In the winter time we refill the bird feeders regularly. Invariably I'd get bird seed all over the floor as I'd try to refill the container from a large bag of seed, so I decided to resolve the issue once and for all, and have some 3d printing fun along the way!
The solution was a funnel with a wide exit, and a shoulder that would enable it to sit securely on the top of the container being filled.
Didn't spill a single seed!
I drew the funnel in Sketchup, using a simple construction method, first drawing the cross-section of the desired shape and then using the "follow-me" tool to rotate that shape about a vertical axis. I've also been playing with various screen-recording tools, to find ways of enhancing blog presentations. As an experiment I've recorded the Sketchup drawing technique in "screencast-o-matic" and shared it below.
Finally... The birds were very happy with the refilled feeders!
It's a great illusion of impossibly stacked little cubes, and readily printable, believe it or not! The STL file and full detail is posted here on Thingiverse. Credit goes to Jonathan Wong for explaining how he constructed the printable version of this illusion and providing instruction on how you can draw your own version. Some additional reference to the famous triangle may also be found here.
The printing challenge: This is a challenging print in a number of respects. The nine "inverted pyramid shapes" have a very small area of contact with the print bed and don't actually support each other until over halfway built. You need to have laid down a good first layer, well bonded to the print bed. Even then, what may happen is the print head will clip any slightly curling edge as it moves about, and knock one piece over, destroying the entire print. However, there is one version of the STL file in the Thingiverse share that has a bracing piece between all the pyramids to give greater support on the print bed.
Above is what happened when my print head clipped off a slightly curled edge of one of the pyramids. I had to abandon this attempt.
For my second attempt I used a Z-Lift feature in Slic3r (the STL slicing package) which raises the print head by a prescribed amount as it moves between printing sections, lowering it again to resume printing. (Z axis lift is discussed towards the end of this older post here by RichRap.) This feature worked ok but as the object grew there seemed to be degradation of print quality with a lot of gapping in the print, even though I had only changed one parameter i.e. the z-lift. My observation was that this z-lift may have been allowing a little bit more time for retraction to take place and plastic would not resume extruding until a good length of print path had been travelled. While my retraction settings may not have been 100% initially, this setting seemed to exaggerate the problem.
Rather than spend more time examining g-code and tweaking settings I said I'd give Kisslicer a go at slicing this object. I know from past use that Kisslicer prints sub-sections to completion before moving on to the next sub-section on the same layer; meaning it prints perimeters then in-fills that section before moving on. In contrast, Slic3r prints perimeters then returns later to infill after completing all perimeters. With an object like this, with its nine base triangles, Slic3r does a lot of zipping around in contrast to Kisslicer. My hope was that Kisslicer's approach to printing would decrease the risk of knocking one of the pyramids off its base, and the less zipping about would result in less retraction movements, maintaining print quality.
Kisslicer actually printed the object to completion first time (above photo), but my choice of settings produced some quality issues also. Kisslicer has different Retraction terminology, with what it calls Destringing (Suck & Prime), a whole other evening of experimenting! The "Destringing" settings I had, resulted in quite a scraggy print and left me with a bit of clean-up to do, quite the opposite of the gapped print Slic3r produced with too much retraction.
Finally, here's a short video clip showing it rotating in and out of its illusion position.
Tech Notes and Conclusions:
The object was printed in ABS plastic with a layer height of .3mm and a layer width of .45mm. It was printed on a RepRap style 3d printer, with 3mm filament fed to a .5mm j-head hotend, on a heated bed. Gentle cooling by a low powered fan was used across the object once it climbed off the print bed. This is not my typical practice when printing in ABS (usually no fan), but helped strengthen the narrow walls as they grew.
This object has very little surface area in contact with the print bed, has many thin walls growing to points, and leaning at angles. At its default size it's a challenging print with a .5mm print head nozzle. It might be worth scaling up to a larger size or else using a finer nozzle if you have one.
I'd be interested to learn how others may have got on printing this object. If you have any tips or even quentions then feel free to add a comment below.
Quick post... There are many hooks on Thinkiverse, but I noticed this Headphone Hook by Misguided had employed a curve on the hanging tab to add strength to what otherwise would be it's weakness, a 90 Deg bend with a flat tab. A few minutes in Sketchup enabled a modification of the design to produce a very useful door hook!
I narrowed the "U" so the door would close, even with the hook over the top (3mm gap). I also added two ridges to the "U" to grip the door and give the hook a snug fit. The printed item looks well and is very strong when printed in ABS plastic.
I've seen hooks on sale in the shops but they tend to be for narrower doors. I was able to print a hook that fitted our internal doors perfectly (45mm - 1 3/4"). I've placed a bunch of sizes in the Sketchup file and posted it to Thingiverse .
