Upgrading a 3D printer
Installing a ‘job-finished’ switch
Recently, as the price of 3D printers started to fall, I took the plunge and bought a Creality Ender 3 printer.
As those of you who have also taken the plunge will know, once you have the bug, the add-ons, upgrades, etc. soon follow. One upgrade I thought would be good to have is a method by which the printer will shut itself off. This enables you to make long prints that finish at some ungodly hour without the worry of the printer idling away until you can get back to turn it off.
The mandatory internet search came up with an Arduino-controlled motion sensor that would detect when the printer stopped moving the extruder head and the heated bed, indicating that the printer job was finished.
A return to programming
I must confess that my last in-depth association with programming was during the 1970s. Since then I have simply been a user of information technology rather than a developer of it. Consequently, the process involved in making the switch-off add-on by this method looked a bit problematic. I would need to rewire the printer’s 240V circuit to accommodate the 12/240 relay, create space and boxes to house the Arduino and the relay, and mount them on the printer — all in all, quite a job and one that would also clutter up the printer.
However, the Ender 3 printer has one feature that I could exploit instead. Once the job is finished the bed moves forward as far it can on the Z-axis, a position it doesn’t reach when printing. A microswitch fixed to the printer so that it is activated once the bed moves to that position could be used to disrupt the 24V circuit, thereby effectively switching the printer off. It’s not as flash or sophisticated as the motion sensor but it is basically a stand-alone unit that can also be used as a circuit breaker for a number of other applications if you want. Not only that, but in its final configuration it could be a portable 12V power supply as well as a 240V outlet, all contained in a box 300m long, 160mm high, and 130mm wide.
Safety first
You could simply use a 240V microswitch positioned at the front of the bed so that the printer disconnects itself from mains power at the end of the print job. However, as you can see from the photographs, the switch is located in a fairly vulnerable position, close to where you prepare and set up the printer, insert the SD card, and the like. In my view it’s not ideal to have 240V power held in place by the microswitch’s spade bits. To reduce the pressure required to activate the microswitch I added a lever to it. This also reduced the requirement to place the switch exactly at the right bed height, making it operate more reliably.
To make sure that the 12/240V relay is safe and unable to short out on the power supply, I first printed a smaller box and lid for it to be isolated within the larger box. Having roughed out the location of each component I cut a hole for the 240V switch; another for the fan to help control the temperature of the power supply; and drilled holes for the main power cord, microswitch, and fan wires.
“This enables you to make long prints that finish at some ungodly hour without the worry of the printer idling away until you can get back to turn it off”
Keeping it cool
As you can see from Diagram 1 there are two sets of yellow and black wires coming from the computer power supply. (See Diagram 2 for how to set up the power supply to deliver 12V.)
These are two of the numerous 12V wires available. The power supply has its own inbuilt fan. I added the external fan because the unit is in a cramped box and I wanted to make sure it wouldn’t overheat, as it will keep running even once the 3D printer job has finished. This does mean that the computer power supply and its extra cooling fan keep running after the printer job is finished.
No doubt some of you are wondering what the point of that was. Well, as we know, all things electrical and mechanical have a finite life. However, computer power supplies are meant to be able to run continuously, and they’re also cheap to obtain — in my case, free! The only reason I added a fan to the switch-off box was because of the confined space. In a larger box the computer power supply’s own fan would be adequate. My main concern was to eliminate the printer’s unnecessary idling time when the small heater head cooling fans and the mainboard and its fan run for no purpose, long after the job is completed.
The correct switch
A word of caution here: if you intend to build this switch-off box, make sure that the microswitch you use is one that breaks the 12V circuit when it is pressed. The more common one makes the circuit when it is pressed and is of no use in this application.
The finished switch-off box is a stand-alone unit. The printer just plugs into the box’s power point and the microswitch is the only add-on to the printer itself, with a short plug-in lead to the box. As there is no modification to the printer, apart from the microswitch, it can be used with or without its switch-off-box add-on.
If you are considering diving into the world of 3D printing, the Creality Ender 3 isn’t a bad start. I bought the very basic model and have since incorporated a number of upgrades to make it easier to use. I started with a glass bed plate, which eliminated a whole lot of hassles in getting the builds to stick to the original flexible mat with which the printer was supplied. Before printing I lightly brush the plate with a 1:80-part mixture of PVA glue and water. This gives the surface just enough stickiness to hold the build as it progresses.
New motherboard and another upgrade
Unfortunately, the original motherboard went on the blink about six months after I bought the printer, so I invested in a new upgraded motherboard, which came with a self-levelling probe that has completely eliminated the tedious adjustment of the bed springs before each print. (I had previously also fitted heavier bed springs.)
In my last upgrade I replaced the plastic top on the stepper motor that feeds the heating element with an aluminium version. This has greatly improved the accuracy of the amount of filament supplied to the heating head, thereby improving the quality of the finished prints, as it has eliminated over and under extrusion. I also printed a small attachment that fits below the cooling fan and directs airflow around the extruder tip to cool the PLA as it is laid down.
All these small improvements have made the printer more reliable and less finicky to prepare and use. Now once I have loaded the model onto the SD card I can leave the printer to get on with it, only coming back to it at a time that suits me.
“All things … have a finite life. However, computer power supplies are meant to be able to run continuously, and they’re also cheap”