Part 1: Make your filament at home for cheap
Tags: 3D Printing, Filament, Filament Maker, Filament Extruder

Plastic is everywhere and it’s cheap yet we pay $20 a spool for 1kg filament which only contains 750gram of filament, rest is the empty spool weight. I started looking for ways to make cheap filament in my garage but recently because of coronavirus, all local stores in my city ran out filament, and e-commerce websites like Amazon wouldn’t deliver it due to restrictions imposed by the government which only allowed them to ship essential goods which don’t include filament spool. So, I started thinking…

It will take lots of labor!?

Not really. Once you’ve assembled the part — it works exactly like a 3d printer, in fact, it’s much easier to operate than a 3d printer as you are making the same thing over and over unlike in 3d printing where you are trying to print different models which require slicer tweak or design changes or strategically placing the support at the right spot. Here we’ve no print bad, no bed leveling, no support requirement.

Assembling it is easier than a 3d printer as it has no movable axis which needs careful calibration and alignment.

3d printer uses filament to lay uniform-sized filament width/height. In comparison, extruder uses plastic pellets to extrude filament.

Once the machine is built, it will take you 4–8 minutes to tweak the initial extrusion process, after that you’ll end up with 10–20 kg filament in one go depending on your batch size.

ROI on filament extruder

Most people make mistakes while calculating the ROI of filament extruder, so if you calculate ROI of a filament extruder, please keep in mind that:

Most people will never see positive ROI on their 3d printer or filament purchase. 1kg spool only contains 750gram actual filament. Strong materials like Nylon12 is $35–45 per 1kg spool while, pellets can be bought for $3–4 per kg in 25kg bags. The extruder is made from off the shelve standard parts like motor, gearbox, temperature controller, thermocouple, all of which have a resale value. You can easily dismantle an extruder and sell its parts or sell the whole unit or use its parts in your other projects. What’s the resale value of the filament you’ve already used? Most likely zero or negative value. While the extruder has good parts that have good resale value.

Once you’ll keep these points in mind, you’ll see the ROI gap is quickly bridged and you’ll make back your investment much faster than you realize.

How does extrusion screw works?

It’s very important that you watch the video linked above to understand what I am talking about. If you want the constant rate of water coming from the top of the screw, how do you achieve that? Obviously, by keeping the screw’s rotation speed constant. For example, if the screw rotates at exactly 5RPM then we might get exactly 5liters of water per hour. But if the RPM changes from 5RPM to 6RPM then back to 5RPM we’ll get different 5 liters of water per hour, then 6 liters of water per hour then again 5 liters of water per hour.

The same is the case with the filament! If we want a constant volume of filament coming out of the nozzle where the screw pushes plastic through the nozzle, we must have a constant rate of screw rotation.

That’s it molten filament is like chewing gum, if the constant volume of filament comes out of the nozzle — you need a pinch roller set up to pull the molten filament at constant RPM — that will give you constant stretch which gives constant diameter.

But I want my filament to be exactly 1.75mm, I’ll stick to buying filament from expert companies

You may stick to the commercial filament but keep in mind, no filament is EXACTLY 1.75mm. Most of the filament on eBay or amazon has listed ± 0.02mm tolerance. That means the diameter swings from (-0.02mm) 1.73mm to (+0.02mm)1.77mm. But that’s what’s listed on the filament label and their listings when in reality the tolerance is usually way worse.

Without any PID diameter control, I get ±0.03mm with the extruder I’ve built. It results in flawless prints and no noticeable imperfections humanly possibly to discern.

Why there aren’t good affordable filament extruders then?

Yes, I’ve heard it a countless times from others that extruding filament is bad. And the reason they often cite is some guys on Youtube who bought mini desktop extruders and failed to extrude the filament with a consistent diameter.

The usual problem with those extruders is that they don’t have enough power (horsepower/torque) so their motor stalls either partially or completely, this makes the motor’s rotational motion nonuniform which causes the molten plastic to come out at different rates leading to diameter inconsistency.

Why can’t they just include powerful motor in their machines then?

First of all the 1HP induction motor weights 8–10kg and the gearbox weights about the same. So, let’s say it’s total weight is 20kg of adding a powerful motor and gearbox. Another 10kg for the screw and barrel.

Now, if I want to sell an extruder that includes 30kg weight, I am already looking at $300 (using $100 per 10kg air cargo charge)in the international shipping fee.

Let’s say if a company makes the same extruder as I’ve made for $600, adding a $300 shipping fee the price is already $900 — how many hobbyists going to buy it? They also can’t put a used motor/gearbox/AC drive in a new extruder — how many would buy it? $900 is the price before even including company profit margin and labor charges.

