MakerBot Cupcake Heated Build Platform v2.0

Overview

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This is a new and improved heated build platform. It is lightweight, compact, lower cost, and sexier than the old heated platform. It is also easier to put together and simpler in construction.

The major breakthrough on this board is twofold:

1. We use a PCB for both the heater element and the support circuitry.
2. We use a lasercut aluminum heat spreader for uniform temperature.

After a bit of trial and error, we came up with an optimum trace resistance of about 4.5 ohms which gives us a 30 watt heater at 12v. This allows us to get up to 100C pretty easily (under 10 minutes).

Big thanks to Jordan Miller for his early support and research into heated build platforms. Thanks also to Nophead for his pioneering research into heated platforms and his work identifying appropriate materials to for printing on.

A few notes on the design:

  • There are 2 separate heater traces with their own sets of LEDs. We are using the larger of the two. Ignore the other set unless you want a lower power heater, in which case you simply use the opposite side of the board.
  • There is a small amount of SMT soldering required, but even that can be avoided if you absolutely are unwilling to try SMT. The only SMT part other than the thermistor is the 4.7k ohm resistor.

Get It!

Please support open source hardware and buy the kit from MakerBot Industries.

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Interface

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Heater Connection

The heater connection consists of two large solderable pads on the bottom of the pcb. They are marked with positive and negative polarity. The heater itself will run with either polarity, but for the leds to turn on, the wires must be hooked up with proper polarity.

Thermistor Connection

The thermistor connection also consists of large solderable connections. They are GND, 5V, and SIG. The rest of the thermistor circuit is placed next to these connectors. Once those components are soldered in, the connector cable can simply be soldered to the pads.

Part List

Build It

Building this PCB requires soldering. The majority of components are (relatively) large 1206 SMT parts. These can be soldered by hand, but we recommend you use a SMT soldering toolkit and solder the board with a hotplate.

Step 1: Apply Solder Paste

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Using the solder syringe, apply a dab of solder paste to each of the square pads for every single component.

Step 2: R2 - 4.7k ohm resistor

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Place the resistor with tweezers. Orientation is unimportant.

Step 3: C2 - 0.1uF ceramic capacitor

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Place the capacitor with tweezers. Orientation is unimportant.

Step 4: 1K ohm resistors

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There are 25 of these resistors. Place them on the appropriate pads around the perimeter of the board. These parts are optional, so do not panic if you lose one of the parts during assembly. Orientation is not important.

Step 5: Red LEDs

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There are 25 of these LEDs. Place them on the appropriate pads around the perimeter of the board. These parts are optional, so do not panic if you lose one of the parts during assembly. The arrow on the bottom of the part must point towards the outside of the board. There are also tiny green markings on one edge of the component that denotes the end that should point towards the outside of the board.

Solder With Hotplate

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Once all components have been soldered, put it on a hotplate and solder it up. Be very careful to not overheat the board. If you have never done SMT soldering before with a hotplate, it is a great thing to learn with a friend. Make sure to not go above 240C if possible.

Solder 3-pin Connector

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Solder the 3 pin wire to the 3 pin female connector. Some cables will not have a red stripe on one side. If that is the case, use a sharpie to mark one pin as a reference.

Insulate 3-pin Connector

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Once you have soldered the connector, insulate it with some electrical tape.

Apply Solder to connection pads

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If your pads do not have this much solder on them, add a bit more with a normal soldering iron.

Solder Wires to Pads

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Using a soldering iron, first tin the wires (put a bit of solder on the exposed wires). Then, solder each wire to its appropriate pad.

  • The red zip-cable wire should be soldered to +.
  • The black zip-cable wire should be soldered to -.
  • The reference pin on the 3-pin cable should be soldered to GND.
  • The middle pin should be soldered to 5V.
  • The last pin should be soldered to SIG.

Solder Extenders to Thermistor

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Trim about 50mm of wire from the red/black zip cable. Strip the ends and solder one to each thermistor wire. Make sure no wires are touching.

Insulate Thermistor with Kapton

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Use Kapton to insulate and separate the thermistor wires.

Attach Thermistor to Heated Build PCB

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Using kapton tape, attach the thermistor to the bottom of the PCB. Make sure the thermistor goes through the hole in the PCB and that the wires can reach the pads for R30.

