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3-D Printer Chamber, Part 2

October 3, 2016

Disclaimer (October 2016):  

I started writing this article, but never finished it.  I got sidetracked, or distracted by something shiny, and never finished and published it.  For that, I apologize.  However, there is quite a bit of important information in this unfinished article.  Unfinished or not, it needs to be seen.  So here it is, in the RAW form.

Original draft (October 2013):

In a previous blog post, I talked about a chamber that I am making for my 3-D printer.  This post is a follow-up, discussing what went right, and what went wrong.

One important thing that went right is the overall concept.  I am super happy with how it ended up.   It was a lot more work than I was hoping for, but oh well, it was worth it.

The spool holder looks nice, and it is, but it only holds 3 spools comfortably.  With more than 3 spools, you can’t slide them back and forth enough to align any one of them with the hole for the filament.  On the other hand, I switched to 5 pound spools and it is nice to have that much filament on hand.

One major problem was with the filament feed tube.  The amount of force required to push/pull filament through that tube was much greater than I had anticipated.  Part of this is due to how the feed tube is bent (vs. how it is done in a standard Replicator 2), but I think this is still a problem with the standard configuration.  I ended up designing a system that uses a second stepper motor to push filament, on demand, down the tube to the extruder.  There is now a sensor on the extruder that detects when filament is needed, and activates the stepper motor.

The filament feed stepper motor is controlled by an ARM Cortex-M4 microcontroller.  Yes, it’s overkill.  But the board costs US$13, so who am I to complain.  Added to that is a stepper motor driver and some power supplies.  Currently the programming is very simple, but it does detect if too much filament is fed in too short of a time.   When that happens, it stops feeding filament and blinks some LEDs.  This saved my rear end several times.  I don’t want to see a 5 pound spool of filament filling the printer chamber.

I am 90% convinced that when people add a little oil to the filament it is for the feed tube and not the extruder itself.  Adding oil to the tube greatly reduced the force required to get the filament through the tube.   Before the extra filament motor, this was the only way to get reliable printing.  Even after adding the motor, oil is still highly recommended.

The feed tube is made out of Polyethylene, or PE for short.  PE is a difficult material to work with, since it is slippery enough that friction is not enough to hold it in place, and almost every glue does not stick to it.  (But not slick enough to make the filament slide easily!)   I was constantly having issues with the tube slipping out of the new feed motor block.  I finally fixed this by heating a small section of tube with a hot-air solder station (like a tiny heat gun) and then pushing the tube together.  This caused a nice ring-like bulge around the tube.  The feed motor block was then designed to hold this bulge in place.  The end result is a very secure tube attachment.

Update (Oct 2016):  There are Teflon tubes available that might work better since it is more slippery than the PE.  But the difficulty with Teflon is in attaching it.  The heat-and-melt approach didn’t work, mostly because Teflon melts at a higher temp and gets somewhat toxic at those temps.  I’m still using the PE tube, and add some oil about every hundred hours of printing.

Originally the new stepper motor was mounted on top of the chamber, outside of the soundproofing.  That didn’t work so well, because you could hear the motor when it was feeding.  I then mounted it inside the chamber, but screwed directly into the plywood top of the box.  That was about the same loudness as before, since the plywood was being used as a sound board, magnifying the sounds.  The third try had the stepper motor mounted to the already existing t-slots that was holding the lights and fans.  These T-Slots were hanging from the top of the box with elastic cords.  This is the key.  The elastic does not allow the vibrations of the motor to transfer to the plywood.  The result is very quiet.  It’s not perfect, since some sound travels up the filament and out into the room.  But the room has to be very quiet to actually hear it.

Update (Oct 2016):  I removed the elastic cords and mounted the T-Slots to the plywood top with some 3-D Printed brackets.  This is more secure and didn’t change sound leaking through.  It’s not a lot of sound, so it doesn’t bother me.

