Monthly Archives: April 2014

Dryer Box

How to build a heating Dryer Box

Plastic absorbs water. Moisture absorption (also known as water absorption) is the capacity of a material to absorb moisture from its environment. Type of plastic, temperature, humidity, how stored are all factors to how much is absorbed and how fast. When heating and then trying to mold plastic this a bad thing. Heated water turns to steam, expands 100 times it size and generally just makes a mess of the pull. So, how to get the water out of a sheet of plastic before molding?

Easy, you dry it. Yes, dry it. Heat the sheet plastic to a warm but not mold able state and bake the water out. Then mold, the now dry plastic with no problems. Polycarbonates are partiality sensitive to absorption.  So all you car body makers out there, need a Dryer Box.

A Dryer Box is easy to make. Think Easy Bake Over scaled up. Using heating duck board, a few 40-100 watt light bulbs, and temperature controller you can build a box with a few shelves that will hold your plastic the 4-24 hours it needs to dry before use. Times very based on temp, water absorbed, type of plastic, square area exposed excreta. Search for your plastic type, the recommended drying temperature and time. 

Simple materials to come by. I got mine at Granger.  Cuts easily with a box knife and yard stick.  Goes back together with the aluminum tape. Folds nicely with V groves. You can even use the tape for door hinges. It is important to put in a vent. You want the water to escape so add a 2″ vert hole in the top. Note the step cut in the door edge above. this makes a good seal. Worries about making a box, watch some HVAC videos that cover it all for you and you will be a pro.

I mold 2’x4′ sheets so mine is bigger than 2’x’4 on the inside. Works great. holds several sheets at a time.  Is a good way to dry paints, wet molds, cure epoxy, bond solvent type glues and all manner of other uses.

This a quick build in a few evening. Wear gloves and protective gears as the board is fiberglass and will be exposed until you get it all taped up. 

The simplest way is to use a grill temperature probe from the Grill department from your big box store (about $10)  and swap out light bulbs until you find the combination that keeps the box at temperature you want. I fine 2- 60 watts and a 40 keeps the box at a nice 125-130F.   The other way is to build a  STC-100 controller. There are several videos, here is one   How to build a Temp Controller with a STC-1000