A New 3D Printer- Bambu Lab H2C

UMMD is still a great printer 9 years after I built it, but its 1mm nozzle makes it unsuitable for printing small, detailed objects, which I need to do more often than printing large objects. I could swap the nozzle for a smaller one, but then I'd have to go through the whole recalibration process, and the next time I want to print something big, I'd have to swap it again and recalibrate again. Ugh!

After surveying recent 3D printer offerings, and making a couple prints for the Arrakis 3.0 sand table on Bambu Lab machines at the Milwaukee Makerspace, I bought the Bambu Lab H2C that came with the AMS 2 Pro four filament dryer/feeder, and added the AMS HT filament dryer, several spools of filament, the engineering build plate, and the vision encoder plate.

Bambu Lab H2C with AMS HT and AMS 2 Pro filament feeders/dryers. There's a nice touch screen color display for local control, or you can control the printer from the wifi connected slicer, Bambu Studio. One especially nice feature is that the display shows a render of the file to be printed or that is printing.

The H2C/AMS 2/AMS HT has some interesting features. 

The vision encoder plate works with the toolhead camera to check and adjust squareness of XY motion.

3 cameras- one to monitor the print process and make timelapse videos, and two mounted on the toolhead to spot errors like layer shifts, spaghetti, etc., and to align the nozzles of the extruders, and XY motion.

Vibration compensation- at the start of each print, the machine vibrates the toolhead and print bed and automatically compensates for resonances, maintaining high print quality. The vibration is a little noisy.

Vortek hotend swapping system- a motorized rack that holds 6 induction heated nozzles. To be honest, I'm not so sure about the reliability of this system. Time will tell. Reviews I have seen that include prints having thousands of nozzle swaps indicate that it is reliable. The idea behind it is that you assign specific filaments in the AMS 2 Pro to specific nozzles, so during a multicolor print, there's no purge waste. Swapping the hotends reduces filament waste compared to swapping filament using a single or dual extruder alone, but it wastes a little bit more filament than a printer with multiple toolheads, such as the Prusa XL or the Snap Maker U1.

Induction heater for the right side extruder- the extruder that swaps hotends uses induction heating to bring the hotend up to print temperature in about 8 seconds. You'd think that would make swapping nozzles really fast, but cutting, retracting, and loading filament with the AMS take a lot longer. Using induction heating allows wireless operation of the hotends, which simplifies wiring going to the toolhead, and that bodes well for reliability.

Automatic venting/filtering of enclosure air- There's a HEPA filter, fan, and automatic vents that work to reduce VOCs and particles from some filaments. I have noticed that I still smell ABS when it is printing.

Automatic bed leveling (I know, they all do that these days). This is a particularly interesting topic to me as I spent a lot of time developing kinematic mounts for my printer's beds so that they wouldn't have to be leveled (trammed) before every print. In fact, I haven't trammed UMMD's bed in at least 2 years. In the H2C the bed is lifted using 3 screws all driven by one motor and a belt, however, the bed is leveled (trammed) using 4 corner screws (whaaaat? That's so 2012!) and is then secured by tightening some screws in slots on the side of the bed assembly. When a print starts the toolhead probes the bed in several places and makes a map of the variations in bed height. It can't physically adjust the bed tram- that would take three Z axis motors- so it just tweaks the Z axis position/extrusion during printing, based on the height map, probably just for the first few layers. It seems to work OK, as it was able to map the factory trammed bed right out of the box, without retramming.

The AMS HT and AMS 2 Pro are both capable of drying filaments and storing them in (almost) air tight enclosures and feeding the filament to the printer. The AMS HT can get up to 85C, while the AMS 2 Pro is limited to 65C, so the HT is good for drying filaments like ABS, nylon, and PC. Both units report temperature and humidity to Bambu Studio, and the HT displays them on the front of the unit. You have to periodically replace desiccant packs in the AMS units to keep them drying filament properly.

Bambu Lab filament spools come with an attached RFID tag. The AMS 2 Pro and HT both have RFID chip readers that will automatically configure the printer for the filaments in the AMS units, if they are Bambu Lab filaments. The RFID tag also allows the printer to monitor the quantity of filament left on each spool and communicates it to the slicer (Bambu Studio) so you won't run out mid print. The spools are perforated to expose more of the filament to the warm air when drying. You don't have to use Bambu Lab filament with the RFID tags, but then you'll have manually assign filaments to hotends, and watch the quantity of filament on the spools yourself.

When a print is started, the printer goes through a list of about 10 calibrations and adjustments before it actually starts printing. If you print a material that requires chamber heating, it can take 20 minutes before the printing actually starts after you hit the print button.

