Main Parts Of FDM 3D Printers

Last Updated: February 9th 2020

Having an understanding of parts before choosing a 3d printer will ultimately result in achieving better quality printed models.

However, understanding in more detail what each component does is priceless. Knowing your printer components can help you:

For simplicity sake, we will be using a typical FDM printer for demonstrational purposes. ↓

Other printer technologies do work differently and can be more complicated, however, the “general” idea is the same.

Besides, if this is the first time wanting to learn about 3D printers, then you would likely want to purchase FDM technology before moving up in complexity.

For a better understanding on the differences between FDM & SLA printers technology, check out this article.

*FDM stands for Fused Deposition Modeling which is an additive manufacturing method whereby thermoplastic filament is heated to melting point and added layer by layer to build up the final 3D part.

Choosing Parts That Make Up Your 3D Desktop Printer

The important element is to get as much knowledge as possible regarding the components that come with the printer of your choosing.

Familiarize yourself with the performance of each part and you are half way to buying the printer that suits your requirements.

Better yet, when your printer starts having problems you’ll instinctively know where to look and troubleshoot for solutions.

Here are the parts & features that make up your printer and factors to consider.

Build Volume For Print Size

The build volume is sometimes called “build area”.

However, volume is more accurate as it is an indication of the maxim size of a 3D object you can print.

For example, the image below is of the LulzBot TAZ 6, it’s build volume is 280mm x 280mm x 250mm (x,y,z), which is close to the volume of a basket ball.

You can see the build volume indicated in green, which means your printed object cannot be printed any bigger that this volume.

It is therefore imprtant to get an idea of how big you want your prints to be before deciding which machine to buy.

Filament Diameter

There are two “standard” diameters of filament that can be used for FDM printers, these are 1.75mm & 3mm diameters.

This will depend on the printer you get (which extruder & hot end it has). However, as a general rule (there are expection), Bowden extruders work best with 1.75mm diameters and printers with Direct drive usually work best with 3mm diameters.

1.75mm or 3mm Filament Diameter?

So you haven’t bought your printer yet, which diameter of filament should you go for?

If you’re expecting a definative answer, then you are going to be greatly disappointed as it depends on your requirements.

However, based on the current market, the 1.75mm gets a slight edge over the 3mm for the following reasons:

  • They are a little easier to get, which in turn dictates what the “standard” is or will become
  • They allow for finer control due to the smaller diameter
  • They require less force to extrude. Forcing 1.75mm of plastic through a 0.3mm end takes less effort than its fatter counterpart

Having said that, the overall advantages are fairly minor and there is no reason to replace a functional 3mm extruder for a 1.75mm.

Let’s dive in a little deeper on the advantages and disadvantages of filament diamters based on what several 3D printer enthusiasts say on Stack Exchange [R].

I found this interesting and thought you’d likely want to hear what others had to say, rather than listening to the point of view of one person.

1.75mm Diameter Pros

  • More popular, easier to buy
  • Needs smaller extruder than 3 mm
  • Easier to use with bowden tube
  • Generally speaking, a 1.75 mm filament will make it easier to use a smaller nozzle diameter (<0.4 mm), allowing for more precise prints in some cases
  • 1.75 mm filament will give you better flexibility with flow rates as it has a higher surface to volume ratio, allowing for faster melting in the nozzle, and allowing you to push your printer to higher volume extrusion rates

1.75mm Diameter Cons

  • 1.75 mm filament is indeed more popular than 2.85 mm, however the smaller diameter means that manufacturing tolerances really need to be tighter along the length of the filament. Therefore buying more expensive higher quality filament is needed for better print results.
  • A possible second-order disadvantage of 1.75 mm filament can be water absorption. The surface-to-volume ratio is higher – there is more surface per unit of the filament through which water vapor can be absorbed. It is important to keep filament dry, and sometimes necessary with both 3 mm and 1.75 mm to dry the filament in an oven before use.

3mm Diameter Pros

  • More rigid – easier to print with flexible plastics. (particularly with plastics). I couldn’t make my 1.75 mm printer print with NinjaFlex using standard bowden extruder
  • Quality is less affected by changes in diameter – it is a concern mostly when using cheap plastics
  • Can extrude faster
  • The converse of the above points is also usually true. “3 mm” filament (which is usually actually 2.85 mm) will allow for better control and higher extrusion rates on wider nozzle diameters
  • 3 mm filament allows the printer to spit out a lot of plastic at once, letting you build must taller prints much faster

3mm Diameter Cons

  • 3 mm filament on the other hand, creates very high tension when the spool is about to end. Sometimes the last couple of meters are unusable because of this and you have to throw the rest of the spool away.

FDM Extruder Types

For FDM there are two extruder types, the Bowden extruder & Direct Drive extruder. This component by means of a motor, feeds the filament to the hot end ready for melting.

Let’s look at the two and compare them.

Bowden Extruder

The motor on Bowden extruders are located away from the hot end which reduces the weight of moving parts. This in theory allows for more accurate prints as momentum is greatly reduced, particularly making a difference at higher speeds (less momentum to overcome during instant changes in direction).

