Chapter 26 - In which I start to actually print things

First off, my apologies for being late with the updates again - it's becoming quite a habit. I've made a fair bit of progress over the last 3 or 4 months, and I'll try and cover it all in a couple of posts.

When I last posted, the printer had just printed its first proper part, and as a reward had gone on holiday to the garage over Christmas. Whilst in the garage, I decided to tackle one of those issues that had bugged me from the moment I installed the bed. Here's what I'm talking about:

The heads of the screws that hold the bed in place stand proud of the bed surface. Sticking up like this annoyed me, as I couldn't use the maximum size of the printbed, but also because they represent a threat of collision with the head - something I only discovered by doing it!

I removed the printbed and used a hand countersinking tool to recess the screw heads:

That's much better:

This was all in the middle of January. Jump forward to mid February, and the printer is back on my workbench and I'm starting to iterate towards some decent print settings. I've started using the most awesome slic3r as my gcode generator, as it is simple to set up and seems to produce good prints. If you haven't tried it yet, it's well worth it. It seems as if the strangely shaped cube in my last post was a result of skeinforge - I don't know what happened, but slic3r is giving good prints so I' gonna stick with it.

The following photo shows some of the cubes I printed to start getting the settings correct. As you can see, they start off awful on the left, and get better as I reduced the layer height and nozzle size in slic3r. I also changed the size of the cube from 20x20x20 to 20x20x10 and then 20x20x5 as it was possible to tell how good the settings were without needing to take the time of building the full height.

The settings that I have settled on (for now) are: Layer height of 0.3mm, perimeter speed of 30mm/s, a temperature of 220C and a bottom layer height ratio of 0.7. I'll include a full slic3r config file at the bottom of this post with the complete settings in, for anyone who is interested (or would like a starting point). This resulted in the final cube on the right, which looks like this close up:

This cube was printed with a nozzle size of 0.45, which is a bit big still hence the poor fill on the top layer

Tuning of the first layer height ratio took a long time, and seemed inconsistent (and I know why now - will come to that in a later post). This photo shows the consequences:

The first layer was too high, and came unstuck - the was the skirt, before the first layer of the object went down!

At this point, my feedstock (3mm "Architects Stone" PLA from Faberdashery) was being stored in the box it came in, on the floor, and being unrolled by hand as I was printing. It looked as if there was some tension on the feedstock and consequently on the X-carriage. I decided a filament spool was the first upgrade I ought to print, and so went off to thingiverse and downloaded http://www.thingiverse.com/thing:8317 and http://www.thingiverse.com/thing:10254.

I figured I'd try to print the arms of the spool holder first. In the immortal words of the Top Gear team, how hard could it be?

Pretty hard, as it turns out. Not only did I have to contend with varying height ratios for which there was no cure (I must have levelled the bed 3 or 4 times, grrr!) but also I had not 1 but 2 cabling breaks, right here at the main terminal block on the carriage:

The heater power wire had broken! The printer is wired with single-core cable, and it broke here as there is no strain relief. I've added some loops of cable to all the wiring now, to try and prevent this from happening again. I also had a thermistor wire break, at the same place. Thankfully this caused the printer to fail safe, with either pronterface or the firmware switching the heater off.

Here is a rather poor photo of an arm in progress:

Finally I got my first parts off the machine - the feeling of having actually made something is fantastic!

So, up next - more parts for the spool holder, more problems and more resolutions!

Example slic3r config, as used in april 2012:

bottom_layer_speed_ratio = 0.2

bridge_flow_ratio = 1

bridge_speed = 60

duplicate_distance = 6

duplicate_x = 1

duplicate_y = 1

end_gcode = M104 S0 ; turn off temperature\nG28 X0  ; home X axis\nG28 Y0 ; home y axis\nM84     ; disable motors

extrusion_axis = E

extrusion_multiplier = 1

extrusion_width_ratio = 0

filament_diameter = 2.86

fill_angle = 45

fill_density = 0.5

fill_pattern = rectilinear

first_layer_height_ratio = 0.7

g0 = 0

gcode_arcs = 0

gcode_comments = 0

infill_every_layers = 1

infill_speed = 40

layer_height = 0.3

nozzle_diameter = 0.4

output_filename_format = [input_filename_base].gcode

perimeter_speed = 30

perimeters = 2

print_center = 100,100

retract_before_travel = 0.5

retract_length = 3

retract_lift = 0

retract_restart_extra = 0

retract_speed = 30

rotate = 0

scale = 1

skirt_distance = 12

skirt_height = 1

skirts = 2

small_perimeter_speed = 30

solid_fill_pattern = rectilinear

solid_infill_speed = 30

solid_layers = 3

start_gcode = G28 ; home all axes\nG92 E0 ;reset extruder\nG1 E3 F1200 ;Prime extruder 3mm\n;G1 E2 F1200 ;retract extruder 1mm\nG92 E0 ;reset extruder

temperature = 220

travel_speed = 130

use_relative_e_distances = 0

z_offset = 0

Chapter 22 - In which I mount the hot-end, and find useful things in the garage

Firstly let me apologise for not posting in a while. Things have been busy here, and as usual the write-up get left until later. We resume our story just as I have built my DIY nozzle and heater block....

With the hot end assembled, it was time to mount the thermal barrier. It was a tight fit in the heater block, so I got it started by hand and then used a ratcheting clamp to squeeze it fully home.

