3D printer build log

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Re: 3D printer build log

Postby Andrew Davie » Wed Nov 19, 2014 10:43 pm

A few more bits and pieces have arrived. In particular, the NEMA 17 stepper motors, the 170mm diameter borosilicate glass print plate, and the PTFE tubing for guiding the filament from the extruder to the effector.

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In the above, I have placed three of the NEMA 17 stepper motors in their mount locations. The one on the left has a thin cork insert between it and the frame; this will hopefully reduce noise and vibration. They were cheap, so I thought "why not". In the middle, the red circuit board is the stepper motor driver board, and hopefully it will be able to live down under the print surface pretty much were it's sitting now. It needs to join with the Arduino board, so thickness might be an issue. I'm still to learn how to connect the stepper motor to the board; four colour wires with no markings :) black/blue/red/green. I'm sure it's not too difficult :)

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The above shows the heated bed (black hexagon) sitting nicely in the frame bed area (size is fantastic), and on top of that -- possibly too hard to see -- is the 170mm borosilicate glass. Onto the heated bed I need to attach four wires -- DC power (12V) on the rectangular pads, and underneath there are two more pads connecting to a thermistor in the middle underside of the hex heat pad. I need to somehow firmly mount not only this hex heat bed onto the frame, but also the borosilicate glass print bed onto the heat bed. I placed some small screws through the holes on the hex heat bed, and they fit and hold the bed quite nicely (but not screwed in, of course). So I'm going to 3D-build/print some mounts; the idea is that these screws will attach to an underneath mount which will attach to the inner side of the aluminium frame. Something like two screws going horizontally through the mount into the inside groove of the aluminium horizontal bar (and not visible from outside), and between them, the vertical downward screws visible in the picture will tighten onto a nut seated in the mount. On the top-side of the same screw, there will be a flat part which pushes against the rounded print glass bed. Six of those and the glass bed should be relatively firmly held in place (at least lateral movement will be negligible). So, I should be able to knock that up in a few days.

Anyway, moving on... next time I write, I hope to have the mounts/fixes sorted for getting the hot bed and print bed mated firmly to the frame, and to have worked out how the stepper motors correctly wire into the RAMPS 1.4 board/assembly. At that point I may very well have to start thinking about understanding and testing the RAMPS software... a bit daunting at the moment, but one step at a time...
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Andrew Davie
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Re: 3D printer build log

Postby Andrew Davie » Sun Nov 23, 2014 4:17 pm

I printed some neat carriages I found on thingiverse.

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What I really like about this design is the way that the rubber belt self-locks onto the carriage, by wrapping around the little islands and meshing with its own teeth. Most other designs use cable-ties or some less elegant solution (such as requiring a belt of an exact size). This design allows the use of (cheaper!) open-loop belts, and also allows re-tensioning should that be required down the track. The print was in ABS, which is really a bit of a pain to work with. It likes to warp, shrink, and lift off the print bed. I use it because it has higher heat tolerance and seems to print "smoother" looking objects.

These carriages will be screwed onto a platform behind them, which in turn will be attached to linear bearings and a rail mechanism that I showed earlier in the 3D design. The rails haven't arrived yet, so the carriages are just hanging loosely at the moment. I attached the arms, so my mockups are getting closer to the final version each time.

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This is how it's looking now. I have put the PTFE tubing (the white tube; teflon) into the push-fit connector. The filament is fed through the inside of the PTFE tube to the inside of the "hot end" which is the metal heating/melting print heat. The heated bed (the black hexagon at the base of the machine) works just fine; I put 12V through it at 2A and it heated up nicely. There's also a nice blue LED on it to show it's on. I designed some simple side-clamps to hold the whole thing solidly to the frame. I will probably rework these, though, so that they also press down on the glass plate.

I've started to read the wiring documentation for the RAMPS and Arduino boards, which are the brains of the whole thing. I don't think I'll have too much trouble getting it set up.