This in theory means that Bowdens should print faster, but like everything, there are other factors that affect print speed.

Bowdens come with challenges too. The filament is fed through a hollow tube (a guide) which can cause problems too. For example, consider having your feeder tension too high, pieces of your filament can get grounded up into tiny dust particals and collect inside the tube which in turn creates friction.

This friction can essentially slow down the forward movement of the material and ultimately cause under extrusion problems. These dust particals can also enter the hot end causing blockages.

Like everything, there are advantages and disadvatanges and the trick here is to determine which suits your requirements most.

Pros of Using Bowden Technology

  • Increased Build Volume: 
    Having small print head catridges and being smaller and more compact than Direct Drive extruders, this allows for greater build volumes, which in tern allows for bigger prints.
  • Smoother Movements: 
    Being mounted on the frame of your printer (rather than the moving print head), much less weight is on the catridge. As mentioned above, this can create even more problems at higher speeds due to overcoming greater momentum.

Cons of Using Bowden Technology

  • More Powerful Motors: 
    Extra power is required to push the filament through the hollow long tube (guide) and more power translates to more expensive parts.
  • Smaller Material Range: 
    Imagine pushing a long flexible material through a tube. Because of its length, it is likely to bend and twist inside the tube… however with Direct Drive technology, it is pulling the material directly into the hot end (less chance of the issue occuring).
  • Decreased Response Time: 
    More friction in the tube means slower response time. Bowden extruders require longer and faster retraction to avoid stringing.

Direct Extruder

For direct feeders, the extruder pushes the filament directly into the nozzle as it is located directly above the hot end.

This method has its advantages, especially related to direct printing. The closer location of the extruder to the hot end means the motor has far more control over what it can do with the filament.

It is a combination of pulling the filament at close proximity (as opposed to pushing it over a long distance) that enables this control that should in theory produce more accurate prints. However, there are also downsides that can counter act the possitives which we discuss below:

Pros of Using Direct Drive Technology

  • Better Control:
    As the extruder is mounted cloae to the print head, the motor has more control and can easily push the filament through the nozzle. This allows for better extrusion.
  • Faster Retraction:
    Once again, as the extruder is close to the nozzle, it can quickly retract filament inbetween printing stages (travel stage) which reduces the chances od oozing / stringing.
  • Less Powerful Motor:
    A less powerful motor is required due to the short distance the filament need to travel to the print head.
  • Larger Range of Filaments: 
    Once again, due to the shorter distance the filament needs to travel, this allows for a wider ranger of filaments (even softer, pliable filaments).

Cons of Using Direct Drive Technology

  • Burdened Movements:
    With the extruder mounted above the hot end, weight is added. With added weight to moving parts that need to overcome momentum, this can causing more wobble and loss of print accuracy in all axis directions.

Hot End

This device has a simple job but is also one of the most important… to melt the plastic ready for application in order to build up your model.

Although this page is specifically created to discuss the components that make up a FDM printer, it’s still worth noting the potential health issues associated with printing plastics.

Often it is believed that running your printer while being away from the room is safe, but after the plastic turns into fumes, nanoparticles eventually settle everywhere, such as on bedding, door handles, top of closets, the floor and any other surrounding areas.

It is important to remove these fine mists of plastic, as you are at risk of breathing them in every time you re-enter the room. This is quite easy to achieve using a vacuum cleaner!

As always it is worth wearing a mask that covers your noise and mouth for an extra measure of safety.

Important Factors Of Hot Ends

  • Maximum Print Temperature (important depending on what material you are using)
  • Nozzle Size (depending on material type and print speed, especially for larger prints)
  • Fixtures (types of nozzles you can fix onto your hot end)

There are several types of hot ends, but for the time being we will break them up into two types.

  1. V6: Generally used for smaller print sizes
  2. Volcano: Has a larger nostril to allow larger amount of plastic to be extruded for larger print sizes
Source: Thomas Sanladerer YouTube Channel

3D Printer Nozzle Type & Size

Since talking about the hot end, it is only right to talk about the nozzle which is actually the tip of the hot end where plastic comes out.

Various nozzle sizes are avaible and can be exchanable when needed depending on your design’s desired results. These sizes can range from 0.25mm up to 1.0mm with the most common size being 0.4mm.

But that’s not all, they also come in a variety of metals for reasons discussed below:

Let’s take a look at what different size nozzles acheive and why they come in a range of metals too?

Standard Size 0.4mm Nozzle

The thickness layer created by the nozzle is essentially the resolution, and the resolution determines how fast the printer can print your model.

As a nozzle gets larger, the layer thickness increase and therefore has a decreased resolution. It’s this decreased resolutions that allows for quicker print speeds. Conversely, as a nozzle gets smaller, the layer thickness decreases and therefore has an increased resolution, this in turn provides finer detialed prints but also slows down print speed… hence why a 4mm nozzle is a good trade-off for decent resolution with decent print speed.

