Breakdown, a broken banjo bolt, and glue everywhere.

My SD300 broke down at the end of 2015, its first serious fault.  The machine had clocked over 6000 hours of build time, plus an additional 10,000 hours of power-on time, so maybe it was just about time something broke.

I had to mail-order various replacement parts from overseas, so I did the work in short sessions over the course of several months.  The machine is running now.

It started when I had left the SD300 running unattended, which wasn't uncommon.  I came home to discover the machine halted with a severe fault, a broken-out panel underneath, and a puddle of solvent-glue.


No doubt there was a glue leak somewhere inside, so I removed the exterior cowl to trace it back to its source.

Opening left side cowling to reveal cable carriers, wiring harnesses, and power driver circuits.

Solvent-glue had leaked onto the cowling panel and melted through the bottom.

There was melty plastic residue all over the cable carrier for the iron bridge.

Rolling back the cable carrier revealed even more plastic residue.

A vinyl wiring harness had disintegrated where it crossed under the steel-armored tubing at the end of the cable carrier.

The solvent deposited plastic reside everywhere it leaked throughout the SD300.

The source of the leak was a tiny, hollow banjo bolt that had broken in two.

Evidently the leak originated at a hydraulic connection, referred to as a banjo fitting, where a steel-armored PTFE tube was attached to a manifold by way of a hollow bolt that had been broken in two. This is a common type of connection in hydraulic equipment, but the SD300 employs an uncommonly small size: that's a tiny 5 mm screw thread!  It was really tough to find a matching replacement in North America, but I eventually managed to source a replacement through Airlines Pneumatics in the UK.

But the SD300 needed more than just replacing the broken bolt because the solvent glue had traveled along the armor of the PTFE tubing by capillary action and destroyed a vinyl wiring harness that had been routed through the same cable carrier.  The damaged harnesses and fittings needed to be replaced, too.

That's enough about the damage.  The machine is repaired, but I'll post pictures of my repair work separately.

Glue Smear, a super-easy quick fix

Every now and then I've noticed a shiny stripe of SolGL glue across the top layer when a model is being built.  There shouldn't ever be glue on the top surface because it can contaminate the Anti-Glue pens, which makes the model difficult to clean.  Whenever it appeared this stripe was always perfectly centered, with neatly-defined edges.  What's really strange is that it usually appeared when I'd just installed a new roll of fresh, clean material.  How did it get there?

After considerable searching I finally discovered the source of the contamination: looking into the material-supply chamber with the supply roll removed from the machine there's a bar across the bottom of the chamber to prevent the PVC from dangling out the bottom of the machine as it unrolls.

In the years I've been using the SD300 I have never cleaned there because the media door blocks the view of that area as the door opens.

When the door is fully opened, it totally blocks any view of that part of the machine.  But when the door is closed, a full roll of material could easily come into contact with that area.

With the media door mostly-closed, I could see debris had accumulated in there over the years.  And the bar was had traces of SolGL glue that had probably splashed there when I performed maintenance operations over the years.  The glue stayed wet because SolGL doesn't dry up on its own, so naturally it rubbed onto PVC in the media chamber.

No doubt a professional serviceman would have cleaned this area, but I never called in a serviceman because I'd always tried to maintain the machine for myself and it hasn't ever needed professional repairs.

I thoroughly cleaned these hard-to-reach areas using copious volume of alcohol to dilute the SolGL glue and paper towels to soak it up.  Sure enough, that stripe of glue stopped contaminating the tops of models.

A free, easy fix!

SD300 Issues from emails

Through email I've learned a lot of tricks and solutions to SD300 issues.  Occasionally I've relayed a solution from one user to another, who then devises an improvement of his own.

A user in Romania found his Anti-Glue cartridge had dried out while the machine wasn't being used, so here's a trick I learned from a British user: add water to the cartridge by injecting it into the breather hole with a syringe or needle-tipped squeeze bottle.  (49 gauge fits)  One user drilled a larger hole and refilled it through a funnel.

This technique could also be used to extend the life of an Anti-Glue cartridge in case you've spoiled one.

