Easily Print an Unusual Shape




Introduction: Easily Print an Unusual Shape

I lost the end cap from my barbecue during a move last year and I kept hoping the piece would turn up somewhere. In the meantime, I covered the end with duct tape, but it had a very unfinished feel and looked even worse. Unfortunately, the end cap never did turn up but I have gotten better at modeling replacement parts for things that break so I decided to make a new one.

I've had some success making unusual shapes from scratch, but it usually takes a few test prints to see where the design is off. I thought of a way to use a feature of Tinkercad to replicate a shape exactly, with a minimal amount of fiddling. This piece fit just how I wanted after the first print.

I was making some things in Tinkercad recently when I noticed that you could import SVG files. I've imported a lot of models and I've used the picture import features, but the SVG files are a little different. If you import an SVG file, it becomes a simple extrusion of the shape in the file you imported, rather than a topographical relief of the image's grayscale values.

If you have a Char Broil propane grill like this and would like to download the STL file, go here.

Step 1: Trace and Clean Up the Image

I wanted to get the shape exactly how it was originally, I figured I could worry about the dimensions later, so I traced the shape on paper with a pencil. I would have gotten better results with a pen and if I had scanned the paper instead of taking a picture with my phone's camera, but this still worked.

I brought the photo into an editing program, converted it to greyscale, turned up the contrast and brightness until I had just black and white with no grey. I filled the shape with black so it was a solid black semicircle. I didn't clean up the shape too much, and there were still some jagged edges, but I was testing to see how much detail and noise Tinkercad would eliminate when the shape was imported.

I found this great online converter that will make an SVG file out of almost any other type of image. I ran the edited image through

Step 2: Extrude the Shape

If you are new to 3D printing, Tinkercad is your best friend. Even if you are familiar with higher end software, sometimes you just want to put something together quickly and don't want to spend a ton of time on it. The interface is very intuitive and is surprisingly powerful. Another added benefit is that it's a web hosted CAD software, so you can bring your designs anywhere and you can use it from any computer with an internet connection.

I opened up Tinkercad and imported the drawing as an SVG file. Using a pair of digital calipers, I measured the thickest, outer part of the original by it's length, width and height and made the first piece match those dimensions in Tinkercad. I copied and pasted that piece, aligned it to the original and stretched it's height, and squished it's length and width to match the original. I copied and pasted the new shape and again aligned it with the other ones. I turned the new shape into a hole, reduced it's length and width by the thickness of the walls of the original, and raised it up out of the hole by the thickness of the walls. Once I was sure everything was aligned, I grouped the pieces together and exported the piece as an STL file.

Step 3: Rounding the Edges (optional)

I use DesignSpark Mechanical (free) for models where I am trying to get very exact measurements. It's also very good for rounding and chamfering corners.

I started a new project and imported the STL file. I triple click on the model to select everything, and right click to convert to solid while merging the model's faces. After this the model is a little easier to work with. I triple clicked on the bottom edge until the entire outer rim was selected. If you right click on this line you can change from rounded to chamfered. If you drag the yellow arrow it will round the edge and you can type in a number to snap the rounded edge to. After this, you just export the modified shape as a new STL file.

Step 4: Finish

This part fit perfectly on the first print. I expected I would have to hot glue the piece into the handle, and after doing that the piece stayed in through Memorial day weekend (lots of grilling). I printed the piece in PLA, which does have a low melting point, as does the hot glue. However, since the handle is designed to be cool enough for your hands, I don't expect to have any trouble with the part or glue melting.

Sometimes I paint my printed parts to match, other times I leave them raw because I like to show that they are different somehow. Sometimes I intentionally print the replacement part in a color that will stand out, and other times I just use a neutral color. I think of these little repairs as something like the brick repairs you see on an old stone building damaged in a battle. You don't want the repair to be completely invisible, because there is a story there.



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    10 Discussions

    What I usually do is to take a photo, import it to my 3D software and draw the shape on the photo.

    1 reply

    Thanks, I'm glad you like it. This wouldn't work for everything, but in this case it was just a few different versions of the same shape, so tracing the outer edge worked perfectly.


    2 years ago

    Thank you for posting! I have some caps on a pottery wheel I need to replace but had no idea where to start with 3D printing.

    1 reply

    Thanks for the comment! I think this could definitely work for that purpose. Tinkercad is very user friendly, but can still make some pretty exact models. Just make sure you use a pair of digital calipers to measure all of the dimensions of the original piece.


    2 years ago

    A nice project! Now I've got an idea hoe to make replacement parts

    1 reply

    Thanks! This process would work for a lot of objects that are just several different diameters of the same basic shape. Let me know how it works out.


    2 years ago

    would it have been easier to do a relief imprint of the part instead of a pencil tracing? by relief I mean lightly coloring over the area with a pencil or pen like the way you would color over a grave stone to make the words appear or a leaf to sew all the structure and veins? the relief sketch when scanned should be the exact size.

    I did enjoy your help explaining modeling programs (yay free) for 3d printing. I will reference this ible when I try to.start 3d printing. Thank you and keep up the good work.

    1 reply

    Good idea. It might have given me a more accurate shape, without the rounding at the corners, but since I was resizing the extruded shape in the software, it wouldn't have improved the dimensions. If I had done the pencil rubbing method you describe and then scanned it, I might have gotten close to the original dimensions.

    I used the single shape to create all of the tiers of the rest of the part, so there still would have been some measurement involved with the calipers.

    Nicely done! Printing one off replacement parts is one of my favorite uses for 3d printing.

    1 reply

    Thanks, me too! Functional prints are the most rewarding. This was a fun project because I was able to make something that fit on the first try. I've seen some other ways to extrude a shape from an image, but this is the simplest I've found.