What are 3D printers for? Printing new 3D printers! I’ve finished printing the CoreXY parts for my new printer. CoreXY is the method I’m using to control the X and Y axes (left/right, forward/backwards), using parts designed by Louis Zatak who put them on Thingiverse. He also provided parts for Z axis bed lift as well , using the same belt trick that the CoreXY uses.
The dimensions I’m printing are probably much too large – I went for 50cm cubed, which might end up with a print volume of about 44cm cubed, which is 8 times larger than my current printer (an Anet A8).
There will be problems, I’m sure – with 50cm rods, the x-carriage will probably droop near the middle. I have an idea how to solve that if it happens, but we’ll see if it’s necessary!
All that’s left to get for this new printer are some rods for the x-carriage, the y axis, and the z-axis, and a hot-bed. The hot-bed is not strictly necessary, but it will make it work much better. without a hot-bed, prints might curl upwards, and will probably have trouble sticking to the print bed.
After this is finished, I have a plan to build a brief-case sized foldable 3D printer.
The CoreXY design is compact and may be foldable, so I’m going to try find a way to have the z-axis fold upwards towards the CoreXY frame, and then fold the arms of the mechanism inwards. In my head, it works…
One of my students wanted a straight barrel door bolt printed for his door, because his dog kept on opening it. I designed one up in FreeCad in a few minutes and printed it out with an Anet A8 3D printer during today’s CoderDojo class.
The design was deceptively simple. Even though the shape of the thing looks difficult, it’s actually quite easy.
First, we make the base-plate, which I set as 4mm thick for strength. Instead of making three separate pieces, I opted to build it all as one long one. You’ll see what I mean.
Next, I put a cylinder right along it. This will be the outside of the barrel. Notice that I have it overlapping 2mm into the base. The walls of the barrel will be 2mm thick.
And to strengthen the barrel’s connection to the baseplate, I added a cuboid reaching down as a tangent from the cylinder.
I grouped those together using the Union tool.
Next, I worked on the bits that I needed to cut out of the barrel.
First, there’s the cylinder for the bolt. I made sure the leave 2mm in the near end so the bolt didn’t just come right out of the lock when opening it.
Then there’s the channel that the bolt handle slides along.
When locked the bolt handle needs somewhere to slide down into. It needs to be the same width as the channel from the previous step.
Finally, I separated the barrel into three pieces. First, by cutting a 1mm gap to cut off a chunk that connects to the door jamb.
And then a slice that has two uses – first, to let us put the bolt into the barrel in the first place (we’re not printing the bolt inside the barrel, so need a way to put it in). It also acts as a place for the bolt handle to rest when the lock is open. Its width is the same as the earlier two channel cuts.
Lastly, I needed to add 8 cones where the screws should go.
I grouped all of those together then did a cut of that group from the original group I made, which resulted in this:
The bolt itself was next.
First, create a cylinder that is .1mm in radius less than the gap in the barrel and long enough to reach the jamb end from the near end of the main body of the barrel.
Next, add a cylinder for a handle. Its radius should be .1mm smaller than half the width of the channels it slides in.
And then a sphere which serves no real purpose but it looks nice.
Finally group the bolt together into one object, and pull it back in the lock to make sure it fits. If it doesn’t, then adjust whatever you need to!
When we printed this out during class today, the print was difficult to remove from the glass on the hot-bed afterwards. I found it much easier to remove later on when I printed another of them for myself. The difference was that in the class, the hot-bed was still about 60°C, while at home, I was busy with other things and didn’t notice it had finished printing for a while, so it was more like 40°C. So, if you have difficulty removing a part from your 3D printer, maybe just let it cool.
I printed out a terrain piece for a friend to use in his Warhammer 40k game. His group was so happy with the print that they told me they would pay for more, so I went looking for more designs that would suit their purpose (technological debris on a sci-fi backdrop).
I found this really nice design of a crashed “killabot” (pictured above) – a robot driven by a race of aliens called Orks.
I priced it at €5.65 – €0.65 for the cost of the filament, and €5 for the time to setup and print it. This is actually quite a ridiculously low number compared to other people that print things professionally (see 3dhubs.com for your local supplier!).
It was going to take about 8 hours to print, according to the slicer program (Cura). I set it to print about 10:30pm.
