II. Instructional
Parts List
Heated bed has the following parts:
Solder work - 6 minutes
Surface gluing - 11 minutes
Taping down wires - 5 minutes
II. Heated Bed
Tools List
Assembling the heated bed requires the following tools:
I.Introduction
Heated Bed
I.Cut List
Heated Bed
The heated bed is the surface on which the extruder prints 3D parts. It rests on the bed holder between the two z-axes, providing the vertical movement so things can be printed on a flat surface.
The bed is heated so that objects being printed will stick to it and then can be pulled off easily after it cools. This is because the surface of the heat bed - PEI - has a property of sticking to plastic when hot, and releasing when cold.
These are parts that are cut from stock material, and not purchased in the ready-to-use size
II. Functional Knowledge
Heated Bed
In order to heat up, the PCB Heatbed is connected to a power source which flows current through the circuit on the bed. The PCB Heatbed itself is a giant resistor. As electricity passes through it, it gets hot.
The temperature of this PCB Heatbed is regulated through the thermistor, which measures the heat bed temperature. This thermistor is connected to the control panel, which sends electricity through the heated bed so that the heat bed reaches the desired printing temperature. The printing temperature can be between 40-120 degrees Celsius.
Although the PCB Heatbed itself is a giant copper circuit, there is a layer of PEI (polyethylimine) plastic that is pasted to the top of the heated bed with double-sided adhesive tape. The PEI plastic is the layer on which the 3d printer prints objects.
This PEI Plastic is sticky to the plastic 3D prints when it’s hot and unsticky when it’s cool. Printing on the PEI Plastic when it’s hot makes it so that the 3d printed objects can stick well to a 3D printed surface. Then they can be removed easily once the print is finished and the bed cools off.
III. Instructional
Heated Bed
Step 1: Prep your soldering iron
We will be soldering wires in this module. Set up your soldering iron or locate it in the workshop.
Use a high temperature (at least 650 degrees F) on your soldering iron.
III. Instructional
Heated Bed
Step 2.1: Apply the adhesive onto the PCB Heatbed
Peel the backing off of the double-sided adhesive.
Place the adhesive’s bottom edge carefully onto the blank side of the PCB Heatbed - 3/16” from the edge. Note that there will be about 3/16” space between the adhesive and the aluminum bed all around. Rub slowly back and forth as you flatten out the entire adhesive onto the PCB Heatbed.
Applying the adhesive flat is the first step towards polished 3D prints. A flat surface allows for a great quality first layer on all your prints. However, if you have bumps caused by trapped air pockets, the plastic sheet should smooth it out in the next step.
III. Instructional
Heated Bed
Step 2.2: Check for air bubbles
Look for any air bubbles on the adhesive.
Cut them with a razor blade or pop them with a pin. Then smooth it out so that the air bubble is no longer there.
This ensures that the adhesive is as flat as possible.
Step 2.3: Remove the other side of the adhesive covering
Peel away and discard the remaining adhesive covering.
III. Instructional
Heated Bed
Step 2.4: Place the PEI Plastic onto the PCB Heatbed
Remove the greenish protective plastic covering from both sides of the PEI plastic.
Like the adhesive, place the bottom edge of the PEI Plastic first onto the PCB Heatbed - 3/16” away from the edge. Note that - if you want it centered for aesthetic purposes - the plastic is smaller than the bed, so move it forward the same amount as the gap on one of the sides.
Then rub the PEI Plastic flat onto the PCB Heatbed starting from the bottom.
The PEI surface is about 3/16” or 5 mm from the edge of the aluminum.
III. Instructional
Heated Bed
Step 3.1: Prepare the 3 solder pads on the bed for attaching the power wires and thermistor.
Touch the solder wire to the pad.
Then touch the soldering iron onto the solder and bed.
It’s best to use a low angle to get more of the iron onto the solder and pad. This makes it so that more of the hot iron can melt the solder.
Do this for all 3 of the solder pads.
III. Instructional
Heated Bed
Step 3.2: ‘Tin’ the power wires
The frayed ends of the wire could later cause an electric short circuit that stops the 3D printer from working. We will twist the solder the wires to ensure this doesn’t happen.
Twist together the ends of the wire so they are tightly wound. Then bring your wire to the solder iron and solder all the wire ends.
When you're done there should be no loose, frayed ends.
Tin this
power wire
Tinning the ends of heat bed wires
Twist and tin the power wires so they don’t fray
III. Instructional
Heated Bed
Step 3.3: Solder the power wires onto the PCB Heatbed
Pull the red and black wires apart approximately 4 inches from the end to allow them to reach their respective pads as shown. Loop them as shown on the next page.
Place tinned copper braids onto the solder on the pads and heat both to create a solid connection.
The negative lead (black) will go across pads 2 and 3 from the left, and the positive (red) will go only on pad 1 from the right.
III. Instructional
Heated Bed
Step 4: Tape down the wire
It is important to reduce stress on these solder joints so we want to avoid harsh bends in the wire.
Avoid bending the wire at a sharp angle. Don’t do this.
Bend the wires in a heart shape such that the top edge of the bend is below where it says “CAUTION” on the PCB Heatbed.
Tape the wire as flat to the board as possible so that it can be positioned correctly later on. See pictures on next page.
III. Instructional
Heated Bed
Step 5: Insert the thermister
The thermister is a sensor that detects the temperature of the heat bed.
Fit it snug into the middle hole on the heat bed until it touches the plastic on the other side. Press the lead coming out of the hole down to form a neat bend. Then, secure the thermister in place with kapton tape using an X taping-pattern.
III. Instructional
Heated Bed
Step 6: Secure with a final piece of tape
Apply one more piece of kapton tape across all the wires to secure them flat against the bed surface.
IV. Troubleshooting
Heated Bed
V. Completion Checklist
Heated Bed
Wires Soldered Together on Heated Bed�The red and black wires are soldered together such that the solder is one large blob connected them together.
This will cause a short circuit if you turn it on.
To fix it, try putting the soldering iron on the spacing between the red and black wire. This could melt the the soldering off the PCB Heatbed
VI. Design Considerations
Heated Bed
When building the heated bed, you want to consider how well 3D printed objects will print to the bed and how much work it takes to prepare the bed for printing.
Printing Surface
PEI Plastic - Don’t have to prepare the print surface. When it heats up, things stick to it. When it cools down, it’s easy to remove 3d printed objects from it. (See text when in functional / prcocedural knowledge).
In the future, it’d be possible to automate printing.
Tape or Adhesive - The PEI plastic requires no additional adhesive. This makes it faster because you don’t have to prep the print surface for every print. For example, you don’t have to use adhesive or blue painters’ tape - both of which are consumables and must be reapplied every few prints.
PEI enables automatic part processing possibly in the future. Because it auto handles the printing and print removal process.
Use double-sided adhesive (which can withstand high temperatures).
You have to cover the heat bed with a glue stick in other cases. PEI eliminates this need.
Glass - Glass print beds are sometimes used as a printing surface. In this case, you need to prepare the printing surface with glue so that the prints do not detach.