Occasionally users have reported an odd phenomenon where unused support material doesn't tear away cleanly because the layers are stuck together and the unused plastic has a gooey, melted texture.  I'm not sure it's the same, but I recently experienced something like it while cleaning the model in the picture.  Most of this material is unused support material.  It should all be shiny like the area at lower left.  The problem area is at top-right, which didn't peel away cleanly.  Each layer of unused material was littered with tiny spots that were tightly bonded to the layers underneath--and it appears that the shiny Anti-Glue film was interrupted by little spots where the layers were unintentionally glued together.

My first theory was glue might have dripped after ironing a new layer to the top of the model block, as pictured in this previous post.  So I watched the machine carefully during the next build.  No droplets.  But when the machine applied Anti-Glue there were spots in the film--holes through which glue might unintentionally bond the base layer to the model and support material.

I watched more carefully as the machine ironed the next layer of material, and noticed it already had smears of glue across the top surface--right out of the feeder!  How was that even possible?

Aha!  There were scraps of plastic clinging to the underside of the iron bridge, which contains the jets that spread glue on the top of the model.  My current theory is that those scraps hung down enough to touch the PVC as it was being rewound into the feeder, drawing glue into the feeder by simple capillary action.  Right or wrong, the issue hasn't occurred since I cleaned around the glue jets underneath the iron bridge.

It's not obvious how to get access to inspect and clean the underside of the iron bridge so I made a video.

Return Tool Error

While the SD300 was building a model on Tuesday night it made a distinctive 'click' noise, just once while it was using the Anti-Glue pens.  It didn't sound bad, but it was an unfamiliar sound I'd never heard before.

It never made the click noise again, but a few minutes later it began exhibiting problems putting the Anti-Glue pens away.  Eventually the machine stopped with a "Return Tool Error" message.  In SD300 lingo the Anti-Glue pens are named Tool #4, Tool #5, and Tool #6 so this message means it was unable to return a pen to its holder.

That wasn't too alarming.  Maybe that click noise had been a pen or holder had been knocked loose.  I removed the pen from the plotter and carefully returned it by hand.  The machine resumed building for one more layer but the error happened again as soon as it tried to use the Anti-Glue pens.  I installed a brand new set of Anti-Glue pens, but the error kept coming back.

When the machine had logged 24 consecutive errors I decided to give up.  It was late, so I dashed off an email and went to bed.  By Wednesday morning I already received two helpful replies from the folks at SolidVision, which recently merged with FISHER/UNITECH.  I appreciated the very prompt response but I had to go to work because I only do 3D printing as a hobby, so I didn't have an opportunity to do any troubleshooting until the following evening.

Jason Harris offered me several options, but he suggested the solution might be as simple as squeezing the spring on the affected pen holder.  The pens holders are spring-loaded clips, likely the same ones used in Roland DXY-series pen plotters.  A spring is supposed to ensure an empty pen-holder is narrower than an occupied one.  Could it really be this simple?

Curious, I brought out the calipers and measured the pen holders both with and without pens in them.  The openings on the working pen holders were all about 7.9mm wide, but the malfunctioning pen holder was open about 8.4mm.  That didn't seem like much difference, but I carefully applied pressure to the spring until the bad pen holder measured less than 8mm, then I restarted the machine.

It worked!  Then it worked again!  Just to be sure I repeatedly pressed Pause/Resume to make the machine take and return the pen a dozen times, and the pens returned to the holders every time.

This week my SD300 has logged over a thousand build jobs.  I've occasionally had issues that resulted in canceling a job or damaging a model, but this is the first time the machine itself had exhibited a fault.  In hindsight I consider that a very good record, especially considering how easily the fault was resolved.  Admittedly there are challenges cleaning the support material from some models, but the machine itself has never demanded anything more than clearing a jam or replacing spent consumables.

Test Model vs. "Clean Bubbles"

In Monday's post I concluded that whenever the SD300 has been idle for a week or more that it's wise to either build a Test Model or run the Clean Bubbles maintenance routine to clear bubbles out of the glue delivery lines.

But which method is better?  Is there a difference?

I ran some tests, reviewed the logs, and weighed the glue cartridge: a Test Model takes 15 minutes, uses 8 grams of glue, and consumes some PVC material. The Clean Bubbles routine takes about 1 minute, uses 5 grams of glue, and doesn't consume any other consumables.

So Clean Bubbles is better, faster, and more economical.

