Reprap blog

Experimental Dual Unit Designs

30-4-2017

The Hangprinter Hackathon at Bitraf produced some technical progress.

Besides dividing the Hangprinter into two units, the GT design also tried out the concept of spanning up linear actuators between winch and ABC anchor points:

This concept works wonderfully in theory, and you can even use belt for the yellow loop to make it easy to build. In practice you need to keep the loops very tight, or the belts will skip. We did a quick and dirty patch to solve this. The dangling bottle of water in the picture above is what keeps our D-line tight.

The Hangprinter GT turned into a quite bulky installation, so the design won't be continued. It did shed some light on a few pros and cons with dual unit Hangprinters in general.

• Pro: Easy to snap together. Few parts that need to fit each other.
• Pro: No absolute requirement of wireless communication.
• Pro: Lighter moving unit allows quicker accelerations.
• Pro: Increased modularity. ABCD actuators, electronics department and moving unit can be swapped out independently.
• Con: Stepper- and hot end cables must be extended manually.
• Con: Max stepper cable length (a few meters) limits mounting options.

The Benefit of Large Spools

The spool radii are doubled as compared to the standard Hangprinter spools, in order to decrease line buildup. A doubled spool radius reduces spool buildup to ca 1/4. Let's step through the maths to kill some time:

To wind in $$2r$$ of line onto an empty spool with radius $$r$$, we would need to rotate the spool by 2 radians. A spool with $$x$$ meters of line already wound onto it would have $$\epsilon(x)$$ of buildup added onto its radius $$r$$. It would wind in $$2(r + \epsilon(x))$$ of line if it were rotated by 2 radians. Without buildup compensation the resulting error would be

$$\text{err}_r = 2\epsilon(x).$$

To wind in $$2r$$ of line on an empty spool with radius $$R=2r$$, we would need to rotate the spool by 1 radian. A buildup of $$\delta(x)$$ would cause an error of

$$\text{err}_R = \delta(x).$$

The circumference of the spool with radius $$R=2r$$ is twice as long as the circumference of the spool with radius $$r$$. The buildup caused by $$x$$ m of line should therefore be ca halved on the big spool, which gives us the approximate total benefit of doubling spool radius:

$$\text{err}_R = \delta(x) \approx \epsilon(x)/2 = \text{err}_r/4.$$

But wait, there's more. The spools depicted above are also 2 times higher than standard Hangprinter spools. This should cut buildup in half once again.

If that isn't enough then there's also the possibility to tie in lines mid-air, and run a single line around each spool. This wall of text has already gotten the line buildup down to 1/8 of what we had before anyways, so let's wait and see if this is really necessary.

The buildup problems of Hangprinter version 2 were mostly on the D-axis, which had doubled lines (mechanical advantage 2). We can drop that on version 3 since it has a light moving unit. To summarize, we cut D-axis buildup to 1/16 and leave ABC buildup at 1/8.

After all this theory let's rest our eyes on some Hangprinter version 2 parts designed and printed by Alexander Osika:

When the version 3 is up and running, I will focus my dev time on adding closed loop control, auto calibration and DC motors, in that order. Well, at least that's the plan right now. I'll prioritize improvements that apply to both single- and dual unit Hangprinters, and keep both branches alive.

- tobben

25-4-2017

- tobben

Babel Tower Time Lapse

15-4-2017

To recharge before the Hangprinter Hackathon in Oslo next weekend, I threw together a Babel Tower time lapse.

Enjoy!

- tobben

First Pull Request Merged

4-4-2017

The Hangprinter repo on has had its first merged pull request! Committer was awigen. See commmit here. The code is about adding an axle to the worm. I've been wanting one for a long time, so I was very happy about the pull request. After some further refinements, the worm now looks like this:

Finally I'm not alone in the repo anymore =)

- tobben

Hangprinter.org

2-4-2017

Check it out: hangprinter.org! Big thanks to Piyush Dharnidharka for taking the initiative and building the page.

It has a practical Hangprinter Calibration Calculator page that implements the equations from the calibration manual.

There's also an about page featuring some links and a text.

- tobben

Push Fit Sandwich

27-3-2017

In this forum post, NOVAprint confirmed what I had suspected was a weakness in the sandwich design. A gap might open between the snelle and the sandwich gear, so that line wraps around the center cylinder. I never really liked the super-short screws in the sandwich either, so I've designed a push fit solution:

The master branch of the repo has been updated both with scad-file and new stl files. Be warned that I haven't tested these files. If you want the old files, they're back in the version 2 branch of the repo.

I've been alone in the repo for so long, it has turned me into that guy.

- tobben

Sstruder v2 and Helsingborg

27-3-2017

I got the chance to test the improved extruder design recently. It worked better than the previous Sstruder, so stls were pushed to the repo today.

