Diagnosing Periodic Artifact in 3D Print Due To Inconsistent Extrusion

A common error when setting up a 3D printer is putting motor control parameters that don’t actually match the installed physical hardware. Sometimes this is glaringly obvious: maybe the X-axis moves 5mm when it should move 10mm. Big errors are easy to find and fix, but the little “off by 0.5%” errors are tough to track down.

In this category, a specific class of errors are specific to the Z-axis. When X- and Y-axis are moving around printing a layer, the Z-axis needs to hold still for a consistent print. And when it’s time to print another layer, the Z-axis needs to move a precise and consistent amount for every layer. This is usually not a problem for stepper motors typical of hobby level 3D printer Z-axis control, as long as the layers correspond to an even number of steps.

When the layers don’t map cleanly to a number of steps, the Z-axis motor might attempt to hold position in between steps. This is fundamentally a difficult task for a stepper motor and its controller, rarely successful, so most control boards round off to the nearest step instead. This rounding tends to cause periodic errors in the print as the Z-axis rounds a tiny bit higher or lower than the desired position, and failing to meet the “precise and consistent” requirement for a proper print.

With a freshly configured Azteeg X5 Mini WiFi control board in my open-box Monoprice Maker Select printer, seeing a periodic error along the Z-axis when printing Sawppy’s wheels immediately placed suspicion on Z-axis motor configuration.

Debug Periodic Print Layer Artifact

Back to hardware measurement I go, and reviewing motor control parameters. After over an hour of looking for problems in Z-axis configuration I came up empty-handed.

Then a key observation when looking at details under magnification: the error is occurring every 6 layers, and not at a consistent location all around the print. This little bump is actually in a spiral shape around the wheel, which would not be the case when rounding off Z-axis steps.

Following this insight, I went to review the 3D priner G-Code file and saw the print path is on a regular cycle printing the six spokes of the wheel. It printed the same way between 5 of those spokes, but the sixth is slightly different and that slightly different behavior cycles through the six spokes as the print rises through each layer.

It turns out this print artifact is not a Z-axis configuration issue at all, but the result of inconsistent extrusion. When moving in one pattern (5 of the spokes) it extrudes a certain amount, when moving in another (the final spoke) it ends up putting a tiny bit of extra plastic on the print, causing the artifact.

The Good And The Bad Of Living With Azteeg X5 Mini WiFi

Once the Azteeg X5 Mini was properly installed in my Monoprice Maker Select, the printer went right back to work making parts for Sawppy. I’m extremely happy about how quiet the stepper motors are running. The loudest noise by far is the power supply cooling fan, which is at least a steady white noise that more easily fades to the background versus the constantly varying sound of stepper motors printing an object.

The first test print with X5 Mini in control showed signs of under-extrusion. Tuning extrusion parameters is a continuing challenge but I blame the printer hardware and not the electronics control board for that issue. This was eventually solved by upgrading the entire print head, a story to be covered later.

While the core functionality is pretty solid, some of the auxiliary features of a Azteeg X5 Mini are rather less so.

The most irritating problem is its WiFi feature. Out of the box it acts as a WiFi access point with default name and password. There is a menu to change the default name and password so my printer wouldn’t be vulnerable to pranksters in range. After changing those menu values and rebooting as recommended, I can see my new “AP SSID” and “AP Password” values in the menu. But the actual access point continued using the old SSID and password as if the menu had no effect. I’d like to think such a glaring security issue would be patched by now, but I just have to wait for them to fix this.

Separate from the WiFi issue, there are some problems upon startup, manifesting itself in one of three ways:

  1. Upon power-up, the status LEDs usually start blinking. But every once in a while, the onboard LEDs are solid on and not blinking. The board does not respond at all in this state.
  2. Even if the LEDs start blinking and the board responds, it may boot into a state where all control communication looks OK but nothing moves. It will talk to my OctoPi as if everything is OK: The board will accept G-code and show progress processing them and return “OK” after every command… but no motor movements occur.
  3. Even if the board responds to movement, occasionally the homing cycle at the beginning of a print job fails for no reason I could diagnose.Homing error

In all three cases, the workaround is to turn off the printer and turn it back on again. This can get annoying at times because it sometimes require multiple on/off cycles to get there. Once printing actually starts, everything performs well. And the best part – no smell of stress electronics threatening to burst into flames.

 

Azteeg X5 Mini Finds A Home In Monoprice Maker Select (Wanhao Duplicator i3)

After an Azteeg X5 Mini passed the nondestructive test of driving a Monoprice Maker Select, it was time to turn the jury-rigged nondestructive test configuration into a more permanent installation. The first step was to clip off all the old connectors and replace them with proper types to match their corresponding locations on an X5 mini.

MMS Brain 03 - Connector switch

Then our new brain needs to be installed inside the enclosure. Since the old and new control boards are shaped nothing alike, this required new mounts at new locations. I drilled four holes to install half-inch long #6-32 standoffs.