From now on, when I want to build a model after leaving my SD300 idle for a week I will 1) first clean the glue trap with a paper towel, 2) run the Clean Bubbles routine in SDMove, and 3) confirm liquid glue has been deposited in the trap.  (Repeat Clean Bubbles if the trap is dry.)

Bubbles in the glue lines tend to resolve themselves, but it's nice to discover how trivially easy it is to prevent the problem in the first place.

Another mystery solved

I think I solved another mystery or two.

Jason Harris at SolidVision told me when I was setting up my SD300 that it might give a false 'replace cutting knife' error around layer 4 or 5 if the build material wasn't stacked tightly at the edge of the build table.  It happened to me once in June 2010 the first time I used my SD300 after a long vacation.

A British SD300 user once told me that he tended to build several batches of models near the end of each month.  His first build job would usually be sticky and the support material would be hard to remove, but all subsequent jobs would be normal.  He worked around the problem by always building the built-in Test Model if he hadn't used the machine that month.

Today I built my first model since 17 December 2011, so my SD300 has been sitting idle for two weeks.  I noticed something strange immediately.  Normally the SD300 starts by bonding a layer of PVC onto the build table with an even layer of SolGL adhesive, but this time the adhesive was spotty.  The adhesive appears here as dark spots underneath the red plastic--it should have been spread under the whole sheet, not just little spots as here.

Then I noticed a shiny droplet of SolGL glue near the edge of the table, on top of the PVC sheet.  I'll bet it dripped there when the SD300 measured the material height with its micrometer, which is attached to the same unit that spreads the glue.

Ordinarily the machine's next step would spread anti-glue (masking fluid) onto this surface with a device like a felt-tip pen, but the droplet of SolGL glue would obviously contaminate the pen so I paused the SD300 and wiped up the glue with a paper towel.

Then I let the SD300 continue building to see what would happen.  The next layer had fewer bubbles than the first, and the following layer didn't have any bubbles at all.  I'm guessing air had seeped into the glue delivery system while the SD300 sat idle, but the air had all been cleared out now.

I wondered if I should cancel the job and start over now that the problem had apparently cleared itself up, but out of curiosity I let it keep running.  Lucky thing, since what happened next was a revelation.

Starting at layer 4 in every job the SD300 automatically verifies the condition of the cutting knife by cutting a test pattern at the edge of the table.  When this build reached layer 4 I heard a loud noise from the media feeder clutch which usually signals a cutting-knife failure.  I watched closely as the SD300 automatically  repeated the knife test a second time: the knife was good but the material was too loose.  The machine raised the table and repeated the test again: the test succeeded this time, but the leverage from the knife dislodged the material so the PVC sheets loosened from the table.

The SD300 started building layer 5 by ironing a new sheet to the top of the model.  Ordinarily it measures the stack with its micrometer to confirm the thickness of the last layer, but this time it started taking repeated measurements over and over.  The red light came on and the SD300 displayed "HEIGHT CHECK ERROR" on the panel.

In my experience, the SD300 tries not to abandon a build if it can possibly continue so I tried pressing the material back onto the table and pressed the continue button.  The SD300 obediently measured the model several times more, apparently trying to get a usable measurement, but stopped again with the same error.

The logs demonstrated the SD300 had made a good-faith effort to continue, but with the material flopping loose from the table it couldn't get a measurement within 446 microns.  This was an error of over 100% because the last layer had only been 188 microns, so there was no sensible way the machine could have compensated.

So the only solution was to cancel the job and start again.  Then it worked just fine, which makes sense in hindsight:

• The air bubbles in the glue lines had formed while the machine was idle.  The bubbles would have cleared themselves within a few layers, but I could have cleared them manually by using the Clean Bubbles function in the SDMove maintenance utility.
• The droplet of SolGL glue was also caused by the air in the glue lines.  It could have contaminated the  anti-glue pens, but the contamination would have eventually resolved itself.
• A height check error within the first few layers of a job probably indicates there were bubbles in the glue lines, but the problem has already resolved itself by the time it's been detected.

All these issues are self-rectifying within a few layers, so I accept my British friend's solution as the simplest: just run a Test Model build job whenever the SD300 has been sitting idle.  A test model uses very little material and it gives the machine an opportunity to work these issues out of its system without needing to understand them.  Or I could just ignore these potential issues, since the worst that seems to occur is that I might have to re-run a job that fails within the first few layers.

