As Alistair said, it can vary. Also the nature of the 3D printer (and materials) can vary. Ideally you want the replicated part to be made of a material that can withstand the heat and cold and UV. Some plastics can, some can't. There are also 3D printers (non-consumer) that can 'print' in metal. 

> On Jul 15, 2019, at 10:48 AM, David McNeely <davmcneely40@GMAIL.COM> wrote:
> 
> So, for those of us who know nothing about 3D printing:  Does one require a
> part for a pattern, or is all the information in the files for making the
> part?  If a pattern, then it seems that the new part would have the flaws
> of the old part.  How were the files generated?  From copying a preexisting
> part?
> 
> Sorry for my ignorance.
> 
> mcneely
> 
> On Sun, Jul 14, 2019 at 6:23 PM Alistair Bell <albell@shaw.ca> wrote:
> 
>> I think... I might be mistaken about the source, but I think there are
>> files for 3D printing of that part at thingiverse.com.
>> 
>> Yup...
>> 
>> https://www.thingiverse.com/thing:34856
>> 
>> For at least some of the plastic NLA parts, 3D printing will be our
>> saviour.
>> 
>> Alistair
>> 
>>> On Jul 14, 2019, at 5:21 PM, KIM BRENNAN <kimbrennan@mac.com> wrote:
>>> 
>>> On our ancient vehicles I rarely remember that sometimes parts become
>> unavailable. Case i point the little plastic housings for the rear license
>> tag lights. I found one of mine dangling (broken), and went to order from
>> the usual places and “out of stock”. BusLab (in theory) has them, so I
>> ordered a couple of replacements. Hopefully I won’t get a charge back due
>> to them no longer having any….
>>> 
>>> I went to one of my “out of service” Vanagons. Plastic housing (and
>> clear lens and screws) looked like new. Must have been replaced at some
>> point in their life. On the other housing on the Van I was fixing, the
>> screws are stripped, so that will be a fun repair if or when I have to
>> replace the bulb on that side (if it isn’t working right now, it will flunk
>> Virginia safety inspection.)
>>