Another source of noise was through vibrations of the printer itself working through the base of the chamber.  Originally the printer was on a plywood platform that was itself supported using about 3 inches of shredded rubber from tires (called rubber mulch at the local hardware store).  The result was that the rubber was both not elastic enough (vibrations were transferring through) and yet too elastic (printer was shaking too much as the extruder moved around).

The shredded rubber was in a tray made from 1×4 inch pine boards on the sides, and 1/8th inch thick hard-board on the bottom.   I removed the rubber and replaced it with about 65 pounds of concrete.  The wood tray was sealed with silicone caulk before adding the wet concrete.   The concrete tray has some cut up mouse pad as feet.  Above the concrete is some more cut up mouse pad feet and the plywood platform.  This worked really well, although if the room is very quiet you can hear the printer.

Temperature control was another big issue.  Before I did anything to specifically address it, the temperature would start out around 72F and over the span of 4 or 5 hours would rise to over 110F.

I first addressed the heat by getting an aluminum extruder upgrade.  Then I used thermally conductive epoxy to attach heatsinks to the extruder, Y-Axis motors, and the new filament feed motor.  There is a small 40 mm fan on the feed motor, as well.  At some point I will add aluminum arms to the bot, but it seems to be working fine for now.  The goal of these changes were to help the bot handle the high temperatures.

Next, I did changes to actually reduce the temperature inside the chamber.  There were already two 80 mm fans inside to circulate air, but I added a third one that blows air across the glass door.  Mounted on the outside of the door is a quiet 120 mm fan, also blowing across the glass.  The two fans, inside and outside the glass, help to transfer the heat outside.   The fan on the outside normally runs at 12v, but I am running it at 5v.  This results in lower airflow, but it is much quieter.

With these changes, the printer can easily print with temps up to 110F, but the actual temp hovers closer to 102F.

The next temperature issue was the low temps.  It takes this chamber a long time to warm up.  Many hours.  Adding 65 pounds of concrete makes this take even longer.  My goal was to have a consistent but high-ish temperature to reduce warping and other things.   Having the chamber start out at 72F and slowly rise was not the plan.

I fixed this by adding a heater and temperature controller.  The heater is basically a heat sink with some power resistors and a fan attached.  It dissipates about 76 watts, which is intentionally on the weak side.  It takes a long time to heat up, but it doesn’t create hot spots inside the chamber.  Plus, it is easier to just keep the heater on 24/7 since it keeps large temperature swings from throwing the platform out of level.  I am using an industrial temperature controller and solid state relay to control the heater.  This is able to keep the chamber within 1 deg F of the desired temperature.

The desired temperature is in the 95 to 100 deg F range.  When the printer does it’s thing, the temp will rise to about 102F.  The end result is a consistent temperature!

Update (Oct 2016):  I keep it at 101F, 24 hours a day, 7 days a week.  Because of the insulation, it doesn’t take that much power to keep it at temp.  I don’t dare run it hotter because the printer electronics can’t take much more, and there are a lot of PLA parts that might start getting soft.

So far, everything is working nicely.  I have done several 12+ hour long prints, and many 8 hour long prints.  Obviously there were some failed prints along the way, but I feel comfortable doing large and long prints on this thing.

One nice side effect of everything is that I can spray the glass build platform with hairspray and place it inside the chamber to dry.  Between the heat and the many fans, the platform dries in minutes!  I have another 80mm fan mounted on the T-Slots on top of the chamber (just under the filament spools).  If I need to dry a build platform while I have another print going then I can use that fan to help dry the plate– it just doesn’t get pre-heated at the same time.

Future changes that I see are to better address the temperature.  Currently the lights add about 12 watts of heat, and are always turned on.  These are RGB LEDs, so I wanted to add some color control anyway.  But if they were turned off when not needed then the chamber temp could be reduced to below 100F (or work more reliably in the summer).  Also, adding some temperature control to the door fans would reduce outside noise.

