(still in the process of writing everything up to post it)
Contents
- Overview
- Pre-Assembly Check
- Marlin Firmware Flash
- MOSFET
- Heatbed Connector
- Power Supply
- Rocker Switch & IEC320 C14 Plug
- Drylin Polymer Bushings
- TITLEPLACEHOLDER
Overview
The Anet A8 is a 3D printer based on Josef Průša's open source Prusa i3 3D printer. The latter is a part of the RepRap project, a community effort that seeks to create self-replicating machines via low-cost desktop 3D printers. The Anet team in Shenzhen, China made some mechanical and safety sacrifices to the Prusa to create a cheaper DIY kit than the original. Due to both its low cost and infamous safety issues (see here and here), there is a large community of Anet A8 users that contribute to both the printer's Reprap Wiki page and participate in the official Facebook support group.
As mentioned previously, after building and upgrading the printer myself, I do NOT recommend that others purchase an Anet A8 unless they are familiar and comfortable with electronics and prepared to shell out additional money for the safety upgrades. There are too many issues in the base package that need to be addressed by the average consumer, and after totaling up all the hardware upgrades plus the cost of the printer filament needed to print any additional upgrades, you might as well purchase a safer, more well-equipped printer such as the Creality CR-10, which is currently the best bang-for-your-buck 3D printer on the market as of this writing.
The non-printed hardware upgrades I made to the base kit are as follows:
↿ Back to top ↾Pre-Assembly Check
Before starting the assembly of the frame, I did the obligatory electronics check using the factory firmware (I later replace this with Marlin for thermal runaway protection). I plugged each component into the mainboard and wired up the included LCD display. I then wired up the included 12V 20A power supply (after making sure its voltage was switched from 240V to 120V since I live in the US) and plugged it into a wall socket. Make sure you keep yourself and other important persons away from the exposed mains on the power supply, that stuff is deadly. As soon as you plug it in, Fan 2 (the fan that cools the extruder) should turn on and stay on. You can unplug it from the main board once you've verified it's working properly.
The main priority was to check that all motors and endstops were functional, and you can do so via the Position > X/Y/Z Pos. Fast menu options. Changing the values up and down should prompt the motors to move appropriately (for the Z motors, both should spin in tandem), and clicking the microswitch endstops down should cause the Min endstop values to change from Off to On until they are depressed.
The extruder was tested in a similar fashion. Position > Extr. position was selected and the values changed up and down. The extruder gears should turn slowly in response to those changes.
For Fan 1, I went into the Fan speed menu option and adjusted the speed up and down to see if the fan was adjusting speeds as expected.
To test the heatbed, I selected Quick Settings > Preheat PLA in the menu, which caused the heatbed to begin heating up. You verify this by making sure 4 LEDs turn on, 1 on the heatbed itself and 3 on the main board. The temperature of the heatbed should rise (watch the display, don't actually touch the heatbed), and when it finishes the lights should go out.
Don't forget to hit Quick Settings > Cooldown afterwards to turn the heatbed off. I prefer my houses not on fire.
↿ Back to top ↾Marlin Firmware Flash
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MOSFET
One of the main safety issues with the Anet A8 has to do with the main board and its connection terminals. As it's built, all the current needed for both the heatbed and other components such as the motors and extruder hotend is forced through one pair of connectors on the main board. This has led to fires for some users in the past since so much current passes through that one connector. Newer iterations of the printer have beefed up the connectors slightly, but it is still a risk that is best lowered, and you can do so with a MOSFET module.
MOSFETs (metal-oxide-semiconductor field-effect transistors) are common electronic circuit components which control the flow of current through a gate via an applied voltage. The 3D0109 Heatbed Power Module is a general-purpose circuit board designed for 3D printers. It allows current through to the mainboard as expected, but relegates the current to the heatbed to a different connector behind a MOSFET. The voltage gate of that MOSFET is controlled by the main board via its original connector, only now it's hooked up to the MOSFET module's Control In port via a 2-pin JST-XH connector rather than to the heatbed itself.
It's important to keep in mind that, like the Anet A8, most of these parts are mass-produced in China with low quality control. The MOSFET module I received actually came with cracked solder joints. Funny how an upgrade intending to prevent fires almost caused one in my house. Quality check your parts when you receive them!
Luckily, the shoddy soldering wasn't too hard to fix. The solder on the module seemed to be lead-free solder, so I removed it and resoldered the joint with my own leaded solder. One of the surface-mount diodes in the front (the one marked D1) also looked to be slightly out of alignment, so I gently heated up the connection and nudged it into its proper position.
This was how I ended up wiring my components. My setup only used one MOSFET for the heatbed current. There are other setups that use two MOSFETs, one for the heatbed current and one for the extruder current, but that isn't very necessary as the current going to the extruder's heating element isn't nearly as high as the current going to the heatbed.
↿ Back to top ↾Heatbed Connector
The A8 stock heatbed draws around 10A at maximum load, and the 6-pin JST VH connector used on the heatbed is rated for that same amount of current, meaning it's technically suited for the task. However, because only one of the heatbed's pairs of positive and negative pins are being used, a lot of current ends up being forced through a single pin on the connector. In addition, the contact surface for each pin is very low, causing them to heat up the plastic connectors and cause melting and ignition. This has resulted in burnt heatbed connectors on many A8 printers, and in the worst cases, fires. A potentially weak pin connection due to the crimp/connector quality may also be to blame for the issue.
One of the safest changes you can make to prevent this problem is to solder the wires directly to the heatbed. This ensures a secure connection provided your soldering skills are up to par, which can be a challenge since in this case the soldering is being done on a heatbed, which will pull heat away from the pins very quickly because it acts as a natural heatsink. The thickness of the wires you should be using won't help either.
After slowly working the JST VH connector off with some pliers, I removed the remaining metal pins from the heatbed. The solder used on the pins was lead-free solder, just like with the MOSFET, so I had to remove that first in order to use my leaded solder. Unlike with the MOSFET, I was forced to use solder wick to remove the original solder as opposed to just a desoldering pump.
I cleaned up the area with some rubbing alcohol and reconnected the wires, replacing the stock power wires with thicker 14AWG silicone wires. During the actual soldering process, I connected both of the new power wires to both positive and both negative pins respectively to help reduce the current endured by any single connection.
Once the soldering job is finished, the only thing you'll need to do afterwards is provide some sort of strain relief to the connection so that the solder doesn't get stressed. This can be done with printed parts such as an angled connector and/or cable bracket.
↿ Back to top ↾Power Supply
The default PSU is a 12V 20A DC power supply. 20A is
↿ Back to top ↾Rocker Switch & IEC320 C14 Plug
If your rocker switch doesn't utilize any sort of illumination, then your wiring will be much simpler and you can just do something like this instead.
↿ Back to top ↾Drylin Polymer Bushings
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TITLEPLACEHOLDER