I am new to 3d printing so don’t understand the limitations of the different filament types yet. I have watched some YT videos on the different characteristics so I know the basics. But what I don’t know is given a particular variable, vibration in my case, at what point would a filament not be suitable?
I am intending to print a mount for a rumble motor, something a little more powerful than you would get I a playstation controller, but not massively more powerful. This will be used inside only so UV is not an issue. I will be printing a P shaped bracket so I can mount the motor onto something else. The motor could potentially get used as little as a few hours a week up to several hours every day, with the motor running intermittently during these times, a bit like it would when using a play station.
Ideally I’d like to use PLA for this part (due to it being more eco friendly than the other filaments) but I don’t know if the rumble motor would eventually cause issues and cracks? Could I use PLA for this type of application or will I need to go for something less brittle.
I imagine the part design will also play a part and if there are any weak points and if they can be designed out.
One thing to note is that I intend to sell this part and I don’t have the months of time ti would take to run tests to see if there would be any cracking issues.
I think PLA is the least suitable filament for that purpose because it is rather brittle and stiff and might shatter after some time. At least, the motor might loosen after some time.
I would first look at TPU. It allows for quite some elongation without breaking so you could mount the motor with some tension and force spikes won’t do any harm.TPU is available in a wide range of hardnesses. If you chose a harder type, printing should not be too difficult. In general, TPU is much more demanding than PLA or PETG.
My second consideration would be Nylon, which also is very durable. I think, a variant without any fiber reinforcement (carbon/glas) would be best, but also quite difficult to print.
Maybe PETG is also up to the task. That is cheaper and much easier to print.
If that us an option, I would try PETG first and if that breaks, print it again in TPU.
Btw, manufacturers emphasize eco-friendlyness of PLA because it can be composted, but that is at least misleading in my opinion. It will not disintegrate in decades if you put it in the soil. You need a special process for that. And also the various additives typically added are silently ignored. So I would take that with a grain of salt.
Thank you @Alex_vG for the detailed reply. I’d not considered TPU as I thought it would be too flexible. One thing I do need to ensure is that as much of the rumble force is transferred through the printed material as possible. The forces will be transferred from the motor, through the printed part, onto a 2mm metal plate, onto a 10mm moulded plastic part then either a 2mm metal plate or a 15mm moulded plastic part. Finally it would then go through either a sock to a persons foot or a shoe and sock then foot.
Do you think there is a TPU that would be stiff enough to transfer the forces and not absorb them very much?
Maybe I will need to just try a few materials to see what works best.
The other thing I would like to do it to print in multi color so AMS compatibility would be nice, although not essential, I could ditch the multi color if not possible.
I would advise to reconsider. A minimum of engineering may be expected by your customers, depending on use case and cost of course. And vibration/fatigue are rather demanding subjects. For example
describes a vibration path through a multi-material system with a High (mechanical) Impedance Mismatch. That is a method employed in the control of sound transmission through parts and in particular walls to reduce the transmitted sound and vibration. So it is rather opposed to your inteded purpose. For maximum vibration transmission however, you’ll want as short and stiff a transmission path as possible. Ideally, you’d actually tailor your transmission path to correspond to 1/4 of the wavelength of the frequency you are targetting. In that case, your transmission can act like an amplifier, reducing motor requirements for a given vibrational amplitude and spectrum.
Fatigue is then another step up where I doubt that you’ll get away without actual verification by testing. At least if you are truly worried about it being a factor. With a reserve factor of 10 or more from static calculations, many industries safe themselfes the trouble. In aerospace, we are overweight if our reserve factor is above 1.5 on the maximum loads conceivable and hence of course do the calc’s and verify them by testing.
The latter is also advisable for other applications as the actual material properties can vary, in particular with 3D printing. On a much simpler recent use case, I found a 20% difference in TPU part weight between CAD and printed object weight. So that is a 20% porosity of the printed model. With each pore acting as a stress concentrator, print settings can have a very large effect on fatigue. Not a problem for free-to-print stuff or own use, but if you want to sell a product …
I’d suggest for you to first set yourself some assumptions and requirements. What displacements at what frequency are you targetting, what forces act where, what are particular constraints in terms of space and environmental conditions (if your product touches a shoe, sock or even bare foot, you should think about cleaning: Thish may already limit your available materials to the higher temp range), sketch it all out, do a few simple calculations in your design iterations and think about what parts need what testing for you to be confident to offer a product sale and to thereby take on the responsibility for its longetivity.
So, are you advising potential customers that they will be beta testers for an untested part? Providing refunds for failed parts? Ready to accept a degraded reputation for your business (if any)?