Tube Winding
A brief overview of the proper steps when manufacturing a tube using the X-Winder.
Safety
Always wear gloves when handling epoxy and composite fibers.
Keep hands, feet, hair, etc. out of the way of the X-Winder when in operation. It is a large machine and there is a good chance it could cause as much damage to you as it will to itself.
When using ovens, avoid accessing them while hot, and wear necessary safety equipment when handling hot objects.
Setup
Select the desired tow spool and epoxy. The epoxy that is used should have a setting time that is longer than the estimated wind time to avoid issues with X-Winder operation.
Ensure the X-Winder is clean and in working order: motors turn smoothly without overheating, tow spool rotates freely, belts are secured tightly, no residual epoxy, etc.
Mount the desired mandrel to the main rod, making sure that everything is tight and does not slip when rotated.
Make accurate measurements of the tow line and the mandrel, as well as the start and end lengths of the wind pattern. (Note that generally the ends of a wind are inconsistent with the bulk, so it is best to wind 2-3 in. longer than the desired tube length and then cut to size after.)
Input these measurements into the X-Winder software along with desired wind angles and layer count.
Cut a piece of bleeder/breather cloth that will fit around the mandrel for use after the wet wind.
Depending on the estimated wind time, this is a good point to think about pre-heating the curing oven to the desired temperature.
Dry Wind
Pull the tow through the rollers to the delivery head. Be sure to place the line between all spacers and check that no fraying occurs as the tow is pulled through.
Tie the end of the tow to the mandrel slightly ahead of the start location such that the knot is not wound over. This knot has to be secure since there will be significant tension as the wind starts. Tape can be used to help secure the knot.
Run the software for part of a layer, checking for proper spacing of the wind and wind behavior at the ends of each pass. It is a good idea to check each different wind angle and verify that things look good and the X-Winder is working as intended.
If everything is good to go, cut the tow and unwrap the partial wind. Remove the mandrel to prepare it for a wet wind.
Wet Wind
Wrap the mandrel in wax paper such that the paper is snug to the surface but can still slide off without too much effort. The wax paper should be longer than the intended wind length but shorter than the mandrel. Tape the ends of the paper to the mandrel so that it cannot rotate independently during winding.
Apply several thin coats of mold release agent to the surface of the wax paper, allowing 5-10 minutes to fully dry.
Place mandrel back on the X-Winder, making sure that starting and ending wind measurements are within the wax paper region.
Mix one pump of resin and hardener and pour into the epoxy tray. Pull the tow through the tray until epoxy has reached the delivery head. Ensure that the epoxy regulator is properly tensioned.
Tie the end of the tow to the mandrel slightly ahead of the start location such that the knot is not wound over. This knot has to be secure since there will be significant tension as the wind starts. Tape can be used to help secure the knot.
Run the wind program. Watch to make sure things are running smoothly and that the first few passes are looking good.
Every 10-15 minutes, check the epoxy tray to make sure there is enough to cover the bottom part of the tray. Do not overfill the epoxy tray, as this will cause a buildup of heat as the polymerization reaction occurs, which can melt the tray or cause curing inconsistencies.
It is good practice to pause after each layer just to give everything a quick inspection before proceeding.
At the end of the wind, cut the tow and take a moment to appreciate the fact that the hard part is over!
Finishing and Curing
Wrap the wind in one layer of bleeder/breather cloth. Try not to overlap too much as it might dry out the surface.
Tape and secure one end of a roll of shrink tape just off of the end of the wind. Run the shrink tape program or simply have the software spin the mandrel as you slowly wrap the shrink tape around the wind. Be careful: try to avoid wrinkling the tape and keep an even overlap as you move across the wind. Cut and secure the other end once the wind is completely wrapped.
Remove the mandrel and rod from the X-Winder and place in the curing oven. (The temperature should be above the activation temperature of the shrink tape.)
After the wind has been completely cured, cooled, and removed from the oven, the shrink tape and bleeder/breather cloth can be removed.
Remove the tape holding the wax paper to the mandrel, then remove the composite tube from the mandrel. Peel away the wax paper from the inside of the tube.
Congratulations! You have produced a composite filament wound tube. Inspect it for any defects or flaws and appreciate its cool pattern. It is now ready to be cut, sanded, turned into a rocket!
Clean-Up
Disassemble the parts of the X-Winder which touched epoxy. Thoroughly clean these using a solvent such as acetone.
Check for and remove any fraying residue and clumps in and around the area.
Discard any epoxy mixing cups, used shrink tape, used bleeder/breather cloth, excess tow, and all other waste.
Make sure the X-Winder is unplugged when not in use.
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