Baseball Game Home Run Plastics
This is a vacuum formed plastic that I make with my backyard BBQ grill and a vacuum box made with parts around the house and a vacuum cleaner.
I previously wrote up how to vacuum form a Major league Baseball game home run plastic. I have recently had multiple requests for another rerun to make new plastics. The quality of the vacuum form is not as good as the original but it's stronger. After 60 years there is nothing much left of the original plastic, so there nothing you can lose replacing it.
I have remade the form three times tweaking the dimensions and played around with the way we make them. My mistake was not writing down all the little changes we did during the forming process from the daily temperature outside, oven heating time, oven temperature, was it windy, how much blank sag did we have and it still worked. Number of rejects verses good pulls etc.
The recent plastics pull quality has dramatically improved and I want to show this and some tips to get the best out of this arrangement. If you have the need to make something and a vacuum mold is needed maybe it is worth your time to make a similar set up.
My back yard Vacuum Box Set Up
TIPS using this set up
• Use a vacuum cleaner or wet/dry or similar.
• The filter must be clean, If not the vacuum pulled will dramatically reduce. I keep a clean filter for when I do a vacuum forming.
• The seal to your vacuum forming box needs to be good, I use duct tape to seal the hole to the box. The hose size and my collection of hole cutters were not aligned. And I was too cheap to buy the correct one if it exists.
• I use this Weatherstrip material below for the plastic holder seal to the window screen frame. This product seems to be the best as it accepts the heat and stays together well during the forming. Better still I can reuse it multiple times during a batch run.
Weatherstrip from a box store
The Heating Cycle.
Tips during the Blank Heating Step
• BBQ Grill. Yes, it really works! Remove all surfaces that touch your food just in case.
• The size of the oven needed is important as a kitchen oven is only so large and is probably out of bounds unless you are Clay Harrell, but I have a suspicion he waits for his wife to go out before he uses the oven in his kitchen!
• The temp in the grill needs to be about 250 degrees F and above if using the PEFG material. The HIPS material is less critical on heat input needs to over 300 degrees F. To get this to work tweak your burner to the minimum to just before they blow out.
• If it is too windy you will need to try this another day. If you leave the lid closed and your gage says it’s over 350 degrees F then you need to reduce/tweak the gas a bit more.
• Temperature control is not that critical as by opening the lid you can release the heat and it only takes a few minutes if the gas is set very low to get the oven hot again. In this time you can get the material to heat up satisfactorily.
• The position of the grill heating deflection plates is critical (not as shown in the picture). We must get even heating as the plastic gets to its sagging point. I have found that no more than one inch of material sag is all we need. If one side gets more sag due to uneven heating then we risk getting webbing and the blank is immediately scrap. I have destroyed more blanks than I care to mention due to this one problem.
• An 8’ X 4’ sheet of 0.060” thick PETG makes 14 to 15 blanks if you cut it perfectly. Last October I was only able to make 3 acceptable plastics from one sheet. I was able to get 8 this last time now I have this process better researched.
Vacuum Box and Wooden Form
• The form needs to be raised of the pegboard about the same as its thickness. I use six stacks of three quarters currently and it works perfectly now.
• I use soft foam weather strip to seal the box to the plastic holder. It can accommodate the plastic holder book clips shape. It’s also OK to double it up if needed to make the seal.
• If we leave the blank in the oven too long it obviously gets hotter and the material sags more and this excess material can form a crease or web when put on the form before the vacuum can do its job. This destroys the blank.
• Too little heat and it will not pull over the center of the form.
• Just right is when the sagging is uniform and it’s no more than ¾” to 1”.
• The form by necessity is less than Ideal due to the sides of the home run target being little steep. The secret we found to get the blank to form is to use a hot gun.
• Keep the hot gun moving and keep its nozzle no closer than 3” from the work. Continue to heat the plastic with the vacuum still on and it will slowly pull in as it softens and the vacuum will do its magic. It makes a close to perfect pull.
I started out making white background plastics and have now moved to a more ivory color, this is I believe a better representation for older games. As they are made on request I could use any color shade you want.
I will provide a daily pictorial step process on how the plastic batch is made in a little while.