Resurrecting old Makerbot Cupcake. Print bed trouble.

[mason sage]

Hey Guys, first of all Thank You for taking your time to help me out. 

So anyways, my teacher gave me this 3d printer (makerbot cupcake v1.0) and its just a complete mess of wires, everything was put together incorrectly. So there is a heated printer bed with this one, and there are two wires coming out from the bottom of the bed. Im assuming one for thermistor and one for heating element. problem is, I don't know which one is which. any was on how to find this out? there are two pins that come out, one with 2 leads and one with three leads... Why wouldn't hey both have two? 

Also there is a DC motor at the front of the Print bed, that turns some gears for what looks like a roll to wind up the stuff that it is printed on. What is this whole assembly for?

Once again, thank you for your help:)

[Dan Newman]

On 25/10/2014, 3:28 PM, mason sage wrote:
> Hey Guys, first of all Thank You for taking your time to help me out.
> So anyways, my teacher gave me this 3d printer (makerbot cupcake v1.0) and
> its just a complete mess of wires, everything was put together incorrectly.
> So there is a heated printer bed with this one, and there are two wires
> coming out from the bottom of the bed. Im assuming one for thermistor and
> one for heating element.

That would require four wires, not two. Thermistor needs two wires. The
heater needs two wires. At best one of these two wires can be shared
making it only three wires, but that was not done (nor is it a good idea
to do that either).

> problem is, I don't know which one is which. any
> was on how to find this out? there are two pins that come out, one with 2
> leads and one with three leads... Why wouldn't hey both have two?
> Also there is a DC motor at the front of the Print bed, that turns some
> gears for what looks like a roll to wind up the stuff that it is printed
> on. What is this whole assembly for?
> Once again, thank you for your help:)

This sounds like the old Automated Build Platform (ABP). My advice is to dump it
or at least not use the belt portion of it as it worked very poorly and
lead to poor print quality, especially when printing tall prints.

For further information, you need to look at the archives for the
Thing-o-Matic and Cupcake. Thing-o-Matic because that's where the
directions are most likely found for the ABP which you will want to
convert to a HBP (heated build platform).

https://mindtouch.makerbot.com/Archive/Thing-O-Matic/Guides_and_Instructions
https://mindtouch.makerbot.com/Archive/MakerBot_Cupcake_CNC
https://mindtouch.makerbot.com/Archive/MakerBot_Documentation_Archive

Dan

[Dan Laskowski]

Mason -- where are you located?  Sometimes somebody local can help.

[Jetguy]

Sorry for being slow to reply on this, I don't visit often.

The Cupcake heated bed DOES have 3 wires for the thermistor matching the 3 header pins for the A(analog) 6 input on the extruder controller board. This is because there are 3 wires, Ground, 5V, and signal return from the thermistor because a local 4.7k pullup resistor is ALSO located on the HBP PCB. FYI, if you look at the heated bed PCB, the pins are clearly silkscreen labeled on the bottom side.

The other 2 pin header is the heater circuit. That goes to the assigned screw terminals on the extruder controller.

The instructions had users use 2 CD rom audio cables but they cut on so it was just the 2 wires and the other one was left with 3 wires even though the plug ends have 4 pin sockets.

Also of note. The extruder controller temp sensor for the HBP and extruder head checks to make sure a PROPER thermistor circuit is connected at power on. If at anytime the thermistor circuit connection is broken or is miswired, then the extruder controller with report 1024C and LOCKOUT heating of the failed system until the main system power is turned off and on again. This is for your safety to prevent a heater from getting stuck on.

[Jetguy]

John Abella has a nice page with some pictures here http://www.abella.net/?p=602

[mason sage]

Sorry for not seeing this earlier, I work on projects on my weekend. You guys rock, thanks for your help.