I've been designing these HD cam mounts for my frames but the designs are too complex for my printer.  So the idea was to print separately and glue together.

Welders Glue

Worst.  Don't even bother.  There is zero fusion between the glue and the TPU.  My thinking was that since it dried flexible, it would be good for TPU.  Not so much.

RC Car Tire Glue

Again, it's meant for rubbery super flexible RC tires, should be good for TPU, right?  Nope dot com.  And despite using the fast drying variety, for whatever reason, it did not want to dry on the TPU.  So does not work in addition to being messy.

Krazy Glue / Super Glue

Better but not by much.  In some ways worst because it gives you a false sense of security.  For starters, if you use way too much, it actually won't dry.  But typically it does bond and even seems convincingly like a strong bond.  Then you crash.  Then you spend 20 minutes worried that your one and only crappy Go v1 is lost.  But then you find it and curse Krazy Glue and the stupid bottle it comes in.

Special TPU Glue

Watching some youtube videos, there are actually special glue meant for TPU.  I did not try them just know they exist.

3D Printing Pen

I was this close to getting one of these since they sell for less than 20 bucks shipped on eBay ... and decent ones too based on YT reviews.  I actually think this might be the ideal solution to properly fusing TPU together.  You are basically welding it.  But I am super cheap so ...

Good 'Ol Soldering Iron

THIS.  And it doesn't even have to be a throw away soldering iron.  I just used a tip that I don't really need on my Hakko.  Same temp as I normally solder although it's probably smart to bring that down to normal TPU melting temp.  My biggest concern was damaging the soldering iron.  After giving it a lot of thought and thinking it through, I decided that was minimal risk.  After "welding" a number of TPU parts already, I can tell you my Hakko still looks good and nothing blowed up.  The fusion is really the best I can think of.  What's even better is that I can now re-use all that wasted TPU that normally goes to the trash as welding materials.  Two of us were literally tugging at this thing trying to break the two pieces apart and it would not budge.  

You missed one. Hot air gun. Heat up both faces of the item so the surface of the TPU looks melted / glossy and then press them both together while holding them in place until the TPU has cooled down sufficiently for the TPU layers on both faces to have bonded together and solidified again. For large surfaces that need to be bonded this might not work so well because keeping the whole surface of both parts melted before you stick them together could prove to be a challenge.

Good call on the hot air gun. I need to work with really tight spaces though so that's a no go for me.

I did decide to bite the bullet on a 3d pen. I went with the cheaper Mynt3d pen ($30-ish) since I'm not sure I need the precise temperature control of the "Pro" version ($50-ish). The cheaper <$20 3d pens evidently clog a lot and have a tendency to catch on fire which I tend to not like things catching on fire lol.

Although the soldering iron method does work really good, it is not good looking. I'm hoping the pen can provide a bit more precision on the fusing and not look so bad. If it works good, I plan to start offering TPU mounts otherwise I'm personally fine with the messy finish of a soldering iron particularly for camera mounts where all that gets hidden anyway. But for sale, that is just too ghetto.

Would you really put a chamber in a glued support? maybe it's better to refine the print.....

I remember succinctly someone telling me about 3d pens when they first came out and me laughing at the idea.  Dude, I love 3d pens lol.  For starters, *perfect* for "welding" parts together.  There is a slight learning curve though getting used to different flow rates and how to move your hand the best way to keep from globbing up or getting too thin.  But man ... love it.   

Not gonna lie, I made humungous goofy glasses as soon as I got it.