Sawppy the Rover Receives WiFi Upgrade, Increases Range

Sawppy is now back up and running with all its 3D printed parts recreated in MatterHackers PETG plastic. While the pieces could be replaced piecemeal, I decided to take everything apart and reassemble the whole thing so I could take pictures along the way and document the assembly process. Since I was basically rebuilding the rover from scratch anyway, I performed another upgrade: the compact Netgear WiFi router previously installed has been replaced with larger dual-band unit, the Asus RT-AC1200. Test drives have proven the new router gives Sawppy significantly more range!

Sawppy can now rove a decent distance from its handler. Far enough that it’s no longer easy to see exactly which way the rover is pointed, and we need to occasionally refer to Sawppy’s on-board camera video feed to see what’s going on. In the picture below, John is holding his phone showing the video feed while Emily is on the driving controls. This picture was taken as Emily drove Sawppy back towards us. In the relatively quiet RF environment of this industrial park, Sawppy can drive about three times further away than the distance shown in the picture before wireless communication suffers occasional data dropouts.

This range test proved that Sawppy can get far enough away that driving it around becomes a team activity: one to monitor the situation and another on the controls. This is more than enough range for most of our purposes.

What’s still unknown is Sawppy’s tolerance of noisy RF environments. That test will come, eventually…

Sawppy Pilots

Reclaiming Bearings From 3D Printed Parts: Round 2

Now that PETG is up and running smoothly on my printer, it was put to work reprinting all Sawppy parts so I could replace the existing PLA parts with PETG parts. Retiring parts means throwing away things like heat-set inserts, but the bearings could be recovered. I originally designed a few holes into the parts to make bearing removal easier, but I’ve since realized those holes are unnecessary. Plastic — both PLA and PETG — are soft enough for the bearings to flex and move inside their assigned positions. This flex allows us to work bearings loose by twisting a shaft inside the bearing.

Bearing Extraction

I tried describing this with words but my vocabulary really isn’t up to the task. Here’s a video to illustrate the technique.

This works well enough I think those bearing removal assist holes I added before are now unnecessary. I’ll probably remove the holes on my next revision of rover parts so it looks less like a piece of Swiss cheese.

Titan Aero Upgrade for Monoprice Maker Select (Wanhao Duplicator i3)

In order to improve PETG printing performance, my open-box Monoprice Maker Select is receiving a hardware upgrade. The print head assembly (filament extruder and hot end) is being replaced with an E3D Titan Aero, a combination all-metal hot end and geared extruder.

For this first pass, the goal is to be as simple and nondestructive as practical so I could revert if things don’t work out. If this works, I can make things nicer later. Obviously, the first step is to remove my existing print head, leaving just the metal X-axis carriage assembly. Since I’m trying to be nondestructive, the goal is to fit into this space in the U-shaped metal and bolt onto existing holes.

Stock extruder hot end removed

To test for fit, I laid out parts for assembly. Some people are squeamish about using the print surface as a work surface, preferring to leave it as pristine as possible. I have no such qualms.

Titan Aero parts laid out

A few quick tests confirmed there is indeed space within the U-shaped metal to accommodate a Titan Aero. The hole for the actual nozzle doesn’t line up, though, which means the Titan Aero nozzle will have to dangle off to the side of the metal bracket. This wish for non-destructiveness will extract a price in the form of a small reduction in print volume. I decided the tradeoff is worthwhile for now. I designed & printed a simple adapter to mount the whole works on the existing metal bracket. The Titan Aero kit does not include a stepper motor, so I reused the existing extruder motor.

When I was just eyeballing the parts, I thought I could use the existing heater cartridge and thermister. The advantage of this approach is reduced wiring work and we wouldn’t have to change print controller configuration. Sadly, the heater cartridge is a tiny fraction of a millimeter too large to fit and thermister is an entirely different shape. So some wiring tasks and controller configuration changes had to be made. Since the long-term plan is to build a better chassis using these parts, I kept most of the wires for the heater and thermister with the hope the wires will be better routed in that future dream chassis. In the short-term, the wires are just coiled on top of the print assembly.

The final modification was to the cooling fan — when it was powered up for the first time, I heard how loud it was and said “Oh hell no.” I replaced it with a 40mm Noctua fan which doesn’t move as much air but is far quieter. If the reduced air volume causes heat creep issues I’ll revisit this fan replacement, but for now I’m grateful for the silence.