Power Interruption

Last weekend a brief blackout interrupted the SD300 while I was recording a video.  I kept recording and captured the SD300's recovery when the power came on again a minute later.  This video is embarrassingly awkward and rambling, but it's potentially interesting because most 3D printers can't recover as elegantly as the SD300 did in this video.  (More on that below.)


The SD300 is connected to a netbook running on batteries, so it recorded exactly what the SD300 was doing when the power went off.  The log says it was "Taking logical tool 4" which means it was picking up the 1mm Anti-Glue pen for masking fine details, whereupon it suddenly encountered a "WriteFile Error" because the SD300 had lost power and stopped responding.

When the power came on again, the log recorded how the computer re-established its connection with the SD300.  Because the SD300 remembered it had been building a model it calibrated the Z-axis to the top of the model instead of the top of the build table.

Recovering from a power failure isn't always so effortless as it was here, but it's usually quite manageable.

• The computer didn't lose power.  If the computer had also lost power then it would have been necessary to reboot and start the SDView software again.  The computer saves a copy of the current model on the hard drive so it can recover and continue if the computer is turned off during a build.
• The SD300 just happened to get interrupted between changing Anti-Glue pens.  As a safety measure the SD300 won't initialize until it detects all pens are parked in their storage holders.  If it had lost power while it was actually using a pen then it would have requested the user manually return the pen to the storage holder before it would re-initialize.
• Additionally, if the SD300 is interrupted while the top layer of the model is still attached to the material roll then it would need to cut it free before it could initialize the Z-axis.  If that had occurred, the SD300 would have adjusted the table to a safe position, reset the XY axis, and requested permission from the user to "Trim layer?"

Splice in the feeder?

When there's about 1-2 meters of material left on a PVC roll the SD300 usually stops and asks the operator to replace the materials. After removing the used roll I recently noticed what appeared to be a double-thickness where two sheets of PVC were spliced together. I believe this is how all kinds of rolled media are typically manufactured such as paper, tapes, newsprint, etc. I guess the SD300 is programmed to leave a little bit of material on the roll to avoid pulling a splice through the feeder into a model. But could it happen anyway?


I had a weirdly malformed build last June. Now I wonder if it was caused by pulling a splice into the model?

When I'd partly peeled the model there was a giant gap in the support material (right) and the model was slightly split. The model was otherwise okay so I didn't worry about it, but luckily I saved some pictures.


More evidence.

While peeling that model I found a piece of leftover support material that seemed to have a double-thickness along one edge. Was this a splice? It seemed odd enough that I took a picture of it.


The SD300 software archives all the machine's activity so I went back and reviewed the 7 June 2010 logs. (I knew when it occurred thanks to the date on the pictures.) There were several new bits of evidence:

• During the build I had paused the SD300 at layer 41. I think I remember putting in a low PVC roll to use it up.
• At layer 50 it had used up the entire roll and pulled the end of the material into the feeder, causing the feeder to jam. I'll bet it had pulled the splice into the model at this point.
  
• At layer 51 the cutting knife broke. It was a well-worn knife so the breakage wasn't unexpected, but I'll bet it got broken by the splice in the previous layer.
• At layer 68 the iron bridge unexpectedly moved on the Y axis, causing an error. I don't really understand the significance of this, but that's the only time it happened in over 600 logged builds.
  

Mystery solved 11 months later?

Maybe. Regardless, I learned several useful principles from reviewing these pictures and logs:

• Don't reload a nearly-empty PVC roll. The SD300 needs to build many layers before it can accurately calculate how much media is left on the roll, and a low roll could run out before that. Saving a few meters of PVC isn't worth ruining a model or breaking a cutting knife.
• If the SD300 does completely empty a roll, check to see if a splice got pulled in. It's probably not common, but I would've cancelled the build if I'd seen it.
  
• When a cutting knife breaks inspect the model to see if there's anything irregular. The breakage might have been caused by an unusual bump or bubble.
  

Faking a power outage

Yesterday I noticed the SD300 had mysteriously stopped part way through a build. The computer's status monitor said the SD300 was actively building layer 22, but the SD300's display suggested it was waiting for the computer. Pressing Pause/Resume had no effect.


