Turbo Manifold Jigs/Fixtures and Warping - how to manage and prevent questions?

Hi how's it going HPA family, hopefully someone experienced can help or provide guidance with some of these questions. I am a newer welder and have already been practicing basics as well as have quite a bit of time under the helmet. I am now branching off into making a new project and wanted some help for some things I currently am having trouble learning on.

Project: Car Turbo Manifold and associated Jig/Fixture

Questions:

1. What is the best or preferred materials to use for a jig?

2. How do I prevent and/or control warpage best on a jig once made? Some have suggested to make two jigs, one to use for production to mock up and tack on - another to use for QC after that does not ever have head introduced into it. How do the large Turbo manifold manufacturers use a jig properly to make 100s of manifolds without introducing heat/warping?

3. Purge blocks - What material is recommend to use for a purge block? How big should a purge block be? And any other suggestions or good info prior to making/purchasing one?

4. Shrinkage while welding up individual runners? Once I have the manifold cut, fitted and tacked in the jig. I break the end tacks and weld the whole runner up. There is quite a bit of shrinkage with heat introduced which usually does not allow the runner to fit back in the jig correctly as it did when originally cut, fitted and tacked. How do I minimize this or prevent this from happening? From many Turbo manifold welders I see or watch videos on Youtube they do the entire runner welding portion in one pass without a break or cool down time. Is there something they are doing that I am missing?

Thank you in advance to anyone who can help or provide insight. Much appreciated!

Not something I've had much to do with, but general principles from what I've done. There are some VERY experienced chaps who may correct me, so bear that in mind!

1/ for the most part it's been what was lying around, with the flange to the head mounting/support some heavy plate works well to hold it in place with minimal residual stress that distorts parts.

2/ depends on whether it's a "one of", limited production or larger production. Personally, I'd make sure the flange positioning plate was rigid, the positioning plate for the exhaust's turbo' flange was securely located from the main plate, any potential interference or heat sensitive points had position markers also welded to the main support, etc. See also #4

3/ you can buy plugs and bungs to suit, or have them made, but there's a lot to be said for the classic "kitchen aluminium foil" scrunched up and stuck into the various openings, the slight leakage also aids the purging of the air in the assembly.

4/ it doesn't matter how careful you are, there will be some movement as the various sections are welded together. making sure the sections but up to each other without leaving gaps to fill can help a lot, as can welding in sections to equalise the heating. It doesn't matter how careful you are, it's unlikely the fully welded pipes will fit as they did before between the flanges/collector, especially as access constraints may require some creative positioning of the welds. You may minimise problems by welding sub-assemblies - the intermediate pipework sections, the flanges/collectors and any pipe sections initially welded to them for access reasons - before taking them in place for the final assembly. If you took the time to make sure the main plate and supports the flanges were fixed to was rigid, you should find minimal fetling is required.

First off @Gord I appreciate the helpful reply and also getting back quickly.

1. Got it! Yeah I've been using some scrap or buying some thicker plates/square tube to properly have as much support and structure as possible. Thank you for insight.

2. So I am looking to jig these items to make long term production. Initially might not sell as many units but I do want to attempt to design/plan once and never look back. Overdo it in a sense so I have a peace of mind of fitment and quality control. Which these principles and learning through issues can be used in other fabrication or production projects in the future.

3. Didn't know about the slight leaking and aiding in purging -i will certainly test and experiment with the theory. I do have nice quality Tig aesthetics silicone purge plugs I purchased in all sizes - which I use often. But I am also found using the aluminum method as well when trying to get up and running quicker without the setup etc. I do use both method and appreciate the help. I'll test foil with a slight leak to see how the results may be different. Thanks for the tip.

4. Right now I have been trying to weld in small sections to allow cool down and spreading the heat out. But still having the issues as you mentioned warpage is pretty much hard/impossible to fully avoid.

Water cooler or air cooled torch wouldn't play a major role in this regard would it?

Thank you again for the helpful and quick reply, can't thank you enough for the time and help. 🙏

Again, not an expert.

1&2/ I'd suggest you consider the first iteration, or even the first two or three, as 'draft' fixtures or jigs (can never remember which is which), because you can expect to find some fettling or re-positioning is required to get it 'right'.

3/ way I think of it, and I certainly could be wrong, is that if the part is fully sealed it's going to pressurise the weldment and that will potentially trap air in closed end sections and/or blow back through the welds. The gases used in welding are slightly denser than air, so it may be more of a potential issue if the welding is being done to the top of the part.

4/ it may come down to experience, where you can get a good estimate on how the part will move as you do more work. Almost all the welding I've done was with stick (arc), and after a bit of time you can get pretty close.

As I understand it, the primary reason for a water cooled handpiece is because of the greater heat released with higher currents/voltages required with thicker welds can result in uncomfortably hot handpieces, even to the point of damaging them. Besides the additional expense, they will be a lot heavier and bulkier, which may be an issue with access.

Not sure which welders you follow, but my bookmarked ones are -

https://www.youtube.com/@TheFabricatorSeries

https://www.youtube.com/@weldingtipsandtricks andpossibly less relevant

https://www.youtube.com/jimbosgarage

https://www.youtube.com/@6061

This may be of interest, especially from 8:30 on - https://www.youtube.com/watch?v=Fp_ocfHxRhM