Bowden extruder

Bowden extruder DEFAULT

Advantages and Disadvantages of Direct and Bowden Extrusion

One of the most important parts of a 3D printer is the extruder. This pushes filament to the hot end to be melted and extruded. There are three key parts that all extruders share: a stepper motor, a driver gear, and an idler. While the components of extruders are all the same, there are two different types of extruders: Direct and Bowden.

Direct Extrusion Diagram
From: Future Electronics

Direct Extrusion

The difference between Direct and Bowden extruders is the location of the extruder in relation to the hot end. Direct extruders, as the name implies, are directly attached to the hot end and are a part of the print head.

Since Direct extruders are located above the hot end with little space between them, a Direct extruder keeps the distance that filament must travel from the extruder to the hot end to a minimum. This leads to the main advantages of this style of extrusion.

Better Extrusion and Retraction

Since there is less distance for the filament to travel, extruding and retracting the filament becomes much easier. Essentially, the filament is more responsive to the extruder. This means that there is less stringing and oozing that occurs because of worse retraction and leads to a higher quality print.

Smaller Motors

In addition, the closeness of the extruder to the hot end means that less torque is required from the stepper motor than in a Bowden extruder. Because of this, the stepping motor does not need to be as large or as powerful as in a Bowden setup. However, a large motor can provide more power with a Direct extruder, which can be beneficial.

Wider Range of Filaments

Direct extruders are also able to effectively print a wider range of filaments, most notably, flexible and abrasive filaments. While flexible filaments can work with Bowden extruders, Direct extruders can print them more effectively. This is because a Direct extrusion system is more constrained.

Disadvantages

However, the location of the Direct extruder also leads to its main disadvantages. The weight of the extruder on the print head can lead to several problems. Since the print head is constantly moving, additional weight to move around could lead to backlash, banding, overshoot, or frame wobble. Additionally, the size of the extruder can be disadvantageous for some 3D printers, as it makes up a majority of the print head.

Bowden Extrusion Diagram
From: start3dprinting.com

Bowden Extrusion

The opposite of Direct extruders, Bowden extruders are not attached to the hot end or print head. Instead, the extruder is removed from the print head and is most often attached to the printer body. The filament is then fed to the hot end using a Bowden tube.

Lighter, Faster, and More Accurate

Like the Direct extruder, many of the advantages and disadvantages come from the location of the extruder in relation to the print head. The largest advantage is the reduced weight of the print head. Since the extruder is removed from the print head, there is less weight on the print carriage.

Also, because the print head is lighter, a printer using a Bowden extruder can print faster, more accurately, and more precisely. This can result in either higher quality prints or quicker prints, as the print head can move at higher speeds. Additionally, Bowden extruders are more compact and take up less space than Direct extruders.

Disadvantages

While Bowden extruders can increase print speed and reduce the print head weight, there are several disadvantages that make them less appealing than Direct extruders. For one, they cannot use as many filaments as effectively as Direct extruders. While they can print flexible filaments, these filaments tend to bind in the Bowden tubing. Additionally, Bowden extruders cannot use abrasive filaments because these filaments will wear away the inside of the Bowden tubing.

Bowden extruders also need a greater retraction distance and a more powerful motor than a Direct extruder. This is because of the increased friction on the filament in the Bowden tube, which can lead to a less responsive extrusion system, more stringing and oozing on the print, and more resistance and drag with the filament.

There are some companies that are trying to solve some of these issues. One example is Capricorn, which makes a Bowden tube that is supposedly better at printing flexibles and puts less friction on the filament.

Diagram of Bowden (left) and Direct (right) extruders.
From: 3Dprinting.com

Which One Should You Choose?

There are several factors to consider before choosing between a Direct and Bowden extruder. With a Direct extruder, it is important to have a stable printer frame to ensure that the print head can handle the extra weight. With a Bowden extruder, a completely constrained extruder system is important to ensure the filament travels where it should without binding.

It is also important to consider which type of printer you have. A Delta printer needs to have a light print head and must use a Bowden extruder. A Cartesian printer could use either but should have a good frame when used with a Direct extruder. Also, a printer with multiple extruders works best with a Bowden extrusion system.

