and preheat the head, and then go into the 'Move Material' menu, and manually advance some plastic through the head, to make sure that it's full of plastic when the print starts.

Nicolinux mentioned the formula for volume of plastic per second, but didn't mention what the throughput limits are. A well-setup UM2 can print at 10mm³/sec, but some people are finding that they can achieve rather less than that. To begin with, I'd recommend aiming to keep the extrusion rate at 4mm³/s or less. (Your example above - 50mm/s at 0.1mm layers, with 0.4mm nozzle width = 2mm³/s, so you should be fine).

If you want to calibrate your extrusion rate capabilities for various temperatures and filaments, you might take a look at the test piece I recently posted...

http://umforum.ultimaker.com/index.php?/topic/3976-almost-always-missing-layers-underextruding/?p=33427

 

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Looking at your photos, one thing I see is that the brim around your shape doesn't seem to actually connect up to the shape

And the bottom of the part looks warped kind of. This is caused by temperature issues most likely. 75C is a bit hot for PLA - I like 70C. And the fan comes on gradually over the lower 5mm or so. Not sure exactly what is going on here though - my cubes don't have nearly as much distortion near the bottom.

Your bottom layer seems a bit thin. An initial layer thickness of .1mm is very difficult to achieve unless you relevel a few times. If the bed is .03mm too high (1/3 width of paper) then it will build up pressure gradually in the nozzle until finally the extruder skips steps and slips backwards quite a bit and you will get almost zero extrusion for quite a while - possibly why there was no brim touching the cube - just a coincidence.

I recommend .2 or even .3mm for the bottom layer as you then don't have to level so precisely. At least until you get very good at using the printer - some day you can try to get accurate levelling to .01mm and then do .1mm bottom layers.

 

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Morning guys. Yes the brim looks "disconected" from the actual part due to the feeder stopped to feed the PLA right at the beginning of making the part. I had to manually (by hand) force feed the PLA for the printer to start printing. Normally the brim gets all the way to the part (so I'm not too worried about that). I'm going to adjust the settings a little bit (according to you guys) and do the same cube today. Will post the results as well.....thanks.

 

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Ok. So after changing some settings this is the result.

test 2B

test 2A

Settings changed:

Temp to 230 C

Plate temp to 60 C

Retract length to 5.5mm

Retract speed to 35mm/s

Bottom layer to 0.2mm

and I also changed in Cura that the fans turn to full speed at plane 0 (so the fans are 100% all the time)

Looks much better. The corners are straight all the way from the bottom. My brim base looks much thicker too. Is it because the bottom layer was made thicker? Also how about the fans? Should I have them on 100% all the time from the plane 0? Thanks.

 

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Yes,the brim prints at whatever height you set for the first layer.

I wouldn't turn the fans on right at the bottom - the reason they come on later, by default, is because there can be too much cooling when the head is close to the bed; the air flow bounces off the bed and cools the nozzle. That may be why some of your brim lines look a little under extruded.

You shouldn't need to manually force the PLA into the printer, ever. If the filament has somehow gotten stuck, so that it has ground a flat spot on it, and can no longer grip it properly, then it would be better to remove the filament, and cut that damaged part off; there's a chance that the damaged part might get stuck at the other end of the Bowden tube when it gets there, anyway.

The UM2 is set up so that the extruder should skips steps (making a fairly loud click, and jumping the drive bolt back about an eighth of a turn), rather than grinding in place and damaging the filament. It's not totally foolproof, but usually works quite well.

 

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Ok great. Note taken :) I will reset the fan settings to the original value. After I removed the cube I noticed that the bottom layer wasn't melted enough together ( you can see individual lines) that is probably because the fans were on all the time from the start. My question is would not having the fans on on the bottom will cause the corners to cave in? I guess I will just try... Thats what this is all about trial and error. Other than that how does this cube look to you?

 

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I usually do fan on around 5mm up which I think is the default. Cura will turn them on gradually a little more each layer until it gets to the layer that is at 100% fan.

