Infusion meeting with Rocketry

Owned by Sheila Afros
Last updated: May 15, 2021 by Renzo Villanoy
5 min read

  • Small process of infusion reason for different selections in process

  • Foam from composite Canada tooling foam 19 pounds per cubic foot originally wanted 24 but out of stock

  • Rocketry de-molded test infusion with success!

  • Tooling polyurethane closed cell foam. Foam does not have to retain vacuum (the foam does not have to hold vacuum (envelope mold)). Strongly suggested not bagging to the surface of the mold because it may not work and may deform. Suggested instead main part of the mold made of the tooling foam and then fiber glassing over the top but you may lose the structural integrity. Andy Phillips is their composites advisor (practical side of composites manufacturing/processes) industry advisor. Get into contact with Andy Phillips.

  • Andy also suggested Foam CNC undersized, fiberglass over top and then CNC again (and if mdf work then it would be good) (this is long process though).

  • They just used tooling foam.

  • Cost (will be sent over later) of foam

  • Mold CNC by the shop? Yes, Bryan helped CNC it, it took about an hour per mold (each half). Female mold.

  • Large molds? Body tube molds (39’’ by 9’’ by 7’’). Save some time and effort making body panels in parts and then bond together (approx the same strength it joined together properly). MSVII used 1 large mold and used 1 mold to do multiple parts (layout for the door was done separately). One mold done in separate sections, separate the pieces.

  • Bonding process looks more like two seems (butt joint) will need a patch to bond them together. When joining the components put patch and then vacuum bag it again with the patch. Put patch on interior side. Specific steps depend on mold. But in general patch will lie flat is there is step pattern and then vacuum seals.

 

  • Don’t sand finished components (it reduces the strength of the component because it breaks the fiber).

  • Wrinkle – be careful do not sand

  • Split panel with nomex how does one account for the split and patching the nomex

  • What calculations for resin (used more than expected theoretical does not account for the tubing and pools in the bag. Pressure gradient from the cup to the outlet (linear) big pool of resin at one side of the bag. Figure out how much the part needs start with 3 times that amount what diameter of tube. After you figure out what you need and reduce/increase as needed.

  • How does one de-gas resin: put it in a chamber and degas. The vacuum pump was hemorrhaging oil so watch for weird pumps. Is it crucial to de-gas the resin (not sure but there were dry patches so highly recommend de-gassing). Resin itself will boil at low pressure and the volatiles may become vapor (hopefully those bubble will go to the flow front and escape out of the outlet (clamp off inlet and outlet before continuing) (explore composites website) (try to not allow a full vacuum when you need to stop 1st clamp off outlet, vacuum first, and then inlet). Depends on the resin (this may not happen).

  • Clamped off the inlet (put 5 C-clamps and that seemed to do the trick). Disconnected the catch pot off (and it ran itself). Ran the last part (last 6 inches) off of the catch pot. Do not use reinforced tubing if you want to clamp it (no braided vinyl for stuff if you want to clamp, this is the tubing to not use if you want to clamp https://www.homedepot.ca/product/canada-tubing-braided-vinyl-tubing-1-2-inch-inside-diameter-x-3-4-inch-outside-diameter-x-10ft-coil/1001002049 ). Polyester tubing will be fine to clamp. Infusion process took 15 min (840 seconds) (225 centipoise (low viscosity resin)). Working time of the resin around 120 min of pot life. We have about 90-112min for seat resin 114

  • No race tracking. What is resin throttling make a crease at the T-fitting if you need to throttle the resin presenting a flow restriction to the resin. Throttle the part that is going to fast by creasing (explore composites video). Did you trim after? Good idea to leave about an inch to trim.

  • Peel ply, mesh was cut to overlap which ones. Made sure that inlet and out pieces of peel ply had some overlap with the process materials made sure infusion mesh has to be shorter (does not overlap). Decent amount of peel ply at the end.

 

  • Make sure that the mesh and the peel ply do not make the resin rush to the end (one side may reach first). Was there a gauge on the pump? Temp-time-distance not vacuum levels. Bagged the mold the night before to make sure there were no leaks (bubbles coming out of the mold and into the vacuum MEANS LEAK). Minimum 1 hour in vacuum take a picture of the gauge and see that it does not drop (and trouble shoot). If there is a MDF mold will have vapor so things will have to make its way out.

  • Vacuum drop test means checking the gauge noting the pressure, waiting, and then seeing if it has changed (become more positive), the required drop is 0 drop. Waiting 10 min is how long it takes for a leak. Very careful with process material and gum tape (do not drop it) make sure the bag does not have any imperfections. Process material ESPECIALLY vacuum bagging fill (no dust or grit or cause holes) and unroll onto a soft clean cloth. No floor unrolling. No pointy parts. The gum tape also needs to be clean. Store in the container, bag it.

  • Mold manufacturing: it took about 1 day for primer, 1 day CNC, sanding primer 4-5 days, 2000 grit polishing 2 days no repairs (repair the mold more coarse than it should have been, so put epoxy and then sand again, bondo works better, apply thicker layer of primer so it does not get too thick. Clean components before the primer. Best to have 2 people sanding at the same time. Male molds not as big of a deal but female super big deal (cannot round of the corner). Female mold you need caution with corners.

  • Mold release? Wax and PVA. 5 layers of wax, 1 layer PVA.

  • See if our release will eat the mold.

  • Patch work body filler and epoxy. Bondo and smoothing out. (Ask Adrian about tooling)

  • Cut out and then reinforcement material.

  • Cut out (so cut out, the carbon fiber and no core in cut out spot and then cut the top two layers as well)

  • Room temp is fine. Will gel at the time of the data sheet.

  • Keep in mind how long it takes to infuse the distance. Shorten the distance with inlet and outlet ports at different parts of the mold, place inlet in the middle of the mold. Alternating ports?

  • Good candidate with infusion, have a mold that is leaky don’t use.

  • Part specific (panels could go anyway). Easy to tape then wet layup works okay. Wet layups are more tolerant to bagging errors.

  • There is a way to save if you know where the leak is but otherwise we don’t know. Research how to save these parts.