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  1. #1
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    Default Plastics used, when metal should have been.

    In your Latest Projects Thread Russ57 described how he reclaimed a tool that had failed plastic clamps.

    Damn plastics are used far too often, in applications where they will often fail when they are needed.

    And that is why I dislike certain plastics. I understand that it is the atmosphere evaporates the oils, making the material brittle.

    Consider the amount of tools and machines disabled when the plastic knob, lever, clamp, or nut, breaks. If force is applied to an aged plastic component with the oil component evaporated out it can fail when used. UV degradation can also affect the plastic breakdown.

    Of course for the majority of our members living in the southern part of the continent do not have the UV exposure that we have in the tropic zone, but I wonder how you are affected in the southern zone re plastics and equipment.

    How many times have you had to replace or repair a broken plastic component. My experience has been the above situations but also things like the mower wheel centers.The guts had fallen out of my Victa wheels in just several years.

    The wheels went all dry and crumbly and disintegrated.

    What is your story in your area?

    Grahame

    What problems have you had with plastics failing in your neck of the woods.?

    Grahame

  2. #2
    BobL is offline Member: Blue and white apron brigade
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    in general I would agree but I don’t think that Russ57’s plastics failed, it was more a case of the 3D printer bed leveling knobs coming loose and falling of. Same thing has happened to me and the knob on mine are Al. The constant movement is what does it.

  3. #3
    BobL is offline Member: Blue and white apron brigade
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    Some plastics can outlive metals. In 2010 I bought a “Narra Barra” as I had to remove the old cracked concrete floor of the shed and bring in 15 m^2 of sand down a long narrow footpath down the side of the house. It was excellent for the task. 12 years later the black plastic body and plastic feet are all still fine but the powder coated frame is rusty. and the legs the feet sit under are completely rusted out, one leg has rusted so much the foot has come completely off and the other is hanging on by just the rust.

    crappy plastic handles that disintegrate do indeed give me the pips. The plastic threads inside the knobs on my budget DP dissolved after about 5 years of use and I replaced the knobs with wooden balls with galv nuts epoxied into the balls.

  4. #4
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    Thanks BobL

    It is obvious to all by now that I know very little about 3d printers.

    I was in the local Jaycar and was looking at a 3D printer for around a $1000 minus $ change.

    It was a flimsy looking contraption to my boilermakers eyes. A heavy welded frame perhaps?

    The manufacturers must be aware of these problems or it it just treated as ongoing maintainence that an owner must perform? If they used metal in place of plastic would not that allow for use of a locking compound or double lock nuts?

    Or is it something more I don't understand. Do you need to disassemble the printer (tower?) to remove the printed item when completed?

    There are already too many products that prematurely fall apart as they are being used?

    However the plastic parts problems are the ones I would like to hear about.

    Grahame

  5. #5
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Grahame Collins View Post
    Thanks BobL
    It is obvious to all by now that I know very little about 3d printers.

    I was in the local Jaycar and was looking at a 3D printer for around a $1000 minus $ change.
    Personally I wouldn't buy anything 3D from Jaycar or many shop front stores.
    All the best 3D printer deals are on-line BUT then you have to know what you are looking for.
    A shop front purchase suits someone starting out with no assistance because at least you can take it back if you strike a problem.
    A very useful printer that prints smaller volume stuff can be had for about $300-$400 but the cheaper it is the longer/steeper the learning curve.
    For a start you will probably have to assemble it first!
    If you want something that prints out of the box then it will cost more.

    It was a flimsy looking contraption to my boilermakers eyes. A heavy welded frame perhaps?
    Strength is not that important, but rigidity is very important and to some extent they are related. Again you get what you pay for. Printers that incorporate/utilise Al extrusions are usually pretty good.

    The manufacturers must be aware of these problems or it it just treated as ongoing maintainence that an owner must perform? If they used metal in place of plastic would not that allow for use of a locking compound or double lock nuts?
    My printer came with plastic bed levelling knobs and one of the first things I did was replaced them with Al knobs but this did not prevent them coming loose. They work just fine at normal printing speeds but then it's tempting to "up the print speed" which increases the ac/de-celeration as the bed changes direction doing teh printing. Just like most moving things at certain vibe levels things move. There are printers that keep the bed stationary which avoids that problem.

    Or is it something more I don't understand. Do you need to disassemble the printer (tower?) to remove the printed item when completed?
    No, and this may give you an indication of maximum print size.

    However the plastic parts problems are the ones I would like to hear about.
    Yeah I'll stick to those.

    Just like metal there are plastics and PLASTICS. Good/tough plastics cost $$$ and most manufacturers just need to ride out the warranty period so materials are often chosen to go only just past that distance. I used a lot of plastics building ultraclean metal free labs at work - it was not a cheap business.

  6. #6
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    A bit like those small hand powered ring rollers from H&F the pivoting arm is plastic and will snap with the slightest sideways look at it
    Yes they are bending steel flat bar with plastic parts makes sense I didnt even know it was plastic until it broke on me, ended making a new arm fabricated from steel she no break now
    ....................................................................

  7. #7
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    I bought a powered wire stripper, all the frame is made of plastic, 1st couple of times I used it, it went well, tonight I went to strip more and the cutting wheel moves off centre. The plastic is flexing!!!!!
    Couldn't work out why it wasn't cutting the sheathing properly.
    Even the switch mounting plate is plastic, when you go to switch it off, it flexes!!!!

    Wire Stripper.jpg
    I can see myself making up a new frame from Ally, when I get time.
    Kryn
    To grow old is mandatory, growing up is optional.