The gaps in your brim are not good. This cube does not need brim but many of your other prints will.

The gaps are either underextrusion, or more likely a leveling issue. I would re-level but only adjust the rear-most point and I wouldn't touch any of the 3 screws - I would do it only with the front panel control. Make it a little tighter than you did last time. When it asks you to check the front to points just click immediately claiming it's fine.

The great thing about the UM2 versus the UM Original is leveling tends not to change. So once you get it perfect you may not have to level again for weeks or months.

 

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In general the biggest improvements in quality are made by lowering the speed and/or acceleration. This is so that the extruder tends to extrude at a more consistent rate so you don't get over/under extrusion at every line segment due to the head speeding up and slowing down and the delay caused by the springiness of the filament in the bowden. The software in Marlin tries to take into account the position of filament and X and Y and Extruder (called 4 dimensional linearity) all at the same time and does this perfectly but doesn't take into account the delay caused by the bowden stretching.

Changing layer thickness to .06 will also improve quality and you don't have to change anything else but it will print much slower of course. I have found that the quality at .2mm sometimes exceeds that at .1 or .3. But .06 is usually better than .1m At some point the quality starts to get worse again.

But again - slowing down to say 30mm/sec will probably help quality more than going to .06mm. At 30mm/sec the printer hardly has any acceleration or deceleration at the corners which means the flow of PLA is more constant and consistent. Also at 30mm/sec the pressure inside the nozzle is lower and more manageable for things like stringing and unwanted leakage. Also at 30mm/sec (and slower) you can lower the temp so that the UM can more easily "print in the air".

If you really need to print high detail on the side of a pencil or something you should consider getting a smaller nozzle hole diameter at some point. I don't know any way to do that on the UM2 but on the UM Original you can buy other sized nozzles.

 

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As gr5 says, I'd focus on reducing the speed (and/or acceleration) rather than the layer height to get better quality prints. Thinner layers can help with reducing the obvious stepping on almost-horizontal surface, but other than that don't offer a whole lot extra, and just add to the print time. All of the recent high-quality prints I've done (see http://www.extrudable.me/2013/12/17/highqualityultimaker2/, and http://www.extrudable.me/2014/01/02/the-guy-with-the-dragon-part-2/) were made at 0.1mm layers, and based on the results I got, I don't think there's much need to go finer than that on a UM2 for most things).

 

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But yes, in general, if you lower the layer thickness, everything else can stay the same.

Since you will be extruding a small volume per second, you can potentially reduce the temperature since the extruder will be better able to print more viscous plastic at the lower volume-per-second. That may help with the quality of overhanging or bridged parts that lack support underneath. But it's not necessary to do so. Alternatively, you could increase the linear speed, to keep the volume per second the same, but that may trade off some of the quality benefits due to the increased kinetic energy of the head that has to be dissipated at the corners.

Generally, the slower the linear and volumetric speed, and colder you print, the better the quality will be. But the faster you print, the higher the temp needs to be, to give the extruder a reasonable chance of melting the plastic and squirting it out fast enough. Everything is on a continuum - the aim is to find the point (and it varies for each object you print) where the print quality is good enough for the intended purpose, while minimizing the print time taken.

 

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Ok another test done. I adjusted the plate closer. That helped getting the right base. I kept all the same settings except I change the fans to come on to full speed at 5mm and what I noticed that the bottom of the corners still look a little caved it towards inside of the cube. Not as much as the first test, but much more than the second test. Also what i noticed that the top surface has few spots that look like surface is bubbling???

 

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The 'bubbles' are due to the material curling as it hits the lines of infill underneath. The best way to fix it is with more cooling... but if your fans are on, and working correctly (both left and right fans are on, yes? Plus the one on the back of the head that's always on) then you can either cover the bubbles up by printing more solid layers as you suggest, or perhaps reduce the bubbling, and increase the effectiveness of the solid layers you are printing, by increasing the infill density so that the gaps being covered over are smaller.

Finally, you could try printing slower and/or cooler, so that there is less cooling needed as the infill gets covered up.

 

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