Solder First wire to R30

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Make sure the exposed wire is trimmed to the same size as the pad and pre-tinned. Carefully solder it in place.

Mask Components

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Using Kapton tape, mask the other components with Kapton tape to avoid any solder bridge problems and make it easier to solder.

Solder second wire to R30

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Route the wire around to the top pad so it is not shorting on anything. Solder it into place

Mark Magnets

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In order to insure that your magnets have the proper polarity, place them on your Y stage so that they snap into place. Mark the tops with a Sharpie marker.

Insert Magnets

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Take the magnets off the heated build platform and take care to insert them into the wooden build platform. Be careful to preserve polarity and orientation. Make sure they are pushed down all the way to the bottom (non-text) side of the platform and put a dab of super glue on them from the top side.

Insert M3 x 16 bolts

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Insert each of the 6 M3 bolts from the bottom side of the wooden build platform. Thread one nut on each bolt and tighten it down. The nut is very important as it will provide the spacing between the wooden build platform and the heated board.

Place Heater PCB

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Place the heater PCB 'upside down' over the bolts. All the silkscreen markings and components should be on the bottom facing the wooden build surface. The wires should be coming out the upper right hand side.

Apply thermal paste

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We have provided a single use packet of thermal paste with good properties. If you want to get fancy, you can pick up some high-end paste, but the difference will be negligible. Make sure to squeeze it a bit to fully mix the paste before applying. Take care to avoid the thermistor hole as it can affect thermistor readings.
Just to be on the safe side, cover the PCB pads with Kapton tape first.

Place Aluminum Heat Spreader

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Place the heat spreader over the bolts. Take the remaining 6 M3 nuts and bolt it into place.

(You can try using shorter bolts if you have any - the provided bolts can possibly interfere with the nozzle/insulation. Shorter bolts can add between 5-10mm of XY build space - jr.operator204)

Apply Kapton Film

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Before applying the film, clean the surface with a mild soap and water.

The kapton film is a nice thick 0.005". Peel it off from the backing and carefully apply it to the aluminum. Start pressing it into the platform from the center and move outwards. Try to push out any bubbles that may form. If they are difficult to push out, pop them with a tiny needle and squeeze the air out. Don't spend too much time on this. Small bubbles will dissipate after a few heat cycles of the platform.

Users have had success with a rough Kapton surface, so you should sand paper to rough up the surface. 220 grit paper has been tested, but you may have success with other coarsenesses.
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Hook up to Extruder Controller

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Wiring up the platform is pretty simple. We recommend routing the wires out the back of the MakerBot and between the acrylic Z stage and the wood of the top/back. Wiring is as follows:

  • Red zip cable wire - A+
  • Black zip cable wire - A-
  • 3-pin female connector - A6 with ground wire to the top

In order for the thermistor wire to be clear of the top of your MakerBot, bend it at a 90 degree angle.

Setting up the software

In order for the heated build platform to work, you need to do a couple things.

  1. Upgrade your motherboard and firmware to the latest versions
  2. Select the 'Cupcake CNC w/ heated build platform' in the Machine -> Drivers menu in ReplicatorG.
  3. Replace your skeinforge/skeinforge_tools/start.txt file with the following text
  4. Replace your skeinforge/skeinforge_tools/end.txt file with the following text

Important: you will need to re-slice any previous files for the changes to take effect.

start.txt

(beginning of start.txt)
M104 S220 T0 (Extruder Temperature to 220 Celsius)
M109 S110 T0 (Heated Platform Temperature to 110 Celsius)
M107 (fan off)
G21 (Metric FTW)
G90 (Absolute Positioning)
G92 X0 Y0 Z0 (You are now at 0,0,0)
(You have failed me for the last time, MakerBot)
G0 Z15 (Move up for warmup)
M108 S255 (Extruder speed = max)
M6 T0 (Wait for tool to heat up)
G04 P300000 (Wait 5 minutes)
G0 Z0    (Go back to zero.)
(end of start.txt)

end.txt

(end of the file, cooldown routines)
M104 S0 T0 (temp zero)
M109 S0 T0 (platform off)
M106 (fan on)
G92 Z0 (zero our z axis - hack b/c skeinforge mangles gcodes in end.txt)
G1 Z10 (go up 10 b/c it was zeroed earlier.)
G1 X0 Y0 Z10 (go to 0,0,z)
M18 (turn off steppers.)