Once the upgrade was hacked together, the printer can now easily extrudes PETG at decent print speed with 0.3mm layer height. I was initially worried about the adapter bracket holding up under the heat (it was printed in PLA) but the Noctua cooling fan seemed to be doing its job and things never get hot enough for the bracket to be a problem so I’m happy to leave well enough alone. I’ve got a rover to reprint in PETG.

Titan Aero nondestructive install

Hot End Upgrade Options for Monoprice Maker Select (Wanhao Duplicator i3)

The Sawppy rover project has reached a point where I need PETG for more heat-tolerant rover parts, and the stock hardware on a Maker Select isn’t good enough to deliver the prints I needed at the speed I wanted. The working hypothesis is that the stock hot end couldn’t melt PETG at high enough volume to print 0.3mm layer height at a decent speed. Technically Monoprice did not lie when they said the printer could print PETG. It just couldn’t do so at an acceptable pace for my project.

The recommended solution for melting PETG faster is to go to an all-metal hot end. Searching internet forums found two leading candidates. The first is from Micro-Swiss, which offers a drop-in replacement kit to turn the default hot end to an all-metal hot end.

The second leading contender is from E3D, which sells the Titan Aero. It’s an all-metal hot end with an integrated extruder, unlike the Micro-Swiss kit which replaces a few key heating components in the stock hardware leaving most of it intact. The Titan Aero option costs more than twice as much as Micro-Swiss upgrade kit and requires more work to install.

If I was happy with the stock extruder on this printer, the Micro-Swiss option would have been the one I chose. But I was not happy with the stock extruder! It’s been a cause of headaches since day one with inconsistent extrusion caused by slipping filament and who knows what else. Upgrading the stock electronics to a Panucatt Azteeg X5 Mini solved a few other problems with the side effect of making extruder issues much more apparent.

Maker Select Underextrusion

There are various hacks to work around problems with the stock extruder, but now that I’m presented with an option to upgrade the extruder at the same time as the all-metal hot end upgrade that I want, it’s easy to take that step up to a Titan Aero.

Problems Printing PETG With Monoprice Maker Select (Wanhao Duplicator i3)

The first experiment in PETG was printing a servo coupler. It was small, printed at 0.1mm layer height. After the success of that initial experiment, I set the printer to work on a Sawppy rover wheel overnight at 0.3mm layer height. It did not turn out well.

First Complex PETG

Little bits of extraneous PETG strings all over the place! Stringing is usually credited to poor retraction settings, but that’s not the whole story here. Once this print gets above the first 20mm and no longer printing the center hub, it no longer performs any retracts – the wheel is printed in a continuous motion without retracts.

What these strings actually demonstrate is not poor retraction, but very poor layer adhesion. As the print head circles the perimeter laying down filament, it’s not all sticking and instead dragging along little bits of PETG causing these strings. It’s not very visible from this camera angle, but there are visible gaps between layers. And the layers came apart with only minor physical handling.

The layers came apart more easily in the middle sections. This was puzzling – what problem would be worse in the middle of the night but magically recover by morning? The answer: ambient air temperature. Apparently PETG needs more time than PLA to properly bond with the previous layer, and when cooled too quickly it won’t bond. I can’t change the weather on command, but I could turn off the print cooling fan.

Turning off print cooling helped somewhat, but it was not the whole solution. PETG melts less easily than PLA, which is a desired feature when it comes to rover parts that don’t deform under heat. But that attribute also creates printing headaches. The 0.1mm layer height print bonded well but the 0.3mm print did not, leading to the hypothesis that the print nozzle couldn’t melt PETG fast enough to deliver triple the volume of plastic.

To test this hypothesis, the print speed was cut to 1/3 of previous speed. The test object worked well, but this print speed is not acceptable. It would turn a rover wheel from an 8-hour print project to an all-day 24 hour print!

Another test is to turn up the heat on the nozzle, hopefully a hotter nozzle will melt PETG more quickly. This worked… briefly. It got too hot for the liner and it deformed, jamming the print path.

Damaged PTFE liner

The liner was original so perhaps it was just time for a replacement anyway. But when the replacement liner also jammed up within a few prints, I knew this was not going to work.