Finally, the use of flexible or abrasive filaments and the need for quicker printing speeds should also be considered. If you plan on using flexible filaments or abrasive filaments, then a Direct extruder would work best. If you want speed and are using a more standard filament, then a Bowden extruder will work just as well.

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Sours: https://www.fargo3dprinting.com/advantages-disadvantages-direct-bowden-extrusion/

3D printer extruder

On a Bowden design, the feeding mechanism (here indicated with two roller wheels) often sits relatively far away from the hot end part of the extruder.

A Bowden extruder is a type of filament feeding mechanism used in many FDM 3d printers that pushes filament though a long and flexible PTFE (Teflon) tube to the hot end.[1] An alternative type of extruder which is also widely used in filament 3D printers is the direct drive extruder or direct extruder, which sits closer to the extruder hot end.

Advantages[edit]

Bowden type extruders are easier to swap since they are outside the print head. They also have less chance of tangling the filament while it unwinds from the spool. Additionally, they reduce the mass of the extrusion carriage because it doesn't have to hold a stepper motor. This allows for faster changes in print head movement direction, increased print speed, increased accuracy, and decreased instances of artifacting or ghosting along the x and y axes.

Disadvantages[edit]

One disadvantage is that because Bowden extruders push filament through a long and curved tube, more friction must be overcome compared with direct drive extruders. To partially mitigate these friction forces, the tube is made of PTFE, which has a low coefficient of friction. Flexible filaments do not print well because the filament flexes inside the tube and clogs up the machine.

Another disadvantage is that the feeding distance is relatively long, and thus the resistance is high, meaning the stepping motor of extrusion is required to have a higher torque. [2]

See also[edit]

References[edit]

Sours: https://en.wikipedia.org/wiki/3D_printer_extruder
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Direct extrusion and Bowden systems

Array ( [id_post] => 94 [meta_title] => Direct extrusion and Bowden systems [meta_description] => Two of the most important components of a FDM 3D printer are the extruder and the hotend. There are two types of FDM 3D printers depending on how these two elements are located: Direct extrusion systems and Bowden systems. In this article we explain what each one consists of and how to decide which one is the ideal for each user. [short_description] => Two of the most important components of a FDM 3D printer are the extruder and the hotend. There are two types of FDM 3D printers depending on how these two elements are located: Direct extrusion systems and Bowden systems. In this article we explain what each one consists of and how to decide which is the ideal for each user. [meta_keyword] => [content] =>

One of the most important elements of a 3D FDM printer is the set consisting of the extruder and the hotend.

The hotend is the element intended to melt the filament so that it can flow through the nozzle, while preventing heat from being transmitted outside of the so-called hot zone.

For this, the hotels generally have four parts:

  • The nozzle or nozzle: It is the element through which the molten filament flows to deposit in the piece. Its diameter determines the diameter of the extruded material thread and therefore the resolution of the printer in XY.
  • The heating block: It is the element in charge of heating the nozzle up to the printing temperature and keeping it stable.
  • The heat break: Serves as a thermal break bridge. Separate the hot zone from the cold zone.
  • The heatsink: Its function is to keep the cold zone refrigerated, dissipating the excess heat transmitted by the heating block.

Hotend

Image 1: Temperatures inside the hotend. Source: E3D.com

On the other hand, the extruder is responsible for pulling the filament into the hotend so that sufficient pressure is generated inside the hotend so that the molten material flows constantly and homogeneously through the nozzle.

Extrusor directo

Image 2: Direct extruder. Source: E3D.com

There are currently two ways to combine the hotend with the extruder: direct extrusion systems and Bowden systems.

Directo vs Bowden

Image 3: Printer scheme with direct extruder and bowden. Source: Recreus.com

In direct extrusion systems the extruder and the hotend form a single element, minimizing the distance between the pulling point and the nozzle.

In Bowden extrusion systems the extruder is held fixed in the frame of the 3D printer and pushes the filament into the hotend through a tube called a Bowden tube.

Although there has been much discussion about which of the two systems is better, both have great advantages, as well as some disadvantages. Choosing the most appropriate one will depend on several factors such as the type of material that is commonly used, the printing speeds or the quality of the printer's frame.

