Friday, June 1, 2012

Can the Scope be Helpful in Other Ways?

I know that some of you are saying, "Come on Tom.  Things can't be as rosy as you've shown so far!"

And, you are right.  They can't.

The Cube, like any other 3D printer is laying down a series of layers of melted plastic that must adhere to the previous previous layer of plastic that may or may not be positioned directly under it.  Moreover,  that cooling layer is sandwiched between a hotter layer above it and a cooler layer below it.  There can be hundreds of such layers.  I've not seen ANY 3D printer that lays down layers that are perfect at all wall thickness or angles 100% of the time.

ABS is tough, has a feel to it that is a LOT more pleasing than PLA and just plain looks nicer.  But, it has a tendency to warp.  I've already mentioned that I would prefer to use ABS plastic in my other 3D printer.  But, I can't.  Without a heated bed, it warps so badly that I just can't use it.

I love the fact that the Cube has a heated bed.  But, that does not mean that in some circumstances a little warping might not occur.  When that happens, we will see a line that is different in the sides of our printed objects.

One of the reasons I designed my torture test with differing wall thickness and shapes is to see how the Cube/ABS combination performs under completely different circumstances in the same print run.  And, to learn from what I find to design things that avoid potential issues.

A finding is not "Good" or "Bad".  It's "What".

And, the "What" that shows up in my torture test is that wall thickness makes a difference.  That's not surprising to me.  But, if you are a new 3D printer owner, it might be a BIG surprise to you.  Let's take the "surprise" out of it by seeing what it is up close.

I have to apologize for this picture.  All I have here right now is an old Sony Bloggie with absolutely no control over the exposure.  Here is the part that has a wall thickness of 1mm, the thickest of the objects in the torture test.  (I'll replace this picture later with a clearer one)

Part with 1mm walls

As you can see, there is a layer that is not absolutely perfect.  And, that imperfection extends around the part from the sphere to the extruded triangle.  That is what warping looks like.  None of the thinner pieces showed this characteristic.

There is something else that is not so easy to see in this particular photo.  But, CAN be seen under the microscope.  This is the wall of the box from the top.  Notice that it is not solid.

Top of 1mm box

This is a behavior that I have seen over and over in my first 3D printer and in countless images in 3D discussion forums.  Certain thicknesses are more difficult for 3D printers than others.  The trick to avoid this is to know what thickness are optimal and which are not.  Obviously this has repercussions to the overall integrity of the object.

We know we can avoid this by designing our wall at .5mm or .75mm.  We can probably also avoid this by making our wall 1.25mm.  Remember, I said our findings aren't "Good" or "Bad".  They are "What" and the "What" in this case let's me know that I probably am better off avoiding 1mm walls in square boxes.

So, how might this have affected the overal piece?  The clue is to the bottom left and out of focus.  That is a single piece of filament that broke ranks and missed the corner.  And, it's right at the layer that shows evidence of warping.

Seen from the microscope's perspective, it's plain that this errant strand, probably allowed by the hollow wall, started the warping snowball.

Corner of warped layer

This is the picture of the corner and layer where that filament took a shortcut.  As I said, wall thickness DOES seem to make a difference.

But, here is something else that is interesting.  NONE of the prints of the twisted star show any signs of weakness or warping.  The wall is just a little thicker than 1mm.  And, a close look reveals another interesting bit of information that we can use to our advantage.  Not only wall thickness; but, wall orientation seems to make a difference.

Here we see the same wall in two different orientations.  Notice that the bottom orientation shows a different inner characteristic than that of the top orientation.  One seems more solid than the other.  I find that fascinating.

What this seems to suggest that if we have a part that seems prone to warping, etc.  We might just want to try it at a different orientation on the print bed.  I don't know for sure that this will cure the problem.  But, it certainly suggests that rotating the part in the software that we use to convert STLs to Cube files might help.

 In my case, it prompts me to go back into my 3D software and design an STL having several copies of this part with 1mm walls oriented in different ways to see if a different behaviour emerges.

This is a printer/plastic behavior.  Not  a printer/plastic problem.  It's a DESIGN problem.  

I consider that it's my job to use up filament chasing down design problems so that you don't have to!  :)


  1. Awesome posts Tom!

    I preordered also, so I am eagerly awaiting my delivery.

    I'm a consulting mechanical engineer who buys stereoliths and FDMs (Fusion Deposition Models) from a local service bureau several times each month... I already have clients lined-up for Cube time! It's great to know the process limitations, and how part design affects the build.

    Question: Did you receive your Cube via UPS or FedEx? Were you given a tracking number prior to shipment, or did it just arrive? Thanks again

    1. I never did see a trackng number either. It just arrived. The address on the box was in Herndon, Va which is just 10 minutes away. The receiving people in this building called to say that I had a box. And, it turned out to be the Cube.

      I was so excited to get it, I didn't even check how it was shipped.

      Hopefully, everyone will get theirs in sooner rather than later. But, they might be swamped with orders for all I know.

  2. Did the environment change when those errors occurred? That looks like something caused my drafts.

    Can you send me the STL and I'll print it on my machine? You should have my email from a few days ago that I sent to request@

  3. I am sure that the enviroinment influence the plastic processing. I have extensive experience in plastic injection molding and we have all kind of problems when ambient humidity changes. On my machine I will build a small chamber with a small dehumidifier in which I will keep the Cube.
    If you see all Stratasys FDM machines have closed envelope for 3D printing and the printer dosn't start printing unless the envelope has reached 70 degree F. It keeps that teperature constant during all printing process.
    I had problems printing in the Dimension machine when one of the thermocouples went bad and the parts were warped because of extensive temp and humidity.

    1. That is great information. I live on the East coast. So, my Cube will see plenty of challenges in terms of temperature change and humidity. We'll see how it does.

      The information on the 70 degree F is extremely valuable. I was keeping the outside studio at 67 and actually attribute one small lift in a large object to my opening the door at night when the temperature was probably in the 50's. Your comment confirms my suspicions. The good news is that the lift was very tiny so it didn't affect the piece like I've seen on an unheated bed.


    2. Hi Tom,
      Also the reused cartridges have a problem when you put tham back in the machine for the second or third time. If you noticed the cartrige come in a sealed air-tight bag. Once you open it the plastic starts absobing humidity. The best practice for using old(open) cartridges is to dry the ABS (same as in injection molding. Put in the oven at 170F for 1 hour. Be careful to remove the PCB from the cartridge when you put that in the oven so it doesn't get damaged.
      with dried material you get the best results.

  4. Interesting information. But, I don't expect it to hang around too long. LOL!

    I have a LOT of backlog I want to print.

    Even so, every clue we can get for the best prints possible is a great one to know. Again, thanks!

  5. I just received my cube printer but i'm having problems with the converting from stl to cube file. I'm design manager at a portuguese company named Farame. We work with solidworks so we don't have problems creating the models and converting them to stl. However, when we try to convert those files (when we make the "build") in the cube software an error happens and the program crashes. I've tryed in three different ccmputer, working with windows xp and with windos 7 and the result is always the same. Can anyone help me?

  6. Please email me the STL using and I'll at least be able to check it on my system and also the client for the RapMan3.2.