  8. #8
    BobL is offline Member: Blue and white apron brigade
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    It's easy to bag plastics (in/on equipment, environmentally, and aesthetics/looks) but in some ways what irks me more is things like Cheesium pretending to be metal.
    Also consider where we'd be without them in electrical terms, cloth and wax covered wiring, metal bodied power tools. Step outside our domain and things like modern medicine couldn't function without plastics.

  9. #9
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    Swing Arm desk lamps. I have about ten of these mounted on machines, benches etc. Three have failed in the same way. The lamp holder is held into a flimsy metal bracket by a hollow threaded extension moulded on to the body of the lamp holder through which the wires to the lamp holder pass, and a plastic nut. Old age or vibration causes the extension to break away from the lamp holder and leave the lamp holder dangling on the flex. Often you are not aware of this until the bulb fails and needs to be replaced.

    I realise these were not intended for this service, but in 1992 when I was setting up the shed they were a cheap and flexible light source and cost $12. In passing, I notice that the identical new item now sells for $24 - I suppose that a 100% price in 30 years isn't too bad.

    Frank.

  10. #10
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    I suspect the ladder locks failed because the thing was left outside. The pins rusted and seized. Using force to move the lock broke it. I tried to recover the pins to reuse, the plastic was incredibly tough and only reluctantly yielded to a hacksaw. I guess across the middle where they broke is actually a weak spot rather than a plastic failure.
    (i decided it would be easier to make new pins than reuse in the end, and some were missing anyway)

    In my view, good or bad design is more significant than 'metal or plastic' per se. But its probably true that bad design is more often associated with bad material selection. Or maybe some materials are more forgiving of bad design. (nothing built too strong ever broke... But it may not be portable....)

    The 3d printer problem was different, ideally i will put locknuts on. My printer (ender 5+) has a "cube" frame of 40mm t slot square Al extrusion, and is actually very rigid, certainly more than enough for the job. Wouldn't mount a router on it though, but i am tempted to put a laser head for fun. It might survive a dremel.

  11. #11
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    Default

    Quote Originally Posted by KBs PensNmore View Post
    I bought a powered wire stripper, all the frame is made of plastic, 1st couple of times I used it, it went well, tonight I went to strip more and the cutting wheel moves off centre. The plastic is flexing!!!!!
    Couldn't work out why it wasn't cutting the sheathing properly.
    Even the switch mounting plate is plastic, when you go to switch it off, it flexes!!!!

    Wire Stripper.jpg
    I can see myself making up a new frame from Ally, when I get time.
    Kryn
    Hi Kryn, I have the exact same stripper, and there's no plastic on it apart from the switch housing, the bulk of it and the parts that really matter are all quite thick aluminium plate, although the yellow parts are folded sheet metal and do flex. I've put literally thousands of metres of cabling through it and it has proven unbelievably reliable and effective, while also being insanely cheap to buy. So not sure if yours is different to the pic?

    I often look at the plastic flip levers on the Kapex saw fences, and wonder how long they would last every time I have to use brute strength to lock them down, yet they seem to last.

    cheers, Ian

  12. #12
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    Here is a sample of a 2 way brass tap.

    https://www.bunnings.com.au/pope-2-w...d-tap_p3120722

    A 2 way Brass tap with damn plastic handles. One buys a brass tap for longevity. There is nothing in the blurb that says the
    plastic levers are UV resistant. There is no point in going half way with the process if the lever will likely fail prematurely.

    No one would quibble with the tiny amount extra it would cost to make the tap levers brass.

    I cannot duplicate the complicated recess in the levers with tools and equipment available to me.

    Up here in the tropics the UV is the strongest on the planet-Apart from the corresponding latitudes in South Africa.

    No small wonder that up here plastics don't last as long as other materials.

    Grahame

  13. #13
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    Imagine that tap in a bushfire. You emerge from the house after the fire has passed to extinguish the spot fires and the tap handles have melted. While I think of it- if you live in a bushfire zone, make sure you have spare garden hoses stored somewhere safe. Not much use if they're melted.
    Chris

  14. #14
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    Quote Originally Posted by jack620 View Post
    Imagine that tap in a bushfire. You emerge from the house after the fire has passed to extinguish the spot fires and the tap handles have melted. While I think of it- if you live in a bushfire zone, make sure you have spare garden hoses stored somewhere safe. Not much use if they're melted.
    Hi Chris
    The picture was of a Pope brand but it looks exactly like the one I got from Hose Link. Inside the hoselink the swivel ball s are - you guessed it - plastic-white Delrin maybe?

    Good plastic but no match for the heat a fire can provide.

    Even with the old style taps, I think the washers would cop a hiding from the extreme heat.

    Grahame

  15. #15
    BobL is offline Member: Blue and white apron brigade
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    At the tree loppers yard where I mill timber there is one tap outside the big shed and there at 4 hoses that connect to it,
    Chicken yard water supply
    Pressure washer
    Hose to Bandsaw mill for blade coolant
    External dunny

    So I thought 4 way diverter would useful so I bought one like Grahame's BUT I forgot to allow for hand washing so one of the hoses repeated gets removed.
    Over use of that tap handle meant it lasted a couple of years before it broke.
    One of the tree lopper monkeys thoughtfully provided a small pair of multi grips but over use eventually munted the spindle.
    So I went and bought one of these die cast hobbies.
    Screen Shot 2022-04-30 at 5.15.05 pm.png
    This also only lasted a couple of years before it started to leak, must have been the chlorine in the water.
    My next step will be to make up a 4 way setup using brass T-pieces and individual brass garden taps.

    We have one like Grahame's at home at that has lasted for over 2 years but it's under cover and never sees direct sunlight.

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