Given these data points, the hypothesis of “hot end couldn’t melt PETG fast enough” has merit. We know slowing down works, but is unacceptably slow. We know heating up works, until the liner quits.

I was not willing to accept the slowdown, so the alternative is to upgrade the hardware.

First Simple PETG Print is a Success

Once the Maker Select reached “good enough” status it was back to work printing PLA parts for Sawppy in parallel with my Maker Ultimate. This allowed me to iterate through designs much more quickly and was instrumental in getting Sawppy built in time for its first public appearance at JPL’s IT Expo.

A few problems surfaced at this event, but the one that prompted a complete reprint of Sawppy was PLA deformation under Southern California summer heat. This is where the current 3D printer story line rejoins the rover construction story line. With this experience of plastic deformation, I now have motivation to try using a different material. There are a few options, and PETG presented the best tradeoff between temperature tolerance, ease of printing, and cost.

The first object to be reprinted in PETG were the steering servo couplers. This proved to be a weak point that needed to be addressed. The design was printed at 0.1mm layer height so the sideways hole for the M3 thread heat-set insert would have clear definition. (This turned out to be unnecessary – later couplers were printed at 0.3mm layer height and functioned adequately.)

I knew PETG had different requirement for printing, starting with print nozzle temperature. I started with my PLA print profile and dialed up the heat. In order to test layer bond in the print, and also to get a feel of PETG failure mode, I put the result in a vise and cranked the handle. I was happy to see PETG deformed rather than shattered as PLA would. Examination of the deformed object showed layer bonding is good. This is a good start for printing PETG.

PETG crush test

Bolt Test Print on Monoprice Maker Select (Wanhao Duplicator i3)

After upgrading the control electronics of my Monoprice Maker Select to an Azteeg X5 Mini (which is a major change) there were a handful of issues to chase down. Some documented recently on this blog, others too minor to be worth writing about. Once the biggest problems were resolved, the printer was in a decently usable state. Not perfect, but acceptable. Or so I thought… time for a test.

The test print object is a bolt with its corresponding nut. There’s no practical reason to 3D print my own fasteners – buying them would be cheaper, faster, and stronger. The purpose of this exercise is to test dimensional accuracy. While we could print a calibration cube and measure its dimensions, it’s not as satisfying as fitting one precision part into another. A successful test would allow threading the printed nut onto the printed bolt. Also, we’d end up with a simple little fidget toy.

A good reference for dimensional accuracy is this page in the Slic3r manual. Most of the information on this page areapplicable to 3D printing in general and not exclusive to Slic3r users.

The 3D data for test print was pulled off McMaster-Carr’s web site which has CAD data for much of its merchandise. Here is the bolt, and here is the matching nut. Several iterations were printed to fine-tune settings. In this picture, the bolt on the right was printed at 0.3mm layer height. This proved too coarse to properly recreate the thread and did not work. The bolt on the left is printed at 0.1mm layer height, which was able to recreate the thread profile with enough accuracy. But that by itself was not enough – it also needed an XY compensation parameter of -0.2mm before the nut will smoothly install on the bolt, shown on the left side of this picture.

Requiring a dimensional adjustment of 0.2mm is not great, as that is half the width of our 0.4mm print nozzle. In theory we should be able to do better, but for now this is good enough to resume printing Sawppy parts.

Bolt Test

Rovers Gonna Rove at SGVLUG/SGVHAK BBQ

The annual summer BBQ for San Gabriel Valley Linux User’s Group (SGVLUG + offshoot subgroups like SGVHAK) was this past weekend, so obviously a few projects from the group made a showing too. This included our SGVHAK rover and my own follow-up Sawppy the Rover.

Sawppy joined the socializing first, hanging out next to some of the seats attracting attention from members who haven’t seen the motorized rover model before. (And some who have but just wanted another look.)

SGVLUG BBQ 1

Later in the evening, SGVHAK rover joined on the party. The rovers would occasionally run around sometimes at the same time and sometimes into each other. They sort of got into the way of people at times, getting underfoot like a big cat might. Fortunately nobody tripped and fell over a rover.

SGVLUG BBQ 2

This was Sawppy’s first public outing since conversion to PETG, a conversion motivated by earlier PLA parts that deformed under heat. This weekend turned out to be a great test since the entire region is in the middle of a record-breaking heat wave. And this time, Sawppy did not melt under the scorching sun.