The filament swapping process, and several of the preparation steps before a print starts, move the toolhead back and forth which flips out the filament cutter levers located on the right and left sides of the printer, making a clunking sound each time it does. The vibration compensation, which causes the toolhead and the bed to vibrate for a few seconds at the start of each print, is also a little noisy. 

Swapping hotends/filaments can take 30 to 45 seconds, depending on the length of the PTFE tube between the AMS and the printer, which can add significantly to the print time if there are a lot of color swaps in the print. If you're printing 4 colors on each print layer, that's 4 filament swaps, adding a few minutes to each layer, even if the actual printing takes only 30 seconds or so for that layer. Multiply that by the total number of layers and you'll see that multicolor printing can be a time consuming process on this printer. It's best to keep the PTFE tube between the AMS and the printer as short as possible.

I have only made a few prints so far, using both PETG and ABS filament spools that I had in stock (not using the Bambu Lab spools yet), after drying the spools in the AMS units. The prints have been as close to perfect as any I have ever seen. There are no VFAs, nearly zero stringing in PETG prints, no warping, delamination, or lifting from the bed with ABS prints. The only defect I had was two different colors of PETG not bonding to each other completely in one print. 

The only real print defect I had among the prints I have done so far. This was easily repaired with a couple drops of ethyl acetate to solvent weld the unbonded joint. this was my second multicolor print, so go easy on me. There is a calibration to run that should prevent this sort of thing, but I didn't have the recommended filament colors for it, so I have not run it yet.

The printer has a USB A port on the top front left corner of the box that you can use to load/store print files, and store timelapse videos, which the printer will make either as a fixed time interval per image or a series of images made each time the print layer changes, with the extruder moved away from the print. The latter wastes some filament as the extruder has to be "repressurized" after each layer change. Time lapse video is turned on/off in Bambu Studio or at the local control screen on the printer. FAT-32 is the preferred thumb drive format. For drives >2 TB, it wants exFAT. Bambu Lab sells an inexpensive add-on kit to trigger an external camera to make timelapse videos.

There is a setting in BS that allows a spool of filament in the AMS 2 Pro to serve as a back-up, so if you have a little filament left on a spool and a fresh spool of the same filament, you can start the print with the almost-empty spool and the new spool will take over when the first one runs out. You can merge 2, 3, or 4 filaments in one AMS 2, so theoretically, could make a 4 kg print using a single AMS 2 Pro.

Filaments can be merged manually in BS using these selections. If two filaments are the same material and color there is another setting that allows the printer to merge them automatically. This looks like a good way to use up the remnants of multiple spools of filament.

I haven't tried TPU on this printer yet, but I did on a P1S at the makerspace and it came out horribly under extruded. I have read that the PTFE extruder feed tubes create too much friction with the filament and the result can be uneven filament feed resulting in poor print quality. However, you can bypass the PTFE tube and feed the filament straight into the extruder (as UMMD does) by making a bracket to support the filament spool over the open top of the printer. I have also read it's a good idea to reduce the maximum volumetric extrusion rate and print speed. I will be making such a bracket because I like to print TPU parts. TPU's toughness and flexibility are very useful properties. 

One of the first PETG prints I made on the H2C. All surfaces are as close to perfect as I have ever seen, and there were only a few hairs. 

The top of the tubes. Excellent print quality.

My first multicolor print, all PETG. This is a comb to smooth out the sand in the Arrakis 3.0 sand table. This print came out perfect. I later printed a similar comb for Arrakis 2.0 and had a problem with two of the colors not bonding.

I printed this 100 mm threaded (M100 x 6 mm from F360) cylindrical box and cover to check the roundness of circular prints. I had to print the cover twice in order to get it to fit right. I reduced the top and bottom surfaces of the threads in the cover by 0.1 mm each to make it fit. It seems as circular as can be. The printer had no trouble with printing the overhanging threads without any support material.

This is what the threads looked like in F360. The tips of the threads have plenty of clearance, but the upper and lower faces are too close together. I moved the upper and lower faces on the cover threads by 0.1 mm to loosen things up enough to screw the two pieces together.

A large, transparent ABS print in the H2C. No warping, no delamination, and the whole thing stayed stuck to the bed throughout the 8 hour printing process. The walls are 3 lines thick (1.26 mm) everywhere. This is a spool of filament I opened about 2 years ago, and dried in the AMS HT for 8 hours prior to printing. The surface shows some irregularities, but they are primarily optical effects from using transparent filament. The surface feels very smooth.

Ms. Kitty has no complaints about the print quality, either.