3D printing mega-post: How to get decent prints (April 2015 Edition)

OK, so I’ve been learning a lot about 3D printing, and have been doing it for about a week. At this point, I feel a have a handle on the basics. So, I wanted to write down an overview of the things it took some time for me to learn. To catch you up, here is what I’ve written on it to date:

Buying a printer:
As previously discussed, the 3D printing world is very-fast moving. So, at the moment, I still believe that the Printrbot Simple Metal is the best “bang for the buck” – at the moment. Not only do things change quickly, there is game-changing technology coming in mere months!

For example, TIKO is a fundamentally different design for an additive 3D printer which solves several of the structural problems with existing printers. Not only that, but they are set to sell these at $179 – which very well might bring 3D printing to the masses!

Here is the KickStarter for it:

https://www.kickstarter.com/projects/tiko3d/tiko-the-unibody-3d-printer

And here is an overview video:

I really like this idea, and the implementation – I use the OcoPrint app for all of the things I’m talking about in this post, except where noted.

What about the printing temperature?
This is one thing where I am still somewhat confused. I see people recommending 205 or 210 Celsius for printing PLA. That, for me, made a big gooey mess! Then, I found more references where people say that 190-200 is the ideal for PLA. The prints were better, but still pretty messy. Finally – I decided to keep dropping the temperature to see what the “sweet spot” was:

  • 210 – Horrible – my first prints
  • 190 – Not great
  • 185 – Better…
  • 180 – Better!
  • 175 – Pretty good!!
  • 170 – Plastic wasn’t consistently coming out of the extruder; not hot enough

Given that, what makes sense to me is:

You want to extruder to be as close to the bed as possible to make squished layers – AND you want the temperature to be as low as possible. Lower temps = precise prints / Higher temps = messy prints.

In my particular case, a z-axis offset of –1.2 and a printing temperature of 175 makes the best prints possible. So with that said, I have some comparisons. This is really difficult to capture on camera, but hopefully the difference is noticeable:

image

image

Print quality and accuracy:
While I was learning CAD, I wanted to test my skills to see if I could reproduce a small object. I bought a high-precision caliper and protractor (to find angles). I attempted to reproduce this small picatinny rail riser.

WP_20150418_15_00_37_Pro

The adjustable part was a little too difficult, so I just made it a fixed size. Here’s what I came up with in FreeCAD:

image

when I opened in in Cura, it seemed to keep all of the detail – note some edges are sharp and others are beveled or smoothed:

image

Next, consider that the 3D printer can’t print over thin-air, how will it handle “holes” in the print? Well, to minimize this, I turned the model on it’s end. Now, it will print mostly flat surfaces:

image

There are still protruding, cantilever edges which stick out. Picture, as this is printing from the bottom up, how does it print a layer which extends out over the rest of the model? Well, how it worked in this case, the printer printed into mid-air, made a messy foundation, and then the rest of the layers were fine after that. So, if you have a hard edge that sticks out more than a fraction of an inch, you should really build a support gusset in the design to help during the fabrication process.

Anyhow, using the tip close to the bed, and with 175 degree PLA, I was able to get a pretty high quality print! Here it is compared to the thing I was modeling against (sorry for the picture editing, but it was difficult to see otherwise):

WP_20150416_17_45_32_Pro

WP_20150416_17_45_52_Pro

WP_20150416_17_46_14_Pro

WP_20150416_17_46_33_Pro

I can’t even begin to get a good picture of it, but sure-enough, those tiny grooves at the top – the edges that were on the “bottom” of the printing process are crisp and clean. The ones that were cantilevered are messy. You could easily take a square file and file it down though.

Next, the big stuff printed OK, but the small stuff wasn’t very precise. So, I made a random “thing” in FreeCAD which had some features I wanted to test: hard edges, chamfer and fileted edges, and risers for 3mm screw holes:

image

and again, in Cura, it seemed to keep all of the detail:

image

Keep in mind this is a little over 1 inch by 1 inch, this is how it printed with my “best” settings:

WP_20150417_10_19_22_ProWP_20150417_10_22_16_ProWP_20150417_10_23_12_Pro

As you can see above, the first layer gets squished and makes for a good surface, but the top layer is always left messy. Not sure why that is.

Bottom line, these are some of the limitations I found for the precision and accuracy. If you want details any smaller than 4mm or 1/4” – the 3D printer is going to have trouble with that. The bigger the print with bigger details, the nicer your print will be. It’s similar to picture quality or camera quality. The more pixels you have, the higher precision you have:

image

versus

image

versus

image

Similarly, my .4mm 3D printer extruder can print this to that first-cat quality. If you want higher quality, you can either make the print bigger, or get a higher quality printer!