The Earbud Holder from Thingiverse caught my attention recently. There was a comment asking if it could have a key chain loop added... it sure can! It's a matter of personal preference whether you print the version with or without the keyring tab, or take the design further. It's great how designs evolve.
I fitted a small ring and short length of cord to the holder.
Notes:
I dropped the original Core .stl into Sketchup and drew on a tab with a hole in it, to which you could fit a keyring. I then took the evolving cover design from here: http://www.thingiverse.com/thing:38292 and put a notch in each cover so it would still close around the new keyring tab.
I then exported the new .stl files and ran them through Netfabb Cloud Service . It always does a good job of cleaning up the stl. They were now ready for printing... ABS, 50mm/sec, .4mm nozzle, .3mm width /.45mm height.
My first set of covers cracked as I tried to clip them on to the core. They broke along the print lines. On examination it was evident there was poor bonding between layers. I've been pushing the speed in recent times and at this point I expect the plastic just wasn't hot enough for the speed (230Deg C at 50mm/sec).
I increased the temperature to 245 Deg C. and reprinted just the two covers. Now, you know you should never change more than one parameter when troubleshooting, but I couldn't resist altering the layer height/width also, to increase the horizontal resolution and give a better fit between the parts. The covers were reprinted at .25mm height/.375mm width, 70mm/sec. 245 Dec C.
I've uploaded the modified design to Thingiverse: http://www.thingiverse.com/thing:39767
ABS is a tough, impact and temperature resistant plastic. It can be injection moulded and extruded. It has many common uses, from Lego to car bumpers. Being able to print in ABS is an important progression for me in terms of the robustness of the objects I might design, prototype and print.
My first ventures into printing with ABS did present some challenges. It's extrusion temperature, in the region of 240 Deg C, is a good deal higher than PLA (185 Deg C). The rising heat from the hot end to my PLA x-carriage was a first concern but the use of an un-ducted fan to cool the underside proved problematic. The freshly extruded ABS was very sensitive to the cooling airflow, causing poor adhesion of the first layer to the print bed. If' you've only printed in PLA you'll find PLA prints better with some cooling, preventing curling, but the first layer of ABS is far more sensitive and does not like stray cooling at all. Fitting a ducting to the fan (light green part visible in photo below) focuses the air flow across the J-head insulator, also keeping the underside of the x-carriage cool. I may eventually print an x-carriage in ABS for peace of mind.
The big addition to my set-up is the hood (see photo). It's a simple box construction made of 6mm MDF and light timber frame. The front has a clear acrylic panel.
The purpose of the hood is to maintain a steady raised temperature around the printer. I found it levels out at around 28 Deg C at the moment. The printer is located in the garage with a frequently used large door, so heating the whole area isn't practical, and in the winter time the printer extruder and heated bed struggle to get to a working temperature without the hood. The addition of the hood has made a great difference to temperature management in our colder winter months (Ireland). With the hood externally vented it has also eliminated minor concerns about any fumes the ABS might give off if over heated, although I've had to control airflow through the vent to reduce air loss from hot-air convection through that pipe.
Next item to get right for ABS is the heated print bed. PLA is happy with a heated bed in the region of 60 Deg C temperature, and with some PVA coating on the glass bed it will stick well. ABS is a different story. Experimenting by many has resulted with varying guidelines on what temperature is best for the heated bed under an ABS printed part. People seem to have had good success with temperatures ranging from 80 Deg C to 120 Deg C or even higher. This higher heated bed temperature for ABS is required for good initial adhesion and preventing warping as the object grows, but you should reduce the bed temperature after the first layer to prevent wall shrinkage at the base of printed parts. The use of PET tape or ABS juice (ABS/acetone solution) is also found to help adhesion. Some people just ensure the glass is cleaned thoroughly and get very good adhesion straight to glass.
The quickest and easiest way to give a guided tour of my current printer set-up is to post a short video. In it you will see the first layer of the Santa Sleigh being printed. It's being printed with 3mm ABS filament, with a .5mm nozzle at an initial temperature of 240 Deg C, bed temperature of 115 Deg C (approx). First layer is printed slowly but it picks up to about 50mm/s later.
As I move the camera around you will see the host software I'm currently using "Repetier-Host", my wall mounted spools, and the printer electronics, which are now moved outside the box (they need a cover!). Finally, for the keen eye, you will see some timber cross-bracing across the rear threaded rods of the printer. This has enhanced the stability of the unit immensely. My z-rods hang freely from the motors unconstrained. I only use a single trapped z-nut on these rods in each x-end, and no backlash springs.