I also tidied up the stl directory in the repo and experimented with high travel moves. The Hangprinter moved at 360 mm/s without loosing steps or accumulating errors. It didn't move in straight lines, but it reached its planned end point.

I spent the weekend Hangprinting at 3D Meetup in Helsingborg. Thanks to the organizers, you did an amazing job! Based on the feedback from Helsingborg, I think the whole Hangprinter community thing is starting to get legs: [twitter.com], [twitter.com]

- tobben

Tweets

7-3-2017

I posted a few Tweets recently. Reposting them here now.

- tobben

The Tilt Problem

26-2-2017

Hello Reprappers and Hangprinterers! The Babel print gives a lot of lessons, so there's a lot of posts this week. Ca 1.5 m above ground and with 20 m of line on the D-spool, I've noticed a previously undocumented problem.

The D-line from the corner where the B- and C-sides meet consistently sees a larger spool diameter than the other two corners. I suspect that subtle differences between the D-fish rings may cause this effect, or that it is simply the weight of the D-motor causing this. It is interesting that one corner travels faster while the other two corners stay perfectly horizontal relative to each other.

Anyways, structured debugging is a job for future tobben. Present tobben just wants to show you another full figure picture of the print:

My next post will probably drop the SI unit system.

Instead it will leverage on big data and impact the value added Internet things, featuring intelligent solutions for new normals as required by next generation info capitalism in the cloud (with diamonds).

Disruption will make language hyperlocal like a mashup of microservices in a web of buzz. Later it will drop-swap written words for virtual broadcasted brandcasting on a blockchain. (It's just a bit more deep and viral, you know.)

Diversity and non-scalable divergence will immerse the paradigm through the re-realization of a withholding economy, and possible grand scale peer-to-peer destruction facilitated by social analytics and the evolution of physical cookies pushing us towards mobile nanomodularity and some seriously driven development.

;)

- tobben

Changed Anchor Points Mid Print

24-2-2017

I managed to sneak up the anchor points yesterday. The secret trick is to pause and move one anchor point at a time. Then run a few rounds very slowly after each change, adjusting calibration errors manually with small G6-moves.

I my case, each anchor movement still produces visible artifacts on the print:

If you plan on making anchor point movements mid print, I recommend moving them only along the Z-axis and making the movements in increments of ca half the distance between anchor point and origo.

Ok, enough about the errors, time for a full figure picture:

The project of Hangprinting a Babel Tower happens in Sliperiet, Umeå, Sweden. It is part of the +Project (Swedish link here). More about Sliperiet is found here.

- tobben

Slowly but Surely

23-2-2017

The tower is modelled with OpenSCAD. Repo here.

I'm trying to move the anchor points upwards mid print, but I haven't really nailed the re-calibration yet...

- tobben

Community at Embryo Stage

20-2-2017

It seems like some collaboration and maybe even a little community is gathering around the Hangprinter Project. Right now, there are 5-6 builders out there wrapping their heads around the source files, assembly process and calibration.

No one has sent any pictures though, and I'm a bit worried that builders will lose motivation when they bump into challenges (bugs that I wrote).

Hang in there! The ceiling is the limit!

- tobben

D-Wobble Debugged

2-2-2017

Those who have zoomed in on my Hangprints after I added the worm drive will have noticed a periodic error. The following pictured Hangprint shows the problem quite clearly:

This error arose because my Hangprinter's worm has not been mounted straight along the motor shaft.

The above animated wobble is a bit exaggerated. You can see and hear the actual wobble in the following old video:

The root of all this wobbliness is a non-straight flat part on the shaft itself.

The motor is covered in tape because I'm about to start grinding the flat area into straightness. Debugging is so delightful when the cause gets obvious within 10 minutes and the solution involves grinding!

Until next time.

- tobben

Experimental Line Buildup Compensation Feature

27-1-2017

I've conducted a few experiments recently, and I think I've arrived at a usable implementation of the line buildup compensation that I described in an earlier blog post. In this post, I'll try to go a bit more in detail.

The Problem: Account for Changing Spool Radius

Most RepRaps have simple linear relationships between motor position and hot end position. If their hot end is at the position 100 mm along an axis, their corresponding motor is at step number

$$m = 100\cdot \text{s}, \tag{1} \label{1}$$

where $$\text{s}$$ is a constant and $$m$$ is the motor's step count.

Hangprinter can not use this simple linear relationship because it winds line around spools. When there is more line on the spool, the motor winds up more line per step because of the increased radius resulting from line buildup.

We need to change the linear relationship $$m = x\cdot\text{s}$$ with a more complicated relationship $$m = f(x)$$.