Sawppy also got a few different pilots, as anyone who expressed interest was offered a chance to take the helm. Partially to share the toy, but also to get some time seeing Sawppy driven by people who don’t drive the same way I do. The intent was to probe for unknown areas of weakness – after all, this type of activity is how we exposed the weakness in SGVHAK rover’s original steering mechanism.

Fortunately no such flaws were found today. Sawppy survived the evening driving by multiple people (and running over things, and running into things) without any apparent damage. This is a very good endorsement of Sawppy’s design maturity.

Z-Axis Chassis Flex Of Monoprice Maker Select (Wanhao Duplicator i3)

A popular modification to the Monoprice Maker Select (Wanhao Duplicator i3) is a “Z-brace”. A diagonal structure that braces the horizontal Y-axis carriage to the vertical Z-axis frame. Playing with my own printer, I can confirm that the Z-axis can be noticeably flexed by hand, and that a similar printer with the Z-brace modification does feel noticeably more rigid.

But the printer isn’t actually printing under the strain of a human hand pushing it around. It only needs to withstand the stresses or a print, which does not actually apply force in the direction where it is weak. So that leads to the question: how much difference does chassis flex actually affect a print in progress?

I had a chance to quantify this behavior, borrowing a dial indicator that is used to precisely dial in machine tools. It is completely overkill for this purpose but it was fun to get some data to back up (or refute) internet wisdom. I told the printer to work on my hash-shaped test file that makes a lot of sharp right turns, and measured chassis movement through these turns.

MMSel Dial Indicator

Close-up while printing:

Verdict: Z-axis chassis flex is real. It is definitely moving by a measurable amount when performing a 3D print. That said, the amount of movement is very small compared to all the other factors affecting dimensional accuracy and not a major factor in print quality. I’ll prioritize fixing other problems with the printer before I worry about installing a Z-brace.

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

Monoprice Maker Ultimate (Wanhao Duplicator i6) Kills Another Relay

I was willing to stop at “good enough for now” on modifying my open-box Monoprice Maker Select because I needed printers up and running. In the process of designing and iterating Sawppy‘s 3D-printed components, I kept both printers busy pumping out prototypes to see how the designs in my mind survived the translation into real world pieces.

Sometimes there was enough work to keep printers busy around the clock, and this was too much stress for the control boards inside these affordable printers. It’s an inevitable tradeoff between price tag and robustness. In the case of my Monoprice Maker Ultimate, the weakest point in the chain is the main motor relay that controls power going to all the motors (both stepper motors and fan motors) and heaters.

This relay has failed once before, and under the constant workload, another one has kicked the bucket. It has started failing intermittently which shows up as brief interruption in motor power. Since the electronics are not powered through this path, these brief interruptions ruined prints, making them look like the motor drive belt had skipped a few teeth when the reality was the motors stopping briefly as the electronics continued onwards.

Last time this happened, I kept trying to diagnose belt skipping. Wasting a lot of time looking over mechanical parts that were working well. This time I recognize the symptoms and pulled out the control board before the printer failed completely.

Since it wasn’t completely burned out yet, the relay exterior didn’t look bad – only a minor discoloration that might have gone overlooked if we didn’t know exactly where to look.

Relay exterior discoloration

Cutting away the relay’s blue enclosure exposed a familiar sight: the interior is fried.

D6 Second Failed Relay

It’s always easier to do something the second time, but addressing my second fried relay is still time spent not working on the project itself.

Y-axis Pulley Misalignment on Monoprice Maker Select (Wanhao Duplicator i3)

After I tightened the X-axis belts by three teeth, most of the ringing went away. Not all, but enough for me to look elsewhere for the next improvement. The obvious thing to do is to try the same thing with the Y-axis. It was also pretty easy to do but since the improvement was not as dramatic. I still have ringing on both X and Y axis but at least the worst of it went away.

While working with the Y-axis belt, something felt a little bit off. A few minor details didn’t line up the way I would have expected. Pulling out the caliper confirmed the eyeball diagnosis: the Y-axis components do not line up.

I measured the distance between edge of chassis and edge of belt at the idler pulley sitting in front of the printer.