This video clip shows the Santa Sleigh being printed a few layers in (.3mm height/.45width, 25% fill). I've a temporary temperature probe under the heated bed which shows a reading of about 117 Deg C. I expect the surface temperature of the printer bed is a good 15/20 Deg C less. My bed temperature is controlled via a simple circuit (see here). The temperature is set with a variable pot dial. I've various marks on the dial for PLA, ABS first layer and ABS. It's all a bit experimental, but works.
This short video shows the printing of the Sleigh, utilising a time-lapse shot every 20 sec, and a look around the finished item at the end. The printer bed is 200mm x 200mm so you can judge the size of the printed object from that.
Finally for now, here's a clip of the Reindeer being printed. All eight in one go, along with the support struts.
Concluding notes:
Printing with ABS has greater temperature management challenges, for both the hot-end and printer bed.
The single biggest tip I can give is to reduce the printer bed temperature immediately after printing the first layer of any ABS job. This will prevent shrinkage or distortion of the lower 5mm of the object, a phenomena dubbed 'elephant feet' on the forum, because of the inward deformation of the work around the base. I estimate a reduction in bed temperature of about 20 Deg C is not unreasonable, but I would recommend you experiment to find settings that work best for your own set-up.
I've not found ABS parts to be as dimensionally accurate as the same parts printed in PLA. I believe this phenomenon is down to ABS shrinkage. You may want to allow for this in design.
The finished ABS product has a smoother feel and any blips or minor stringing is much more easily removed than equivalent imperfections in PLA.
While the print resolution is the same, ABS seems to look a lot smoother.
If you have any questions or comments regarding the set-up or operation of my printer feel free to post a comment of contact me via the RepRap forum (http://forums.reprap.org).
Thingiverse Santa Sleigh driven by the Snowman! Some red acrylic paint easily added a touch of colour to the white ABS plastic.
A variety of other Thingiverse Christmas ornaments!
The Angel was creating by tracing some internet clip-art in Sketchup, extruding the shape a few mm and cutting slots so the two halves slide together. It's a simple construction but looks well.
I've always had an interest in clocks. They can be hypnotic and fascinating, masterpieces of mechanical engineering, and things of beauty. But could a clock be printed on a home 3d printer? Would it work? I was delighted to see a clock published to Thingiverse (The Makerbot clock) but was disappointed to learn that the hardware kit was no longer available. That didn't deter me.
The finished item is a simple and pleasing open style, weight driven, wall clock with a 9" face and 3ft pendulum.
It was a printing challenge and will test the accuracy of any printer. For the most part the gears came out cleanly and meshed well with each other when the clock was mocked-up. Some test assembly and hand turning highlighted a few sticky points. They where easily sorted with a needle file. I printed using my .5mm nozzle but in hindsight a .35mm nozzle would have resulted is better meshing gears and post print tuning/filing.
The range of parts can be seen in the above photo. If you study the MakerBot assembly instructions you can get an idea of the hardware required, but I had to deviate from the original bill of materials in a number of items. I could only source the tubes that drive the hands in metric dimensions so I had to alter the hole sizes in some of the printed parts to match my brass tubes. I sourced the little bearings on ebay. They were inexpensive and came in a packet of 10. The pendulum shaft and second-hand shaft are welding rods. The weights are filled with 2 Cent coins (Euro). The original design suggested a 1 Cent US coin. They are the same size.
To give added strength and enable wall-mounting I cut a circular backing board from some 15mm chipboard, and mounted the clock base plate to that. I used longer bolts than specified and allowed them to travel right into the backing board for extra rigidity in the assembly. The upper frames were quite light and didn't hold the gears quite as well as I would have liked.
Modifying the mechanism When I first started the clock it was running too fast. The published escapement wheel has 15 teeth. That results is the second hand advancing by two second increments for each pendulum swing. But combined with a 1 meter pendulum, the second hand completes a full revolution in only 30 seconds. That said, I expect this clock was only ever published as a printing show piece and for it to tick/tock away in any fashion could be considered a success!
On examination of the SketchUp file included in the Thingiverse publication I found an alternative escapement wheel which had 30 teeth, allowing a more refined movement of the second hand. The escapement paddles also need adjustment to fit this wheel. (For anyone that really want's to get into the detail I found a good publication on excapement mechanics here: www.abbeyclock.com/EscMechanics.pdf ) That article is a bit over involved for this purpose but does show you how to draw paddles that are a good fit for the escapement wheel.
I exported my newly shaped paddles to .stl, then printed and fitted the two new parts.
The finished clock The clock is probably as good as I'm going to get it now, for a home printed plastic clock it's pretty amazing! It will only run for a few hours on a single wind so don't expect it to replace your kitchen clock any time soon. I've provided a little video clip below so you can see and hear it in action!
The solution was a funnel with a wide exit, and a shoulder that would enable it to sit securely on the top of the container being filled.
Didn't spill a single seed!