This morning, I went to check on my 3D printer (an Anet A8), and noticed it was doing something strange at around the 80% mark – some missing layers in a part of the print were leaving obvious bands in the model.
After checking the Layers view of Cura, I saw that what appeared to be a solid model in the default view turns out to have some errors in it that cause Cura to print out some empty layers (pictured below). This is bad, as it can cause later layers to blob.
Cura has a number of built-in mesh fixing algorithms that can be used. It is not always obvious which one (or combination) will fix the problem so you may need to play with it.
In this case, I managed to fix the missing layers by using “Keep disconnected faces”, which is a last resort option. Here’s the fixed view:
I’ve left the faulty print to continue on, because I think the missing layers were few enough that the thing as a whole will still bond together well, but in future, I’ll take a close look of the layers view of a print before I start an 8 hour print…
I promised myself that the first major thing I would complete with my Anet A8 3D printer was to print another printer.
After calibrating the A8, I found a design online that I liked (the MyCore CoreXY design on Thingiverse (pictured)) and printed out all of the parts needed for both the CoreXY part and for the bed.
I’ve encountered two problems so far: 1. the Y axis rail sliders are designed for LM6UU bearings, but I have LM8UU, so they don’t fit. 2. the MDF I have, which will be used for the walls and floor of the printer, is too thin for the design I printed out
These are easy enough to fix, though.
I can simply adjust the radius of the holes on the Y axis sliders and print them out, fixing the bearing radius issue.
The MDF is slightly harder. I could go out and buy new wood, but I don’t like spending money when there is a free solution in front of me. So, I’m going to thicken up the parts of the MDF box that the plastic parts need to interact with.
If I glue two extra strips of MDF over the existing sheet, that should bring it up to thickness, and should also strengthen the MDF against warping under pressure.
To do this, I needed some G-Clamps for gluing the MDF. I found a wonderful print on Thingiverse which turns out to be very strong when printed at 35% infill. The Anet A8 even did a great job on the knurling detail on the end of the screw (pictured).
I will also need to print out some corner clamps, but there are designs available for that as well.
I love 3D printing! Everything you need, someone has already designed and shared, or you can design for yourself.
After I’ve finished fixing the thickness problems and bearing holes, I need to make a bed for the printer to actually work on. For the first few weeks, it will be an unheated bed, as I haven’t yet ordered a heated bed online. Maybe I could design and build one myself? Or an alternative is to totally enclose the printer and heat the air itself in there to 60 deg – make the thing into a small oven.
Actually, that’s something I’ve been considering anyway – totally enclosing the printer, but having tubes feeding cold air to the fans.
I tried setting this up so that the drum could be rolled from an elastic band or cog against the edge of the drum, but it turned out there was a simpler way – the little air-holes in the drum are an equal distance apart, so I designed and printed a gearbox that could turn the drum using those holes.
It sacrifices a little bit of surface area for the cold side of the drum, but I don’t think it will make a huge difference.
I made a few 1mm errors in the gear box prototypes, but when I corrected them, it worked as soon as I applied power to the motor. The motor I’m using in this case is one of the standard yellow geared motors (like this).
I’m still waiting for the heating element to arrive, but have a few fans I can use to get started on the airflow. I don’t even know what size the heating element I ordered is, so can’t design that side yet, but I can design the cold side while I wait. I’ll get started on that tonight.
The 3D printer I’m using is an Anet A8, and I have to say that it’s a dream to work with compared to my old Makibox 3D printer. I was amazed when I printed out the drum and enclosure for this project and they fit perfectly. With the Makibox, the circles would have been flattened and I’d have to sand away any bits that rub, but this one is just perfect.
Even the gearbox would have been impossible to print on the Makibox. The Anet A8 is so good that when some of my students were asking me for a bill of materials to make a 3D printer, I told them that even though it would be possible to spend €120 or so and make a 3D printer from scratch, they’re better off spending $150 and buying one of these ones instead.
I assembled my new printer last week and found some issues with the z-axis.
The first issue was that the right z-axis motor was not staying in step with the left. if the right moved up 1cm, the left might move up 5mm. It was suggested that this might be an electrical balance problem and that I should turn the potentiometer on the Anet board to fix this. I turned the potentiometer about 90% clockwise and that seemed to do the trick. They were both moving the same distance as each other now.
The next issue happened when I tried to print a calibration cube. It came out 20mm*20mm*10mm. Only 10mm high.