Smaller Nozzle Size

Some companies are manufacturing nozzles as small as 0.1mm. These are not typical though and a nozzle between 0.15mm and o.35mm are typically considered “small”.

So what are the factors we need to consider when using small diameter nozzles?

  • Increased Resolution:
    As mentioned, smaller nozzles create thinner layer thicknesses, finner details and therefore higher print quality.
    * Note: not all printers are compatible with smaller diameters.
  • Slower Print Speed:
    With smaller layers of thickness building up the model comes more time needed to create the model as more layers are need to create the final pritnt. That’s not all, the difference in nozzle size is not linear to the added time  in creating the print.
    For example, printing with a 0.25 mm nozzle could take up to three times longer than printing with a standard .4 mm nozzle [R]
  • Clogging Susceptibility:
    A smaller diameter hole is likely to clog up more for obvious reasons. This is particulatly true for lower quality filaments or non plastic ones.

Bigger Nozzle Size

With 0.4mm being a standard nozzle size, there are much larger diameters on the other end of the scale. A 0.8mm diameter is already considered large, however, there are some organizations that manufacture diameters up to 1.2mm.

So what are the factors we need to consider when using large diameter nozzles?

  • Increased Printing Speed & Rapid Prototyping:
    As more plastic is released, it takes less layers (in Z-axis) to complete the print and thereofre quicker print times (very handy for rapid  prototyping). The other advantage of using larger nozzles is that certain exotic materials such as wood-fill or metal-fill need a larger diameter due to the material properties that consist of larger particles… some smaller diameters could not handle.
  • Resolution Compromise & Heat Loss:
    Increased diameter means faster print speeds, but also a loss of resolution (finer details in finish) in the Z-axis.
    Loss of heat can be an other factor due to the “wider” nozzle and therefore reducing heat reaching the plastic resulting in clogs or poorly binding plastic when layers are added.

Cooling Fans & Their Importance

Often we discuss the importance of heating up the plastic to create the ideal viscousity of flow through the nozzle, but rarely do we talk about the cooling of plastic and why it is just as important.

The plastic is under control while going through the hot end and nozzle, but once deposited, it’s left to its own devices.

If the plastic is resting as a flat layer, the ambient room temperature can naturally cool it down. However, for more complex prints that have “bridge” type structures or “overhangs”, then a cooling fan is in need.

Let’s take a look at the model below:

Notice how to top of the head has a “bridge” like structure? When the plastic is in a molten state there is nothing much supporting it. So the force that we know as gravity takes over and pulls it down (hence why we want to freeze plastic in place quickly with a cooling fan).

Also notice the “overhanging” sections of the model. Gravity is also playing havok with these sections because we are not solidifying the plastic quickly enough.

Source: Video by Tech2C demonstrating the effects of your print with and without a coolling fan.

With these examples, we can see the importance of having cooling fans when printing in 3D.

Also to note, these fans are even more important as your models get bigger in size.

Flat Bed

Your model has to rest somewhere while your printer is adding layers to it. This rest area is called the flat bed and can be made up of different materials such as:

  • Glass
  • BuildTak
  • FlexPlate
  • Metal

Each having their advantages for use.

For example, if we look at a glass flat bed, its advantages are that glass is superbly flat (meaning layers are added on perfectly evenly), very easy to clean, effortless print removal and inexpensive.

Printing on glass flat bed

The trick is to find the right suited flat bed for your requirements and although each person’s requirements are different, generally speaking you want the following:

  1. A smooth printing process: If your flat bed is cold, it can cool down your first layer before the next layer is applied. This means inferior binding between layers and compromised model strength.
  2. Easy removal of completed print: You want to be able to pull your model from the flat bed easily. If fixed too well to the flat bed, a hard yank could damage your finished print.
  3. Easy to clean: Although you don’t want your model to stick too much to the flat bed, it is still important it stays in place during the printing process to allow for accurate printing. This often means using substances like glue which then needs to be cleaned for the next print. You want to minimize this process, especially if you are an avid printer.
Frequently Asked Questions
✅ What’s the standard nozzle size of a 3D printer & why?

The most common nozzle size is 0.4mm diameter which is roughly the mid point of the nozzle ranges. It is often considered a good compromize as it has a good balance between print speed and resolution.

✅ How many types of FDM extruders are there?

There are two types, Bowden and Direct Driver extruders. Bowden extruders are located away from the printer head and push the filament from a distance into the hot end. As it is not located above the hot end, it means it does not move with the print head making for more accurate prints.

Direct Drive extruders are located directly above the hot end and pull the filament into the hot end from a short distance away. This in theory reduces thing from going wrong when feeding, but does add more weight to the moving printing head that can compromize print accuracy, especially during sudden changes in direction.

✅ Which filament diameters are the most common for FDM?

The two most common diameters are 1.75mm and 3mm diameters. Although the both have their advantages and disadvantages there is no real reason to change from one to the other if everything is functioning well.
Having said that, the 1.75mm diameters are becoming more common and willlikely become “the standard” with more variety of material range.