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As some of you may know, 3D printing is getting cheaper, but it's still expensive. And most prices for prints are based on volume. So how do you cut the volume of your print to make it cheaper? You can make it hollow (if you don't know how, I'll show you my method) which can take a lot of price out. But I have an item that at it's cheapest was about $43. If you want to make an item that sells, that's a little pricey for an impulse buy. So how do you cut out even more volume without a lot of manual work? Well I used a tool in a way it's not exactly meant to be used. I'll show you how to use 123D Make to cut as much volume out of a model as you'd like.

What you'll need:

Computer with 123D Make (free!!)
Blender (the modeling program, not the smoothy maker. Also free!!) - optional
A 3D model (If you don't know how to make one, you can easily find one for free online)
A 3D printer or printing service. I'll be using Shapeways in my example as I'm most familiar with them.
Filler - Anything that you can fill your model with. I'm thinking colored wax would be awesome - optional

Please note, if you'd like to make an even cheaper prototype, check out my instructable on prototyping on the cheap.

Step 1: Optional Hollowing Step

A big key to limiting the price of your 3D print is making your item hollow. To do this I use Blender. I'm terrible at Blender, and every time I get used to doing something, they update it. But this method works for me. I'm going to write this for someone that has never used Blender before.

Right click the cube that pops up when you open Blender. Hit the Delete key and click Delete on the popup that comes up. File>Import your model. Right click your model. At the bottom of the window will be a select box that says Object Mode. Click it and select Edit mode. Hit the A key to deselect all. Now at the bottom of the screen there are 3 boxes that have cubes. The first box is selected with a point on the corner of the cube. Got to box 3 (the one with a face of the cube highlighted) and select it.

Almost there, now zoom into your model and select any face where you are making your opening. Right click the square in the center of the face to select it. If the face is part of a flat surface that you wish to make the opening, hold Ctrl, Alt, Shift, and press F. This will select all linked faces on that plane. Hit the Delete key, this time there will be more options other than just delete. This time click Faces

Switch back to Object Mode, and right click your model again. On the right side are a set of tools. Click the wrench (When you mouse over, it says Object Modifiers). A drop down will appear that says Add Modifier, Click that and select Solidify. A new box will pop up, click inside the Thickness field and set your thickness to the minimum thickness allowed for your material. For my example, we're aiming for Shapeways WSF which has a minimum thickness of .7mm. This is a larger model, so to be on the safe side we'll aim for 1mm. Which to be even safer (and because I use inches) I'll use .04 inches. Note that Blender units are what ever your imported model is. Click Apply, then File>Export your model as an OBJ.
Good stuff, how can I import a 3D modeld I have saved on my desktop to 123D make? Every time I try to import something it says "mesh could not be imported" import failed?. How can I overcome this. I need help.
<p>My guess would be, there must be some sort of file error. Try opening it the free version of meshlab, to see if there are file issues, and use the automatic repair to see if that fixes them. </p>
<p>Sorry, I meant Netfabb, not Meshlab. Both are great tools to have though. </p>
<p>could you solve it? , I have the same problem</p>
I'm trying to make r/c car bodies what kind of 3d model files can I import to Blender, and how do I do it, I'm having no luck, my files don't show up when I try to import them onto Blender...
<p>Blender supports a few different file types. What file type do you have? If you're having trouble importing into blender, you probably want to find a blender community to assist you. </p>
It also says its not a valid 3dmk file. I'm new to all this. I don't know wahat it means...
<p>Sounds like you are trying to open a file instead of import. There should be a button on the left that says import, and from there you can import an obj or stl</p>
It also says its not a valid 3dmk file. I'm new to all this. I don't know wahat it means...
HI My name is Benjamin Owen and I am a Recruiter looking to hire a 3D Tech in the PA, York area. No formal experience required. Give me a call or send me an email. 610-771-1087 or Bowen@jobscss.com
Seriously fantastic tutorial man. I can't tell you how much of a difference this little trick makes.... One thing I'd recommend others using this tactic is that if you're designing parts to fit into one another, just play around the parameters or your design. It's usually possible to get the right slicing so that the joints still fit perfectly.
I bet you could fill that with foam filler, add a few layers of bondo and paint, and then polish it to a super clean finish. One could print skeletons for all kinds of sculpture with this technique! I'm getting tons of ideas on how to use this, ty :D
This is incredibly clever, especially for making test pieces!
I can't think of anything I like about 3D printing but the excessive cost would top the list for me I suppose. Bring it down to zero and I still wouldn't like the stuff though. I'm not a big fan of plastic garbage.
I can't think of anything I like about 3D printing but the excessive cost would top the list for me I suppose. Bring it down to zero and I still wouldn't like the stuff though. I'm not a big fan of plastic garbage.

About This Instructable

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Bio: Since middle school I've been involved with engineering and design. It always interested me to make things. I love making things outside the box ... More »
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