So I ran the SDView, the SD300 maintenance app, and brought up the machine's log. There were 3 unusual entries that said "Unknown command in file." Had there been a data transmission error between the computer and the SD300? In any case, the log indicated the SD300 hadn't finished layer 21 because it was "waiting for host" to send the last data, but I guess the computer thought layer 21 had been finished and was waiting to send layer 22. Stalemate!


So, how could I resolve this apparent deadlock?

The SD300 has a robust procedure for recovering from power outages, so I pulled the plug for a few minutes to simulate a power outage. That worked!

When I plugged it in again, the SD300 went through its initialization and recognized that it had unfinished model. After verifying the model's integrity the SD300 asked me to confirm that it should resume the model in-progress. Sure enough, it negotiated with the computer to re-load the model data and it resumed building after a 2 minute pause for "Loading."

Unfeed error?

I ran a build overnight, but it didn't finish. The software had estimated there was sufficient media, but this morning the display cryptically said "Unfeed error." That's a new one.


Curious, I tried to open the media door but something was blocking it. I raised the top cover and looked into the media area and saw something I hadn't seen before: an empty PVC roll lying crookedly in the door hinge. In itself, that would be easy to fix.


I removed the obstruction and the door opened normally, revealing yet another unusual sight. The machine had reached the end of the roll and had apparently pulled a folded-and-creased piece of PVC into the feeder, which was now jammed internally. The feeder had lifted the empty cardboard roll entirely off the rollers and it had fallen into the door hinge.

I cut away the sheet and inspected the roll. It was folded but the crease didn't run all the way to the end of the sheet, which meant it must have been folded after it had unrolled. (The entire fold would have been solidly creased if it had been folded when the roll was manufactured.) No doubt the SD300 didn't recognize the end-of-roll condition, and it got twisted when the roll fell.


There was still PVC jammed in the media feeder, so I selected "un-feed media" from the front panel. It still couldn't eject the sheet, so I carefully tugged to overcome the resistance while permitting the machine to feed the sheet at its own speed. It was easy to see why it was so hard to eject the sheet: it had been folded over so tightly that the thermoplastic PVC had fused into a thick bead on one edge.


The log seemed to explain everything. The SD300 hadn't recognized the low-media condition and thought the roll had several meters of material still remaining. But it recognized the feeder had pulled in the wrong amount of PVC, so it ejected it and attempted to feed it again. That would probably explain how the roll got lifted and dropped again.

Despite the error, the machine prevented damage to the model. It continued happily after I cleared the feeder and refilled the materials. The finished parts were perfect.

Oops. My first failed build.

I left the SD300 running a build overnight, but this morning I found it had run out of material when it had just 5 layers left to build. I decided to change just the PVC roll and let it finish the build while I took a shower...and I intended to replace the rest of the material kit later (glue, AG cartridge, pens). The build completed okay, but later I started building another model without remembering to replace the rest of the consumables.


I left the machine running the second build while I went about my daily errands. While I was shopping I suddenly remembered that I hadn't replaced all the consumables, so I drove home hoping I could stop it before it ran out of glue or masking fluid.

Too late, I found the machine had stopped after building 137 of the model's 200 layers. The last few layers were barely bonded with inconsistent splotches of glue, and the last layer had simply come apart during cutting and masking. The machine was unhurt, but the model was ruined. (Everything worked fine after cleaning, replacing consumables, and purging the system.)


The SD300's log suggests it was able to cope with the diminishing supplies until it reached layer 137, at which point the machine began detecting problems. Typical layers are about ~167 microns thick, but layer 137 measured only 104 microns because the last sheet had come loose. Recognizing an aberration, the machine spent half a minute re-measuring the layer again and again, eventually logging (in colloqual English) "Checked delta is 103micron, not good."

The machine tried to compensate and finish the model anyway, increasing the number of layers to compensate for the abnormally-thin material. But the layer began to come apart during cutting, and an AntiGlue pen snagged on a loose shard during masking. The machine paused itself and reported an error, awaiting an operator to decide whether the model could be salvaged.


I plan to assiduously avoid repeating this mistake in the future. Aside from ruining the model, running out of glue probably poses other risks because the model could disintegrate and drop debris into the machinery.

Luckily the machine had stopped promptly when this model came apart. Cleaning up was made considerably easier by Solido's SDView utility, which gives the operator direct control for maintenance. After this incident I needed to lower the build table to clean away loose bits of plastic, purge the glue system, and clean the glue trap.