When you add all that this same extruder will cost over $1500 to end customer and will no longer be affordable.

This is one of those things where the DIY route is much cheaper!

Don’t get me wrong, a front load washing machine weights 150kg yet the total cost of shipping it to a customer is much less smaller proportion of its price than that of a shipping 150kg mini-lathe, why? because most of the people in your neighbor need a washing machine but very few people need a lathe. That makes it easier and cheaper for the companies to put the washing machines at bulk in a warehouse near you.

Sourcing Plastic

Before the filament became unavailable, I was printing face shields and donated them.

I started calling plastic suppliers in my city and they told me they can supply ABS extrusion grade plastic pellets for $1.40 per kg and the minimum they are willing to sell me is 25kg.

You can ask automotive fabrication shops for the contact of their plastic supplier or they might be willing to source extra through their supplier for you.

These are usually used for manufacturing pipes, rods, sheets through the extrusion process. You can find it at any plastic supplier

ABS pellet bag

Saving Planet

Long term plan is to buy recycled plastic pellets from recyclers, mix it with virgin plastic pellets in 60–40 ratio and sell the produced filament on e-commerce websites. I’ll also help communities build their own machines so they recycle their local plastic waste into filament. Plastic sometimes loses its structural properties when recycled, so it’s important to mix it with virgin plastic but slightly weak plastic is okay for 3d printed parts which don’t need a lot of strength. But if you make the filament with 100% virgin plastic, the produced filament have superior strength.

Why ABS?

It is probably one of the easiest plastic to extrude and it’s available everywhere. Once I learn the ropes of filament extrusion with this plastic, I’ll move on to PLA.

GREEK RESEARCHERS DETERMINE THE EFFECT OF RECYCLING ON ABS FILAMENT

What about PLA?

I finally managed to crack it, no local supplier had PLA pellets but I came to know that most PLA filament is made using NatureWorks Ingeo, they were willing to sell me Ingeo 3D870 grade at $2.75/lb, they sell minimum 25kg. All you’ve to do is complete this form: https://natureworks.wufoo.com/forms/zzcwkzh1m84da3/, you can also ask around you might find NatureWorks local distributor in your country then you don’t have to do it through requesting Academic Sample but I am still in college, so it was pretty easy for me to get this sample. They ship from Blair, Nebraska, and shipping is extra.

Extruder

All we need now is a machine that can create filament from these pellets. The extruder is actually very simple in principle, notice the diagram below of an industrial extruder — our extruder will be this minus the cooling fans and die. You can see there are only a few components that you require for making an extruder.

This is done using a process called Extrusion. You put pellets in a hopper which is just another name for a funnel. From there pellets are moved by a screw into the barrel where they are compressed and melt because of sheer from screw movement against barrel wall and heat from heaters applied to it.

Finally, it’s forced through a nozzle and then drawn by a pair of roller in cold water. It’s the speed of pulling which controls the diameter, so we need a PID controller where we feed the diameter of produced filament and get control signal for puller motor speed. We need a NEMA 23 motor for the puller.

And another NEMA 23 motor for the filament winder which rotates the spool on which filament is wound.

To drive screw, we need high torque and low speed for this process and that’s where the gearbox comes in. It reduces the speed of the motor and increases the torque, which is then connected to the screw.

I was told by my screw supplier that I only need <100 rpm for this and that I should have 1 HP motor per 5kg of processed plastic per hour.

So how much total power this system consumes? I only measured power consumed by heater and motor, it was consuming 3 kilowatts so roughly 50 cents of electricity to produce 5kg filament. If you create PLA then it’s it will cost double as I am able to only make 2.5kg PLA filament with the same power consumption when switching to PLA pellets.

Total filament cost of 5kg ABS filament using this setup is $7.50 (power and pellet price)

Building this machine from parts cost me $600–700. It’s not hard to build it, it’s rather easy, all you need to do is source the parts locally and avoid crazy expensive shipping fees for the heavy stuff. Nearly, everything you need is available locally everywhere.

Filament Tolerance

Good cooling (chilled water), uniform speed of the screw, uniform melt temperature, and good PID controller tunning for puller roller will have you achieve the best consistency in diameter. If you don’t have enough motor torque or heating available then motor might stall and speed of screw might change. Keeping the temperature constant will give you consistent viscosity. Minor fluctuations in pressure/temperature changes will be controlled by puller rollers to help achieve target diameter.

Polymers have high specific heat, they take longer to heat and longer to cool. If you don’t cool filament fast enough, it might stretch later during winding that this will make your filament diameter inconsistent.

If you need any help, reach out to me on Telegram, my username is: alexfromtokyo

Part 2