Step 1: Find Conversion Factor for Infinitesimal Movement: $$\text{s}'$$

Say we want to move an axis from $$x_0$$ to $$x_0 + \text{d}x$$. A simple linear relationship, like in Equation \eqref{1}, will be valid if $$\text{d}x$$ is small enough. We still have to find the correct conversion factor $$\text{s}'$$, but this is easy as long as we can assume $$R$$ to be constant.

Let $$\alpha$$ be the number of radians that the spool rotates when the motor makes 1 full revolution. On Hangprinter version 2 the motors's gears have 9 teeth and the spool's gears have 43 teeth, so we get $$\alpha = 1.32$$. Looking at Figure 1, and assuming $$R$$ constant, we would move $$R\alpha$$ by doing 1 full motor revolution. Now say that the motor makes $$t$$ steps per revolution, and we have our steps per mm:

$$s' = \frac{t}{R\alpha}. \tag{2} \label{2}$$

Step 2: Make Radius Depend on Position: $$R(x)$$

In Figure 1 we approximate the buildup as a rectangular torus shape, and $$R$$ depends on the volume of that torus.

The volume of the torus depends on the amount of line on the spool like so

$$\text{Volume} = h\pi(R^2 - r^2) = vx, \tag{3} \label{3}$$

where $$h$$ is the height of the spool, $$v$$ is the volume per unit line, and $$x$$ is the position along the line that corresponds to $$R$$. Note that we need to give $$v$$ a negative sign if we define the positive $$x$$-direction to be the direction we move when we unwind line. Rearranging Equation \eqref{3} gives us

$$R(x) = \sqrt{\frac{vx}{h\pi} + r^2}, \tag{4} \label{4}$$

Step 3: Make Conversion Factor Depend on Position: $$s'(x)$$

Combining Equation \eqref{4} back into Equation \eqref{2}, we get

$$s'(x) = \frac{t}{\alpha\sqrt{\frac{vx}{h\pi} + r^2}}, \tag{5} \label{5}$$

Just for reference: apart from missing a factor to account for mechanical advantage, the above equation corresponds exactly to the equation I presented in a previous blog post, see \eqref{*}. In that equation, $$x$$ is split up into the parts to account for mechanical advantage and calibration procedures. In this theoretical review, we rather want to simplify our notation, like this:

$$s'(x) = \frac{a}{\sqrt{c_0 + c_1x}}, \tag{6} \label{6}$$

where $$a = \tfrac{t}{\alpha}$$, $$c_1$$ is the factor that multiplies with $$D$$ in Equation \eqref{*} and $$c_0$$ is the rest of the constants below the root sign in Equation \eqref{*}.

Step 4: Testing...

I mentioned in the beginning of this post that I've conducted some experiments. I found that continuously re-applying Equation \eqref{6}, and using the computed values like $$m = x s'$$ doesn't produce nice results.

Similarly miserable results were achieved by applying Equation \eqref{6} at a constant frequency:

Step 5: Make $$\text{d}x$$ Small Enough Using Theory

A problem with the above approaches was error accumulation. Say the Hangprinter reached point $$x$$ with $$m_0$$ on its step counter. A few minutes later, Hangprinter reaches $$x$$ again, but truncation errors have put the step counter to $$m_0 + 1$$. Steps per mm is calculated solely based on $$x$$, so it is totally random whether the next truncation error gets us back to the correct $$m$$, or if the error will be increased to $$m + 2$$. This randomness gives the typical random walk pattern along the vertical edges in Figures 3 and 4.

To get back on track with finding $$m$$ in Equation \eqref{1}, we integrate $$s'(x)$$ from zero to $$x$$. This integral gives us a one-to-one mapping from $$x$$ to $$m$$.

$$m(x) = \int_0^{x}{s'(x')\text{d}x'} = \frac{2a}{c_1}\big(\sqrt{c_0 + c_1x} - \sqrt{c_0}\big). \tag{7} \label{7}$$

I was quite surprised that all this theory and volume calculations got me from a straight line relationship to an almost equally simple square root relationship. I feared that line buildup compensation would be computationally intensive, so I'm quite pleased it's only one addition, one subtraction, one multiplication and one square root extra, compared to no compensation. Even an my old Atmega2560 can handle that. In the actual firmware, I've changed notation again, so it looks like this:

target[A_AXIS] = lround(k0a*(sqrt(k1a + k2a*delta[A_AXIS]) - sqrtk1a));

With the calibration constants I'm using on my own Hangprinter, the compensation makes the following theoretical difference in actual movement lengths:

And finally the first test print to prove it all kind of works:

It's nice to see the printer moving more than 1 m upwards without over-tightening any lines, and then back again to the same millimeter! It almost looks functional.