After much research and questioning, I settled on three steps to take (after taking some wrong turns involving changing steps/mm):
1. check the alignment of the lead screws. The frame that comes with the printer is off by fractions of a mm in some cases, and this can cause pressure that makes it harder for the motors to turn the lead screws. I found that the left motor was off by about .5mm, so I used a drill to extend the holes in that direction and reseated the motor directly under the lead screw (basically dropped the lead screw down through the brass thing on the x-carriage and moved the motor to where it fit best). 2. turn the potentiometer a bit further. it turns out that potentiometer is not for balancing the two motors – it controls the overall current that goes to the motors. If there is too little current, then the motors can’t lift the x-carriage. 3. change the steps/mm back to the stock 100/100/400. The default settings of 100/100/400 are based on the actual hardware. Stepper motors turn through precise degrees, so it is a mathematical issue to figure out how many turns it takes to move the belts or lead screws a certain distance. If the motors, belts, pulleys, and lead screws have not changed, then the default values should be perfect in all cases.
When this was done, I printed out another calibration cube, and this time, it was perfect. See the image – the cube on the right is the latest.
The next issue to solve involves large prints. My first project is to print out a new printer. I’m printing a CoreXY printer. There are STL files available on Thingiverse for this.
I found almost immediately that the default print bed is inadequate.
1. You can’t print directly onto the aluminium, as the plastic will just slip right off. Even if you could, sometimes a print will get stuck and you might have to chip it off, damaging the print bed. 2. The Anet-recommended method is to place painters-tape (a paper tape designed to let people paint without worrying about getting the paint onto glass, etc). This is not good enough, because it involves placing tape precisely so there are no seams, making sure there are no bubbles. It’s annoying work.
The solution I settled on, and others settled on, is to use a glass overlay. I got a cheap picture frame and took the glass from it. It was a little too long in one dimension so it’s currently poking over the edge on one end.
Keeping the glass in place is a problem. The recommended method is to use clips (like from clipboards) to stick the glass to the aluminium, then remove the handles of the clips so they don’t snag on things. I don’t have any yet, so for now, I’ve settled with some teflon tape. It’s designed to not warp in high temperature, so should be fine for a while, until I can print out some proper solutions for this.
The final problem of the day- I was printing out a piece for the new printer. It initially started very well, printing onto the glass like a dream. However, after the print was about 1cm high, it suddenly came lose from the glass and the printer started printing out a “nest” instead.
After examining the print, I found the problem – the bottom had curled upwards from the bed, reducing the volume that was in contact with it, and making it more likely that the movements of the print bed would break the print free.
The curling is caused by temperature differences between the newly printed layers and already-printed layers. As the plastic cools, it shrinks. If there is even the slightest gap under the plastic when this happens, then this will cause curling.
The solution was to spray hair-spray where the print was to contact the bed. This lays down a thin layer of binding plastic on the glass that increases contact between the print and the bed, reducing the chance that it will come lose.
After printing, removing the print from the glass is a simple matter – I whack the bottom of it with a metal ruler. Instant release, and no damage.
I bought a new printer, the Anet A8, which is a Prusa i3 clone. From the prints shown on the “official” Anet A8 support group on Facebook, it’s a very good printer indeed for its price.
The Facebook community are also avid upgraders and publish a lot of posts explaining what they’re done.
My previous machine was a Makibox, which rapidly fell apart. Even when combined with the parts from a replacement Makibox, it still only lasted a few more weeks, and all prints done from it were fixes for itself.
I’ve had problems with the A8 already, but the community is very good and the printer is common enough that there are plenty of articles online about it.
Example problems I’ve had:
Z-axis motors out of sync. There are two motors controlling the z-axis (up/down). They both run basically through the same circuit. If they don’t receive the same power to both, then one might be a bit jerky or not move at all. On the Anet motherboard, there is a potentiometer between the two Z-axis controllers (looks like a little silver circle with an X in it). I just turned that 1/4 to the right and that fixed my problem.