Retractions

When the extruder pushes the filament toward the hotend, the filament compresses creating the necessary pressure inside the nozzle for the molten material to flow properly. However, when we do not want to extrude material, it will not be enough to stop pushing the filament, since the residual pressure due to compression will make the material continue to flow. This is why every time the hotend is moved to a new position and it is not necessary to add material, the filament must be retracted the necessary distance so that it can decompress and release the pressure inside the nozzle. This is known as retraction and is of great importance in the 3D printing process.

Retracciones

Imagen 4: Esquema de la retracción. Fuente: sublimelayers.com

Since plastics are generally not rigid materials, the greater the distance between the extruder and the hotend, the greater the compression of the filament required to achieve adequate pressure at the nozzle. This also makes the retraction distance necessary to release that pressure greater. This is why while in direct systems the retraction distances are usually between 0.8 mm and 2 mm, in Bowden extrusion systems they can reach values ​​of 5 or 6 mm.

Being able to use low retraction values ​​has important advantages. On the one hand, the retraction times are lower, which in parts that involve many retractions can represent a significant reduction in printing time. On the other hand, a low retraction distance minimizes the risk of the molten part of the filament reaching the cold zone of the hotend, thus preventing it from solidifying and expanding causing a jam.

It is this last factor that causes bowden extruders to require more complex and accurate retraction calibration since there is a very small margin between a retraction value that is too low to cause oozing or stringing and a too high one that causes clogging.

Flexible Filaments

Another direct consequence of the distance between the extruder and the hotend is the behavior of the flexible filaments.

In Bowden systems, the filament is guided from the extruder to the hotend through a tube, usually Teflon. Although the ideal internal diameter of the tube would be the same as that of the filament, in practice this is not feasible, both due to small diameter variations due to manufacturing tolerances and the high friction forces that would be generated. This is why all Bowden tubes have some clearance, and although with most materials this is not a problem, with flexible tubes it is.

Tubo Bowden

Image 5: Flexion of the filament inside a Bowden tube. Source: E3D.com

Due to their high flexibility, materials such as TPU and TPE tend to flex within the Bowden tube, diverting tensile forces from the extruder to the tube walls. This makes it very difficult to achieve constant pressure on the nozzle to ensure correct extrusion.

In addition, in flexible materials, the compression of the filament necessary to achieve the adequate pressure in the nozzle is much greater than in the case of other materials such as PLA, which in many cases causes the need to use excessively high retraction distances.

Despite all this, with some experience, those flexible materials of greater hardness can be printed on Bowden systems, especially when used in 2.85 mm or 3mm format,avoid the use of retractions and use a high quality and tight diameter Bowden tube like the Capricorn XS.

Capricorn XS

Image 6: Bowden Capricorn XS tube. source: Captubes.com

Without a doubt, the ideal system for working with flexible materials is direct extrusion. The short path between the extruder and the hotend minimizes the compression of the filament and allows it to be tighter, preventing it from flexing inside. Those so-called compact extruders, such as the Titan Aero or especially the E3D Hemera, make it possible to use all kinds of flexible materials in a simple way and with a high print quality.

Inertias

Despite the fact that both in terms of shrinkage and in the use of flexible filaments, direct extrusion systems are victorious, there is one characteristic in which Bowden systems stand out and that for certain applications can be of great importance: inertias.

One of the basic printing parameters is speed. And although many printers allow speeds of up to 80 or 100 mm / s to be used, there is a threshold speed beyond which it is impossible to print without sacrificing part quality. This is because the hotend cannot move at a constant speed, but each time it changes direction it must decelerate to a certain speed of change of direction and then accelerate again.

This is because of Newton's first law. Due to the mass that the hotend has, when moving it has a certain inertial force, the greater the greater its mass or speed. When making a change of direction, the inertia force is transmitted to the rest of the printer causing vibrations and a significant loss of precision. To avoid this, before changing direction, it is necessary to reduce the speed to a value that will mainly depend on the rigidity of the printer's structure and the weight of the hotend. A less robust and light structure will imply using lower direction change speeds and slower acceleration and deceleration curves, since its capacity to absorb inertias will be less, which will imply lower speeds and longer printing times. The only way to reduce inertia is to reduce speed or weight.