- tobben

Hangprinter Presentation Video and Campaign

15-1-2017

I've been helped by some friends to make a campaign. It has a presentation video and a logo and a picture of me and everything! Get to it by clicking the logo below. Please share, comment and make the Hanprinter Project your own.

The goal of the campaign is to allow Hangprinter to grow faster and more user friendly. Hangprinter needs a dev team. It's made to be useful, so it also needs to spread. To spread more, it needs more of this:

- tobben

Compensation May Allow Bigger Prints

14-12-2016
The line compensation code may increase print volume noticeably. During testing, it has allowed Hangprinter version 2 to go places where version 1 surely would have over-tightened lines and skipped steps.

- tobben

Compensating Line Buildup on Spools

11-12-2016

I've added to Hangprinter-Marlins some code that compensates for line buildup on the spools. Without it, I found that error in steps/mm grew to several percent as print dimensions grew close to 1 m. The problem was particularly noticeable on the D-axis since it has three doubled lines, so moving 1 mm in the D-direction puts 6 mm of line on the D-spool.

The approximation of new spool radii that I've used looks like this:

$$\frac{\gamma\cdot g}{\sqrt{\beta(l_0 + \omega(D_0 - D)) + r^2}}, \tag{*} \label{*}$$

where

• $$\gamma$$ is the number of motor steps required to rotate the spool 1 radian,
• $$g$$ is mechanical advantage (2 for doubled lines),
• $$\beta$$ is the volume taken up by 1 length unit of line divided by $$\pi$$ and the spool's height,
• $$l_0$$ is the length of the line on the spool when printer is home (in origo),
• $$\omega$$ is the total number of lines along a direction (3 doubled lines $$\Leftrightarrow$$ 6 lines),
• $$D_0$$ is the distance from an anchor point to an action point when at home,
• $$D$$ is the current distance from anchor point to anchor point and
• $$r$$ is the spool's radius when there is no line on it.

Setting these variables will require some measuring and messing around in Configuration.h. The comments in Configuration.h are honestly trying to be helpful.

The above equation requires quite a bit of computation. If an Atmega2560 running Hangprinter-Marlin were to perform it more frequently than ~10 times per second, it would risk computing new movements slower than it performed them, leading to unwanted print pauses and jerky movements.

To limit the computational load Hangprint-Marlin is currently only computing new steps/mm once per received G1 or G92 commands. A gcode file with 300 G1 movements would cause Hangprinter-Marlin to compute new steps/mm 300 times.

Computing steps/mm only once per movement is of course an approximation. We will only get steps/mm right at exactly one point along the G1-move. It is tempting to place this point at one of the ends since that would be computationally cheap. However, it would kill precision, even for simple movements like the following


G92 X0
G1 X100
G1 X0

The printer would use different steps/mm settings for the two different G1-moves. It would not end up where it started.

Instead of correctness at endpoints, Hangprinter-Marlin computes steps/mm to be correct at the middle of every G1 move. This solves the trivial example of back-and-forth movement described above, but it is still an approximation. The next theoretical step will be to find an equation describing the error we accumulate from not continuously computing new values for steps/mm.

If you want to improve the approach to dynamic steps/mm I've described above, then you will most probably want to improve lines 1757 to 1763 in Marlin_main.cpp:


float halfway_delta[4];
float halfway[3];
for(int8_t i = 0; i < 3; i++){
halfway[i] = current_position[i] + 0.5*difference[i];
}
calculate_delta(halfway, halfway_delta);
update_axis_steps_per_unit(delta, halfway_delta);


I've taken the liberty to highlight variables and functions with the colors blue and purple. See master branch in the repo to fetch the code.

- tobben

The Worm Drive Works

8-12-2016

Just tested the worm drive. I was so happy to see it work that I made a little video.

Thanks to Simon, Jens and strangers at 3D-printerfestivalen for suggesting a worm drive. The worm itself is printed in nylon by Simon.

- tobben

Adjustable D Line Lengths and New Look

26-11-2016

Just made the D-line lengths easier to adjust independently. This is useful to get Hangprinter's corners in level with bed. Newest changes are at a new branch in the repo.

I'll be testing out d-line-adjustment, worm drive and new extruder with a physical prototype. Decided to celebrate by creating an alternative look. It saves some plastic too.

Cheers!

- tobben

Worm Drive on D-axis

18-11-2016

Click on gif to make it stop rotating.

Check out all improvements at worm_and_direct_drive branch in repo.

- tobben

5-11-2016

- tobben

Hangprinter Calibration Manual v0.1

3-11-2016

This post will make it easier to calibrate Clerck by avoiding the need for measurements like this:

Step 0: Mount Wall Frame Parts

Mount all the lower frame parts at roughly equal heights above your floor. While not theoretically necessary, this makes calculations and measurement procedures easier. We assume your floor is perpendicular to gravity.

