3D Printering: Printing Sticks for a PLA Hot Glue Gun

When is a hot glue stick not a hot glue stick? When it’s PLA, of course! A glue gun that dispenses molten PLA instead of hot glue turned out to be a handy tool for joining 3D-printed objects together, once I had figured out how to print my own “glue” sticks out of PLA. The result is a bit like a plus-sized 3D-printing pen, but much simpler and capable of much heavier extrusion. But it wasn’t quite as simple as shoving scrap PLA into a hot glue gun and mashing the trigger; a few glitches needed to be ironed out.

Why Use a Glue Gun for PLA?

Some solutions come from no more than looking at two dissimilar things while in the right mindset, and realizing they can be mashed together. In this case I had recently segmented a large, hollow, 3D model into smaller 3D-printer-sized pieces and printed them all out, but found myself with a problem. I now had a large number of curved, thin-walled pieces that needed to be connected flush with one another. These were essentially butt joints on all sides — the weakest kind of joint — offering very little surface for gluing. On top of it all, the curved surfaces meant clamping was impractical, and any movement of the pieces while gluing would result in other pieces not lining up.

An advantage was that only the outside of my hollow model was a presentation surface; the inside could be ugly. A hot glue gun is worth considering for a job like this. The idea would be to hold two pieces with the presentation sides lined up properly with each other, then anchor the seams together by applying melted glue on the inside (non-presentation) side of the joint. Let the hot glue cool and harden, and repeat. It’s a workable process, but I felt that hot glue just wasn’t the right thing to use in this case. Hot glue can be slow to cool completely, and will always have a bit of flexibility to it. I wanted to work fast, and I wanted the joints to be hard and stiff. What I really wanted was melted PLA instead of glue, but I had no way to do it. Friction welding the 3D-printed pieces was a possibility but I doubted how maneuverable my rotary tool would be in awkward orientations. I was considering ordering a 3D-printing pen to use as a small PLA spot welder when I laid eyes on my cheap desktop glue gun.

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Mini Spool System for 3D Printing Pen Tidies Things Up

3D printing pens may be toys to some, but they can be genuinely useful tools to repair 3D prints, rescue a support structure, or weld together different pieces. However, [BManx2000] found that the way the filament simply sticks out of the back of a 3D printing pen like a bizarre tailfeather was troublesome.

The solution? A Mini Spool System for 3D Printing Pens, with which you can use your 3D printing pen to weld together the parts after printing them. The unit holds 1.75mm filament coiled under its own tension in a tidy package that doesn’t interfere with feeding. Since different 3D pens are shaped differently, the interface to the pen is a separate piece that can be modified or changed as needed without affecting the rest of the design.

We’ve seen some interesting innovations with filament holders before, like this entirely 3D printed filament holder, but a mini spool for a 3D pen is definitely a new one.

Broken Plastic? No problem!

When a computer case has survived several decades from being a new toy through being an unloved relic to being rediscovered and finding its way into the hands of an enthusiast, it is inevitable that it will have picked up some damage along the way. It will be scuffed, maybe cracked, and often broken. If it has faced the ordeal of an international courier after an eBay sale then the likelihood of a break increases significantly.

If you receive a vintage computer in the post and find it cracked or broken, never fear. [Drygol] has a solution, a guide to plastic welding with a soldering iron.

After a thorough cleaning, the technique is to hold the sides of the break together, run the iron along it to melt the plastic together, and scrape the overflowed plastic back into the resulting trench before it solidifies. With careful sanding, a spot of polyester putty, and some spray paint, the broken case can be returned to new condition.

There is a video showing the process, in this case repairing a crack on a Commodore 64 case.

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3D Print It Or Fix It?

[Tim Trzepacz] is working on a pretty cool MIDI controller project over on Hackaday.io. It involves, naturally, a bunch of knobs and buttons. And it’s one of these nice arcade-style buttons that broke when he slammed on his car brakes and it went flying.

He tried gluing the plastic bits back together, but we all know how that works — temporarily. Next, he thought that maybe he could 3D-print a model of the arcade button’s housing. Besides being a lot of work, [Tim] didn’t have a reliable printer on hand. But he did have filament and a soldering iron.

The rest of the story is a slightly ugly mess, but it looks like it’ll work. (And it’s on the inside of the case, after all.) A working part is a good part.

The irony here is that the original choice of 3 mm ABS filament as a printing material is that it’s cheap and available because it’s commonly used in plastic welding. And there are more elegant ways to melt the plastic than with a soldering iron. And more ways to get it melted than direct heating, like ultrasonic welding and friction welding, for instance.

But we still like to see the occasional quickly hacked together effort, at least one per day. What’s your craziest plastic welding success or failure?

New 3D Printing Technique – Friction Welding

Even though 3D printers can fabricate complex shapes that would be nearly impossible to mill, they are not well suited to designs requiring bridging or with large empty spaces. To overcome this, [Scorch] has applied an easy plastic welding technique that works with both ABS and PLA. All you need is a rotary tool.

Friction welding” is the process of rubbing two surfaces together until the friction alone has created enough heat to join them. Industrially, the method is applied to joining large, metal workpieces that would otherwise require a time-consuming weld. In 2012, [Fran] reminded us of a toy from decades ago that allowed children to plastic weld styrene using friction. This modified method is similar to stick welding in that a consumable filler rod is added to the molten joint.¬†Inspired by our coverage of [Fran], [Scorch] experimented and discovered that a stick of filament mounted into a Dremel works just as well for joining 3d prints.

That is all there is to it. Snip off a bit of filament, feed it into your rotary tool, and run a bead to join parts and shapes or do repairs. Friction welded plastic is shockingly strong, vastly superior to glued plastic for some joints. Another tool for the toolbox. See the videos below for [Scorch]’s demo.

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