Thanks for all the good suggestions. I have put many of them into practice and they have improved my print quality greatly. I have changed the flow %, first layer thickness, speeds, bed temp, and the combing (off). Turning the combing off has been the biggest help. The stringing is almost eliminated (see pic). I added a brim/skirt to one part, but getting it off was no fun. Will see if I can solve the problem another way.
I understand the question of the best way to manufacture these parts. Initially, the volume will be low, and we may run into end user variations that require mods to the design. As the volume picks up, we can adjust the manufacturing method to suit. We intend to be upfront about 3D printing to the customer, who will be “friendlies” initially. Their response will help with the decisions about fit and finish.
Molding of any kind requires a volume we have to reach before it is feasable. I have designed some blind corners into the structure that might be a problem for molding. We will see. Some parts could be metal, others need to be plastic. I can get them all to work OK with 3D plastic (PLA). Haven’t looked into 3D printing hubs yet.
I have been through maybe 100 iterations on the various parts of this device, which I never could have done using conventional prototype machining - just too costly.
As to the head calibration using posts to touch the square body of the hot end: the posts would be on the platform, not the head. They would only touch at two places on opposite sides of the nozzle (not 4 sides as you would imagine). The error would be whatever error there was in the square block the nozzle screws into. With parts made in CNC mills, that should be minimum. The calibration could be done while the head is heating from ambient to extrusion. This should eliminate all the retraction/extrusion mismatches - maybe do 5mm extrusion to purge the nozzle (similar to your anchor). The expansion of the square block during heating might be the main error source, which I don’t think would be significant, since the calibration doesn’t take as long as the heating.
As to the programming. I know enough to be dangerous, but not enough to be proficient. I can add and delete commands, but I don’t know gcode well enough to stay out of trouble. Any suggestions would be appreciated.
BTW, I mounted a small 8in fluorescent tube up the right hand vertical post, which helps visibility a lot - and makes the filament look thicker than it is.