Well, from the department of “the best laid plans,” last week when I was going to try and take pictures of the prototypes, I found out “and by the way, we’re doing thanksgiving at your place.” Given the panic readying for hosting thanksgiving, I think my absence can be explained. Now, I still haven’t had the chance to get pictures with help, but what I can do is post the final processing to make the STL files as fool prrof as possible!
The first step will be getting a copy of Blender. Why Blender? It is free, both gratis as in beer and libre as in speech. I like open source solutions, but I also understand the importance of understanding the closed source “industry standard” programs. Where can you get Blender?
As an alternative, if you use the Steam service, it’s available in the Steam Store for free, and steam will auto update as the program is actively developed.
Now, the following workflow will step by step work for Blender 2.7. Version 2.8 will redesign the work-space and potentially change the exact keystrokes, but conceptually this should work, no matter the version. Once you have Blender installed and the program running you should be looking at the default view which will look something like this:
Your blender may not have all the tabs mine does on the left hand side, as ManuelBastioniLAB and 3d Printing are add-ons I have downloaded, but other than that we should be looking pretty similar and nothing in this process will need any add-on. All of this is default functionality of blender. We will start (as so many projects in blender do) by getting rid of the default cube. It starts out selected, and you can tell this by the orange outline around the object and the orange dot that represents the object’s origin in 3d space. If it’s not selected, in Blender Right click is select. This is one of the most long argued points about the program, and I understand the right click as select… the important thing is it’s really easy to change the default setting if that behavior drives you nuts, but I’ve gotten used to it in my years of using blender, so even if they did change the default left and right click behavior… i’d change it back.
With the cube selected, make sure you are in object mode.
The concept of mode is one of the most important in Blender. Certain tasks are locked to certain modes. For example, I can translate or rotate objects (technically you can scale them, but unless you really mean to scale things in object mode… don’t, and I will get into that later) but I can’t add more geometry to that cube. We can also get rid of the whole object by pressing the letter X. You should get this prompt:
Click delete, and you should be left with this…
You should notice that white and red ring with the cross hairs indicating the intersection of the X and Y axis. That is the 3d cursor. It’s a super important and useful tool, and easy to move accidentally, because that’s what left click does. To get it back to the origin, there is an easy and important keyboard command: shift-c
Shift-C will center the cursor on the origin and try and fit everything in the viewing area. The other little things we see, the strange pyramid on it’s side and the dot with a halo and a tail… that is the default camera and light, but are irrelevant for our uses today. They can safely be ignored.
Making sure our cursor is center, we want to bring in the first STL we exported from Fusion 360 for scaling. Now, I realize there are ways to do this in fusion 360, the easiest being “be better at CAD,” but this is the easiest way I know how to do this. In the upper left hand of the screen, click on the file menu, then choose import, then STL file.
Then you will see a file browser. Navigate to where you exported your STL files. Also, blender will rememebr folders you frequently use. It tries to be helpful like that, so again, yours and mine may look very different here, but conceptually the same.
Yeah, Christmas files… I’m making this for my dad as he loves the show… now, shhhh, don’t spoil the surprise.
I’m going to start with the grip, but the grip, barrel bottom and barrel top files will all be the same, basically. The only oddball will be the barrel greeble, the part that goes in the middle of the barrel.
Select the grip file, then click that import STL button in the upper right corner and you should see this:
What on earth are we looking at! Well, we are like an ant on the top of the grip portion. use the scroll wheel on your mouse to zoom out. Also, the pan vs. orbit commands are the exact opposite from Blender to Fusion 360. If you switch back and forth a lot, you may want to change one. Zooming out, a little pan and orbit and…
Well, that’s better, isn’t it? You can see we have that orange dot, the origin of the model right at the origin of our 3d workspace here, and just like in Fusion 360, the object is oriented in X and Y and Z the same way, the XY plane basically hits at that wide lip around the tab that goes into the barrel. It’s great! We just want to scale it down by 20 percent to get it closer to the size of the real prop.
Now, technically you can scale the grip in object mode… BUT the way Blender handles the data that may or may not affect things when we re-export the STL, because slicers don’t care about anything but the information about the individual vertices. How do we get to the individual vertices? We have to change modes. The mode we need to be in is called edit mode. You can either click the drop down menu that says “Object mode” and choose “edit mode” or you can hit the tab key to toggle back and forth between edit and object mode.
You can now see all the vertices, the edges that connect them, and the faces. All of the vertices in the object are selected by default. You will notice the white circle with the three arrows coming off of it has moved. That is called the Widget, and it shows you where your changes are going to be applied from. By default it figures out the middle of everything you have selected. If we scaled it right now, all the vertices would get closer to that imaginary point in the middle. That’s not exactly what we want to have happen. We want to scale it towards the 3d cursor while it’s at the origin on the 3d work-space. To change what we are scaling towards we need to use this drop down menu here:
This changes the pivot point, the place our edits will take place from, indicated by teh widget. We want the 3d cursor, so click on that, and you will see the widget snaps back to the 3d cursor.
Now, we are in edit mode, we have every single vertex selected (if you accidentally changed the selection to only some, the A key will toggle select all. If you have any vertices selected A deselects everything, then a second A selects everything again), and we have our pivot point where we want it. Now, we need to scale the geometry. We activate the scaling mode by pressing S. Your mouse will turn into a double arrow with a dotted line leading to the pivot point and moving the mouse will let you scale up and down, but that’s not precise, is it?
