Sunday, April 4, 2021

I'm Not Saying to Buy a 3D Printer For Things Like This

I'm saying if you happen to have a printer around, it can solve problems like this.  

A couple of years ago, my old shop vac failed.  That article describes how I found the fusible link that was protecting the motor was nothing more than a piece of solder.  It had heated enough to get soft and open the power connection, keeping the motor from running.  I was appalled.  Nevertheless, I put a piece of solder in it and the vacuum worked - for few weeks until that piece of solder softened.  I eventually tossed out the thing and bought a battery powered Ryobi for cleanups around the shop, the house and when washing the cars. 

When I tossed out the old Shop Vac brand, I kept the 2" hoses and all the accessories but the Ryobi uses a different sized hose so everything sat in a few corners.

The Ryobi actually worked OK, but about a year ago, I got tired of it not being working every time I needed it and bought a different brand, higher power shop vacuum; a Ridgid.  Now I could leave the vacuum in a corner and if I can hook up the old and new 2" hoses I can reach the entire metal shop.  Except the hoses don't mate.  Both ends of both hoses are the same smaller diameter (about 2-1/4") that plug into a bigger hose fixture in either an extension wand or the vacuum body or the fixtures designed to go on the hoses.

As an RF engineer (working at Radio Frequencies), this is second nature.  We always would need  multiple cables (colloquially called hoses) to get across a few benches and need to connect things that wouldn't connect.  There is literally an entire industry of making and selling adapters between things we might try to connect and a set of laws that reflect on what we see.  ("Given a need for N adapters, the engineer will never find more than N-1", and so on).  I knew what I needed, I needed a plastic adapter big enough to plug both ends into.  Nothing more than a plastic pipe that had to be a specific size. 

This sounds like it should be doable on my 3D printer.  It doesn't take long to design a pipe.  Make a cylinder of the right length, right inner and outer diameters and you're there.  A couple of days ago, I made a test piece just to make sure a couple of inches of what will eventually be four inches long would fit the hoses.  It fit just fine. 

I was about to print a full-sized version, when something hit me.  The Ridgid hoses have a feature I've never seen before: the mating sections to the hoses have triangular, saw tooth-like pin on a flexible lever.  It mates with a section on the fixtures or the vacuum cleaner itself and acts as mechanical insurance.  I decided to create a model of that and add it to the full sized adapter. It took a couple of hours to draw that (essentially point by point), turn it into a solid model and set it up to print.  The whole adapter took six hours to print, but here it is coming off the printer. 

And here it is doing its intended job - joining the old Shop Vac hose (right) and the Ridgid hose (left).

Here's a closer view of the Ridgid locking tab.  This doesn't look quite right, so I'll have to look at it a bit more closely.  Perhaps the mating teeth on the adapter are a bit too close to each other.  Or maybe it's just slightly out of position.

As you might expect, I didn't declare it done without vacuuming up around the shop and pulling the cleaner by the hose. No problems.

I'm not sure the adapter I needed doesn't exist anywhere, but I had looked around a bit without finding them. In terms of just the plastic for the print, this cost about 45 or 50 cents. There is no compensation for CAD time or anything else.  I'm not saying it makes sense to buy $300 or $325 worth of printer, filaments, dry boxes, and everything else to print an adapter.  I'm just saying if the printer is in your shop, the problem is solved. 


  1. Brilliant, SiG! I looked into getting one to print stuff for my R/C cars, but decided it would be too big of a time sink to learn to do it competently. I have all the software on this PC, and I've played around with it, but just couldn't pull the trigger on a printer.

    Maybe I should.....

  2. Yes.

    This is just an example of the power of having a printer.

    I'm still at the "baby's first CAD program" level of TinkekCAD so my fix would probably have been a bit cruder, but as I say for most problems with consumer products of all types, you are probably not the first person to experience it and somebody else probably has a fix for it.

    And with a quick search, there's a couple of vacuum adapters with OpenSCAD files so you can customize them to whatever size you need.