Ringing

Image 7: Effect of vibrations caused by inertia on print quality. Source: 2Dprinterwiki.com

And it is here where the Bowden systems play with advantage. By fixing the extruder, which is the heaviest part, and moving only the hotend, the inertia is greatly reduced. This allows 3D printers with Bowden systems to use significantly higher print speeds than those with a direct system, without sacrificing print quality.

Choice between a Bowden system and a direct one.

The choice between a direct system and Bowden will basically depend on whether printing speed takes precedence or the versatility and ease of using new materials.

If you are looking to produce the most parts in the shortest time and in general only few materials and rigid materials such as PLA or PETG are used, a printer with the Bowden system will be the best solution.

On the other hand, if the priority is to use technical and elastic materials and obtain the best possible quality at the cost of sacrificing printing speed, a direct extrusion system will be the ideal option.

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[active] => 1 [created] => 2020-06-17 16:05:47 [comment_status] => 1 [viewed] => 23115 [is_featured] => 0 [post_type] => 0 [id_category] => 2 [lastname] => Meneses [firstname] => Lara [post_img] => 94.jpg ) 1
Sours: https://filament2print.com/gb/blog/94_bowden-direct-extrusion.html
How a BMG extruder works and why it's so good

Direct-drive extruder vs. Bowden extruder

These are the differences

If you deal with 3D printers, you will sooner or later be confronted with the terms “direct drive extruder” and “bowden extruder”. Both extruder variants ensure that filament is fed into the printhead, but differ in the way the filament is pushed into the hotend. Both a direct extruder and a Bowden extruder have their advantages and disadvantages, which we would like to discuss in more detail below and thus make it easier for you to choose when buying.

Direct extruder

The direct drive extruder (A) is installed with the hotend (C) and pushes the filament (B) directly into the nozzle (D). All filament processing components are therefore located in one place on the print head. This creates advantages and disadvantages that you should consider before buying a printer.

Advantages

Since the extruder is located directly on the print head, the motor can simply push the filament through the nozzle.

Due to the proximity of the extruder and nozzle, the filament can be retracted quickly; in many cases, no retraction setting is necessary.

  • Weaker, smaller motors are possible

Because of the short distance between extruder and nozzle, less torque is required from the motor to push the filament.

  • Wider range of compatible filaments

Direct extruders are compatible with a wide range of filaments - they print reliably even with abrasive and flexible materials.

Disadvantages

  • More weight on the printhead

Since the extruder is mounted on the hotend, it has more weight. The increased weight has the following disadvantages:

  • More power requirement
  • Increased wear on toothed belts and bearings
  • Printing speed is reduced

After the feed and the hotend are built directly together, maintenance such as cleaning the nozzle proves to be more difficult.

Bowden extruder

Unlike the direct drive extruder, the Bowden extruder (A) is attached to the frame of the 3D printer and pushes the filament (B) through a long PTFE tube (Bowden tube) into the hotend (C).

Advantages

  • Less weight on the printhead / less moving mass

Since the printhead can work without additional weight, the following advantages result:

  • Clean movements
  • Increased printing speed
  • Nice prints due to reduced vibration on the printhead

Disadvantages

  • More powerful motor needed

A Bowden extruder requires a more powerful motor with more torque to control the filament because it has to be pulled through the PTFE tube.

Increased friction in the Bowden hose leads to a reduced reaction time. Bowden extruders require longer and faster retraction to avoid tension.

  • Smaller range of compatible filaments

Flexible or abrasive filaments can wear out more in the Bowden hose and are processed more poorly than with the direct drive extruder due to the longer conveying path.

Conclusion - which extruder should you choose?

Both extruder variants have their advantages and disadvantages. The biggest difference is clearly to be found in the processing of flexible filaments. If you want to print quickly and do not use flexible filament, you can use a Bowden extruder.
However, if you want to process flexible materials, a direct extruder is definitely recommended.

Sours: https://www.3djake.com/info/guide/direct-drive-extruder-vs-bowden-extruder

Extruder bowden

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Bowden 3d Printer Extruder Vs. Direct Drive

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