All-Metal Hotend (with Accelerometer!) and Berd-Air Layer Cooling

I upgraded my printer with an all-metal hotend and a new cooling system!

The new Hotend is the HE280, from the people that designed my printer. It wasn't immediately obvious to me what the new max temp was (my old hot end maxed out at 235, and some all metal hotends go up to 300). It turns out the recommended max temp is right there in the name: Hot End 280 - 280°C is the max temp. This will allow me to print in PETG and High Impact PolyStyrene (HIPS) and even nylons!

Probably the most important part of this upgrade is the accelerometer that's built into the new hot end. This accelerometer allows super easy calibration of the Z-height (and easier bed leveling). The accelerometer can detect when the nozzle "taps" against the glass bed:

I have never had the bed level calibrated this well before:

Source file: https://www.thingiverse.com/thing:50505

The new cooling system is much more compact than the old fan system. It's the Berd Air from The Maker Hive. It uses a vacuum pump running in reverse to pipe cool air down to the nozzle. Ideally, all the cool air hits the deposited plastic, and none of it hits the hot nozzle. Here's a picture of the air pump, nestled nicely in rat's nest of wires:

I also added some bungie cords to keep the wire harnesses from interferring with the endstops:

Installing the Thermal Elements

Heated Build Plate (also called the "bed"):

The heated bed is a large, 12-inch-diameter PCB, with one giant electrical trace arranged in a spiral. I haven't measured it myself, but it's supposed to have approximately 1 ohm of resistance. The wires that were in the kit for the power supply are only 18-gauge, carrying around 10 amps of current. I should have tossed the 18-gauge wires in my supply drawer and just used 14-gauge wire from the start, but that's going to have to be a future upgrade. EDIT: I upgraded to 14-gauge wires. I don't think the terminals on the control board could have taken anything larger, but 14 fit fine. Unfortunately, no noticeable performance improvement on bed heat-up times.

There is also a thermistor and an LED - the bed temperature is controlled by a Pulse-Width modulated power supply, and the LED flickers right along with the pulses to let you know if the heated bed is on or not.

Extruder Hot End:

Once the RTV silicone set up, I crimped the electrical connections and insulated all the conductive parts with Kapton Tape:

I ran the wires for the effector platform according to the directions:

And then make the connections to the hot end:

...which turned out to be a mistake. The hot end is supposed to sit on top of the effector platform, with just the nozzle poking through to the bottom of the effector platform. Instead, I had this:

I had to disassemble the hot end and feed the parts up through the effector platform to get the proper result:

(Actually, at this point I still had the effector platform upside down. But I would not discover that until later, when I tried to install the cooling fans.)

Here's what it looks like with the thermal elements installed:

Hot End Assembly

The hot end included in my kit did not have a port drilled in it for the thermistor.

I contacted SeeMeCNC support. They offered to ship me a new one, but also sent me dimensioned drawings so I could drill it out myself. I didn't think it was worth making them deal with shipping a new one when fixing the problem was so easy. I just drilled it out by hand.

Once that was done, I inserted the thermistor and heating resistors, and cemented them in place with high temperature RTV silicone:

One of the forum members recommended threading the thermistor port and using a brass bolt to hold the thermistor in place. This would make it easier to swap the thermistor out if it failed. It seems that thermistor failures are pretty rare, however, and I'm expecting to replace this hot end with an all-metal version within a couple years, which would probably require a thermocouple to handle the higher temperatures, anyway.