Next job, I have to make some modifications to the effector assembly so that the arms fit correctly; The spacing should be the same as the spacing on the carriage assembly.
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Re: 3D printer build log

Postby Andrew Davie » Tue Nov 25, 2014 12:06 am

So, I did modify the effector assembly, and have the base part mounted as shown in the picture. There's a really neat assembly 'trick' I learned; embedding nuts inside the plastic to provide firm support for screws. Essentially, create a 'slot' which intersects a long hole for screws, at right angles. Alongside the slot and in the same plane as the screw hole, have a hexagonal hole which starts at the size of the nut (diameter), and shrinks a little bit over, say, 3 mm distance. You drop/push the nut into the slot, then you insert a screw, which goes through the nut. You then tighten the screw and as you tighten it, it pulls the nut into the hexagonal hole that you made earlier, and as it moves in, it 'wedges' in place because of the shrinking size. Then you remove the screw and attach whatever you want with another screw through the same hole. It's probably centuries old, but new to me and kind of satisfying :P

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The other bit of work I've done is to print three 'sliders'. These are temporary (?) make-do things to allow me to build a working printer while I wait for the previously mentioned rods and linear bearings. One of these is visible top-right of the picture. They fit over the aluminium railing snugly, and slide freely up and down (with hopefully little/no side wiggle). Screwed onto the front face of these are the previously printed carriages. This was supposed to be a stop-gap measure, but they slide so nicely and it is of course significantly cheaper -- so, I think I'll build the printer with these and see how it goes. I can always revisit the rail/bearing idea later if need be.

Next job is to finish printing the parts of the effector assembly (specifically, the 'plunger' and the clamps) and then put the belts around the stepper motor gear and the carriages. One issue is that the top of the frame holds bearings around which the belt wraps. Only the bearings I have have a 5 mm interior hole and the design is for a 3 mm hole. So, they're loose. I need new bearings, or a way to easily convert the 5 mm hole to a 3 mm one :)
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Re: 3D printer build log

Postby Andrew Davie » Tue Nov 25, 2014 12:45 am

Here's a close look at what I call the 'plunger', showing both sides. This holds the printing 'hot head', and also the force sensitive resistors (FSRs). In these pictures I show one of the FSRs embedded in the plunger body, sitting in the little cup, and with the 'tail' of the FSR passing through a slot to the upper side of the plunger, sitting alongside the push-fit which guides the filament into the hot-head. So, all the sizing seems correct. The plunger sits on top of the effector, shown in the previous post. On the top of the effector are small 'buttons' which push up into the FSR shown here. As the hot-head hits a surface, it lifts the plunger, which reduces the force on the FSR.

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Andrew Davie
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Re: 3D printer build log

Postby Andrew Davie » Thu Nov 27, 2014 5:00 pm

I inserted the force sensitive resistors and wired the three of them in parallel. So, with my 'effector' assembly fully built, I put a multimeter on the FSR output to see how/if the mechanism worked as expected. With the print head suspended in mid air, I was getting a resistance of about 40k ohms. When I dropped the head down to the print glass plate and put a bit of pressure (how much? -- well let's say if you were gently petting a cat -- that much :) -- then the resistance change was noticeable, moving up to about 60k ohms. With much more pressure resistance became infinite. So, the FSRs work.

What was surprising to me is that there was no visible movement of the mechanism itself. I'd designed it with springs and a sliding inner 'plunger' so that the printer could really press quite hard down to make the plunger move up and thus press on the FSRs. But what actually happens is that a very mild bit of pressure, certainly not enough to overcome any spring pressure, is enough to allow sensing the head pressing on the glass bed.

This is good. I'm putting this one in the "it works!" bin, and moving on.

Last night I found a model of a fan assembly which enshrouds the j-head assembly (that's the silver print head bit) and blows air around the cooling fins, and onto the worked itself, around the nozzle. The idea is to rapidly cool/set any molten extruded filament. And the reason you want to do that is if you're printing overhanging areas, you don't want the material to stay molten and fall down under gravity's pull. You want it to set just as soon as it comes out. Hence the fans.

It's a bit of an ugly duckling, though, and I have to get the spacing exactly right. I'll work a bit on this and post a photo in a day or two.
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Re: 3D printer build log

Postby Andrew Davie » Sun Nov 30, 2014 12:19 am

Lots of little things. It's coming together!

IMG_20141129_234914.jpg
I'm so beautiful.
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I've added a control console, end-stops, pulleys for the top of the drive belts, clamps for the heated bed, a planetary gear spindle mount, and a fan shroud for the print head...

