Extruding Quality
Extruders are a key part of any FDM printer, responsible for pushing the filament to the hot end. They’re also key to a print’s success, as a bad extruder can cause a host of printing problems, including under-extrusion.
There are many contributors to an extruder’s performance on a printer, including the arrangement, the parts, the system, the gear ratio, and more. Additionally, extruders can be arranged in two ways on a 3D printer: a Bowden or a direct drive system. The former separates the extruder and the hot end, guide filament via an exposed Bowden tube, while the latter pushes the filament directly into the hot end.
How It Works
In most 3D printers, the extruder contains a toothed or hobbed gear directly attached to the axle of the extruder motor. A gear ratio separates the extruder motor axle from the toothed gear using joining gears with a difference in the number of teeth to boost either torque or speed. Usually, extruders use a speed-reducing, power-increasing gear ratio.
A Bondtech mini-geared extruder (BMG) is a high-quality extruder from the well-known Bondtech, which specializes in 3D printer extruders, nozzles, and other accessories. The extruder has a power-increasing gear ratio for its dual drive setup and comprises many high-quality components from strong materials. Furthermore, Bondtech’s extruder can be easily arranged in either a Bowden or direct drive setup. If you’re looking to get the BMG for your printer, expect to pay around $80-90.
Before we get into the features and overview of this extruder, it’s important to note that there are imitation devices out there, in many cases making use of the names “Bondtech” and “BMG”. If you see them, be aware that, apart from often using inferior materials and parts, they’re also unfairly taking advantage of the BMG, which is not an open-source product.
Features
The BMG extruder has many different features that collectively make it possibly one of the best extruders out there. Let’s take a closer look!
Dual Drive
As we mentioned, the BMG uses a dual-drive system, where two gears come from opposite sides of the filament path. The gears essentially hug the filament from two sides instead of one like a single-drive extruder would.
A dual-drive mechanism, like the one in the BMG extruder, provides better feeding force, which improves extrusion on your 3D printer. This system is useful for printing all types of filaments but especially flexible filaments, because they can’t bend their way around the gears.
Gear Ratio & Tension
The BMG uses a 3:1 gear ratio, which further improves the feeding force on your printer. That’s because the gear ratio reduces speed while increasing torque and pushing power, resulting in better extrusion and flow for the nozzle.
You can also adjust the tension of the toothed gears on the filament by loosening or tightening the tension screw on the extruder’s main body. Adjusting tension can help against extruder jams and filament grinding and also improve retraction to prevent stringing. The BMG extruder also includes a quick-release lever to allow you to easily and rapidly switch filaments.
High-Quality Parts
BMG extruders are made from precision-focused and high-quality components. Bondtech mentions that the housing components, such as the casing parts, are SLS 3D printed nylon.
The toothed gears are also made of brass rather than steel, as brass is more corrosion-resistant and suffers fewer issues from reduced oxidation than steel. Bondtech also boasts that the manufacturing methods make the parts very dimensionally accurate and strong.
Compatibility
The BMG extruder assembly is overall very compact and lightweight, especially considering the number of features included. Unfortunately, the Bondtech extruder only supports 1.75-mm diameter filament, meaning you can’t print 2.85- or 3-mm filament.
Besides limitations with filament size, the BMG is quite accommodating and can fit any motor with a 5-mm shaft, including the widely-popular NEMA 17 stepper motors. The extruder assembly also has a few different mounting holes, so you can attach it to different carriages. If you can’t fit it on your printer, you can probably find a 3D printable mount online.
The Bottom Line
Overall, the Bondtech BMG extruder is a great extruder for any 3D printer, even delta ones. Its dual-drive system is advantageous for printing flexible materials, especially compared to single-drive extruders. Dual-drive extrusion can also help with retraction, as pulls and pushes will be more forceful and from both sides of the filament.
The BMG extruder is made up of many high-quality parts, but it’s still pretty lightweight and compact. The extruder’s low weight reduces ringing if you’re using it for a direct drive setup. The only potential downside of its compact assembly is that it can be tricky to work the many small components like the drive gears.
The 3:1 gear ratio on the BMG provides more torque for your 3D printer’s feeding system. Even with the increased torque, according to one customer review, the extruder doesn’t damage the filament by overdoing the feeding process. While this gear ratio can reduce under-extrusion and flow issues, you may be limited in speed because the motor has to spin three times as fast to perform only one rotation.
The extruder’s adaptability makes up for the speed limitations, as it can fit any motor with a 5-mm shaft, including all NEMA 17 stepper motors. The extruder also has a built-in fitting for an E3D hot end, but you can still attach other hot ends with 3D printable mounts.
Bondtech offers variations of their extruders to fit on a wide range of printers from brands like Creality, Prusa, MakerBot, Flashforge, and more. Even though it may look like a quick and easy upgrade, some reviews point out that installing this extruder required a large amount of work because of mounting and adjusting firmware to account for the gear ratio.
Specifications
Although there aren’t many specs to discuss for an extruder, the BMG extruder has a few worth noting:
- Motor compatibility: Any NEMA 17 motor; 5-mm shaft
- Hot end compatibility: All E3D hot ends; other brands’ hot ends work with custom mounts
- Setup: Bowden or direct drive
- Filament diameter: 1.75 mm
- Gear ratio: 3:1
- Mechanism: Dual drive
- Other features: Adjustable tension screw, quick-release lever
Where to Buy
You can purchase a genuine Bondtech BMG extruder from one of these online retailers:
Lead image source: electricAGENT via Reddit
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