Keep the flat sides of lower frame parts as parallel to the ceiling frame part's sides as you can.

Step 1: Mark out Origo in XY-Plane

Use tape or ink to mark out a point directly below your ceiling frame part. This point will be used for measurement and homing reference, so keep it fixed and visible.

Step 3: Translate to Cartesian Distances

Now that we use our six measurements to determine six unknowns. Denoting the x-position of anchor point B like B_x, we can list the unknowns:

• A_y
• B_y
• B_x
• C_y
• C_x
• D_z

We orient our Cartesian coordinate system such that A_x = 0. Also, we set A_z = B_z = C_z = 0 from the restrictions in step 0 above. Now the Law of cosines and good old Pythagoras solves the rest for us.

• A_y = -a
• B_y = (s^2 - b^2 - a^2)/(2*a)
• B_x = sqrt(s^2 - (a + B_y)^2)
• C_y = (f^2 - c^2 - a^2)/(2*a)
• C_x = -sqrt(f^2 - (a + C_y)^2)
• D_z = d

Step 4: Take Action Point Offsets Into Account

Since lines are not tied to the center of hangprinter we need to subtract the offsets. These numbers are more or less hard-coded into the OpenSCAD files. I made a branch called calibration_manual_0 that corresponds to the renderings in this post. I'm also listing the values for ya right here. Yeah, right here:

• ANCHOR_A_X = 0
• ANCHOR_A_Y = -(a - 59.8)
• ANCHOR_A_Z = -146.4
• ANCHOR_B_X = B_x - 59.8*sqrt(3)/2
• ANCHOR_B_Y = B_y - 59.8/2
• ANCHOR_B_Z = -136.6
• ANCHOR_C_X = C_x + 59.8*sqrt(3)/2
• ANCHOR_C_Y = C_y - 59.8/2
• ANCHOR_C_Z = -126.8
• ANCHOR_D_X = 0
• ANCHOR_D_Y = 0
• ANCHOR_D_Z = d - 117.0

These values correspond exactly to what you're supposed to feed into Configuration.h to calibrate your Hangprinter.

In Theory...

We could add three more measurements and be able to calculate A_z, B_z and C_z. This would get rid of the requirement to mount the lower anchor points in a plane perpendicular to gravity. I find these three measurements a bit difficult to carry out in practice. Practical difficulty is of course subjective, but the six-measurement procedure is the one I use.

I hope this has been useful, best of luck!

- tobben

Oslo Skaperfestival 2016

25-10-2016

Clerck was demonstrated in public for the first time this weekend!

Fellesverkstedet Fablab and Bitraf Makerspace kindly let me show Clerk by their stand at Oslo Skaperfestival. They even helped me mount and present it! Special thanks to Jens, Martina and Jon for the invitation, the warm welcome and help of various sorts.

The festival atmosphere changed like in a cafe district in April. Sometimes library quiet, doors closed, a few people carrying chairs around. Sometimes tivoli hectic with makers, teachers, hosts, children, amazing machines and zing boom wow bam all along the library hallways.

Six hours of interesting people, pitching, teaching, listening and learning before the atmosphere reverted back to oh so quiet. It faded like the echo of a school bell. Left at the library were only a few makers, discussing the usual topics: production distribution, dinner options and how to make money.

My work will be influenced by the conversations by the festival stand for a time to come. I'm looking forward to it =)

- tobben

PS! added Oct 26

Here's a layer consistency shot of a print made at Skaperfestivalen. Next time, we're going for something a lot taller!

- tobben

Homing the Hangprinter Without Adding Hardware

23-9-2016

I've thought some more about Hangprinter recently, since I'm going to demonstrate it on the 3d printer festival arranged by the Norwegian Museum of Science and Technology in Oslo. I've only ever mounted and calibrated Hangprinter once before, so getting the manual homing to work fast enough worries me a bit. I don't have the time to implement the proposed accelerometer dependent homing procedure before the festival.

The following (almost stupidly simple but still kind of useful) solution will be the first thing I try to make homing faster than the aiming plump technique I've used before (see picture).

If alignment of marks as shown above proves sufficiently precise, I will use a similar concept for automatic homing. Replacing the green marks with and optical or magnetic sensor arrangement should be quite straightforward.

- tobben

Yet Another Very Simple Extruder Design

21-9-2016

I've thought about a second generation Hangprinter lately, including the extruder. My current favourite re-design uses two motors running synchronously.

The motors in the figure above are supposed to resemble Mabuchi 130 servos rather than steppers. The informed discussion in this forum thread and this video demonstration have made me interested in servos again.

