F.D.M. based 3D printers use plastics such as A.B.S. and P.L.A. which are very hygroscopic and are easily damaged by moisture resulting in failed prints, nozzle blockage, sputtering and much more.To avoid this situation I came up with the design of a filament storage unit which also acts as an dehumidifier. The Unit consists of 2 major parts, an air duct and a storage unit.The Unit uses an Arduino, a cross flow fan, Silica Gel Dessicant, Sensors and a 100W heater to maintain a specific temperature and humidity in the chamber.
Step 1: SHELL
The Main structure of the storage unit is made by solvent welding several polycarbonate Double wall panels together.Take a double walled polycarbonate sheet and cut out panels using a utility knife and a straight edge( a ruler or a piece of wood that is straight. 800 grit sandpaper can be used to wet sand the edges and make them smoother. The PDF below comprises the details (dimensions and quantity) of the panels.
The drawing was created using Autodesk Inventor.
Step 2: SOLVENT WELDING (Assembly)
Start by assembling the inner panels. Take the two inner panels you prepared and solvent weld them using Dichloromethane in a syringe, ensure that the workshop is well ventilated. The two panels should be perpendicular and the cut outs for the ducts should be away from each other. Keep the L shaped inner set aside. Now Take 3 side panels and solvent weld them into a C shaped section (use the image below for reference). After the L and C are done weld them together as shown in the image and insert a back panel making sure it is flush with the U and weld it off.to complete the shell take the last remaining side panel and welds it to the opens side perpendicularly to the Back Panel and the L.
The door is designed with a rim that fit over the casing to ensure that the panel is rigid and has reasonable airtightness. I used a rim of about 30mm depth.
(blue - inner panels, red - side panels, yellow - back panel)
Step 3: Pipe Holders
The pipe holders are made by welding two strips of double walled polycarbonate sheets together. A whole was drilled using a hole saw and tangential lines were marked and cut using a band saw ( a hacksaw will also work ). The distance between the 2 cut outs and the diameter can be adjusted according to the diameters of the filament rolls and the pipe you are using in my case I used a pipe of outer diameter ¾ inch. The .stl file for the collar and the Inventor part file are attached below. A total of eight holders are required.
Step 4: Finishing the Body
Weld the pipe holders to the sides of the unit use pieces of polycarbonate as spacers to ensure that the the holders allign perfectly to with the one on the other side. the distance between the holders can be adjusted by the user depending on the diameters of the rolls going to be stored. ensure that the distance is such that the rolls are not to high nor falling down from the space between the pipes.To finish the door 3d print the handle (.stl file attached below) and cut out a rectangular section in the sheet ensuring the flanges of the handle perfectly mate with the doors face and weld it off. Attach the doors to a set of plastic hinges (for eg. Adafruit part no 1215 - https://www.adafruit.com/products/1215 ) using the .stl file provided below and then align the door to the shell and screw the hinge to the shell. Then, push the pipes into the slots and seat firmly on the bottom. 3d print the desiccant tray and the grill and fit it in the lower cutout on the inner panel. fit the grill printed with the settings given below inside the tray and put some desiccant in it.
Settings for Grill
Perimeters - 3
infill - 20%
Top and bottom layers- 0
Step 5: Electronics
There are four major parts in this section. A cross flow fan, A 100 W heater, a power supply and a control unit (arduino and shield). I used the photo- chemical etching method mentioned in the next step to manufacture the shield but any other process can be used. After preparing the shield mount the parts to a sheet of Hylam (material not critical but should be non combustible and capable of withstanding about 200 Deg. C) as shown above and make the connections you can route the wires under the sheet by drilling holes in it.on the side of the shell make a cutout for an AC socket and switch and fit them there. Then connect the socket to the switch and the switch to the power supply. Route the DHT22 sensor to the storing compartment and fix it there. Check the connections and place the electronics back onto the tray and you are good to go.
I added an RGB LED strip to the tray. Code allows me to control the color and the flash pattern of the strip to provide information about the status of the system and it looks cool too. You can customize the code or add effects to suit your needs. The heater is a PTC 100 W 12 V heater i got off Ebay. The cross flow fans are generally used to cool amplifiers and other instruments and can be purchased online. You can substitute a set of 50 or 75 mm square CPU cooling fans if you want.
Step 6: Making the Shield
To make the shield by my method take a printout of the artwork provided on a transparent sheet with the the printer set for the darkest output. Use the artwork to mark the borders on a sheet of P.C.B. then cut leaving margins.Now clean the Copper side using steel wool and fine sand paper until you have a shiny surface (wear rubber gloves, copper is toxic). After cleaning ensure the sheet is dry and clean and degrease the copper surface with a tissue soaked in alcohol. Now take the sheet to the dark room. Cut a piece of the photo-polymer ( Dupont Riston) you have approximately of the size of the P.C.B.. Now laminate the P.C.B. with the polymer sheet and leave it to bond properly. After laminating use the artwork to develop the P.C.B..by exposing it to an Ultraviolet light source. You need to develop the board using the Manufacturers recommendations.
You may also use a pre-sensitized copper clad board or use the toner transfer method / CNC milling / Etch resistant marker methods to make the PCB.
After developing the P.C.B., Etch it using etchants such as HCL or FeCL2. After you are done etching wash the P.C.B. and trim it down to the borders.Drill Holes for the components using a Dremel or proxxon moto- tool in a drill press stand. Now take the following components and solder them to the P.C.B.
N channel MOSFETS x5
10 k resistors x 6
JST connector(for dht22) x1
PCB Terminal Plugin connectors x5
test fit it on an arduino and upload and test the code.
designed using proteus 8
Step 7: Further Details
I used a Silica Desiccant that changes from Amber to Dark green so that I would know when to replace the desiccant. Based on how long the desiccant functions, you may need to increase the volume of the tray or the change intervals. In regions with very high humidity or in the humid season , you may need to add a gasket sealing tape to the door to ensure that there is no moisture infiltration. The design may be extended to add a filament feed mechanism that ensures that you don't have to expose the filament rolls to the air but that will need a lot of rework to create rollers to allow the rolls to rotate freely. You can use a set of bowden tubes to guide the filament out of the case from the back.
The Arduino / shield arrangement is useful for prototyping and can be replaced with a custom board using an ATtiny or other Atmega processor on a custom made PCB. You can also attach a digital display to monitor the Temperature / humidity values and also incorporate an audible alarm for critical levels. A web based remote monitoring solution has also been considered but that will be left for another instructable.