We are looking for a solution to hold two Power cables on a 3D printed part. This part is installed in a vibrating environment. So we need the cables to be pressed not to move and not to transfer vibrations to electrical components. We have thought about a C shape holder, but it would surely not maintain cables enough. We also looked for components sold on the market but nothing meets our requirements. Here is a picture to help you to understand. Thank you in advance !
A clamp and strain relief are used all over the place. You'll see this everywhere from domestic electrical plugs to the cable exit of power tools.
The choice of cable and sheath/insulation is a factor too. For example, vehicle power cables are designed to handle vibrations (but also high temperature and to be light weight, so maybe not the perfect compromise for your use). Thinner cables might help you, so optimise that, perhaps. Similarly, the extra flexibility of finer stranded conductors would help, as might using multiple wires for each power rail, and using individual wires instead of multi-core cables.
Reducing the strain by way of a cable drag chain etc will mean the clamp can be less substantial, strain reliefs can be more flexible, and wear on the cable sheath reduced.
As with automotive and aviation electrics, use rubber grommets where cables pass through enclosures. Use cable sleeving on long runs subject to abrasion. Soldering wires can weaken strands when flexed, so crimp or fasten them instead. Do not tin (solder) wires that enter screw terminals, as it will loosen with time due to the softness of the solder; the same goes for crimp terminals. Instead, use bootlace ferrules.
In your position, it sounds like you'll need to experiment. Try a design, and when there's a failure, improve the design to address that specific weakness. You might need to use a tougher PCB, a tougher cable clamp, tougher connectors, more flexible cables, tougher sheaths. Look at other design solutions: connections between loud speakers' voice coils and terminals, other 3D printers...
When all else fails, glue-gun the heck out of it. It has been done! Electronics can be encapsulated in specialist epoxies to prevent vibrations weakening components' leads (among other reasons). Just remember to allow for heat dissipation - most circuit designs will have some components that are at their limit already.
I would suggest modifying your 3D printed part so that you can use cable lacing to secure the wires. It's how NASA builds wires into cables and harnesses for space vehicles. If it can withstand vibrations during launch, I'm pretty sure it would work for your application. I was lucky and learned from a retired NASA technician, but you should be able to figure it out from the NASA standard.
Reference chapter 9 of NASA-STD-8739.