YPulleyWithout moving the caliper, I compared that distance with the equivalent in the back, between the chassis and the drive pulley mounted on the Y-axis motor shaft. We’re off by more than the width of the belt.

YMotor

The first question: Is there an adjustment I should use to fix this? The idler pulley in front is pretty fixed in its place with no room for adjustment. This is also true of the motor bracket in the back. So the answer seems to be: No, there is no adjustment.

The next question: Is there a quick modification I can make to address this misalignment? There’s no good candidate in the front – swapping positions of the idler pulley and the holding nut would just make things worse. In the back, we could try to flip the pulley around on the motor shaft, but the set screws were installed tight.

While I was debating how much force I should use before I risk ruining the set screw… I realized I forgot to ask an important question. This should have been the zeroth question, so to speak: Is this misalignment causing a problem?

Um… well, I guess it isn’t the biggest problem at the moment.

So we’ll leave this on the to-do list for now and revisit later.

 

Sawppy at Hackaday LA

Sawppy at Hackaday LA

I brought Sawppy the Rover to the June 2018 meet for Hackaday Los Angeles. As is typical of these events, there were two scheduled speakers who gave half-hour talks then the floor opens for anyone present to do a quick 2-minute “Lightning Talk”. I presented Sawppy the Rover to the Hackaday LA audience.

I remember the first time I signed up to do a Lightning Talk months ago and was horribly nervous. I still get nervous when it came time to hold the microphone and speak to the crowd, but it gets a little bit easier every time I do it. I really appreciate the opportunity to practice public speaking in little 2-minute chunks.

The audience seemed to really like Sawppy. When I started driving my rover down the center isle between the chairs, a lot of cell phone cameras came out to take quick snaps. Several people came up to ask for more details afterwards during the socializing session, including Jacob who just bought a book that’s all about Curiosity and is at least as big of a fan of the Mars rovers as I am. Jacob says he wants to build a Sawppy of his own, and I said I’m happy to help his efforts. There was also a little boy who seemed to be around 7 years old, asking questions about Sawppy that were far more sophisticated than I had expected of that age. I was definitely impressed.

At least one of those cell phone pictures has already made it online. It’s not exactly being internet famous but I’ll happily take it!

Tightening Belt To Mitigate Vibration Artifacts on Monoprice Maker Select (Wanhao Duplicator i3)

Now that my open-box Monoprice Maker Select (Wanhao Duplicator i3) is up and running, it’s time to take a closer look at the less than perfect print output. This was totally expected at this terrifically low price point, and part of the point of this exercise was to learn how to analyze 3D printer problems and how to address them. This printer is not just a tool – it is a project in and of itself!

The first (and as it turns out, a recurring) issue is a vibration artifact in the print after a sharp movement. After some web searches, I’ve learned this was called “ringing” because it’s the after effect of a sharp impulse, like ringing a bell. Looking at the printer, I thought the obvious culprit would be the Y-axis movement. It has to move the build platform so it would have more inertia to overcome and cause problems.

To confirm this hypothesis, I wanted a test object to print in perimeter-only “vase mode”. I created one in Onshape that would cause the printer to take a lot of sharp right turns, which should expose ringing effects.

Here’s the part of the object where the print head moved in X, holding Y steady. The ripple on the left is the Y-axis ringing after making the sharp turn.

Y ringing visible but less bad

And here is the counterpart, where print head was travelling in Y and holding X steady. The ripple on the left is the X-axis ringing after making the sharp turn.

X ringing is bad

And this is why we do a test before blindly going in to fix a problem that might not actually be there. Despite the original expectation for Y to exhibit large ringing effects, it was actually the X-axis!

Now that we know, we’ll try the easy thing first: tighten X-axis belt. A glance behind the machine showed the belt is currently very loose despite effort of spring tensioner.

MMS X Assembly

The low-cost method of holding the belt, using a M3 bolt and zip-ties, also makes it easy to modify. In this case, we just need to cut the zip-ties, pull the belt tighter, and put on new zip-ties. A silver sharpie was used to mark the starting point.

Silver Sharpie Marks Starting Position

The marker is so we could clearly tell that we’re tightening it by three teeth (for overall length reduction of 1.5 teeth.) Now if we need to tweak this in the future, we know how the changes relate to the original out-of-the-box condition.

