I’ve been spear-heading the injection molder project with @msearra. I’ll do a full project run-down thread once the machine is done, but for now we’ve run into a bit of a problem and need suggestions on how to fix it.
To start, we’re trying to build the wall-mounted version of this injection molder:
Our machine currently is at this stage:
We had the fortune of having our rod fit inside our metal tube absolutely perfectly - so perfect it actually created a suction. However, as part of the build we had to weld some brackets onto the main barrel in the spot the plastic enters. After welding those brackets on, our rod no longer slides freely throughout the entirety of the tube - it gets stuck right at the welded section. Our assumption is that the heat from welding deformed the tube. You can see the welded section here:
Today we tried various different techniques to fix the issue:
We used a brake cylinder hone to grind away the spot where the rod was catching. The grinding stones on the hone were ground down to nothing and it hardly made a difference.
We tried using the hone sitting inside a cylinder of sandpaper instead, which seemed to work slightly better since we could use a lower grit. Unfortunately it was hard to maintain contact with all sides, and it still didn’t seem to be working.
We forced the rod through a few times using brute force and twisting. We did eventually manage to get the rod through the entire tube, but it didn’t make it such that it would slide easily and we’re doubtful that it would eventually get to that point.
We’re thinking maybe the tube deformation created a small bend, in which case no amount of sanding in that spot would really allow smooth travel (we don’t think). Even if we forced it beyond the initial tight spot, it was still just as hard to push it thereafter. We could theoretically buy a new tube and re-weld the brackets, but we have no way of knowing the same thing wouldn’t happen again. Ideally we can salvage this one.
Any ideas? Throw them our way!