  3. They may not be for everyone, and, well, quite frankly, more traditional methods are often a better solution, but, yes, 3D printers are a thing, a good thing in some instances.

    Now, the true question is, how easy is it for the average idiot (typical home person) to create and use the printer? Without having to modify the machine, create weird dryers for the filament, or sacrificing small animals or fruits?

    1. It depends on how geeky you are, Beans. You can buy 3D printers that are 99% ready to go out of the box. The filament gets heated by the print head, and deposited onto a "print bed" where it cools and solidifies.

      And you have to (or should) learn the software. You can download the files for thousands of objects, and print them, but you'll still need some PC-foo to download the software and feed it to the printer.

      We're not quite up to Star Trek level replicators, but the progress over the past decade has been staggering.

    2. Now, the true question is, how easy is it for the average idiot (typical home person) to create and use the printer? Without having to modify the machine, create weird dryers for the filament, or sacrificing small animals or fruits?

      The printer wasn't quite ready to use out of the box. It required assembly and then it required leveling the bed. The assembly instructions are well-documented but there are some videos that go through it step by step.

      I may well have the advantage in using it that I've been running CNC tools since about 2005 and the workflow is second nature. First CAD, then CAM, then onto the machine. There are handy tricks to know you can find in videos, like Elmer's Disappearing purple Glue Sticks that help stick the work to the heated bed. I'm sure I'll learn more.

      Something like this adapter might be something I could have made with PVC pipe and glue, saws and sandpaper. In real life, it would be made with injection molding and that's another specialty. I'd say it's not hobbyist level, but I've seen guys doing it online. I think Come and Make It blog in my sidebar does it, but he's not quite hobby level since he makes a living at making things.

      The dryer boxes are more "buy this and this" than "make this".

    3. Sig, Beans, Ohio Guy. I looked at the price of a made for the purpose shop vac male to male connector and decided it would be easier to just machine one on the metal working lathe.
      I quickly discovered that the OD of the vac hose was smaller than the ID of a PVC connector so that meant meant gluing a piece of pipe into each end of the connector, waiting for drying, and then machining the fitting including using the compound to make a slight taper.
      It's a lot of fun to use expensive machine tools and time to make a $ 4.89 connector, but I simply bought the next connector ready to use.
      As already said, the printer is in the shop and you can make what you need right now.

      As for the software, I'm thinking that as soon as the software is as easy to use as the software I use to drive my craft cutter, I'm going to join the 3D printer club.

  4. One thing I found 3d printers useful for was printing little plastic stand-offs for circuitboards. Drill and tap the plastic posts with M2.5, and nylon screw the boards down. I could apply double-sided tape or glue and stick them into place inside aluminum enclosure boxes, or onto layout panels.

    Also, plastic brackets for 80-20 channel: Cheaper than the aluminum brackets. Depends on your time/money tradeoff though.


    1. I hadn't thought of plastic standoffs, but I've made threaded brass and aluminum standoffs in my micro (Sherline) lathe before. Like most parts like that, making one at a time on a metal lathe by hand just doesn't make sense economically. Better to buy a bag of a hundred from somebody, but I'd be pretty sure you could print a dozen plastic ones in one job.

  5. Meanwhile, us machinists visit the hardware store to buy a suitable piece of PVC and turn it down to proper ID. Still, the knowledge and utility of the printer is of great significance. Ohio Guy

  6. That is really nice work.
    Making it from PVC fittings would have meant a design change to replace the short toothed section with grooves, and a fairly large amount of time gluing and machining.

    I will skip past my usual rant on the subject of why can't we have standard sizes.

  7. Parts that are uneconomical to mass produce due to lack of demand, and parts that the original maker doesn't WANT to produce (planned obsolescence), and parts that no one in manufacturing knows are needed, are all parts that benefit from local production.

    The economics look very different when you include transportation costs, and sunk costs for tooling and production capacity. (And local production avoids most of those costs by its nature.)

