Question for the experts...

[Martian Gil]

Wire melt to 3d printed robots??

Each time I'm arranging the cabinet, I do my best to ensure that wiring from remote operated robots stay away from plastic robots...

 

That makes me wonder - is that something to worry about with 3d prints?
And then another question for 3d prints that are painted... will the acrylic paint perhaps act as a barrier to the reaction - or perhaps make it worse?
I would like to be able to not worry about it - but I have limited space and love far too many robots, lol.

 

 

[Brian..]

Remote wires contain plasticizer to make them flexible. This tends to leech out of the wire and eat into any plastic that they come into contact with. At a guess, I'd say that it's likely to mark PLA plastic. I could be wrong, but I wouldn't take a chance. 

[K-9]

8 hours ago, Brian.. said:

Remote wires contain plasticizer to make them flexible. This tends to leech out of the wire and eat into any plastic that they come into contact with. At a guess, I'd say that it's likely to mark PLA plastic. I could be wrong, but I wouldn't take a chance. 

Brian is absolutely correct. Vintage Japanese remote wire insulation is made of vinyl resin (PVC) blended with plastisizers (the plasticizers essentially soften the PVC and impart flexibility to what would be an otherwise rigid insulation material). The plasticizers migrate over time from the wires to the plastic body of the toys or remotes, with which they are in contact with, and produce "melt marks" by dissolving in and softening the plastic. This is especially true of the vintage remote wiring where aging has allowed for more plastisizer availability on the surface of the insulation giving it that slightly tacky/oily feel. 

 

PLA (Polylactic acid polymer) by its nature should be quite susceptible to plastizisers, and consequently melt marks. Modern wire insulation formulations still contain PVC and some form of plastisizer; and while some of the newer plastisizers may be less prone to separation and migration the principle is the same. Just to be on the safe side you may want to avoid long term contact of the remote wires with the printed surfaces of Brian's outstanding robot creations .

 

 

 

 

[Martian Gil]

excellent explanation gents, thank you!

K-9, bonus question - relative to an observation while making a repair on a plastic robot today... while pondering this situation...

 

I noticed that the robot I'm working on had an instance of wire melt to an internal frame member.

Having other donor toys, I was able to replace that wire with another portion of "aged" wiring.    
Is there any benifit to using that aged wiring in that scenario?   
If any of the melt from placticizer / voc's is reduced over time, I could see where that might be a good move - when replacing wiring in a plastic robot... 

I'm overthinking this - but I think from now on when building a kit or making a repair, I'll try to use old wiring when possible - and when flexibility isn't needed.

interesting topic.   Thanks for the info! 

 

[robothut]

The problem seems to be mainly with the styrene plastic and the wires they used for toys back then. Since  styrene Plastic glue will not melt of work at all with PLA 3d printed parts I think your safe. with 3d printed PLA parts and modern day wires.

[K-9]

2 hours ago, Martian Gil said:

Having other donor toys, I was able to replace that wire with another portion of "aged" wiring.    
Is there any benifit to using that aged wiring in that scenario?   

I wouldn't think so, new or "aged" vintage wiring still have the potential to form melt marks internally over time. The plastisizer is not volatile, it's simply an oily material that eventually finds its way out of the wire's insulation and into any plastic that it's in direct contact with. If the wire is physically separated from (not touching) the interior plastic surfaces it can't cause any harm; it has to be in direct contact for a significant period of time to form a melt mark.

 

Now that you and Brian brought this topic up I suddenly feel strangely compelled to check on some of my stored plastic robots... and assure myself that I've separated the control wires from contact with the robots and their remotes !

[K-9]

13 hours ago, robothut said:

The problem seems to be mainly with the styrene plastic and the wires they used for toys back then. Since  styrene Plastic glue will not melt of work at all with PLA 3d printed parts I think your safe. with 3d printed PLA parts and modern day wires.

That's true John, it's likely to be much less of an issue with the newer wires and PLA. Solvent based glue containing toluene and/or MEK is very aggressive towards polystyrene, less so towards PLA. Ethyl acetate is commonly used for cleaning PLA residue from 3D printer surfaces primarily due to it being less toxic than other PLA solvents. It all depends upon the nature of the particular plastic and the rate at which its acted upon by a particular solvent. Plastisizers are simply non-volatile large oily molecules that behave as solvents.

 

For all practical purposes I think that new wire will be compatible with 3D printed PLA in the long run. Maybe someone can get back to us in 40 years and let us know how Brian's and John's robots have held

up !