X Axis Belt Tightened by 3 teeth

This change didn’t completely eliminate ringing, but situation is a lot better than before. It’s good enough to move on to the next problem.

SharpHash

Using OctoPi To Avoid Monoprice Maker Select (Wanhao Duplicator i3) Usability Issues

The Monoprice Maker Select 3D printer is a re-branded Wanhao Duplicator i3. Which is itself part of a lineage of 3D printers that can trace their ancestry to the Prusa i3. Josef Prusa invented an effective design that has seen wide adoption, including manufacturers who are very inventive at cutting cost. Now a serviceable 3D printer can be purchased for iPad money. Or even Chromebook money if buying used/refurbished.

That’s not to say everything is great. There are some definite trade-offs made to hit this price point, and the customer sitting in these cheap seats has to sacrifice some nice features of more polished printers.

One infuriating usability problem is the microSD card slot. It is on the side of the control box whose sheet metal enclosure has an over sized slot to make sure manufacturing tolerance issues won’t end up covering the card slot. Great for cheap manufacturing, but it also means is there’s plenty of room for a card to enter the sheet metal opening and miss the microSD slot entirely. If the user fingers release the card, thinking it was in the slot, the card drops into the enclosure and the user has to open the enclosure to retrieve the card.

Another usability issue is the control panel. First, the LCD is a primitive dot matrix display with very limited viewing angle. Second, it doesn’t always respond even when tactile feedback was returned by its control knob. It’s not clear if this is a problem in the knob (tactile feedback without electrical connection) or if it’s a software issue, but it is annoying either way.

One way to avoid both usability issues is to control the printer using OctoPi, the prebuilt image to run OctoPrint on a Raspberry Pi. The web-based interface eliminates the need to deal with the knob and LCD UI. And OctoPi’s G-Code upload/management functionality means never having to use that microSD slot.

Personally, I didn’t feel OctoPi delivered a lot of value for my Monoprice Maker Ultimate (Wanhao Duplicator i6) because the Ultimate had a well placed memory card slot for full SD cards and a decent control panel. In the case of the Maker Select, though, an OctoPi has saved a lot of aggravation.

Maker Select with OctoPi

 

OctoPiUI

Replacing Printing Surface on Monoprice Maker Select (Wanhao Duplicator i3)

The default printing surface that shipped with a Monoprice Maker Select feels similar to BuildTak. It is a good general purpose surface but some other materials will work better for specific plastic filaments and/or better fit personal preferences. Upon recommendation of this Hackaday printer review, I tried a PEI surface. My experience using it for printing Monoprice PLA has been stellar. So now that we have a second hand open-box Maker Select printer whose print surface was well used by the previous owner, the solution is obvious.

PEI 0 - scuffed surface

We could try to squeeze a little more life out of this surface, or replace it with a fresh sheet that came with the printer, but now that the printer has proven to be sufficiently functional we’re going straight to a sheet of PEI purchased from GizmoDorks’ Amazon store.

The first step is to remove the sheet. Historically most adhesives are easier to remove when warm and this is conveniently a heated bed. Setting the bed temperature to 40 degrees C warms things up a bit without risking skin burn. It peels off leaving only minor residue behind to be cleaned up.

PEI 1 - Peel

The PEI sheet is 8″ x 8″ which is only a tiny bit larger than the official 200mm x 200mm print area. It is definitely smaller than the sheet of aluminum on the printer. This means we should put in a bit of effort finding the proper position for the sheet on the bed. Fortunately the well-used surface clearly shows where the hot nozzle touches when homing at the start of a print, giving us our axis origin which we can mark off with a bit of masking tape.

PEI 1a - Zero

The PEI sheet is then placed against this origin to test for fit. We see that the upper-left corner conflicts with the screw used to level the bed.

PEI 3 - Align

PEI is brittle enough we can use a knife to cut the surface of the sheet at that corner and breaking a little bit off to clear the screw. After that we can peel off the adhesive backing and stick the PEI sheet on the bed. When doing this – check twice and commit! I hesitated and tried to adjust, which put a little wrinkle in the adhesive. This is visible towards the upper left. Thankfully the wrinkle didn’t noticeably affect top surface flatness, so I just have to live with a slightly crooked PEI sheet and a cosmetic blemish wrinkle.

PEI 4 - Stick