IMG_20141129_234734.jpg
I'm sexy from up above, too. You can just make out the small pulleys I printed for the top part of the looped belts.
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The end-stops to limit carriage movement.
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The control console (front) and the heated bed mounts (three white bits around the glass circle).
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The neat planetary gear spool holder. Filament spools sit on this and spin.
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There always has to be one of these issues... the below is a mounting bracket for the electronics. This connects to the horizontal railing under the heated bed. Unfortunately, one has to connect it (or rather, put the nuts for connecting it in the grooves) before the lower base is assembled. The lower base is the first thing assembled. That means to get this mounted, I have to disassemble the entire thing and start again. LOL...

IMG_20141129_234958.jpg
The problematic electronics mount.
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Next on my plate, installation of the fan and getting the wiring sorted so that it all sits inside the nylon mesh (which is visible in some of the pics). The wires go up that mesh 'tube' (along with the teflon tube for the filament transport), and then do a U-turn and come back down hidden inside the aluminium tube grooves to underneath the hot plate to connect to the electronics.

IMG_20141129_234840.jpg
First pass at a fan mount/shroud for the print head.
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One thing missing from this entire lot is something called an extruder. This is the stepper motor and mechanism that pulls filament off the spool (which sits on the top of the planetary gear), and pushes it through the teflon (PTFE) tube down to the print head. I think I'll mount the extruder just in front of the "back" vertical mast. I'm not far away from having to think about applying power...!

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I bought myself a filing cabinet for screws and parts. I got the colour I wanted, not what I asked for!
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As a reward for my hard work I bought myself a filing cabinet. It's kind of neat industrial retro looking. I woke up last night thinking "I'll buy the teal colour, as it's really ugly and it would be cool to have something so ugly." But when I got to the store I chickened out and asked for red, to match my toolbox in the same area. But the only colour they had was teal; so I got what I wanted, but not what I asked for :)
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Andrew Davie
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Re: 3D printer build log

Postby Andrew Davie » Thu Dec 04, 2014 5:45 pm

I'm working on a device called an 'extruder'. This pulls the filament off the reel, and pushes it through to the hot-head where it is subsequently melted for printing. There are two main types of extruders; Bowden and Wade. The Wade sits on top of the J-head (hot head) and essentially goes along for the ride as the hot-head is swept back and forth to do the print. Think of colouring-in pictures... the hot-head is the pencil. Anyway, sitting on top is a Wade. There's disadvantages to this, though; extruders are heavy because they come with a stepper motor. This extra mass means that moving the print head quickly becomes difficult, and stopping it accurately also difficult. So another solution is a Bowden extruder. The Bowden doesn't go along for the ride; it sits on the sidelines, and feeds the filament to the hot-head from afar. To do this, it pushes the filament. To stop the filament bending, it is fed through a tube... in most cases a teflon (PTFE) tube which has very low friction. It does, I was surprised; quite slippery stuff to hold. Anyway, what I've been working on is a modified extruder. Now the more torque you can get out of your motor, the better you can feed filament to your print-head. I found a *Wade* extruder design which I liked, and I've modified it to be a *Bowden* extruder. Not quite as simple as just putting it in a different place; these things tend to be designed for exact purpose, so repurposing them requires a bit of hackery.

IMG_20141204_160010.jpg
I'm so pretty too.
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The stepper motor turns the small gear, which in turn turns the large gear. This thing isn't fully assembled yet... but as the large gear turns it turns a hobbed bolt (that's a bolt with a gear tooth cut around the middle of it somewhere). That bolt grabs the filament and pushes/pulls it as the case may be. I've knocked up a white mounting plate and this whole mechanism will sit at the front top of my machine facing the user. I really want to have those lovely gears working and highly visible as it's printing.

IMG_20141204_160044.jpg
Missing a lot of bits; bearings, bolts, etc., but this is the internals.
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There's quite a mishmash of screws, nuts and bolts to get this all assembled, and not quite sure where I'll source them yet. I'm learning that having draws with trays of many different screw/nut/bolt sizes is actually quite time saving in the long run. There are actually 26 individual nuts/bolts/springs/washers/bearings that I need to source to get this assembled!

See you next time...
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Re: 3D printer build log

Postby Andrew Davie » Tue Dec 16, 2014 9:54 pm

For the record, I asked permission at work to use the 3D printer for private work and was OK'd.

Well, I've made some progress. Firstly a few of my 'spare parts' combined with some extras that I have bought have now given me enough parts to build 3 printers, not one. My father-in-law has commissioned me to build one for him, so that will be #2 off the assembly line, and you can see in the picture here that I have the basic frame put together. Looks like it's going to be the same colour scheme.