Using It

Using the heated build platform will allow you to print much larger things with higher quality and significantly reduced warpage. It does take a bit of getting used to so be patient for your first few builds as you get used to it.

Warmup

The most important thing is that you must have that platform fully heated before you use it. The start.txt file adds a 10 minute warmup period to attempt to guarantee that your platform is at the proper temperature. If this does not work for you, increase the warmup time or pre-heat the build platform manually through the control panel.

First Layer

Printing onto hot Kapton with ABS is a bit trickier than Acrylic at room temperature. The ABS does not stick quite as well, so there are a few options to make this easier:

1. Squish the first layer down so it sticks better.
2. Print with a raft and squish it down nicely.
3. Print the first outline slowly (skeinforge does not handle this yet)*

  • ReplicatorG now implements the Raftless plugin in Skeinforge (standard) which automatically slows down the first layer.

NOTE: I have had very good luck sanding the kapton down to give it some tooth which makes things stick to it better! - Bre

Build Surfaces

There are a few other materials that may work better for printing. Here is a table of materials / temperatures and printing results. As you can see, the tables are incomplete. If you are so inclined, we would really appreciate help expanding the data on how materials work and at what temperatures.

ABS Plastic Adhesion

50C 60C 70C 80C 90C 100C 110C 120C 130C 140C 150C
Kapton Poor Poor Poor Poor Moderate Good Excellent The New Hotness Excellent Good Not So Hot
3M Painters Tape ?? ?? ?? ?? Poor* Poor* The New Hotness Excellent Fair Fair ??
1/8" Acrylic ?? ?? ?? ?? ?? Very hard Too stuck! Too stuck! Too stuck! ?? ??
Glass Poor Poor Poor Poor Poor Poor Poor Poor Poor Poor ??
  • it might just be my imagination, but the blue masking tape seems to work better the first time you use it.

Some other surfaces that have been tried with ABS:

  • Avery full-sheet labels - sticks OK but tears when build is removed
  • LD glossy sticker paper - sticks extremely well but adhesive fails at high temperatures
  • grill paint - doesn't stick
  • PET - doesn't stick
  • matte acrylic lacquer - sticks but degrades after 1 or 2 builds
  • duct tape - doesn't stick

PLA Adhesion

50C 60C 70C 80C 90C 100C 110C
Kapton Moderate Good Excellent ?? ?? ?? ??
3M Painters Tape ?? ?? ?? ?? ?? ?? ??
1/8" Acrylic ?? ?? ?? ?? ?? ?? ??
Glass Moderate Good Excellent ?? ?? ?? ??

Troubleshooting

My HBP "flickers"…

This means that it is working properly….when the red lights are off, the platform isn't heating, when they are on it is heating…as long as it isn't flickering fast or flickers when you tap it or just turning off and not turning back on (see below) then that just means its working properly.

My HBP turns on for a little bit and then shuts down. What do I do?

This design is pushing the Gen3 Extruder controller to its limits. What is happening is that the MOSFET controlling the electricity to the HBP is overheating and then shutting down.

There are a couple things you can do:

The quick and dirty hackers way

Wire it up to the 12v directly. During testing the board would level out at around 110/120C. This is actually just about the ideal range for ABS. Keep in mind that you'll need to be much more proactive about turning the power on and off since every time your power supply is on, your print stage will be hot. Of the wires coming off the ATX power supply, the yellow ones are 12V and the black ones are Ground. Wire appropriately.

The proper gentlepersons way

  1. Check that the big tab on the MOSFET has a good connection to the pad. If it doesn't look good, just take a soldering iron and put it on there for a few moments to reflow the solder.
  2. Assuming your MOSFET is soldered properly, the next best thing is to run a fan over it. Getting air flowing over the extruder controller PCB will almost always keep it from shutting down. You can even wire it up to the Fan pin and use the M106/M107 commands to automatically turn it on and off for your build.
  3. If using a fan is not an option, you may want to try heatsinking. You'll need to get some sort of tiny heatsink. Options include modifying an existing heatsink, using a wad of aluminium foil, etc. You'll want to attach it to the the mosfet with some high temp adhesive. I'd recommend JBWeld as it's easy and cheap to aquire (hardware store) Here is a link to one from Digikey http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=CA&WT.z_homepage_link=hp_go_button&KeyWords=HS227-ND&x=0&y=0
  4. If all else fails, you can try to switch to the Fan pin. First step is to switch the HBP wire to the other mosfet. Now go into the control panel and turn the fan on. If it doesn't die after a few minutes, then you're good. Your options now are to either a) modify the start/end to control the mosfet at the beginning/end and just run it full-blast or b) recompile the ArduinoSlave firmware and switch the fan and heater pin definitions so you can have temperature control. This is a bit beyond the scope of this wiki, but is within the realm of the possible.