I printed out a calibration cube and it was only half the height it should be – 2cm*2cm*1cm instead of 2cm*2cm*2cm. The problem here is a mixture of the slicer’s code, and the firmware of the printer itself. I think I have this sorted now – the steps per mm were off in the Z-axis. After some experimentation with the console in Pronterface (and some measurement of movements with a ruler), I think I got it right. List of gcodes are here.
clogged nozzle. Well, this one is an old friend… Sometimes you will find that the extruder doesn’t extrude anything at all. In my case, it was a clogged nozzle – there was a lump of plastic at the top of the throat leading down to the hotend and nozzle. I had to melt it out with a tea-light candle, because it was just /not/ moving. I then poked a guitar E-string through the end of the nozzle (0.4mm – too thin for a needle) to make sure that was clean.
cables a little too short. There is no “play” in the cables, so I found that sometimes the extruder stepper’s controller wires would literally get pulled out as the X-carriage moved. Solution – remove the clip that was holding the black plastic wrap to the back of the LCD, so that the wires could be moved.
Overall, I am /very/ happy with this printer, but I’m still wary from my experiences with the Makibox, so the first project I’m working on with this new one is to print yet another printer – the Smartcore CoreXY.
I’ve done the back corners of the printer. Now, I can tackle the front.
The front corners are where I will put the motors that control the X/Y coordinates of the hot-end.
So far, everything I’ve printed is symmetrical, but the two belts are at different heights, so in this case, one motor will be higher than the other.
I’ve decided that the right motor (right when facing out from the printer. left when facing the printer) will be the top motor.
I’ve designed the model for this so that it can wrap over the end of the case edge (and you can screw into it) and bolt the motor into the model.
front right top corner, with model Nema-17 motor in place
front right top corner model
It’s best to print this one on its side, so there is no support needed, and less cleanup in that space between the walls. After printing this out for the first time, I found that the wall space in my print was too tight, so I adjusted the STL file to add 1mm more space. this should not matter much.
CoreXY printers have two timing belts overlaid on each other around the box. To allow the belts to move, bearings are placed in various corners. Today, I’ll tackle the back top corners of the printer box.
In the image below (taken from a scene of this video), you can see how it’s handled usually:
image showing back corners of CoreXY belt system
Because I’m trying to avoid using any rods are other forms of complex structure, I decided to come up with a printed solution that I could attach to the wooden corners of the box.
The design with bearings and a washer in place will look like this:
back top corners of print, with two bearings and a washer in place
This slots neatly over the wood at the back top corners of the box.
The design is not yet perfect. I anticipate there will be pressure towards the center of the box on the bottom bearing, so I should have screw holes at the bottom of those walls as well. But, I think this will do for the “bootstrap” printer.
An improvement I will be making as soon as the prototype is complete, is to replace the metal bearings with 3d-printed bearings, like in this video. That will get me closer to having a purely 3d-printed 3d printer. Also, 3d-printed bearings will be cheaper than metal bearings, reducing the cost for future printers.
So to create the corners, we will need to print out two each of the outer back top corners, and the inner back top corners. Don’t slot them together until you have your bearings. Otherwise you will find it difficult (or impossible) to separate them without breaking them.
inner back top corner. bearings and washer go on the pole
outer back top corner. the hole on the top slots onto the inner corner’s pole to keep it still
Once your pieces are printed, place an LM8UU bearing on each pole, then a washer, and then another LM8UU bearing. Slot the bottom piece with the pole into the top piece so that the pole goes into its corresponding circular hole in the top piece. You might need to shave the top of the pole slightly to make this fit. Don’t shave too much.
Finally, place the corner pieces over the back top corners of the box and bolt them in place. For the other edge and corner pieces so far, you could use screws, but this one will need bolts because there will be inward pulling force on the pieces from the belts going through them.
where to put the inner back top corner pieces
I don’t yet have the bearings for the corners, so the photo below is of installation on one side without the bearings. When the bearings arrive, I’ll update this post.
back top corner. the belts loop around the pole on this (after bearings are added)
KV Printer 1 will be basically a 50cm^3 cube, giving quite a large printable area.
Obtain a 5mm plywood sheet and cut 4 50cm^2 squares in it. These form the base and walls.
Next, we need to stick this together at the corners. To do that, print out 2 corner pieces and 6 edge pieces. Using these as templates, drill 2mm diameter holes in all corners of the wooden squares (they’ll be 20.5mm in from X and Y), then screw the squares together like in the third image below.
outer corner for 3d printer
outer edge piece for 3d printer
placement of outer corner and edge pieces
Notice that we have not yet fastened the back top edges together. That will be done in the next post.
The finished product at this stage looks like this:
printer box after installation of back bottom corner and side edge pieces