5.jpg
Twins
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This time around I built the arms using a purpose-printed jig, sitting on top of the aluminium frame parts for rigidity and exact-lengthness.

1.jpg
The jig for building exact-length arms
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They came out pretty well. Probably a few tens of microns at worst. Very nice jig came from thingiverse.

Next up I finally pulled the finger out and started to have a look at the electronics. This printer runs off an Arduino board, with a 'daughter' board containing the drivers for the stepper motors. You can't see the Arduino here; it's underneath the red board. I downloaded the Arduino IDE, and the Marlin software which is what runs the actual printer. Compiled the software and dumped it onto the RAMPS/Arduino, connected the LCD and *voila*!

3.jpg
The RAMPS 1.4 electronics and LCD display
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2.jpg
Close-up of the normal display
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Actually it was a lot more painful than that, and I had to do some customisation of the software to set various parameters for my particular hardware layout. A few gotchas here and there, but I'm very pleased with the result. It's showing a temperature error, but since I have none of the sensors/motors hooked up yet, all I really wanted to see was a display. The display goes to a menu when you press/rotate the button next to the LCD, so the basics of the control electronics seem to be working just fine.

4.jpg
Electronics @ home
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The above shows roughly how it will look when everything is mounted on the machine itself. The RAMPS electronics sits under the hot plate. It's a bit tall, so I may have to raise the hot-plate a bit, which means decreased print volume... but really I don't mind a few millimeters less, as I don't tend to print tall things anyway.

Next, parts for the rather neat extruder have been rolling in. I printed all the black and the white plastic bits you see here, then screwed in the NEMA 17 stepper motor. The hobbed bolt (which pulls the filament through on a toothed profile) arrived today, so I could finally get it all assembled. I've mounted it top-left on front of the machine. I really like the spinning gears, and wanted it to be prominent. You can see it in the next few pictures...

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The extruder @ top left
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7.jpg
Extruder close-up
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8.jpg
Another view showing the quick-release tip screws
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This is a rather nice design, quite complex. You may be able to make out the long spring-covered screws. These simply tilt-up and allow the push-roller to flip down, giving easy access to the internals of the mechanism in case of jamming or mis-feeds. It's a modification I've made of a wade extruder; by putting push-fit nozzles on each end I've turned it into a Bowden extruder. It works OK when I manually turn the gears; I can't wait to get the connectors I've ordered so that I can hook up the stepper motors and start to get this thing actually doing stuff under software control.

Soon....
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Re: 3D printer build log

Postby Andrew Davie » Sat May 16, 2015 1:42 am

Well, the connectors arrived, and more particularly the power supply has come. So, I 3D-printed a case/cover for that using the work printer, and gingerly applied 240V. I appear to have gotten the connections right - after poking around with a multimeter, the only live bits seem to be the correct bits, and I'm getting a good 12V (10A) out of each of the two power connectors. So, I decided to actually power up the machine, such as it is. It's been quite the number of months since I've played with it, so I didn't really expect anything of anything, except for the LCD to light up. So, it did just that, and I was playing with the menu options, one of which was something like "set home position". I pressed that, and the print head/arms kind of moved. Ever so slightly. But, hey! So I looked at other menu options, and there's a move option, so I tried that, and well bugger me dead as we are wont to say here... I can actually turn the knob and the print head moves (via the carriages moving up and down the posts) exactly as it should! I have a very stable and obvious X/Y movement already, which is achieved by differentially moving the carriages on the three masts (which in turn are moved by the stepper motors driving the belts connected to the carriages). It's a big surprise to me; I barely remember plugging in all the wires, yet alone actually checking they were all correct. But, correct they seem to be. Great news is that my home-brew carriages (which I'm using instead of expensive rails) seem to actually be working. We shall see how accurately in good time, but working is working.
So, it's not printing yet... but a huge step forward. I brought it home to do a bit of work on it on the weekend. I'll try and get a quick video of the movement up, too.
Things to do - mount a fan to the print head, finish the print head assembly, get the software configured for the new laptop I'm using, recompile and check downloading to the board, check comms to the board and a front-end GUI for movement. Get the bowden extruder working so that it pushes filament. Check the heated bed and print head are heating... well, absolutely heaps to do actually. But, so saying, seeing the print head actually move correctly via the really weird delta control of the three carriages... well, that's a big motivator.
Cheers
A
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