The RepRap community's relationship with servos is long, complicated and rather fruitless even though the promise of mechanical simplicity and low weight has always been present. There seems to be something hard about servos. Still, 2d-printer-engineers manages to churn out servo driven movement platforms, lots of them. Are those Inkjet engineers better than us? No, of course not.

Anyways, if the servo usage doesn't pan out at all, I can always try two Nema14's instead. Pinching filament between two motor shafts would still be cool and simple. Not as cool as servos though.

- tobben

Why Optimize Chaotic Production?

10-9-2016

RepRappers have noticed me that basing the story line of my my Master's thesis on productivity numbers doesn't resonate with them. This tickled me to think about and formulate why I do what I do, hence this post.

In the thesis, I really wanted to say that we can afford producing in humane, joyful ways, and that D3D-Porteus can help. Also, in this title and previous posts, I have used the word "chaotic" loosely. With chaotic I mean "distributed between people with their own budgets for time and money".

In centralized production, unrelatedness, vulnerability and boredom are hidden costs because they are hard to count but easy to feel. In chaotic production, the producer carries the total production cost, both in time, money and emotion, and also decides how to work and when to stop. Chaotic production must be optimized to meet the producers interests. Optimizing chaotic production must include preserving creative joy.

The answer to the question posed in the title is then the inverse of unrelatedness, vulnerability and boredom, namely:

1: Close Relations

As humans we are evolved to thrive in small groups that help each other. Helpers feel pride and helped ones feel gratitude. It is hard to help and get love in return from distant factories. Producing everything centrally wastes opportunities to feel more pride and gratitude in our lives.

2: Resilience

Centralized factories are single points of failure. Shit just happens sometimes and when it happens we better know how to produce our stuff ourselves.

3: Fun

We are born capable of having interests and we thrive when we get to follow them. Chaotic production doesn't have bosses with the licence to bore. When you're allowed to listen to your heart you will recognize its sense of humour. If you live in an industrialized society you will probably not end up starving in the streets even if you listen to a funny heart.

- tobben

Portable Gcode and Short Status

5-9-2016

Today I asked a question on reprap forums that has puzzled me for a long time. Why don't we share gcode instead of 3d models? The technical obstacles are small and it would be an obvious optimization of chaotic production. See the forum post for details. Hoping for an interesting discussion there.

Now that my Master's is finished I'll try to make a living out of it. I'll continue to post report-like documentation here and list day-to-day activities over at my log on the OSE wiki.

As a start, I've co-founded a limited company that is offering RepRap Assembly Workshops and other course activity to schools and youth clubs around Norway and Sweden. See home page in Norwegian here. I tried to make a logo in Blender. It's my first one, and it ended up looking like something you would expect to see on a tube of tooth paste, but I kind of like it because I made it myself:

Before I dive into searching far and wide for jobs, I need to work on my RepRap family in Norway and Sweden. I need people who know RepRap that I can talk with and share knowledge, experiences, hardware and services with. As a start, I'll head to Oslo this week and visit Bitraf and Fellesverkstedet. I hope I can get to know them by helping them with their projects. If they want to cooperate on one of my projects, I plan on suggesting a new D3D-Porteus based on GuixSD, or to work on portable gcode as described in the forum post I posted today.

- tobben

Optimize Chaotic Production

29-6-2016

I presented my Master's recently, with a story line that was very RepRap centric. I'd like to re-present and develop my thoughts with some colors here. Be warned that this is a post about why I RepRap, not how I RepRap.

I live in the EU and have a lot of contact with the US. I'm among the lucky ones by all metrics, but I also see a lot of frustration.

The plots above tell so many stories I, could stare at them for hours. I see how the computer age takes off, and robots starts to produce stuff crazy fast while people go furious. It's like a very odd movie plot, it makes me scratch my head. I've experienced the frustrations of modern western life but I'm surprised by the glaring and obvious stagnation and frustration in the above stats.

EDIT 30 June: There's a really nice presentation of what frustrates western middle classes in this report's Figure 4. The accompanying text explains western middle class stagnation with globalization. It may be right, I don't know what caused what. I just think that our computers and robots should have prevented stagnation regardless. They are so powerful and even supposed to be personal. END EDIT

Computers are machines for thought work, they should lift our burden of thought and give us peace of mind. Well, at least in theory (my dreams)... It would be so nice to just reboot the computer revolution and make it better. Computers could make people independent, resilient, and proud if used right. Like cars do.

Many are still inspired by T-Ford's successful production style. Bringing a machine to the masses has meant setting up a central production line for at least 100 years, including the years of the recent computer revolution. Only around 2007 was central production first rivaled, by copyability through self-manufacture. The RepRap 3D printers then got so easy to copy, partly thanks to self-manufacturing, that the number of producers grew exponentially.