Update (Oct 2016):  My printer has been running in this configuration for quite a while now; over 5,000 hours on the odometer.  I get amazing and reliable results.  I am currently working on more aluminum upgrades to the Replicator 2 printer, including aluminum carriage, aluminum arms, and a heated build platform.  The heated platform is going to cause a problem with cooling, and so I am working on a new cooling system to augment the heater.  The heated platform isn’t for ABS, but rather to print PETG, so I won’t have to run it that much hotter than I already do.


Common Job Application Pitfalls

July 9, 2014


So you’re applying for a job, now what?  The normal thing would be to send them your resume and cover letter—and that would be your first mistake.  I’ve read countless resumes, interviewed many applicants, and mentored many who were seeking a job.  Very few people do it right.  This blog post covers common mistakes when applying for a job, including mistakes in your resume.

I need to state up front that I am specifically talking about engineering jobs, although much of this applies to all jobs.  Just don’t write me angry emails because I got something wrong for people trying to become a cartographer, chef, or bus boy.

Before applying for a job, remember that it’s not just a job but a career.  You will hopefully be working there for 10 to 40 years, so behave like your life and livelihood are at stake—since it is!  This job is super important to you, and you need to show the employer that you realize this.  After all, why should they hire you if it isn’t important to you!?!?  I’m not telling you to grovel.  Just put in the effort that is proportional to the importance.   Read the rest of this entry ?


Critique of “Science and Design”

September 16, 2013

I was in a civil debate with a friend, and he wanted me to take a look at the article Science and Design, written by William A. Dembski of the Discovery Institute.  Rather than do a quick review with him, I decided to do a better critique here on my blog.

Understand that I am going to especially focus on scientific accuracy.  That’s my “thing”.  It is a pet peeve of mine when religious people (of any faith) make scientific claims that are not supported by the evidence.   With regard to scientific stuff, I will hold no punches.  Deal with it.

When the quantum physics of Bohr and Heisenberg in turn displaced the physics of Galileo and Newton, scientists realized they needed to supplement their deterministic natural laws by taking into account chance processes in their explanations of our universe.

Right out of the gate, Dembski makes a fundamental error in his understanding of science.  Newtonian physics (and Galileo too) was not “displaced”.  As with most scientific theories, the theories were expanded upon or improved on.  We still teach Newtonian Physics in school because it is useful.   This is a minor point, and I am being a bit pedantic in pointing it out, but his misunderstanding about science is common and needs to be mentioned. Read the rest of this entry ?


3-D Printer Chamber

August 28, 2013

About 6 months ago I got a new 3-D Printer, a Replicator 2 from Makerbot.  While the printer does a good job, it does have it’s flaws.

3-D Printer Chamber Overview

The first issue is sound.  While the printer is is only a little louder than a normal ink jet printer, it can take more than 12 hours to do a single print.  Over time, especially when sleeping, the noise can be more than a little bit annoying.  Most 3-D Printer owners never do anything about the noise, other than locate it in a good part of the house, and it is never a problem.  But this is me!  Two of the more interesting flaws are not unique to this printer, but hinder almost all 3-D printers at the hobbyist level.  Being the inventive type of person that I am, I set about solving some of these issues.

The second issue is one of temperature.   When the plastic is extruded, layer by layer, it comes out of the nozzle at about 220 deg. C.  It then starts to cool.  If it doesn’t cool just right, the print can warp as different parts of the print cool and contract at different rates.  With some practice, this can be managed, and warping kept to a minimum.  But drafts and other things can also effect print warping.  An open window near the printer could, in theory, cause problems should a cold breeze come in.  Some of the better 3-D printers are somewhat enclosed to help minimize this issue.  I thought I could do better.

My solution to both of these issues is to build a chamber for the printer.  This chamber is basically a box that the printer goes into, and insulation makes it both soundproof and allows some elevated and consistent temperatures inside the box. Read the rest of this entry ?


