Practical 3D Prints – Chapter 1

Preamble:

The purpose of this series is to demonstrate how you can use freely available 3D modeling tools to make useful items to 3D print. The two applications I’ll use primarily are TinkerCad and Mesh Mixer. I’ve started learning FreeCad but at this point I’m not comfortable with it enough to include it in this series. I may do that in the future. Depending upon what I’m making I also use the following programs to assist my 3D modeling shenanigans: The Gimp, Ifranview, SVG Converter, Image to Lithophane, and Image to Lithophane Generator.

The Problem:

I’ve been in the process of putting the last finishing touches on setting up my fused glass studio in the remaining space in my 3D printing shop and one of the tasks has been to find a home for all my mini lap grinding disks. Here is the state of things now.

I figured there must be something I could come up with that would “clamp” on to that 3/4 inch back board and this is what I cranked out…

The Solution:

I opened up meshmixer and Imported a sphere just to get things rolling.  I then went to the Meshmixer primitives selector, dragged and dropped a cube and then delete the sphere I had originally imported.

I wanted to keep this as simple as possible.  AlI needed was a retangular bar that would have a U channel at the bottom that would slide snugly over the back board.  The bar itself would have two posts for hanging the disks.  I next measured the thickness of the plywood, the width of the center hole and the width of the disk from the bottom of the center hole to the edge.

          

With the disk measurements I was able to deternine how to space the posts so that the disks would not overlap when I hung them up.  I wanted the channel that fit over the back board to be the exact width of the plywood becuase the PETG that I would use would shrink just enough to make the bar fit sungly.  I had 44cm of space between the top of the backboard and the bottom of the shelf so I had plenty of room to work with there.  Next up was to create the bar that would hold the disks so I took the cube primitve I added to the project, selected Edit, then “Transform” and plugged in the X, Y and Z values to give me a basic bar.

Now in order to do boolean unions I needed to make my bar “solid” becuase the the primitives that are added are just an empty shell. I selected Edit, then “Make Solid”, changed the solid type to “Sharp Edge Preserve, changed the Solid Accuracy and Solid Density to 256, and selected “Update”.

Once the calculations were done I selected “Apply”.  I then selected “Align” from the Edit menu. I changed the Source to “Base Point”, the Destination to “Surface Point”, and the Transformation to “Translate Only”.  The bar is now centered and resting flat on the plane.  You’ll see why later.

Now I got back to the Edit menu and select Duplicate twice.  I then hide one of the duplicate bars using the object browser.

I select one of the visible bars (It doesn’t matter which one since they’re both the same) and select “Transform” from the Edit Menu.  What I want to do now is create the block that I’ll use to “subtract” from the main bar to create the channel that will fit over the 3/4 inch (17.5mm) back board.  I change the following paremters on the transform popup:  X = 40mm, Y = 50mm, Z = 17.5mm,  make sure “Enable Snapping” is checked, and set the “Snap Step” to 1mm.

I then use the transform handles (red arrow to drag down, the blue arrow to raise the block) to drag the block down so it extends 1mm below the bottom of the bar and then raise the block 4mm so it’s centered in the long bar.  The step snapping makes it easy to do this accurately.  I then select “Accept”. I’m now ready to “subtract” the block from the bar to make the U channel that will fit over the back board.

I press my “shift” key then select the main bar with a right mouse click and then next, the block. They need to be selected in that order for the block to be subtracted from the main bar otherwise the main bar will disappear when you do the boolean difference.  When two objects are selected the Edit menu will now change to options that can be applied to multiple objects.  I select “Boolean Difference” and after a few seconds of calculation the block is removed from the main bar and I now have a channel that will slide over the back board.

Now I’m ready to add the posts that will hold the grinding disks.  I go back to Meshmix Primitives, select a cylinder, and drag it on to the plane.

I need the post to be smaller than the holes in the grinding/polishing disks so I can hang them.  I change the X,Y, and Z values to that the post is 12.5mm in diameter and 45 mm tall.

Now I need to make the post solid so I select Edit then “Make Solid” and perform the same steps I did when I made the main bar solid.  Once this is done I select “Accept” and then perform an “Align” the same way I did for the main bar.  What this does is center the post on the main bar so that when I position the post all I have to do is drag the post up left/right and it will be perfectly centered on the bar.

Now I use the transform tool to move the post so that it’s a quarter tthe way up from the bottom of the bar (I’m just eyeballing it here). I then use the tool to grag the post up vertically until it’s just barely above the bar and then sink it back in just a little bit so that it will merge completely into the bar.

I then go to the objects browser and un-hide the duplicate bar.

I select the bar and use the transofrm tool to change the size to 20 X 40 X 25mm.  I then sink this piece into the post about a 2mm or so.  This will create a notch in the post with a small lip up front to keep the grinding disks from falling off.

Next I select the post first then the smaller bar and perform a Boolean Differance.  A small notch is cut out when the operation is completed. It looks good to me so I select “Accept”.

Next I select the notched post then “Edit” and  “Duplicate”.  I select “Transform” and slide the duplicated post about 30mm from the top of the main bar.

Next I need to measure the space between the posts to make shure there would be enough clearance between the disks so they won’t overlap.  I had measured about 95mm from the bottom edge of the center hole to the bottom of the disk.  222mm between the posts would provide plenty of room for the disks with no overlapping.

Next I select the two posts and perfrom a combine.  This is nice shortcut so that when I perform the Boolean union I only have to do it once for the combined posts.

I select the main bar, then the posts, and perform the Boolean Merge.  My disk holder is now ready to print.

I printed the holders on a Creality MAX with a 0.6mm Nozzle, 0.2mm layer, 3 outer perimeters, and 30% Infill.  This is the final result.

Well I hope you enjoyed this post and found it useful.  My goal was to show you how you can make useful printable items with just a mesh editor like Meshmixer.  For my next “Paracctical Prints” blog post I’ll be diving into a more organic shape using both Tinkercad and Meshmixer.  Until then…

Happy printing!