Virtual Casting Mould in Blender – 3D Printed Cast / Peanut Candle

Video | Posted on by spapasavva
  • 00:00​ – Intro
  • 00:30​ – Moving and Transforming
  • 02:05​ – Big Nuts
  • 02:39​ – Remeshing
  • 03:55​ – Making Virtual Cast
  • 05:20​ – Boolean Modifier
  • 05:19​ – Splitting The Cast
  • 06:39​ – Real Life

In this video I’m going to share how I made a virtual mould in blender, of a peanut which I then 3D printed and used to cast a positive object.

I made this 3D model of a peanut by taking several photos and using a process called photogrammetry. That workflow was documented and is available in the previous video which I will link to it in the information card above.

To start with I import my STL file into blender and saved the document.

Once imported I then right click on the model and selected Set Origin and Geometry To Origin.

For this to work you want to make sure the 3D cursor is on X=0 Y=0 Z=0 which is a virtual coordinates, and will help with keeping this concentric later. If the cursor isn’t where you expect you may need to press Shit+S on the keyboard and select Cursor to World Origin before setting the geometry.

I then orientate the model so the top of the peanut is facing upwards and the seam intersects with the X Axis. If the Transform tool is not visible you can select the tiny arrow and pull that outwards. By clicking on the Axis letter the view re-positions and I can use the transform tools to make my adjustments.

I also change the scale. The longest dimension of the model peanut is nearly 83cm and I’m not sure that that is. But I’m going to change that to 145mm which is roughly what size object I’d like to 3D print. I then copy the scale factor over to the different axes.

Once I was happy which took an entire bottle of wine, I pressed Ctrl+A while the peanut was selected, and clicked on All Transformations to Delta. That sets the current rotation and location to zero, and scale to back to one. This will also save me having to do any maths if I have to fine adjust anything later as well notice if anything moves out of alignment by accident.

Now for some reason the dimensions of the peanut are much bigger than what they were in real life – and if I exported 3D model from the photogrammetry software Agisoft, directly into the Prusa-Slicer I got this error and it was roughly half the size that it should have been. If I then rescaled and exported an STL from prusa-slicer into Blender the peanut was 40 meters long – it was a giant peanut. This side of things confuses me a little so I’m just going to work with what I can see on screen.

My mesh is open at the bottom and I will need to close this, but before that I make a copy of the model and hide one viewpoint. I may make more copies as I go along so I can compare processes and easily repeat stages if I need to.

Now to close the hole in the mesh I will use a modifier. While the visible peanut mesh is again selected, I go to the Modifier Properties, and then the Add Modifier drop down menu and finally Remesh. I also toggled off the real time display and render as this slows the process down, and I’ve already done a trial of this and I know which settings work.

I select Sharp and change the Depth from 4 to 11 and the Scale to 0.99. And as I’m easily impressed, I commit to this by pressing CTL+A or the dropdown arrow and Apply. The software does a little processing, and the spinning wheel of doom appears, but eventually this will plug any gaps in the model. I can also compare this with my originally imported peanut. I suspect there’s another way to do this so if you know a way please share this in the comments section as this software is a massive piece of headache.

Anyway, moving on. I’m now going to import or create another shape into the scene which is what I’ll subtract the peanut from to create the mould. I press Shift+A and select Mesh and Cylinder, and then use the Transform Tools to change the dimensions to what I require. 

If these are concentric to one another when you click between the cylinder and the peanut the origin should not move. You can also compare this between axis views. If for some reason your origin is not set to the cursor (or X0Y0Z0) or when you select the two shapes they are not aligned, you can right click on the shape and select Set Origin and Origin to 3D cursor. And then geometry to origin. And then Ctrl+A and Location to Delta. It gets a bit confusing so you may need to repeat your stages to identity where you’ve created a problem.

I also reposition the cylinder, so the base of the peanut intersects base of the cylinder, and becomes the opening for pouring the casing materia. Once that’s done, I also press Ctrl+A while the cylinder is selected and press All Transformations To Delta.

I’m now going to subtract the peanut mesh from the cylinder. I select the cylinder, navigate to Modifier Properties, Add Modifier and Boolean. I select difference, and under Object select Peanut. To commit to this, I either pressing Ctrl+A or Apply in the dropdown menu. The spinning wheel of doom appears again, and I have to wait. If I hide the peanut from view and orient to the bottom I can see into the cylinder and the negative space within.

The next stage will be to slice this cylinder in half and to do this I begin by pressing Shift+A and select Mesh, and then Plane. I transform the plane to a smaller size and rotate it to interact along the peanuts seam. I can hide the cylinder from view and reveal the peanut to help me see what I’m actually doing.

I duplicate the cylinder and use the Boolean modifier to split the mesh along the plane. I use Difference on one and Intersect on the other to create the two halves. You can split the virtual mould in as many segments as you need and even add additional pouring holes and vents to let air escape if necessary. I have made two half moulds and one that splits into quarters, and I’ll show you that now away from the virtual world on my camouflaged kitchen table.

Ok this is the last mould that I printed. And it’s done in four section and I also chamfered the edge ever so slightly so I could place a wick through there because this is going to be for a candle.

And these are a couple other ones I made from a different scan. The texture is a lot more detailed here. While this one still has the gaffa tape on. You can only imagine what Eduardo Paolozzi would have done with a 3D printer and photogrammetry.

And these are a pair of semi-spent nut candles he says with a silly grin on his face. You can see a little detail, but I guess the point with wax is they change shape and become covered in drippings over time.

Just a note – when working with molten wax and making the candles I made sure to heat the wax at a low gentle temperature, and to not rush. I also made sure to avoid working anywhere where other liquids were present, especially water as if wax comes into contact with water this can cause an explosion. I have a vivid memory as a child while sitting in candle lit darkness after a power cut, my brother though it would be a good idea to pour water onto a candle – and nearly setting the kitchen on fire and set him on a path of religious devotion and a receding hairline. On that note I’ll leave this video here and you with this question – what should I scan next? Should it be a cheese – the vest answer will get scanned or is it photogrammetrasied.