Repairing Broken Injection Molded Parts With A 3D Printer


The value of a 3D printer is obvious for people who hack hardware as a hobby. But this repair project should drive home their usefulness for the commoner. [James Bruton] used a 3D printer to recreate a hopelessly broken injection molded plastic part. This is a suction cup mounting bracket for a Tom Tom GPS module. The sphere which makes it adjustable had broken off of the column holding it. For 100% of non-hacking consumers that’s the end of this item. We can’t see a fix that would restore the strength of the original part.

The replacement starts by measuring the broken part with precision calipers. [James] then grabbed a copy of 123D, which is free software. He starts by modeling the sphere, then builds up the support column and the base with a cut-out. It’s obvious he’s already very familiar with the software, but even the uninitiated should be able to get this done pretty quickly. After slicing the design for the 3D printer he finds the part will be ready in about 11 minutes. The first prototype is a bit too small (the ball requires close tolerances to work well). He spins up a second version which is a bit large and uneven. A few minutes of filing leaves him with a smooth sphere which replaces the original part beautifully!

You can see the entire design, print, and assembly process in the clip after the break.

28 thoughts on “Repairing Broken Injection Molded Parts With A 3D Printer

  1. “We can’t see a fix that would restore the strength of the original part.”
    I don’t have one of these so this is purely speculation. By the looks of the part in the image, if the break happened right at the base of the ball then you could probably use a small screw/bolt with a washer and insert it from the back of the plate. Maybe add a little super glue to keep the balls from spinning off the screw. If all else fails.. MIGHTY PUTTY! I also like the added comment of “For 100% of non-hacking consumers that’s the end of this item.” – I think you mean “For 100% of people with disposable income and/or no drive to fix things.”

    1. Hi James here for Probably worth watching the start of the video – the ball isn’t the only thing broken, the suction pad is also broken and missing, hence making the new custom part to fit the TomTom bracket to a donor sucker mount.

  2. I didn’t see a full picture of the original ball joint part, but I did see the ball lying to the side in one of the photos. It looks like it broke cleanly off at the stem. Which means that a carefully-drilled hole plus a screw would have restored it just fine.

    Of course, if you’ve already got the 3D-modelling software and a 3D printer, this gives you an excuse to use them :D

    1. Yeah, a screw and some glue would probably have done the job and only taken about 10 minutes of work.
      But it’s nice to see how these 3d printer guys are operating there printers.

    2. In the first minute of the video we see the original base to which the ball was connected, its a circular plate, with the post for the ball coming out one of the thin edges.

      Looking on the interior surface behind where the post came out, we see several fins of plastic for structural strength, I didn’t get a good enough look to see if a screw could have been run out between these, or if one of them lined up with the post and would have to be removed to make room for a proposed fastener.

      The working space involved is very small, and the area to put the screw in from is apparently normally behind a suction cup assembly that, sadly, had also snapped off this part. I don’t know if the suction cup could have been removed under normal circumstances to allow us access to where we would be placing a screw.

      To sum up: it may have been possible to reinforce / repair with a screw, but the space is tight and the original base was otherwise broken so not in itself worth re-using.

  3. This is much more interesting from the standpoint of rigging adaptors for various items.
    To give a specific example, tablet holders designed for the back of car headrests are very cheap and plentiful (they apparently make excellent rugrat placators). On the other hand, the same type of clamp with a 1/4″-20 mount for a tripod or the equivalent for a mic stand is several times more expensive. A little adaptor on the other hand will convert the much cheaper holder for more esoteric purposes.

  4. This is ridiculous, how is this news worthy? Because it involves 3D-printing? Yes, you can make plastic parts with 3D-printers.

    I have a printed wheel on my desk, got that? A _printed_ wheel! Its a wheel made in a 3D-printer!!

    Does it mean i invented the wheel? No, and no one should believe it either.
    I made a wheel and 3D-printing is just an other tool for making it. And as with any other tool the possibilities are endless, please don’t make a post about common sense, its not HackaDay-ish.

  5. Solvent is best if the part is reactive, with plastic powder build up at weak place even better. For plastics that don’t melt with solvent but melt with a solder tip thermal repair is best. For this part I would use a wood or sheet metal screw. Drill half as big a hole as normal, start screw in, then heat with lighter or gun and screw in more, don’t get it so hot that it’s gooey. 2 or 3 heats maybe needed to sink screw, let cool.
    Solar rot maybe the cause of the break or cold flexing.

  6. The title is a bit misleading. Yes, it’s useful to copy an injection moulded part. I was expecting a real hack that had him using the printer to print onto or fill in gaps in an existing part, i.e. repairing rather than replacing it.

  7. Despite what all of the naysayers are saying, I believe that this is a good hack and good information to include on this site.

    It also answers a question I’ve been wondering about: Can a 3d printer be used to fabricate parts in applications that are subjected to fairly high amounts of mechanical stress? The answer appears to be “yes”.

  8. IMO all depends on how “the commoner” is defined I suppose. IMO this video does a great job in demonstrating the impracticality, and the cost ineffectiveness of a 3D printers for repairing items that are relatively inexpensive when purchased new. However for constructing items that don’t exist or for repairing items there are no replacement parts are available, and no new products doing the same job aren’t available a 3D printer is practical. The latter is a job that in reality doesn’t come up in the lives of most very often.

    Off topic; the domain name xrobots Robots James has chosen become confusing in the way he speaks it. I understand he is says X (x-ray) using the ITU phonetic alphabet. The name xrobots could be deciphered as just that or exrobots, using the phonetic X it could be deciphered as xrayrobots. No wonder people sometimes agonize over what name they are going to choose.

  9. I like the article I just don’t think this is stuff that a “commoner” would or could do. Not only is he reverse engineering but he is also 3D modeling and reassembling using his new part.

  10. A 3D printer is a useful repair tool.
    So is JB Weld. :-)

    It would be nice if the data files to print all the plastic parts
    of an item were included with the instruction manual or posted
    on the web for people to use… I suspect this will one day become
    the norm. Once nearly every home has a 3D printer it may become
    common that you are expected to print up your own enclosure and
    other parts…

    Batteries not included.
    Enclosure not included.

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