Hi there! I’m working on printing some of the many wands from the Harry Potter movie series. I’ve attached a reference picture, which basically shows they are long and skinny but usually have a fair amount of detail. I’ve gone through several iterations, without success.
I can’t print them as a single piece, because they’re too tall.
I can’t print them laying down, as that would mess up the detail and they’d need supports.
I’ve tried doing cuts and printing them with various connector types including plug, dowel, and snap, and every time the connector pieces just don’t fit, get stuck, and break.
I’ve tried doing cuts without any connectors, which does work, but it makes it really difficult to line things up for gluing.
Since these models are so skinny, attempts really don’t use much filament, but they do use a lot of time.
The key to successful gluing is to use dowels not pegs. The reason for this is that the dowels can be printed separately and if they are too tight or too loose, you can simply scale them or an easier method is the use the X-Y contour function on them which will scale them uniformly around the edge.
In this example, by providing a -0.25 contour, the entire dowel will shrink by 0.25mm or half a mm across a diameter. The beauty of using dowels is that they take less than 5 minutes to print so if you wanted to you could even clone a bunch and set up different parameters for each sample thus saving time. Then it just comes down to trial and error as to which dowel size fits best.
You also you want to do is to use triangles, as they are the most versatile while taking up the least amount of space, and at the same time, providing torsional strength so that your parts will not twist.
The second part is to not be stingy with size of the dowel. Based on your example, it’s looking like you have a 10mm rod. Make the dowel 60% of that width and make the depth at least 6 mm 10 if you can afford it so that you have depth to play with. This also is helpful because you can always cut a down if the hole is slightly too short.
Another trick is to cut the place the parts on the seem and print it on a smooth plate. If you don’t have a smooth plate, you can always turn ironing on for top most surfaces. I find that this gives the best option to glue two items together.
And last but not least, make sure you are generous with the wall loops. 3 should be a minimum but 4 is even better and why not 6. This will give the dowel and the dowel hole extra strength.
@Olias Thank you soooo much for your detailed reply! It’s clear you’ve had a lot of experience with this and I really appreciate you sharing it with me.
I’ve re-generated everything using the information you provided. It’s going to be three prints total:
Print 1 will be four triangular dowels, each with a slightly different diameter
Print 2 will be the top 100mm of the wand (I prefer printing whole objects instead of having it travel between objects)
Print 3 will be the bottom half of the wand
I am using the smooth high-temperature plate for this print - as much as I love the textured one, I figured that smooth would be best for this purpose.
I took into account everything else you mentioned - 20mm dowels (10mm out of each half), triangular dowels, and 6 wall loops. I was already using brims and I also use the Bambu liquid adhesive for everything. It’s going to take a few hours to print this wand, but hopefully it works now. I will update you with the results.
If you by any chance happen to live in the area of Fresno, California, I’d love to meet up and thank you in person. If not, well, I am extremely grateful for the time and effort you put into your response. Thank you!!!
Printer your joiners (“dowels”) on their sides, not standing vertically. The triangle shape will allow this without supports, and the parts will print cleanly.
The joiners are much smaller diameter than the things they’re joining. 3D prints are particularly susceptible to stresses along the layer lines. The joiners will be more prone to separating along layer lines when bent. If you print them sideways, you eliminate this weakness. They will be much stronger and your prints will be more survivable.
If you print these from ABS, you can use Acetone to join the parts together. Acetone will dissolve the plastic, allowing the mated surfaces to “melt” together. Then when the Acetone evaporates, the plastic rehardens again. Joints are about as strong as if there was no joint.
I’d consider making the center hollow and using a wire reinforcement. 17 gauge (1.4mm) fence wire or coat hanger wire could relieve the stress on the layer lines.
Or a length of 1.75mm filament, if you can find some.
These connectors are available without a plug, just one hole on each side: dowel
Choose a dowel diameter large enough to fit a toothpick. Set the depth (length of the dowel) to a value 1mm to 2mm greater than the length of the toothpick. Print the halves without the dowel (delete it or move the dowel to another print plate). Then use the toothpick as the dowel. This is more stable. Glue the parts together. You could also use two toothpicks and therefore two dowel holes next to each other so that the two halves do not twist against each other.
I went through printing wands also, and found that printing them up made them eventually break at a seam with vigourous playing. If you need durability, I ended up printing cut in half length wise and gluing together. Didn’t look quite as nice as their is now 2 seams, but way more durable.
Folks, let me offer up a tip to bonding two pieces of plastic together. One needs a solvent based adhesive. Typically they keyword “plastic welding” is used because that’s exactly what happens, the two parts are chemically dissolved and the two parts are mixed together just like when two pieces of steel are arc welded. This is fundamentally different than glue. Glue relies on an intermediate agent to create a bond between two dissimilar items. Epoxy is another method. The difference between glue and epoxy is that epoxy comes in two parts while glue cures once it leaves the dispenser.
For PLA, the one product I found is the same one used for welding acrylic. It is this product below. I’ve tested it and when I tried to break two pieces apart, the surrounding material broke not the bond itself. That tells you that the weld is stronger than the material.
Here’s the second tip: For the surfaces that are to be bonded, make sure they are printed on a smooth plate. The smoother the surface being bonded, the more chemical reaction takes place. This material above is very runny. Even though it comes in a tube and you can apply it directly, I cut up a paper cup or form a tinfoil cup and pour the cement into the cup. Then, I apply it with a small paintbrush. Do this quickly before the pieces start to dry(it says it has a 5-6 minute working time). Note that you will discard the paint brush so get a bunch of cheap ones.
If you’ve ever used PVC pipe cement, this is similar material and is made by the same company. BTW: In a pinch, PVC pipe cement also works on PETG. I haven’t tested it on PLA though.