When rebooting the computer revolution we should try the new RepRap-style of production. In the thesis I show that RepRaps are very popular and numerous. I also show that they are actually produced and forwarded virally. To formalize this observation, I present some data collected by Spanish RepRappers (see Figure 5) and import a structural virality measure used by researchers on other viral phenomena.

In the presentation I point out that chaotic production requires low unique parts count, good documentation and low price, just like assembly line production. I suggest that software freedom and self-manufacture are additional efficiency requirements not found in assembly line production.

I set out to optimize the chaotic and distributed RepRap production and discover that I can do so by optimizing RepRap Assembly Workshops, and particularly the software that they use. I collect all the data I can find about RepRap Assembly Workshop arrangements on the Internet. See my data in good looking pdf here or in practical spreadsheet here.

I end up packaging Marlin, Arduino IDE, Slic3r, Printrun and OpenSCAD in a live OS. Open Source Ecology tested the live OS for me, and they liked it quite well. I've also used it myself in a four-day 3D printing course for kids this summer, and I found it handy. Technical details of the live OS is another post, but files are hosted here.

That was my little story line, hope you liked it and look forward to some more technical stuff in the coming months. Download thesis here, and presentation slides here.

EDIT 30 June: Sorry for messing up the RSS-feed. Restructured the blog to make it load faster. See list of links at bottom of page.

EDIT 7 July: Please use this thread to comment and ask questions related to the thesis or this blog post.

- tobben

Update and Clerck Build Instructions

8-2-2016

I've been working on Open Source Ecology 3D printer workshops (see my work log for exactly what I've been up to) the past month, and will continue to work on that until mid summer.

Clerck would love to be developed further by anyone even if I'm on another project right now. The following instructions should not be considered "the ultimate way", it's simply how I did it on my first try with the prototype. The best absolute source of Clerck information is the OpenSCAD files in the Github repo. A special branch was created for this build manual, called build_maunal_0. Hangprinter.scad is the most high-level entry point.

This build manual will be short and terse. Ask questions the forum thread to fill in knowledge and information gaps.

Clerck Assembly Manual v0.1

Step 0: Sourcing

For vitamins bill of materials, see the Appropedia article. Some info on hardware specifics is found in used_hardware directory in repo. For printed parts bill of materials, search stl directory of build_maunal_0 branch in Github repo for the shown STL files. You'll also need the Hangprinter-Marlin firmware. It's in the firmware folder of the repo.

Step 1: Cut Lines to Length and Tie to Spools

Cut all nine lines to desired lengths. If you know the distances between the origin (middle of print bed) and the mounting points (walls and ceiling), then you can use those to calculate good line lengths. I use twice the origin/wall-distance plus ca 1.5 meters along all axes. As there are 4 movement axes on this printer, there will be 4 lengths. We call them the A-length, B-length, C-length and D-length.

After this step you should have:

• 2 A-length lines
• 2 B-length lines
• 2 C-length lines
• 3 D-length lines

Tie the A-length lines onto one spool, then the B-length lines onto another spool etc.

Step 3: Sandwich Spools, Gears, Bearings and Spacers onto Bottom Plate

The bearings and spacers should push-fit onto the middle cylinder of the bottom plate. Ensure that geared spools rotate freely by rotating and wiggling them by hand.

Step 5: Assemble the Tble-extruder

I used the E3D Volcano as my hot end. Its build instructions are found here. You could use any hot end, but big nozzle diameter and long melt area are key for high print speeds. The Volcano has worked well for me in that it was easy to install, doesn't clog and drools surprisingly little compared to its big nozzle diameters.

Be warned that the forthcoming alignment task fiddly. If I had any time to work on the Hangprinter project's modules, this extruder would be drastically changed to reduce fiddlyness.

Step 6: Mount Extruder Motor

The small extruder gear is push-fit onto the extruder motor shaft, which should have one flat side. Remove two neighbouring bottom screws from the bottom of the motor before mounting.

Note that this step is very dependent on motor size (maybe unnecessarily so). If you have another motor than 17HS4401N, then double check that your motor fits (see lines 2, 3 and 4 in measured_numbers.scad). The extruder motor hole is created on line 262 in parts.scad, if you rather want to change the CAD file than change the motor.

Step 8: Mount the A, B, C and D-motors

Match motor gear height and placement with corresponding spool.

Look at your printer from above to confirm you can read "CBCADAB" from left to right before preceding.

Step 9: Assemble Wall and Ceiling Parts

I hung a wooden platform in a lamp hook avoid having to drill screw holes in the ceiling (see picture).

The end of the A, B and C lines are attached to the M3 screw holding the corresponding fish line ring. More details on that in a previous post.

