Welding Plastic with Iron Filings & Plastic Particles - Page 1
Forum section: electronics / general

author: jonovid
author_rank: Super Contributor
timestamp: May 21, 2025, 02:58:46 am
content: theory of operationto weld plastic. the plastic must be heated to its melting point. but Not burnt!by adding iron filings to plastic filament extrusion . the same type extrusion process as used for 3d printing filament.when this plastic filament with its added iron filings is subjected to induction heating.the iron filings heat the plastic in the filament extrusion that is feed through the middle of the induction heating inductor coil.the hot plastic filamenttesting the theoryapplication of welding plastic with induction heating in a handheld applicator device or gun on hard plastic .with the plastic filament with its imbedded iron filings been feed through the middle of a cable.the induction heater and its inductor coil that is the plastic welding nozzle. with a filament feeder in the handheld applicator.Induction heating handheld applicator for welding plastic with iron filings.do not have the resources to test this theory at this time.the plastic filament must be the same type of plastic as the intended plastic work piece.mixing the right amount of iron filings to the filament in the extrusion process is unknown.if anyone is interested in testing this theory

author: CatalinaWOW
author_rank: Super Contributor
timestamp: May 21, 2025, 04:03:21 am
content: Might work, but seems it would be easier to use plain filament with the appropriate nozzle from a hot air gun. The big problem in both approaches is getting weld penetration. Melt in the pieces being joined so that the finished seam is one continuous piece of material, not a layer of plastic surface adhered to the other. This problem might be better solved with the hot air approach. Or if you want a high tech approach use a laser for heating.Process control is the key to success. Adding the right amount of heat and the right amount of filler. Just like it is with metal welding, but with the distinction of a vastly lower thermal conductivity. That is both a boon and a bane as it reduces the total heat required since the heat doesn't readily escape the work area, but also limits the depth of heating in a given time. The other problem is the much narrower window between melt and material destruction.My experience with plastic welding is that it takes a lengthy application of low heat to the base parts raising them to near welding temperature. The filler and surface of the base parts can then be heated and melted fairly quickly to complete the weld. The first step isn't easily done with the gun type approach you suggest.

author: coppercone2
author_rank: Super Contributor
timestamp: May 21, 2025, 08:07:07 am
content: and its bad for chassis because for us it means there is metal in your broke fluke multimeter that voids the safety of the dielectric.Kinda scary actually that people might repair a 87V with this, and compromise its safety. same with those metal staples. at least if its all plastic, even if repaired, its betterElectronic enclosures rely on the plastic being plastic for their isolation..... though I don't know how safe a plastic weld is (probobly not very?)I stopped doing DIY enclosure repairs on hand held instruments or instruments where it looks like its important for safety. Most test gear has metal anyway under the plastic, but some consumer goods are sketchy

author: kosine
author_rank: Regular Contributor
timestamp: May 21, 2025, 09:49:53 am
content: Iron will rust, you need to use magnetite powder. Adding this to plastics is standard practice in the food and pharma industries so objects can be metal or x-ray detected if they fall into the processing lines. (They normally also use blue colourants as it's not a common food colour, but other colours are available.)Once it's in the plastic you can also melt it in a microwave oven, though it can take a while. You can typically get away with up to 20% w/w loading of the magnetite but also need to add about 5-10% colourant to cover the black. Getting good colour matching takes a bit of experimenting, but it can be done.

author: jpanhalt
author_rank: Super Contributor
timestamp: May 21, 2025, 03:40:15 pm
content: I have done only a little plastic welding. My welder is like a hollow tipped soldering gun. That provides hot air to melt simultaneously the base plastic and the rod.You then push the rod to cause it to fuse to the base plastic. The biggest difference from steel welding is that you don't create and work a puddle of molten plastic. The surface of the base plastic is softened just enough to be sticky and bind to the filler rod. If there's an exception to that, it probably would be for plastics like polypropylene.The problem with heating an iron filled welding rod by induction is that you would still need hot air to make the base plastic sticky in the welding zone. It is probably impractical to heat the entire base plastic to that temperature. Hot air alone does both.

author: thm_w
author_rank: Super Contributor
timestamp: May 21, 2025, 09:30:40 pm
content: Good idea but adds complexity as mentioned, what is the benefit over using a normal extrusion hot end?And how do you control the temperature of the plastic?Quote from: Simmed on May 21, 2025, 10:28:39 amThat is essentially JB Weld which is amazinghttps://www.popularmechanics.com/home/tools/a44601908/j-b-weld-just-how-tough-is-it/

author: CatalinaWOW
author_rank: Super Contributor
timestamp: May 22, 2025, 03:40:37 am
content: I you just make the surface of the plastic sticky create a surface patch with little strength. Ask me how I know. The situation is exactly analogous to weld penetration in metal welding.