Alternate Wiring - Relay

We attempted to drive the board from constant power with the following results:

- 5v: temp went to 68-70 degrees and held
- 12v: temp went to 140 degrees and continued rising (others report it going to 190 and above)

Driving the board as directed above didn't work. Adding the specified Digikey heat sink to the MOSFET didn't help. We chose to drive the HBP with a relay.

Relay wiring details:

85: goes to extruder controller "A-" port
86: goes to 12v positive (constant)
87: goes to the red wire on the HBP
30: goes to 12v positive (constant)

The black wire on the HBP goes to ground, not on the relay. The relay we used was a small Hella relay, probably for a car horn. The extruder controller provides constant power, and switches ground. Be sure to look at the diagrams for your relay before hooking anything up.

Radio Shack has this relay: 12VDC/30A SPST Automotive Relay - it works perfectly, following your instructions. They also sell the quick disconnect crimp-on connectors that fit the tabs on the relay. It took me about 10 minutes to get this mod up and running.

I made a basic wiring diagram for hooking this up, should help clarify things and links to a higher resolution version:

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Alternatively, you can get a Relay Board designed specifically for this purpose, that carries two of such relays.

Alternate Alternate Fix - MOSFET replacement

I don't own a MakerBot, but I have a suggestion for those having problems with the MOSFET overheating on the red board. I looked up the schematics for that board in the wiki, and see that the SOT-223 MOSFETs specced for that board are not logic-level gates. So, when they're being turned "on" with 5V, they are not actually fully on and are dropping a considerable voltage drain-source at high current. Replacing them with a logic-level MOSFET such as the NDT451AN, available on Digikey for about $1 each, should help tremendously with how hot those MOSFETs are getting when driving high current. The R_ds with 5V on the gate should decrease by an order of magnitude with this replacement part, and correspondingly the power dissipated as heat by the MOSFET will decrease by an order of magnitude. (Disclaimer: Like I said, I don't own a MakerBot (yet), so I can't do this mod myself to verify - but from experience in driving high currents in other projects, this should fix the problem).
-Rob_EE

My HBP temperature now reads 255 all the time

It is fairly common after use for the sensor wires (the grey ribbon wires) to break at the attachment point to the HBP due to repeated flexing during use. This causes the thermistor to open-circuit and give the maximum temperature reading. If this happens during a print, the platform will cool and the object will probably detatch and slide off the platform. It is fairly easy to re-solder the sensor wires, but some preventative action should be taken to reduce the flexing at this point, such as:

Files

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The Heated Build Platform v2.0 is licensed under the GNU GPLv3 or later licenses. If you modify the designs, please keep in mind you need to release any changes you make to them.

  • You can download the individual files from Thingiverse.
  • You can download the source code .zip from Google Code.

Schematic

The schematic is very basic, but here it is for your perusal:

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Modification

Here is what we found to make the most awesome build surface for ABS on the heated build platform, 4" wide 1 mil thick Kapton tape:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=380034872037

We took the heated build platform, removed the thick kapton (which had been sanded, and the extruder had dived in and dinged a corner), cleaned the aluminum, countersunk the holes, found the correct flush head screws at Ace Hardware, reassembled it, then planed it flat (600 grit sandpaper taped to flat glass) until the aluminum build surface was perfectly flat.

Then we put this tape on, without sanding. We were careful to work from one side and make sure there are no bubbles. The plastic seems to stick wonderfully, and the part just pops off.

If the build tape gets dinged up, we just peel off the old one and stick on a new one.

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Painters Tape

After seeing this photo:

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I talked to Bre about it and he said that he's been running the blue painters tape on the HBP for close to 100 hours without a problem. I started using it this week for ABS and found that it sticks better than either new or sanded kapton in my setup.

Unless otherwise stated, the content of this page is licensed under GNU Free Documentation License.