You can scale precisely by typing in a number. Numbers greater than 1 scale things up, less than one and greater than zero scale things down, and negative numbers… turn things inside out. To scale it down by 20 percent we type in the number “.8” not using your number pad while scaling and hit the enter key. The number pad is used for other things, some we will get to, though most are beyond teh scope of this specific task.
I have indicated where you can see what you are scaling by. It functions like a text box, so you can backspace if you make a mistake or don’t know the exact number you want to change to, and that will come up in a moment. Once we are done with that scaling, though, we can change back to object mode with a hit of the Tab key, and that will lock down all those vertices and keep them safely protected from accidental manipulation while we export the new, smaller STL file.
Up at the top, click file, Export, then STL, and it will take you to another file browser just like the import one. You can export the STL over the one that was too big, or some other folder, as is your choosing. You can then delete the grip object just like we did the cube with the X key, and then repeat all those steps for scaling down the top and bottom parts of the barrel. It should go faster as this time when you tab into edit mode, you will already be set to pivot around the 3d cursor, and remember you can recenter the 3d cursor with shift-c if it gets moved. I leave those two parts as an exercise for the learner, but will focus on the middle bit of the barrel as it has a few more steps we need to go through to make it drag and drop easy to print.
After importing the middle barrel greeble, you may be looking at something like this:
Well, I don’t see it in the work-space… but it is in the outliner on the right. It’s here… but where is it? Shift-C centers the cursor and tries to make everything visible so if we hit that…
Well, that’s… way up there. But you will notice, that orange dot means that the objects origin is still down where we want it, and on the left hand side of the screen there is a button labeled “set origin.” Now, we don’t want to move the origin, but that button does more than it’s label lets on.
Geometry to origin. That’s what we want. It will transpose the geometry so it’s imaginary center of mass will meet that little orange point way down at the middle of our XY plane. Choosing that gives us this:
It’s better, but it’s not right. I want the big flat bottom flat relative to the XY plane so if you drop the file into your slicer it’s ready to go and will print with ease. To make these changes, as well as the scaling, we need to be in edit mode, but we also need to change how we are looking at this. I want to look at the bit edge on. Remember when I said the number pad numbers did other stuff? With numlock on, it controls the view. Numlock on, pressing three on the number pad will put us into the right side view like this:
That’s better, but there is still perspective distorting the view. Numpad 5 will turn off perspective and give us the orthographic views we got in Fusion360.
You can see the view name where the red indicator is in that last image. From this angle it will be pretty easy to rotate that part flat relative to that green line which is the y axis. First, though, we should tab into edit mode and get ready to rotate. By default rotation is done relative to the viewing plane. Because we are locked to the right view, this will rotate the object around the X axis without any extra work on our part, and that’s good, because I want to be precise as I line this up. I zoomed in a bit before hitting the letter R to rotate all my vertices, and things look like this now:
I have indicated where you can see the precise amount you have rotated and again, you can type to be super precise, or use the mouse to eyeball things. If you are using the mouse, pressing shift will put you in precision mode, effectively gearing down your mouse so a bigger movement makes a smaller change. if you prefer to type numbers in, positive is clockwise from the view, negative is counterclockwise.
For me, I like the numerical precision, and so I first tried -50 degrees, but that wasn’t enough. -55 was too much, and then -53 wasn’t enough, but -54 degrees was also too much. I bounced back and forth and landed at-53.4 degrees to get the base level to my eye. You will notice the edges of the top and bottom of the part don’t have “jaggies,” or jagged points, indicative of a lack of anti-aliasing on a diagonal line on a pixel based display.
Lock in the change with enter if you are typing or a left click if you used the mouse. Now, I want to scale this part down like the other with the same keystrokes, “s.8” and then enter.
With that done, we can tab back into object mode, and from there, click file, export, STL and throw this in the slicer of our choosing, and it will start off flat against the build plate without the user needing to do anything. This makes it easier for sharing the STL files. The parts are individual STLs so they can be printed one at a time or all together, the parts that need supports can be printed separately from the parts that don’t need it, and this means it will fit on the smallest volume printers possible.
I mention this given that I know several people here are prop professionals. I’m a hobbyist, but I strive towards professional results and a professional product. To me, a professional STL file is all these things. Individual parts that fit together (sanding for the best fit is ok, but in a perfect world it should be pretty close popping off the bed), and are drag and drop ready. While some STL file repositories can have demanding users on one side trying to print files that someone found “somewhere on the internet” or ripped from a game with no effort put into making sure the file is printable, I do think to a certain extent, you should get what you pay for. While some people may want to give away the hard work of their STL files when built to this level of detail and ease of use, I certainly feel that if you are going to be selling files of this nature, drag and drop, and make it fit.
I will confess, that rant comes from my sister buying STL files for a Halloween mask that would have had about half a square centimeter or less of bed contact for each part, and needed metric tons of support material, and then the top half of the mask didn’t actually connect to the bottom half without melting the plastic in boiling water and trying to manipulate it that way. For fifteen bucks, I’ll sand and filler and sand some more, but I would expect the geometry to actually… you know… match up and not have a half inch gap between pieces. Now, my sister did have my help, so I could look at the files, rotate them in the slicer, change some settings, and get the most build plate adhesion with the best detail, but if she hadn’t had my help, she would have had a big mess of plastic spaghetti.
Ok, rant over, and happy making!