MMS Brain 04 - 6-32 Standoffs.jpg

This position was chosen mainly so the power supply exhaust fan blows air directly onto the heat sinks. A secondary bonus of this position is that the X5 mini’s USB port, microSD card, and WiFi antenna are exposed through the opening previously used by the factory brain’s control UI screen, which will not be missed.

MMS Brain 05 - New home

A few zip-ties to organize the wires and the printer is up and running on its new brain!

The primary objective was accomplished: the printer no longer smells like burning electronics when heating up its print bed.

The unexpected bonus was the silence while printing. These motor driver chips are far quieter than their predecessors. I used to be able to tell by sound when a print has completed, but not any more. Now I would walk into a room thinking a print has completed because it was quiet, only to see it was still printing away.

The biggest downside of this upgrade is the fact all my previous STL slicer profiles are now obsolete. I have to create entirely new profiles and start tuning them for the new brain. It’s work, but I was willing to make this tradeoff for a control board that is so much quieter and doesn’t threaten to burn down my house.

Trying an Azteeg X5 Mini on a Monoprice Maker Select (Wanhao Duplicator i3)

The first step of this process was to determine if an Azteeg X5 Mini would even work with an Monoprice Maker Select. We’ll find out by trying to run the printer with the board with minimal (ideally zero) modifications to both. This way, if an unsurmountable deal-breaker is encountered, everything can be restored to the way they were.

When the printer control box was opened, there was no visual indication what was emitting the smoke scent. I had expected to see some discoloration on the circuit board or component, but this is fine: it’s a good thing we’re taking on this project before anything goes seriously wrong.

MMS Brain 01 - Before

The upgrade was done incrementally. Connectors were moved over in associated groups and tested with each group. The first group to move over were the X and Y axis motors and associated homing switches. A ViKi 2 LCD display was borrowed for the duration of this test.

MMS Brain 02 - Incremental Move.jpg

One expected annoyance is that these two boards used different connectors. Fortunately they were the same pitch so most of the connectors could be persuaded to fit (even if not properly) for testing purposes. The only nontrivial electrical work was for our Z-axis. Prusa i3 style printers like this one have two Z-axis stepper motors driven in parallel, but Azteeg X5 mini only has a single Z-axis connector. This required soldering up an Y-connector to electrically connect the two motors in parallel.

Several items in Azteeg X5 Mini’s configuration had to be modified for this particular printer chassis. Number of steps per millimeter, how to properly interpret temperature readings, all fairly normal items for configuring a 3D printer. There were no deal-breakers which is great news.

At the end of the day, all connectors were (crudely) hooked up and printer configuration updated. Heating up the nozzle and print bed allowed verification of temperature control by double-checking their temperature readings using a separate temperature probe. And finally, it was time for a test print!

The test print showed that X/Y/Z axis are working correctly, but the print exhibited signs of under-extrusion so the extruder needs tuning. This is a minor flaw which means we’ve successfully confirmed that we can use the Azteeg X5 Mini in this printer.

Next task: replace crude connections with proper connectors, and find a way to physically mount the Azteeg X5 Mini in this printer.

Smell of Smoke Prompts Monoprice Maker Select (Wanhao Duplicator i3) Upgrade to Panucatt Azteeg X5 Mini

Making parts around the clock for Sawppy was a stressful tour of duty for my 3D printers. Yesterday I described how my Monoprice Maker Ultimate burned out its relay, the second one since I bought the printer. Fixing it and bringing it back online gave me two printers… until the Monoprice Maker Select started smelling like overstressed electronics upon print bed warmup.

My first round with this product ended with a room filled with smoke. Back then I didn’t know enough about printer internals to diagnose what went wrong, I just sent the whole thing back on the generous Monoprice warranty. (For store credit that I used towards the Ultimate.) This time around I know a bit more, enough to understand what people are talking about on the forums. The controller board on these machines have some noted weaknesses and smokey smell is the least of my worries. This problem needs to be addressed before something really bad happens.

The easiest thing is to send it back to Monoprice for another replacement, but we’re not going to do that this time. I bought this open-box unit with the expectation I’ll use it to learn more about 3D printer internals, so let’s start hacking away and do a brain transplant instead.

I could replace the brain with an identical unit, but based on the internet forum information, the problem is a design weakness of the board itself which means I’m likely to end up with the same problem again. It was certainly the case with my Maker Ultimate relay problem, so let’s do something else.

On recommendation of a local 3D printing enthusiast (and enlisting his help in the upgrade process) I will try replacing this printer’s brain with a Panucatt Azteeg X5 Mini with SD2224 drivers based on Trinamic’s TMC2224 chip. There will be no control UI, I’m going to skip the Viki 2 LCD board as I plan to control the printer via OctoPrint.

Next step: test to see if Azteeg X5 Mini is compatible with the Maker Select chassis.

Azteeg X5 Mini