Prepping for a print:
OK, at this point you bought a printer, set the z-axis and are familiar with Cura, or you have an Octopi setup. You are ready to print! “What’s next?”, you ask. Again, great question! Well, I’ve only worked with “PLA” plastic so far, to the rest of this will be about that.

If you don’t have a heated bed, you will need something on your print bed. This medium needs to be tacky enough for the first layer of plastic to stick to it, but also easy to remove – and be resistant to a putty knife. You often need to “pry” up the print from the bed. It will be firmly attached! So, the answer is to use blue “painters tape” – which you can get at any hardware store.

image

So first, lay down some tape – here is 4 rows of 2 inches:

WP_20150418_11_14_41_Pro

This alone, won’t do. When I tried to print on this, the first layer didn’t stick and the extruder nozzle got all gunked up with melted plastic. It was a mess. It turns out, there is a slick residue on the surface of the tape. So, take some isopropyl alcohol and wipe down the surface of the tape, and wipe off the excess.

image

It dries in just a few seconds. Run your finger over the tape now and you’ll feel that it seems very tacky! You can get this kind of alcohol at any drug store, and I just used a paper towel to do the wiping.

Checklist before you hit the “print” button!
OK, I messed this up several times, so here are some things to consider – assuming that you have the machine calibrated already:

  • Ideally use fresh painters tape. Definitely replace if there is any damage to the old tape. You are dealing with printed layers that are a fraction of millimeter – a small bump in the tape is going to mess up your print!
  • Wipe down print bed with alcohol and make sure it’s dry.
  • Make sure you have enough plastic filament for the print (both Cura and Octoprint will tell you how many meters of filament it will use. 1 meter=3.28 feet)
  • Make sure to start with the fan off (in OctoPrint, click the button to make sure it’s off)
  • Open the .gcode file and remove or fix the starting temperature – look for “M109”, it’s often the first line of the file. If you don’t, you CAN’T change the printing temperature during the print. For me, I usually remove this line – or you can set it to “M109 S175” to print at 175 Celsius.

image

  • “Home” to X and Y home, but have the Z up perhaps 30mm (hit the up button 3 times) – so that you have access to the underside of the extruder while it’s heating up.
  • Pre-heat the extruder to the desired temperature, and wipe away any extra strings that ooze out. Use pliers or a paper towel – nozzle will be VERY hot (175 Celsius is 347 degrees, for example)

OK, now hit “Print”!

The cost of printing:
One other side note. As you print things and have failed prints, how much do they cost? Well, it depends. I don’t mean that lightly, I mean it can vary dramatically. The primary indicator is of course: how much plastic you use. How much plastic you use is usually going to depend on how dense the object is. By default, these programs will create an 1/8” shell to your object and then you can set a percent of how filled you want it to be. 0% means it will be hollow beyond that 1/8” shell, and 100% means that every bit will be fully made of plastic. Anything in-between, it creates a cross-hatch. Here it is filling in 15%:

WP_20150416_20_06_48_Pro

You set this, I use Cura and it’s right on the Basic tab:

image

while you are at it, you might want to set the printing temperature here too, if you use the same temperature every time:

image

Then, you can export to .gcode and these things will be all taken care of. OK, with all of that said – the things listed above:

  1. The fan shroud
  2. The picatinny riser
  3. The small 1”x1” object

those were all printed with 100% fill and together they cost about $0.51 cents in material.

Bottom line:
As you can tell, this has been a time-consuming, but pretty fun exercise. Hopefully between this and my other posts – this gives you all the of the basics for those who might be considering getting a 3D printer.

I bought a heated bed for this printer so that I can try bigger prints. I also need to actually install that fan shroud now too – which should help with temperature control.

If you already have one and have tips for me – or if I’ve misstated something, please let me know in the comments below!

Posted in 3D Printing, General, New Technology, Raspberry Pi, Uncategorized
7 comments on “3D printing mega-post: How to get decent prints (April 2015 Edition)
  1. Laura says:

    Impressive explanation!

    Like

  2. AmyJo DeFelice says:

    Wow great information. 3D printer is not in my immediate future..it is great to read all your detailed info on prep

    Like

  3. Oker says:

    Hi!

    Can you please share the Freecad file for the picantinny?

    It would be awesome if you can share, for example, in Thingiverse 🙂

    Thanks!

    Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Archives
Categories

Enter your email address to follow this blog and receive notifications of new posts by email.

Join 2 other followers

%d bloggers like this: