The Walking Beam Project

Ladies and Gentlemen,

It is my honor to present the crown achievement of Pawel’s 3d printing craftsmanship so far! The Walking Beam project! Brace yourselves- a long post is coming!

It would be good at the beginning to explain what is a walking beam and how did I get the idea to make one? I am working in sales of steel industry at the moment. We are dealing with lifting of steel coils that weight tens of tons. A coil can be sometimes 2 meters in diameter and weight for example 35 t. In order to speed up feeding of processing lines, the coils are put on “saddles” and then transported by special cars or by walking beams. A picture tells a thousand words, so here is a scheme of walking beam in action.

The coil rests on a saddle (1). The beam is lifted with the coil resting on it (2). Then it moves to next position and is lowered (3). The coil now rests on next saddle and the beam moves back to the starting position (4). It is easy to imagine that the beam can be longer than 3 saddles, and that it can transport more coils at the same time- smart and very effective.

I decided to make a model of such a machine that would transport wine corks.

The big industrial walking beams are driven by powerful hydraulic cylinders. My goal was to make everything mechanic (gears). I also wanted to have only one “power source”- a single rotating handle that would go in one direction and allow for all the cycle to take place. Furthermore it would be fun to rotate the handle several times before the cycle was done. The target were 3 handle rotations to lift/lower the beam and 5 rotations to move it left/right.

The question was: how do we make the machine first to lift the beam (keeping it still in horizontal direction), then move it only left, then down and then right? I needed two systems: lifting and transverse. Each needed to have its “action phase” (move or lift) and a “pause phase” (when the second system would be working). They should also be able to automatically switch between each other. And of course all had to be driven by one handle going rotating in one direction :)

First let’s talk about the lifting system. The heart of the mechanism I used looks the following:

I divided 360 deg into 3/16, 5/16, 3/16 and 5/16, that is 67.5 deg, 112.5 deg , 67.5 deg and 112.5 deg (three rotations for lifting and five for transverse, remember?). The 5/16’s are parts of two circles representing “pauses”. Their radius difference is equal to desired lifting distance. The 3/16’s are the lifter’s “action phases”. The beam is resting on the top of the lifter, which is rotating with constant speed. The animation below demonstrates how it works.

Now it is time for transverse movement. How to make it go left, pause, then right and pause when the drive is rotating in the same way? At first I thought about some particular half-gears with reducers and different number of intermediate gears. This seemed a bit complicated though- it will do nicely as another project. For my walking beam I used a simpler solution. I fixed the transverse drive gear (TDG) in one spot and made it rotate with constant speed in one direction. Then a frame was put “around it” with teeth on the top and bottom. Depending on whether the TDG is touching top or bottom teeth, the frame would move left or right. The lifting system was used to change which teeth are touched. I got the “action phase”, “pause”, “action” and “pause”. In addition, to prevent unwanted movement, final teeth in the frame were removed. The schematic animation below shows the idea in action:

This system has one big flaw- it can only transport the corks in one direction. At the same time it is simpler to implement and more robust to inaccurate synchronization.

Having the idea fixed I started designing the machine. I calculated gear reductions, movement distances, general overlay- well, some theoretical stuff. Then it was FreeCAD time. Finally I had an excuse to learn a bit Python. It was not very tempting to make every gear or spiral “by hand”, and having a nice procedure that could do it for me made my life much easier. Especially that there were lots of different gears to be done.

I was advised by the organ between my ears to first allocate the moving elements in space and then think how to make the supports and frames. The machine was supposed to be compact and should allow for easy dismounting and access to the parts. And of course each element was to be designed in a way that would allow printing it. It took quite a few evenings, few weekends and finally I got the design ready:

Doesn't it look awesome already?

One could ask: “why didn't you start printing when you had some parts of the design ready”? Well I did. At least few gears that I knew that were in their “final” form were printed during FreeCAD period. The rest was being modified a lot on the way. Fixing any shape by printing it puts a big constraint on other part’s shape. Being perfectly honest- I made one or two design mistakes on the way but in the end the errors were insignificant. I was able to repair them with few moves of a file and a tiny bit of glue.

In general all the parts were printed in their desired final shape and required only surface cleaning from the printing residual trash. Most important elements’ surfaces were additionally treated with acetone to get a nice smooth finish. Also due to 3d printing limits five parts were intended to be made of several elements glued together.

OK enough talking! Here are all the elements of the “Walking Beam”! Next pictures show the assembly of the whole machine. Isn't it even more awesome?

I am particularly proud of the spirals. If you take a closer look, they have different slopes and one is a single helix while the other is a double helix. For the double helix system I also had to make the gear with inclined teeth so it could fit within the gap. Here are some close-up pictures.

Finally I present to you the movie with the Walking Beam in action!

Thanks for sticking this long. I do hope you (or at least your inner-geek) enjoyed the content. I had great fun making this project and am looking forward to doing some more. Your “views”, “likes” and “shares” are an awesome recognition to all this effort and for sure will boost my engines to spend more time on 3d printing. Thank you!

Tablet drive- GCodePrinter

When I was looking through the old posts for the total price of the printer I noticed that there was a plat to buy an old PC to run the control software on.
It is no longer the case. Some time ago I got a Lenovo tablet as a present. In the Google Play Store I noticed an awesome application called GCodePrinter. It costs like 4 euro and changes your toy-tablet into a mighty tool for steering devices of the future! OK, I I got a bit too excited ;)
If your tablet has this magic cable that allows USB to be connected to it (for memory sticks etc), you can try to put the printer under its control. Here is a picture of my printer being driven by a tablet. It looks super geeky great and works too!

Spoiler: the printed part is an element of the big awesome project.

As I wrote, it looks nice and all. Unfortunately it might get into some trouble. I made some nice prints, but one time it happened that the tablet went to hibernation (or something) and second time there was some communication error. This of course resulted in the stop of the print, and the part got wasted (I still have to find out a way to safely restart broken prints). For that reason, although it looks cool, I prefer to print bigger parts under PC control. It simply seems more reliable.

Y-axis upgrade

I mentioned in the previous post that for the last months I was working on a bigger project with the 3d printer. Just at its beginning I noticed that there was something wrong when circular objects were printed. They were a bit oval, definitely not nice and circular. I figured out that this is because of loose tension on the Y-axis belt. I could theoretically adjust the tension on the end points where it is attached to the moving bed. Unfortunately way my printer is built makes it a bit hard to do (you would have to dismount a big piece of the bed which is tricky to put back together).

The printer worked but the results, especially the precise ones with complex and circular borders did not look very well.

I decided to add a new part that would divert the belt a bit thus putting required tension on it.

After a short session with FreeCAD, even shorter slicing in new version of Slic3r and around half an hour of printing I had the necessary part. After adding the metal screws with some nuts and using spare bearing and washers the part was installed onto the printer.

The results after the upgrade were very satisfying. The circular objects looked circular :) After this moment I was convinced that was ready to work on parts that require decent level of precision.

A small digression- during the printing a major damage happened twice to the Y-axis pulley gear (you can see it in the picture above). It broke at its bottom. Of course I had to print the part and replace it. As you can image since the printer was broken it was not an easy task. Fortunately the glue held long enough to make the new print. It seemed that there will be no trouble but the part broke again. It seems the tension on it is too big (the engine's shaft is not going all the way through the pulley). The second time I made the part full in plastic- no saving for inner layers. I also treated the surface with acetone vapor to make it even stronger. Till now all is good. Of course I made an additional spare pulley (just in case) :)

Fun with earrings

Good day everybody,

This post is a teaser before I publish the info about the big 3d printing project I have been working on for the last few months.

