Since we first started prototyping the Zero, if became obvious that a huge challenge would be creating an ideal conveyor belt for a 3D printer. We have been testing, learning, and building different conveyor belts constantly.
This begs the question: what makes the perfect material for a conveyor belt on a 3D printer? Sadly, today we do not have the answer. However, our 2+ years of research have helped us identify the features that we want in a conveyor belt.
Our MK1 conveyor belt consists of three components: one-sided cardboard, high-temperature spray adhesive, and what you might call “thin-Tak”. It’s a BuildTak-like surface, but at less than half the thickness of standard BuildTak. Standard BuildTak gave too much resistance when bent around the conveyor belt rollers.
We found this combination to be very functional. It prioritizes the ability for many different materials to stick well to the conveyor belt. However, we have also discovered that it holds on to 3D prints a little too well. The search for the perfect conveyor belt continues, and we are testing a new combination every few days.
This is perhaps the most obvious feature we need in a conveyor belt. The belt must be flexible in order to bend over the rollers at the front and back of the printer.
In our testing, we have tried to achieve flexibility using a variety of materials. We have tested papers and cardstocks of different thicknesses. We have tested flexible plastics and fabrics, and metal foils of different materials and thicknesses. To no surprise, all of these materials have been flexible, and worked with varying degrees of success.
Rigidity is the most surprising feature we’re looking for in a conveyor belt. When reflecting on this, it seems kind of obvious: FDM/FFF 3D printers today all deposit plastic onto a rigid surface, wether it’s aluminum, glass, or another material.
The rigid build plate of traditional 3D printers is absolutely necessary. The rigidity keeps the print in its position, and resists the warping of the plastic as is cools.
Think of it this way: If you placed a flexible sheet of paper or aluminum foil on a normal 3D printer’s build plate and tried to print on it, what would happen? With no clamps to hold it down, your prints would not be very successful.
Now pretend that the foil cannot move around, but it is able to curl up at the edges. Maybe the bed of the printer does not move, and the XYZ axiis move around the bed to create the model, like on a Delta 3D printer.
As the molten plastic sticks to the foil and then cools, it will deform the foil. This will make the 3D print fail, or at a bare minimum not give a dimensionally accurate part when it completes.
On a conveyor belt 3D printer, we create something you might call “faux-rigidity” through tension. When the conveyor belt is tightened from the front to back of the 3D printer, the tension of the belt creates a semi-rigid surface that we can happily print on. However, this rigidity only applies to the direction of the conveyor belt.
The single direction rigidity causes problems when printing any model that has a significant width on the X axis. If you’ve seen videos online of conveyor belt 3D printers, you might notice that typically test models are very thin in the direction of the X axis.
The best material for a conveyor belt on a 3D printer has to achieve some sort of rigidity in all directions. Many 3D printers use thin stainless steel which is rigid, but still flexible enough to be used as a conveyor belt. However, stainless steel is a rather expensive material.
We chose single-sided cardboard for our conveyor belt because the flutes of the cardboard add rigidity to the X axis. The tension on the conveyor belt adds rigidity on along the belt axis, and we are able to successfully print nearly any model that will fit within the build volume.
I believe every FDM/FFF 3D Printer should have a heated bed – it just makes life so much easier and allows you to print in more materials. How does a heated bed affect a conveyor belt?
Heat will cause nearly any material to distort in shape a bit. Plastics in particular are very susceptible to moving around when subjected to heat. 3D printer users everywhere are far too familiar with this when parts warp on the print bed.
On our MK1 conveyor belt – at elevated temperatures – the BuildTak-like material can warp. This can cause the conveyor belt to not lay nice and flat on the heated bed. We print PLA with a 50ºC heated bed, and we have had a lot of success.
If you are seeing a MK1 conveyor belt warp when heated, we would recommend scoring the back of the conveyor belt. This allows the stress of the heated plastic surface to ease up, and should allow the conveyor belt to lay flat.
Prints need to stick
Perhaps this is another very obvious feature – prints need to stick to the conveyor belt!
Different printing materials stick better to different build surfaces. PLA is happy to stick to something like BuildTak or PEI, but can be difficult to stick easily to something like PET tape or Kapton. However, TPU or PETG could be quite happy being printed on a PET-covered print bed.
Creating a conveyor belt that can be easily used with any FDM/FFF material in the 3D printing universe is a challenge that we may not be able to overcome. Instead, we are working hard to create a variety of conveyor belts that users can choose from depending on what material they want to print most often.
Prints need to release
If a part is too stuck to the conveyor belt, it will not be able to release when it arrives at the end roller.
We have seen a handful of instances when a small part will not release, and just travels along the bottom of the conveyor belt.
The second issue can be seen when parts are confronted with a scraper at the end conveyor roller. We have placed a part-removal bin in front of the conveyor belt, and seen parts refuse to leave the belt. This causes the conveyor belt-driving motor to skip steps, and leads to print failure.
This nightmare scenario is most often seen with small parts. With long parts, usually the end of the part detaches nicely when it is ready to leave the 3D printer. The rest of the part is stays nicely adhered to the conveyor belt.
Like any 3D print surface, the conveyor belt is a consumable item that will need to be replaced over time. For that reason, it is important for the belt to be affordable.
It would be simple to create a stainless steel conveyor belt and sell it for $700 (Yes, it would likely need to cost that much). Our mission is to empower people with an affordable product that pushes the boundaries of 3D printing.
Taking the easy route and making a very expensive conveyor belt wouldn’t help that mission. Instead, we will keep researching how we can create an affordable conveyor belt that functions well.
Today, we are a small start-up trying to create a product that empowers people and their ideas. We’ve sold 10’s of printers, not 1000’s. Because of this, we are unable to buy large volumes of conveyor belts custom-made for our application.
We are working with off-the-shelf components and combining them in creative ways to make better conveyor belts. We need to create conveyor belts at the volume that makes sense for the stage the business is in.
The search continues
There is still no definitive answer to what makes the best conveyor belt for a 3D printer. Over time, we’re confident the world will find an answer as the technology develops. For now, we will carry on researching what materials work well.
At the end of the day, it is highly likely that one conveyor belt will not make sense for every user. Instead, a series of conveyor belts is a far more attractive idea. Users should be able to choose a belt that functions well for the materials and types of models they need to print.