Hypocrisy, Drunk Driving, and Gun Control

December 16, 2012

Disclaimer:  The point of this article is not to argue for or against gun control.  The point is to illuminate inconsistencies in the way humans think, and to make you stop and think about your own thought processes.

In the United States in 2007 there were 12,632 homicides with a  firearm.  This does not include firearm related suicides (another 17,352).   Accurate statistics of gun ownership is not available, but most estimates are around 200-250 million legally owned firearms in the U.S.  Also in the U.S. during 2007 there were 247 million registered automobiles, and 13,041 fatalities from drunk driving.   In 2006 there were 22,073 alcohol related deaths (I assume this includes deaths from DUI).

For our purposes today, the homicide rates from firearms and guns/DUI is identical.  Of course they are not perfectly identical, and they flip flop on which has more depending on the year.  But the numbers are close enough for this discussion, as absolute accuracy is not required.

Every life is precious.  Every life has untold value left untapped.  The loss of every life has a ripple effect on family, the community, and society.  So why do we not treat fatalities from DUI the same value that we treat fatalities from mass shootings? Read the rest of this entry ?


Guns, Statistics, and Reporting Bias

May 25, 2012

Let me start this post with a little disclaimer.  This post is not about gun control.  It’s not pro or anti-gun.  It is about authors who write bad articles.  Articles where the facts are reported in a misleading way– intentionally or not.  This is irresponsible and has fostered a lot of incorrect assumptions about our society and has influenced the creation of worthless laws.  This post could be about almost anything:  climate change, health care, renewable energy, etc.  But I choose to use guns as an example– so you’ll have to just deal with it.

A recent Huffington Post article proclaimed:  Gun Deaths Exceed Motor Vehicle Deaths in 10 Cities.  The article quotes some numbers from a recent study and then goes on to make some interesting statements, including:

  • …gun deaths continue unabated — the direct result of the failure of policymakers to acknowledge and act on this ubiquitous and too often ignored public health problem.
  • And while the health and safety regulation of motor vehicles stands as a public health success story, firearms remain literally the last consumer product manufactured in the United States not subject to federal health and safety regulation.
  • Comprehensive regulation of the firearms industry and its products could include: minimum safety standards (i.e., specific design standards and the requirement of safety devices); bans on certain types of firearms such as “junk guns” and military-style assault weapons; limits on firepower; restrictions on gun possession by those convicted of a violent misdemeanor; heightened restrictions on the carrying of loaded guns in public; improved enforcement of current laws restricting gun possession by persons with histories of domestic violence; more detailed and timely data collection on gun production, sales, use in crime, involvement in injury and death; and, public education about the extreme risks associated with exposure to firearms.

The general idea of the article is that somehow we can reduce the loss of life through gun laws and regulation.  Before we get into this, let’s look at the statistics.   Read the rest of this entry ?


AfterShokz Bone Conduction Headphone Review

March 31, 2012

I recently got some AfterShokz headphones, by VoxLinc, LLC.  After looking on the net for reviews of these headphones, and not finding anything by qualified people, I figured I should post my own.

(Disclaimer:  This review is based on my experience and opinion.  That’s all.  Don’t sue me if you don’t like what I have to say.)

The claim to fame for the AfterShokz is they don’t actually go into your ear.  They sit on the cheek bone just in front of your ear and use “bone conduction” to get the sound to your ear.  At least that’s what the marketing material claims.  The benefit of this is that you can still hear whatever is going on around you.  You can ski, bike, or even drive without the safety hazard of not hearing what is going on.

But let’s get to the meat of things, shall we?

These headphones work just OK for the stated purpose:  listening to music while biking, running, skiing, etc.  And that’s it.  The sound quality is just barely adequate.  They don’t sound as good as the standard Apple earbuds that come with every iPod/iPhone/iThing (the same earbuds that are universally panned by critics).  But the sound quality isn’t distracting if you are doing strenuous exercise when sound quality isn’t your top priority.  But if you’re just sitting around at home or in your office then these headphones will leave you wanting.

Read the rest of this entry ?