Hi Hartatak,
I’ve not yet been able to print that much with nGen, but I recieved my order of 6,6kg nGen a few days ago, so there are definitely some impressions i will be able to share when i get to printing.
So far here’s a report of what I noticed so far whilst printing with nGen, I do mostly compare nGen to XT in the following text as everyone (even Colorfabb) describes nGen as the “next level” of their Polyester filament line.
nGen is relatively easy to print, with a printing temperature of 220-240C it’s within the working range of most 3d printers, if you were confident with ABS you shouldn’t have a problem with nGen.
XT prints quite a bit hotter at 240-260C and usually has flow issues at the lower temperatures. The use of an volcano hotend (extended heat zone) is advised in both cases.
nGen needs a bit more temperature on the heated bed (80C) compared to XT (70C), but both are far less then ABS (110+C) and neither nGen nor XT show issues with warping.
Both materials can be stuck to the heated bed with buildTAK (unremovable if printed too close to the sticker) or just apply a bit of gluestick. The gluestick method is my preference, it’s easy to apply, quick to remove and the gluestick lets go off the print nearly completely when cooled down after printing.
nGen was a bit easier to get to stick to gluestick, use lower speeds if the lines don’t stick as well as they should.
nGen seems to be a tiny bit softer compared to XT, that’s especially noticable when drilling with a drill press, nGen gets cut like nothing else. Due to the higher glass transition temperature (usually equal to the bed temperature) nGen doesn’t create as much of a ridge at the drill hole ends.
nGen seems to be a little bit “weaker” in general when compared to XT.
I would describe nGen as the little brother of XT, it’s definitely an engineering plastic, but XT is still the non plus ultra.
Both filaments are very tough so the chances of the drive gear grinding trough the filament are very low.
nGen is available in a lot more colors, also those that were (and are) desperately waited for in XT (ie. dark blue).
If you want to give Colorfabb engineering plastics a go I would start with nGen due to ease of printing, availability in colors and the price tag.
nGen colors are up to 10€ cheaper (per spool) compared to XT.
Black, white and grey come 5€ cheaper and clear nGen / XT cost the same.
I still have a lot of clear and black XT in stock and I will definitely use that. It’s very hard to tell which material is “better”.
As I said earlier the two materials are very similar and the only times when you’d need to stick to one instead of the other is when there’s a very demanding application for which you could precisely tell what physical properties the 3d print should have. For 99,99% of all prints both XT and nGen will suit your needs.
In the long run i will most likely use nGen more often then XT, the main reason for that is the price.
I can imagine using XT for parts that need FDA approval (only XT is foodsafe), additionally XT has the advantage that it’s available as a carbon-fibre reinforced version called XT CF-20.
XT CF-20 is probably the strongest filament Colorfabb has produced this far, but due to the price tag of 50€ for 750g and the fact that you need a hardened nozzle I would only use it for parts that specifically need the stiffness of carbon fibres.
I’m excited to see what Colorfabb will release next, maybe they’ll expand the color portfolio of XT or release new colors like translucent ones. Other reinforcements (glass fibre, kevlar, …) might also give the edge over standard filaments.
PS: If you decide to buy nGen you will notice that certain grey colors are available as metalic or normal colors, I’ve been going with the normal dark grey and it has a bit of gloss to it, I don’t think the metalic look will make a big difference, if you need specific colors or effects you should allways consier going with a big spool of clear nGen / XT and then paint it.
XT was only glueable with super glue and adhesive spray or expoxy glue, i didn’t test any glue on nGen, but I guess the same ones will work. If possible you should allways avoid glueing either filament, handling large surfaces full of super glue and adhesive primers is a pain in the ass as you have about 3-5 seconds of working time, then the glue is dried completely. Epoxy glue works a bit easier but it smells terrible. I nearly allways design screw holes in one print and a hexagonal cutout in the second one. After printing i can use my vice to press fit a normal nut into the second print and then I can screw both halves together.
PPS: due to very low warping both filaments are recommended for large printers and you won’t need to split them apart to avoid warping, however you should keep an eye on the support removal, it’s sometimes very difficult to break nGen or XT support pillars away so only place support where you can easily remove it.
This review / comparison was written in multile parts so please excuse the lack of structure 
Cheers,
Marius Breuer
