Production level molding

I'm embarking on a molding project that will duplicate a small scale production mold. We've all seen the molded boards, such a Inland Surfer or Placebo. For boards that are going to be mass produed this methodology offers many advantages.

1) Identical production
2) Parts (boards) come out of the mold nearly finished
3) Lower direct materials inventory needed
4) There is no shaping involved so less skilled labor is required. The "press" can be run by less skilled labor.

Molding a board requires a multi-part mold. I plan on just using two parts a TOP and a BOTTOM. The two will mate during production to create the board that is INSIDE.

The process of creating a mold with fiberglass as opposed to metal of some kind, uses a plug. I will be duplicating an existing board so my plug, in effect becomes the board.

In typical mold production the plug, in situations like this, is disposable. I will in fact be "screwing" the board down to a table to prevent movement and create flanges in the mold top. Also, I will be using tooling gelcoat to form the inner most layer of the mold's surface, subsequent layers will be chopped strand mat and polyester resin. The heat generated by the curing polyester resin can reach temperatures in excess of 300 degrees which is hot enough to create dimples in EPS foam. If the plug is a simple EPS structure, it can be ruined from the mold making process.

I have chosen an old board that has no tucked under rails. Negative relief angles are exceptionally hard to mold and require complex mold building. When building yoru mold you need to always rememer de-molding. A negative relief angle will prevent the board from popping out of the mold unless there are multiple pieces of the mold that can be removed.

This is a picture of the rail of my donor board. You'll note that the bottom is flat with no tuck in the rails to create a negative relief issues.

Oops that's not the right picture.

Let me try again

To give a better idea of negative relief angles, I drew this MARVELOUS picture (using crayolas )



In the second picture you can see the slight rounding on the bottom to effectively mold this area without a negative relief angle would require either a part line at the high point of that "presumed" rail OR a three piece mold on each side. The mold for the top "part" can be done with just two pieces.

I need to do quite a bit of prep work on the top surface of my plug. Whatever is on the surface of the plug will transfer to the mold as a mirror image.

The fisrt task is removing traction and residual adhesive - see misposted picture above.

The first step in my plug preparation is to clean up all the surface imperfections...which would include removing the old traction and residual adhesive. Some traction can be pulled up simply with a good yank. The more stubborn stuff usually just needs a bit of heat applied.

Pass a heatgun or hair dryer back and forth over the top. Concentrate in one area close to an edge to get it started and then pull while applying heat to the area that is being separated.

Didn't you carve your donar board out in thirty minutes, cause you could do that again and hand lay-up over it and not have to go throught the long time of trying to get the traction pad off, and sanding the surface to a smooth perfect shine. Just a thought,, maybe save you some time, and sanding if you have not already spent a ton of time on this. In the end you would end up with the same mold. Maybe this is a better sugestion if you would not have torn the pad off already,, I am thinking of doing this same process with the board I am shaping now, or one in the near future!!!

Spot on Jon, you can build a plug in short order and work from there. It would still need to be laminated and polished up as you point out.

I believe that removing the traction and cleaning the residual adhesive will take less time than building from scratch and it'll be cheaper for me. From that point on it is the same investment of time for either approach.

Most production shops do just as you're suggesting, build the plug and then move on to the mold. I don't have any intention of doing anything with the mold or resultant product, so...I just grabbed a board that was easy to create a mold with. We should point out that the plug need not be rideable, so a single layer of glass, no fin boxes, etc is all that's needed.

You'll have to post up your mold build as you go along.

Have you researched the health risks of the chemicals used with molds yet? You're now in the territory of toxins that make epoxy fumes and PVC dust safe as drinking water in comparison. I strongly believe molds are something hobbyists should stay as far away as possible from.

Thanks for your concern caskimmer, I do appreciate your knowledge. You are so right the potential toxicity is nothing to take lightly. I grew up in this environment when my father was a production manager with over 500 employees and OSHA camped in their facilities. I would make you proud of my safety practices.

Kiddies - do heed caskimmers warning and don't try this at home unless you know what you're doing.

Thanks again 'bro.

cool

I have all the traction except for the arch bar off. Took baout 1/2 hour. The arch bar is being stubborn! I'm guessing because of the extra thickness it's not transferring heat well. Hopefully I'll have that off this evening.