    The cruise control buttons on the steering wheel of my 2003 Ford Ranger fit a couple of those points. They are made of soft plastic that crumbles after a certain amount of time. I replaced them from NOS, but they have crumbled again. I'm pretty sure I can print a replacement for the crumbling switch cover that will work fine. Ford never made a replacement part as it wasn't supposed to be needed. No one else made one, as the potential market is small. The failure is due to age and chemistry, so stored parts are failing, as are salvage parts. Perfect candidate for some small on-demand replacement manufacturing... as long as the market for 17 year old Ranger parts is big enough to justify SOME expense.

    The other thing to consider is using the printer to produce the TOOLING. I might produce a negative mold for the soft parts, and then use Sugru or an epoxy to cast the actual part. I can't pull a mold of the original, as it's already failed, but I can scan and clean up the part or design one from scratch.

    The DOD is experimenting with print on demand parts because they don't have the original spares, or none were produced, or they've suffered over time, or they simply can't get them to where they are needed in time.

    I can't wait until some of the DOD printers start hitting the surplus market...

    1. You raise a really important point, Nick. Things aren't there for sale with no regard to what it costs to produce, just as most buyers won't buy something regardless of costs.

      A few months ago, I had to replace my toothbrush (electric - Sonicare) because the on/off switch's cover - the flexible part I pressed on crumbled away leaving no seal, an uncomfortable peg to press, and a no-longer sealed electronic assembly. Maybe I could have gotten a replacement and maybe I should have made a mold and poured some sort of rubber compound into it.

      There's a long story down that road, that I won't bore you with. Suffice it to say a toothbrush is more easily replaced than a pickup truck, but that implies the new one is at least as good as the one you're replacing.

      BTW, in the 1980s, DOD was going through a big effort to replace 1970s-era semiconductors because the new versions of those parts often didn't work in their hardware. The new parts met the original specs but were newer process semiconductors, virtually always faster and "better" by the usual measures, but caused something else in the old boxes to not work because of their faster switching.

      Spares are a BF Deal for the DOD.

    2. DOD also has a real issue with the original drawings and specs for a lot of things not being available anymore. And the guys who "just knew" what this or that needed, have long since retired. I did a project at a training command and they had their own really big machine tools. They were obsolete, had been decommed, and Trainor Command picked them up because they had parts to produce that could only be produced on the big machines. One thing that caught my eye was a right angle block, cast iron, 12ft high and 10ft wide. It was used to fixture a part on an even bigger milling machine.

      While I was working in the other bay I could hear the mill running and it sounded like they were trying to get it to play "Mary had a Little Lamb". When I asked him about it, he laughed. "No, that's resonance in the piece. I'm trying to find a combination of speed and feed that WON'T make any musical notes."

      Kinda like this only he was cutting not just running the motors.


    3. I've never deliberately gone down the rabbit hole of trying to make it play music, but the first time I heard the motors change pitch while cutting a circle it made me drop what I was doing and watch. It can be interesting to cut intricate shapes because of that side effect.

    4. I once programmed a vibration tester to play rudimentary tunes, but my efforts were not appreciated.

  8. I guess I am just too old school in finding solutions. Had an almost identical problem with my vac in that the original hose failed due to being brittle and the new hose was not exactly the same diameter as old where the tools connect. Found a piece of PVC pipe that fit side A and was too tight for side B. Heated it up with a high power heat gun until the plastic was a bit soft and jammed part B into it, voila, it re-sized to fit nice and tight. Yanked out the tool and let it all cool down. Same result, just not as elegant.

  9. Nicely done. Speaking of RF adapters, back in my Production Engineer days I ordered some N-type adapters that were "beadless". I discovered what beadless actually meant when parts arrived with the connector shell and connector pin in a bag without the insulator usually found between the two. Sure didn't get much use out of those adapters!

  10. This comment has been removed by a blog administrator.