Internal Envelope Vac Bagging

Findhan Strain

Split Tooling• 5083 Aluminium (cost)• CNC’ed• Finished with 800 grit • Not well polished as good

surface finish not essential due to time constraint

• Multiple layers of Frekote 700 NC

First Layer• Leave material over the edge• Trim with v. sharp blade• May require further trimming after

debulk

• Do not cut tool or release agent

First Layer• Place first layer in tool• Rough Trim first ply on both

halves

Debulking• After debulking the initial half layer: 20 mins with perf release film• Further trimming if required along split line – possibly leave all until

after debulk

Subsequent layers• Layers laminated on half of tool• Prior to closing

• Layers seen here above tool are plies 2, 3 and 4• Place a layer of non-stick material

eg backing film between last inch of each ply (not shown here)

Subsequent Layers• Instead of this approach, could simply close two halves of mould and

lay one full layer around mould after the first layer• This product required a localised thickness at the centreline so ply overlap

provided this build-up

Tool closure• Bring two halves together carefully• Overlap both ply no.2s from each

half• Remove backing film between layer

2 and 3• Place and overlap layers 3 from both

halves• Repeat for plies 4

Tool Closure Detail• Ensure good compaction

between overlapping layers• Place bagging materials on

carefully• Plenty of slits in perforated

film• Ensure film and breather are

well taped down to avoid them slipping off when placing the bag through the middle

Bag Preparation• Cut a BIG bag• Takes a much bigger

bag than you think!

• Place PS tape at one side

Bag Preparation• Close bag over on top of tape• On reverse side of bag, place PS tape

on the outside• Inner and outer tapes must connect to

ensure no leaks

Bagging Preparation• Place bag through the middle of tool

(shown here also going through a cylindrical tool at the same time)

• Place vac ports inside bag

Bagging Preparation• Pull bag through and

back on itself• Attach bag to

remaining tape, ensuring all tape is once again connected at any intersection• Bag now sealed

Draw Vacuum• Draw vacuum• Can place arm up the middle if done correctly!

Finished Part• Tool split with hammer and chisel at

non-machined faces• Part removed with ease due to good

release, easy geometry and split tooling

Mould Split Line• Can be minimised with pin-point machining• Leave rough cut then hand polish• Final CNC-ing

• Can be degraded by Stanley knife when trimming• Usually hard to completely avoid this

• This ridge is quite small for 3 bar + vac bag!