Print Bed - Type 1
Print Bed - Type 2
Parts for this section
300mm x 300mm MK2 (MK2a, MK2b or MK3) PCB heatbed
310mm x 310mm x 3mm aluminium plate
300mm x 300mm x 3mm sheet of borosilicate glass
300mm x 300mm x 2mm (or thicker) self adhesive cork (this is optional but a nice upgrade)
M8 x 30mm Idler bar (cut 8mm smooth rod)
4x medium/large bull clips
8x 20mm springs
8x M3 x 25mm screws
4x M3 x 12mm screws
12x M3 nuts
300mm x 300mm silicone heat pad with built in thermistor
310mm x 310mm x 1/2" (12mm) wood board
300mm x 300mm x 3mm sheet of borosilicate glass
4x large bull clips
4x M3 x 20mm wood screws (pointy end)
Parts for this section
Basic Print Bed
This is a design for a basic print bed that works quite well that I used for many prints. It doesn't have some of the fancy features such as ability to fine tune the print surface height at multiple points, but it's simple and good enought to start.
Simple ... melts the plastic
Built in heat insoliation ... the wood board acts as insolation to retain heat
Cheap to build ... grabs filament from the spool and pushes to hot end
Not adjustable ... holds the extruder and hot end in place
Heavy ... limits print speed
Start with the 300mm x 300mm x 3mm aluminium plate. Confirm the dimentions by measuring its length and the width. Then trace two diagonals linking opposit corners to locate the center. Then trace one vertical line at 99mm from the left side, and another vertical line at 99mm from the right side. This will leave approx 122mm between these verticals. Trace a perpendicularline horizontally to divide the top and bottom equally.
Place the "Y carriage" and mark where the four holes need to be drilled. You can drill these holes using a regular handdrill and a 1/8" drill bit. Work slowlyuntil the hole starts. Using a new drill bit will make you life easier.
You don't need to drill the holes at the bottow. Those were make to test different configuations for the print bed. Same comment for the hole in the middle.
The Type 1 Adjustable Print Bed
This is the surface upon which your prints will be made. The print bed can take serveral forms but our experience is that printing of a sheet of glass (ideally borosciliate) works very well and is simple to build using common materials.
Borosciliate glass is the same kind of glass that is used to make laboratory glass and is easy to find (including our at our webshop) where it's desireable property is it's low coefficient of thermal expansion (it doesn't break with tempurature changes).
Several heatbeds exist on the market, we like the one designed by RepRap. The main types we've found are PCB heat beds (MK2) variations, silicone heatbeds, and aluminium heatbeds (MK3).
Adjustable height ... A great feature to make sure the print surface is perfectly horizontal
Lighter weight ... permits to print at faster speeds
More costly ... a little more expensive but advantages are well worth it
Now we move on to the "Y Carriage" plastic part. You will need four M3 nuts and four M3 x 12mm screws to attach the "Y carriage" to the aluminium plate.
Place one M3 nut in the hexagonal hole in each corner of the "Y carriage". To make life easier, I carefully add a bit of glue, epoxy, or my absolutely new favorit: Bondic.
Bondic (which we sell on in the webshop) is a resin that hardens (cures) with a specific type of light. Yes that's right, it's photosensitive. Even if you get it on you hands it not a big deal until you shine the special light on it. This stuff then hardens and binds any material like epoxy,
Place the "Y carriage" in lne with the four holes and then insert an M3 x 12mm screw in each hole and tighten firmly.
The assembly looks like this.
The view from the top side ... 4 screw heads.
They don't need to be sunken to be flush with the plate because nothing rests on these screw head.
Next we move to assemble the heatbed. You will need the MK2 heatbed and eight M3 x 25mm screws, eight 20mm springs, and eight M3 nuts. One for each hole in the MK2 heatbed.
You will notice that the MK2 heatbed has two sides, the one with the circuit traces on its surface (the top) and the reverse side that has none. These traces are the heating element.
The MK2 heatbed is longer and wider that 300mm x 300mm, however you only need to cut a piece of 300mm x 300mm x 3mm of cork. This is typically sold in rolls. It usually comes with an adhesive back.
This cork serves as a heat insolator to increase the efficiency of the heatbed.
Flatten our the piece and cut a very small hole of approximately 4mm in diameter near but not exactly in the center.
A view of the reverse side of the sheet of cork.
Set asside the sheet of 300mm x 300mm borosilicate glass for later.
This sheet of glass is the print surface. It's the surface that your extruder will place the plstic on. I prefer to use borosilicate glass since this type of glass has a very low coefficient of thermal expansion. It doesn't expand as much as regular glass as it heats up, therefore it doesn't tend to break due to changes in tempurature. A very nice property indeed when the hotend is place molten plastic at temperatures in the 200 celsius range. It's the same type of glass used to make lab equipment.
To control the tempurature of the heatbed, we need to know its tempurature. The software (Repetier Host) will take a reading and if the tempuratue is too low relative to the target, the software sends power to a pin on the Arduino / RAMPS 1.4 board to activate and heat up the MK2 heatbed.
To measure the tempurature we use a Thermistor. We provide a greater explanation about how it works in the Extruder section of this project.
For now gently spread the two leads coming from the thermistor. Be careful since the thermistor itself is a very small and fragile glass bead which breaks easily.
Cut a rectangular piece of Kapton tape, and place the shaped thermistor on it.
Before folding, make sure the piece of kapton tape is all the way up to the glass bead.
Fold the piece of kapton tape over against itself, to seal the thermistor's leads.
You can carefully run your fingernail between the leads to make sure they are isolated from each other.
Trim the excess kapton tape from the sides while still leaving some tape to insure that the leads are sealed.
Place the MK2 heatbed face down, to expose the bottom (the side with no electrical traces). The position the cork sheet on it with with the sticky side down. You can see the sticky side is up in this picture, but place it face down against the MK2 heatbed. Find and mark the little opening that you cut. Now place the thermistor on the MK2 heatbed at the marked spot, and tape it place using kapton tape.
Slide the thermistor leads through the small hole in the cork. Flatten out the cork sheet, remove the paper covering the sticky side (remember the sticky side is facing the MK2 heatbed) and stick-it to the MK2 heatbed.
Place this assembly in a vertical position and insert one M3 x 30mm screw in each hole.
Now place a 20mm spring on the foot of each screw.
Place a small piece of tape over each screw head to help keep the screws in place as we continue moving the MK2 heatbed around with the screws in it.
This is what you're supposed to have so far ... the foot of the screw and spirngs coming out the side where the cork sheet has been applied.
Lay the top of the MK2 heatbed assembly face down (top of assembly is facing downward). It's upside down in this position, and that's what we want.
Now place the 300mm x 300mm x 3mm sheet of aluminium on top while guiding each screw foot through a hole in the aluminium sheet.
As you press down on the aluminium sheet, the spring will push back. So make sure to fasten the nut ont the foot of the screw as you hold the aluminium sheet down with the screws compressed.
Flip the heatbed assembly upside right (face with electrical traces facing up), and place the sheet of borrosilicate glass on top.
Center the sheet of glass on the MK2 heat bed and attache the sheet of glass in place usign 4 medium/large bull clips.
As a last step, you can remove the bull clip handels and keep them asside for later use.
Congratulations you're just completed the the Print Bed !