Step 10: Mount Wall and Ceiling Parts

This is the step where you potentially do screw holes in your walls and ceiling. I use strong double-sided tape for all wall-mounted parts. Placement is really insensitive as long as all plates are, fixed and horizontal. Each side plate should be parallel with one side of the ceiling plate.

Step 11: Thread D-lines

I rested motors on two towers of books while doing this.

Step 12: Mount electronics

Secure locking screw on D-spool-gear and flip the printer upside down. Mount Arduino Mega+RAMPS on an isolating plastic sheet, and mount that sheet using bottom-screws of stepper motors. I used a piece of ice cream packaging as isolation sheet.

Step 13: Upload Firmware

Plug in the USB cable and upload the Marlin firmware found in firmware/Marlin/Marlin. If you haven't uploaded firmware through the Arduino IDE before, it looks like shown in this video. Try to communicate with your RAMPS board through USB cable and Pronterface (no power supply is needed for this). Hangprinter-Marlin uses baud rate 115200. Unplug USB cable when done.

Step 14: Wire up electronics

For those who are new to electronics, take some time to read about general electronics safety. For examle Electronics Safety Rules for Dummies and howtogeek article on static electricity protection. Insulate the hot end. The Clerck design has a high risk of melting its own cables, which will cause fire (see forum thread).

Mount stepper driver chips and adjust Stepstick trimpots to get the right reference voltage (see Tom's video on this and Pololu's product home page). I use Stepsticks with drv8825 drivers, extra long legs and cooling ribs both above and below chip (see previous stuff).

If you connected power to RAMPS during reference voltage adjustment, pull the wall-plug and also unplug power connectors on RAMPS now. Also unplug your USB cable. Wire A-motor to RAMPS's X-contacts, B-motor to Y-contacts, C-motor to Z-contacts and D-motor to E1-contacts. Wire E-motor and hot end as shown here.

If you want wirelessness, wire in the JY-MCY bluetooth antennae as described on the RepRapWiki. Note that the antennae connection will prevent communication through USB cable as long as it is plugged in. I use Blueman Device Manager 1.23 and a Ubuntu 14.04 system for connecting to the JY-MCU.

After doing safety-checks on the electronics and power supply with your multimeter, flip the printer back into upright position and couple the power chords to the RAMPS board. When you're confident that your wiring is right, plug your power supply into the wall and feed your Clerck its first taste of 12V.

Step 15: First Movement

Connect to your Clerck through Pronterface and check that D-motor has a nice constant holding torque. Unscrew the D-stop screw and watch Clerck hang by itself. While holding a hand below it, try sending the gcode line G3 D-1. This tells Clerck to move 1 mm closer to the D anchor point in the ceiling, without recording or counting the movement anywhere. Also, ensure hot end temperature readings are sane and try to heat it to say 40 degrees Celsius.

Did it move? Did temp level out at 40? Is it still alive? Sweet Victory!

Now, don't disconnect and reconnect. RAMPS will reset upon reconnection and the D-motor will lose its static torque for a moment. This risks letting Clerck smash into the floor.

The G3-command is very handy for manually homing the printer on startup. Clerck doesn't have automatic homing yet.

Step 16: Measure Lengths to Origin

See lines 96 (#define ANCHOR_A_X) and onwards in firmware/Marlin/Marlin/Configuration.h. Measure lengths from fish eye to line opening in frame parts. Arduino IDE can be used to compile and upload Marlin. For experimentation with line length configurations, use gcode M665 Q<Ax> W<Ay> E<Az> R<Bx> T<By> Y<Bz> U<Cx> I<Cy> O<Cz> P<Dz>.

Step 18: Additions to Ceiling Plate

Counterweights

I use ca 250 grams of counterweight attached in each corner, with lines running along the outermost D-lines and running through the same vgroove bearings in the ceiling part.

Manual Homing with Aiming Plumb

I'm simply homing the printer using gcodes G3 (move without recording it) after powering on. The gcodes G92 and M114. To help the manual homing process, I've attached an aiming plumb to the center of the ceiling part, see picture and previous post.

End of assembly manual. Ask questions in the forum thread about the stuff that is unclear. If you're building version 2 (worm drive, more rounded bottom plate), the forum thread for that one is here. For the files used to create renderings, see branch "build_maunal_0" in the repo (link). Hope you've enjoyed and wish you all happy hacking!

- tobben

Hangprinter Campaign: Bountysource Salt

Hangprinter Project: [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38], [39], [40]

Print Issue Solution Filter Project: [1], [2], [3], [4]

Sourcing RepRappro Mendel in Larvik: [1], [2], [3], [4], [5], [6], [7]

Archive: 2014, 2015, 2016