Automatic Resin Filler

The Anycubic Photon is a line of LCD 3D Printers. I have the Anycubic Photon Mono X. Why does it need an auto filler?

An autofiller, also known as an automatic resin dispenser or resin top-off system, is a feature found in some LCD 3D printers that helps maintain a consistent level of resin in the resin tank throughout the printing process. The purpose of an autofiller is to enhance the overall printing experience and reduce the need for manual intervention during long or complex print jobs. Here’s why an auto filler is useful for an LCD 3D printer:

1. Minimizes User Intervention: During a 3D printing job, especially for larger or longer prints, the resin in the tank can gradually deplete as each layer is solidified. Without an autofiller, users might need to monitor the resin level regularly and manually add more resin to prevent the printer from running out of material. An autofiller automates this process, reducing the need for constant monitoring and intervention.

2. Consistent Print Quality: Maintaining a consistent resin level is crucial for achieving consistent print quality. If the resin level drops too low, it can lead to improper layer exposure and incomplete curing, resulting in defects or failed prints. An autofiller ensures that the proper resin level is maintained, which in turn helps ensure that each layer of the print receives the appropriate amount of light exposure for accurate curing.

3. Long Unattended Prints: Some 3D prints can take many hours or even days to complete, making it impractical for users to continuously monitor and refill the resin tank. An auto filler enables users to initiate long print jobs and leave the printer unattended with confidence, knowing that the system will automatically replenish the resin as needed.

4. Time Efficiency: For professional users or businesses, time is of the essence. An autofiller can save valuable time by eliminating the need to pause the printing process, open the printer’s cover, and manually add resin. This can be especially important in settings where multiple prints are queued up back-to-back.

5. Reduced Material Waste: If a print job runs out of resin due to insufficient monitoring, it can result in a failed print that wastes both time and material. An autofiller helps prevent such failures, reducing material wastage and the associated costs. 6.

6. User Convenience: The convenience of an auto filler is a significant advantage, especially for users who are less experienced with 3D printing or for those who prefer a more hands-off approach. It simplifies the printing process and makes it more accessible to a wider range of users.

7. Optimized Print Success: In 3D printing, success is often determined by the accuracy of the printing process. An autofiller contributes to the printer’s reliability and the likelihood of successful prints by maintaining optimal printing conditions consistently.

The Homemade Auto-Filler

At the time of creation, I had to print some large parts for work and the 9-hour print that used 430 mL of resin. This was much too large to fit in the 200mL tank, plus I was either asleep or at work for a large portion of the print and wouldn’t be able to refill it.

Some resin auto-fillers use an air pump to pressurize the container of resin, then the pressure forces resin up a tube and out into the vat. This is advantageous because no pumps interact with a resin that can be damaging to other plastics and metals. However, there is no reference to how much resin has entered the vat, especially if the resin bottle leaks. I chose to go with a different route focussing on added a specific volume of resin to the vat over time rather than filling to a certain level.

I chose a specific type of pump called a peristaltic pump, as it does not mix the fluid being pumped with any pump parts.

Peristaltic Pumps

A peristaltic pump is a type of positive displacement pump that serves the purpose of moving fluids, typically liquids, from one location to another. It operates using a mechanism called peristalsis, which mimics the way certain biological systems, such as the digestive system, move substances through a series of rhythmic contractions. The primary purpose of a peristaltic pump is to provide a controlled and gentle method of transferring fluids without contaminating the pump or the fluid being pumped.

I chose this enable/direction/step stepper motor controller for the project because I already had it on hand. Additionally, the driver is very simple to operate from the microcontroller end as it handles the step sequencing and can also limit motor current. The microcontroller only has to set the rotation direction via the direction pin, high or low, and then pulse the step pin to move the motor a set distance.

The Controller

The auto filler I built uses an Arduino Nano. It’s one of the smallest Arduinos but still has more than enough program memory and IO. However, the program will work with any Arduino, and with most Arduino IDE-compatible boards.

In this project, the micro-controller’s purpose is to accept inputs from the user via pushbuttons, and output indicator lights and motor driving pulses as required. The current version requires a re-flash of the program when changes to the autofill cycle are required, but a future update may improve the human-machine interface with a screen of some sort.

The code is available here along with the part files for the enclosure I made. Note that the parts I picked out do not fit in the enclosure correctly.

Github

Assembly and Use

With the project ready to make, I purchased the parts required and laser-cut a housing out of plywood.

The design wasn’t big enough for the stepper motor driver to fit, so I let it hang out where the back panel should be. Then I soldered all the required connections from the buttons and LEDs to the Arduino, plus connected the stepper motor and driver circuit. The stepper motor needs 12V power, so a 12V 1A wall wart power supply was used. The power comes into the enclosure and then is split, one into the motor driver, and two stepped down for the Arduino. After fixing a couple of quick mistakes, it was time to calibrate the machine.

Calibration

The whole idea was the pump would push a specific amount of resin in over a given time, so I needed to measure this for the program. I got a container, found its volume in milliliters, and then proceeded to time how long it took the pump to fill the container. It took the pump 239 seconds to fill the 54ml container to the brim meaning, the pump moved a whopping .225 milliliters per second.

Now this is slow. But it’s still faster than the printer consumes resin, so it’s suitable for the task. This value can be entered into the code along with the print volume, print runtime, as well as how many times should the resin be refilled. The program calculates the timing from this at run time (technically as it is compiled), and then uses those timings to refill the tank.

I was able to test this a great number of times, and it worked well enough for me to use in production. The auto filler ran 5 430ml batches over 9 hours each, and the tank was essentially at the same level the entire time.

Conclusions

Is this auto-filler worth it? Probably not. You can purchase an auto filler that uses a closed loop method for filling the tank for the same amount the parts for this project cost, here. It has the advantage that it doesn’t need to be reprogrammed for every job, but it can’t accidentally overfill the tank from miscalculation.

However, this certainly was a fun exercise, and it predated the consumer auto filler now available for the Photon. It served its purpose, plus it was a learning opportunity for using: Arduinos, digital motion control, stepper motors, and peristaltic pumps.