Bluetooth Makerbot

Wintermute is a Bluetooth Makerbot!

I have actually had this setup for a while but forget to post about it.

I connect to Wintermute, my Cupcake CNC, over Bluetooth using a Sparkfun Bluetooth Mate. It has the same pinout as the FTDI cable usually used to control the Cupcake. This is great except the VCC pin on the Cupcake motherboard is not connected. (This is smart … So you don’t accidentally try to power the whole ‘bot off of your USB port.)

So, I used jumper wires (I think these from Adafruit would work great too) to connect to the normal port, except I used the power pin (bottom left) from the ISP port directly below it. (Click on the photo above to see a larger version.)

Here’s an article where they used a BlueSMiRF Gold module from Sparkfun. It’s a very similar module, differing mostly in the pinout. In that article they did a little more surgery than I’d prefer in order to get to the power, but it’s a good solution nonetheless.

I left off the control pins (RTS & CTS) because they don’t really do much but goof up communications anyway.

Software setup

First you pair your OS with the BTMate. This will be different for every OS. (Hint: The default code is ‘1234’.)

I’m on OS X, so I connect via the screen command in Terminal.

screen /dev/tty.FireFly* 115200

Once connected, type (hit return at the end of each line, the last one is optional):

$$$+
SU,38
SQ,16
SN,Wintermute

If you're using screen, disconnect by typing Ctrl-a, then ‘k’.

You should now be able to start RelicatorG and choose the BT module. (Note on OS X: the cu.* and tty.* forms are functionally equivalent, so use either one.)

I haven’t had any luck with printing directly over the Bluetooth connection, the latency is just too high and rounded corners become huge blobs. However, warmup, noodling, and starting a print-from-SD works great.

Good luck!

-Rob

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LED Board Connector

So I etched the controller board for Wintermute's LEDs. I wanted to connect it directly to the power source, which is a standard PC power supply, so I did a litle carving and came up with this design.

I'll do a full post on the controller board later.

iPhone drawn concept: “Swiper”

I sketched up a quick idea for a mechanical oozebane. This sketch is obviously not dimension or positional accurate.

The concept: Have a arc of very thin, rigid metal (or other material that can handle a lot of heat) that covers the end of the extruder nozzle of a Makerbot Cupcake CNC, a Reprap, or any other plastic-extruder-based CNC machine. The metal will get hot with the extruder and hold the molten plastic in and molten.

It works like this:

Before the extruder starts to extrude, the electromagnet will charge pulling the swiper around and out of the way of extrusion.

When the extruder stops, the magnet will be shut off and the springs will both cut the filament and stop the oozing.

The common solution to this is to run the extruder backwards for a small period of time after stopping. This works a lot better if you have a stepper motor or other means of precisely controlling the motor, but still has a few drawbacks:

The first is that the filament still has a string out of the nozzle that is dragging more of the molten filament out the further you get from the stopping point. Since the motor is off, this molten filament won't be completely replaced and will cause a gap the next time the extruder starts.

The second is that the filament will have a small portion that is exposed to cool air, making a hardened “booger” that will be dropped as soon as the extruder starts again. There's also a widening bubble of air between where the last of the filament hits the melting zone and that is falling slowly. These two things will make a lump followed by a gap after every stop/start of the extruder.

So, this swiper aims to solve both of these. First by cutting the filament off clean and second by keeping the filament hot and ready without forming a bubble.

I am yet to make a prototype, but I think I'm close. I'm totally open to any ideas.

-Rob

Sent from my iPhone.

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