Recently me, my wife and some good friends of us started playing the rpg in the WH40k world- Rogue Trader. Since my second half's character is a member of Adeptus Mechanicus (some tech-nuts priest engineers), I wanted to make earrings that would be appropriate for her status.

Since it seemed cool idea to make 3d printed earrings I made a second small project to demonstrate the constant fight that a measly mortal soul is being in a middle of. Below are the results :)

As you can tell they are already pre-painted. There will be some "rust" added to the wheels and definitely the angels wings shall be white ;)

One more interesting fact about this projects. It was the first time I tried the acetone vapor bath on the parts. You take a jar, drop a little bit of acetone on the bottom and then put the jar into the pot with hot water. Acetone vaporizes very fast and creates "melting atmosphere" in which you put the parts for few minutes. The idea is to melt the outer layer of plastic to give it a smoother surface looks. Here is the picture of the setup.
WARNING! Acetone vapor might be dangerous to you. Always work in a well ventilated location, and if are underage- ask an adult for assistance. I believe in your intellect but I take no responsibility for any of your actions. You have been worn :)

Furthermore, be advised that if you keep the parts for too long, the plastic will melt too much. Small elements of the print are most affected. Well, here is a very "saaad angel". It was irreparable and had to make another one.

And finally, the parts are a bit sticky after you take them out of the acetone vapor atmosphere. Make sure they "dry out" a bit before you make them touch any surface. Here are the earrings after the process drying a bit more (the paper towel was not the best idea, fortunately they were not too sticky at that time).

That is it for now. Await the glorious big project that is to come soon!

Ciao!

ps

If you are interested in getting earrings like that, or have some other idea- just give me a note. Maybe we can work something out together ;)

History continues: " A small success"

One of the best things about having a 3d printer is the possibility of creating objects that would be difficult to get in a shop.
When we moved to a new place, we brought from the old apartment a shower-shelf that you hang on the door. We had no idea what to do with it- you can’t hang it on the wall, and now we do not have the shower door to put it on.
A bit later we got ourselves a plastic drawer box. The shelf would fit on its back quite nicely, providing additional space for whatever you want. Yet it was not mounted, so I always felt that I might drop it off. To feel more comfortable while moving around the bathroom, I designed the following small piece:

It took 10 min to heat up the printer’s bed, 7 min of printing, 2 minutes of polishing, 5 min of painting, 3 minutes for drilling and 3 minutes of mounting. In half an hour I managed to secure the shelf onto the drawer box with two nice holders. A nice, small success :)

Neurological box

After some time, here is a next chapter of the "historical" projects.

As one of the first “serious” projects I decided to help my wife by printing a box for glass plates washing. It appears that during some neurobiological experiments you put samples on a small glass plates (around 70x25x1 mm) and then need to put them in some solution for a while. The tricky part is that the solution is quite expensive, and you try to pack several of them together in a vertical position. Of course there are commercial boxes like that, but getting those in a government funded institution is a real pain in the ass. That’s where the 3d-hero enters!

I used FreeCad to design the object. It was nothing extremely complicated, but due to my lack of experience I used quite a long time to make the freakin’ drawing. Here is one of the first models. The thing was supposed to consist of the box and the led.

For some reason I decided that the walls are supposed to be 3mm thick. Not a good idea, but it occurred only during printing.

I also printed the led first and due to scaling mistake I made it too big… I re-designed the top part of the box just to be able to use the led.

Initially I wanted to make the box in one piece, yet I met the height limitation of my printer. For that reason I split the print in 2 parts. Then glue was supposed to fix the problem.

This is when I encountered the next issue. As you might already know, making a 3d object takes several phases: design, meshing, “slicing”, printing, finishing. Design is design. During meshing you create a standardized file that corresponds to the surfaces (STL). The slicing is the process of creating the orders for the printer using the meshed shells. It is like describing how to make an omelet to a machine- move right 3mm, extrude 0.1mm, move forth 2mm while extruding 0.2mm, and so on. You can do this part automatically using for example an open-source program called Slic3r. From what I gathered, in general it always creates commends as follows: print an outer shell (following the geometry), and then print the “inner” part. The infill is some generic pattern- like lines of 45 deg lying opposite to each other on each layer. Unfortunately for me, my object consisted of only small walls. Because of that, the infill was taking forever to print- imagine drawing a straight line when you have to move in space of 2mm and you can only move in 45 deg to the wall… I tried changing angle, but since the lines are always perpendicular to each other on succeeding layers, it ended up printing one layer nicely, and other by making 2mm lines lying next to each other on a distance of 3cm… terrible. In the end I tried to play with the GCode itself, to force the printer move as I like. I also changed the design a bit- made the walls thinner to save plastic. Here is the second design.

After a real torment I managed to make the first models. They were looking OK, the glasses fit, the led closed- success you would say. Well, there was one more test to make- they were supposed to hold liquid. As it appeared- they did not…

In order to save the prints I started to experiment with the finish. I decided to apply acetone on the surface hoping to melt it a bit and close the micro-holes in the plastic. I found in the net that people use acetone vapor to do that. Unfortunately I do not have the space for this kind of play in the house, so I just applied the substance- first with a cloth (bad idea- molten ABS is quite sticky) and then by shortly dipping the part in it. That was even worse idea… The concentrated acetone entered into the pores and cavities in one of the models and started to dissolve it- at least at the bottom of the box. After it changed the plastic into “plastic” pulp, it was clear that dipping any ABS part in a solvent is not the best way to proceed.

The last resort was to cover the surface with glue. It has worked just to some extent, still leaving several leakages.

There were also other tests- with and without acetone applied. In the end, none gave satisfactory results.

One full print of the box sould take around 5h (due to trouble with the infill and because of the small diameter of my extruder). I made at least 4 prints. Then few hours of fine grinding, acetone/glue treatment, and the result was still not satisfactory. At certain point my wife gave an act of mercy releasing me from the promise of delivering the box, and so the project ended… or did it? :)

Get-back post and the spool holder

It’s been a long time… I believe there were not so many visitors here, so even the disappointment of the lack of content was not so big. People whom I told about this page took a look long time ago, and according to google statistics, there are two other kinds of people getting here: ones that looked for a particular odd sentence and others that were seeking porn. Funny enough the second group of “random visitors” is bigger than the first. It seems naked machines are a real treat :)

Let’s get back to the printer. Even though I haven’t written much (or more precisely- nothing), it does not mean the reprap was standing in the corner catching dust. Well, all right, most of the time it was. Still I managed to do some stuff that will most likely fill two or three entries of this blog. I have to also confess that most of the photos will be made quite late post-factum. Deal with it.

The first things I worked on were connected to the printer. In the old post I described the electronics holders- now it was time for the clumsy plastic spool.

I decided it should be mounted onto the printer on some of a frame. I had quite a bit threaded 8mm rods, so they were to become the main construction. I found out that there will be two kinds of things required: several clamps to bind the rods and the "top" frame part with a fork to sustain the spool on a stick.

In order not to develop the wheel again, I chose the same clamps that were used in the printer itself. After setting up the printer and around an hour of printing I had nice 12 clamps ready. I printed first 1, then another, then 2, then 4 and finally 4. All to be sure that if it starts to screw-up, I will not loose too much time. Here are the models and the result:

After that there was the "U" shape to hold the spool. There was some fun with development of the model, with the following result. Also I give a post-factum close-up picture of the part itself.

And finally, here is the "new" printer with an awesome frame to hold the plastic spool. It makes the threading much easier. During later work with the printer I found out that the spool does not unwind itself during process- it is too heavy and the plastic is a bit tangled. This might cause the blockage or problems with feeding. Yet it is much easier just to turn the spool on the frame opposed to playing with it when it is laying around. And the whole thing is much more compact and easier to move.

That is it for the come-back post. There are much more to come, so if you are just tuning in, stay on ;) Till next time!