 

I mounted a 2.5mm drillbit in a chuck for the electric screwdriver, and drilled and tapped the holes to hold the thermal barrier in place.

 Next I test fitted the heater resistor and its spacing sleeves into the battery clamp. As the following photo shows, there was still a gap to eliminate.

Remembering a tip from the forums, I wrapped the outer sleeve and the resistor with tin-foil, until they were a tight fit within the clamp.

Next I mounted the extruder body to the X-carriage and wired it up. I mounted a terminal block with cable ties through the fan mounting holes on the carriage.

I loaded up the feedstock and performed the E_steps_per_mm calibration for volumetric extrusion as found (prusa method: insert link here).

I performed the calibration with the hotend removed for ease. I ended up with a figure of (EDIT, May 2012:  I found my initial E steps figure during a tidy up - I worked it out to be 488.4)

I prevoius look around my Girlfriend's Dad's garage had provided me with a crimping tool, that I used to fit some PTFE wire to the resistor legs via a pair of bootlace ferrules. Isn't it funny that sometimes the right tool turns up at the right time?

I covered the outer nozzle sleeve in a thin layer of heat sink paste, and set about clamping it into place. I had thought this to be a fairly easy task, but it turned out to be much harder than I had anticipated. The outer sleeve wasn't really big enough and so there was a very large reduction to be made by the clamp's bolt. Eventually I had to resort to a pair of pliers, as the bolt was distorting the clamp too much. With the aid of a very patient girlfriend, it was eventually tightened up.

I fitted the sensor as far into the hole as it would fit, and held it in place with a small peice of wire.

I screwed the mig tip into the barrier, and tightened it up. Then I fitted the heater and thermistor wires into the terminal block, and competed the wiring to the board.

Next up: Will it actually work...?

Chapter 20 - In which problems are rectified, and I make a temperature sensor the professional way

Its been a while since my last post. This is due to having had a week away in Scotland, but also due to progress being slow. I have however made some progress.

Firstly I changed the angle of the X-axis endstop. I had test-fitted the extruder body, and found the endstop was in the way. There is a conveniently provided little square protrusion on the side of the carriage, and the contact of the realigned endstop sits nicely on it.

I then proceeded to fit the print bed. I had spotted this post on the forum, and decided to make the upgrade now rather than later. I had also got lots of peg springs just waiting for a use. I have used countersunk screws to mount the bed, but only because they were the only ones I could get with the correct length. There are washers under the heads to prevent the screws pulling into the bed and cracking it.

The bed is fairly level as it is, but I may tighten up the nuts to compress the springs, making the bed firmer and less prone to wobble. This has the added advantage of giving some extra Z height.

I had ordered some replacement bolts to hobb, as the previous one was too narrow. Once they turned up, I spent an evening in the garage attempting to hobb one of them. It was much harder going than the previous bolt - maybe these are made of something harder? I was also trying to hobb with an M6 tap as opposed to an M3, to give bigger teeth on the bolt. I just couldn't get it to cut the teeth correctly, and it left an un-cut section in the middle of the bolt. I ended up getting very frustrated with it, and walked away trying to decide how to go about making one properly.

I came back to it a week or so later, and had a proper look in the daylight. The hobbing down one side looked pretty good, and fairly even. I figured that I could probably space the bolt such that the good section was doing the driving.

I put the extruder back together, and was pleasantly surprised to find that the good section was in the correct place already. Better than that, it had enough grip to drive feedstock without the idler in place! Whilst working on the extruder, I also moved the motor and fitted the bolts that will mount the extruder to the X-carriage. I reassembled the extruder and idler, and repositioned the motor to get the best interface between the gears.

I also had the time to make up the hot-end temperature sensor. I constructed this in a similar manner to how professional temperature sensors are made. Firstly I soldered the ends to the stripped ends of the PTFE wire:

I then used high-temperature heat-shrink sleeving to insulate one leg, all the way from the small joint at the thermistor head to past the solder join:

I shrunk the sleeving with the kind help of my girlfriend and her crafting hot air gun:

I then used a larger diameter piece of the same sleeving to cover the entire assembly, from a point past the thermistor head to past the remaining soldered joint.

Lastly I trimmed the overhanging sleeving close to the bead. This assembly method should provide a robust and short circuit-free sensor for the hot end.

And Thats all the I've managed to achieve. Next up: The long-awaited hot-end post?

Chapter 19 - In which there is life!

I've been spending a lot of time recently working on the hot-end, but I'm saving the writeup until I have it completed and can make a whole post.

In the meantime, I've made small amounts of progress in other areas.

I have completed the wiring of the stepper motors for the axes. I wired them all the same, and consequently had to invert the direction in the firmware. I have also resisted cutting down the motor cables for any of the motors. I feel like I might need them longer later, in case I want to swap a motor or something. I realise this is unlikely. I'll cut them down later, if I can get the courage to. In the meantime, the excess cable is neatly bundled with the motors, or on the frame.

Once I had all the motors wired up, I fired up ReplicatorG to move the axes and check the direction was correct. I encountered a strange bug, wherein the axes wouldn't move properly under manual control, sometimes only moving a short distance, and other times moving in reverse. Also sometime multiple axes moved at once! I don't know if this will effect the operation of the machine when printing, but I didn't like it.

I went off and installed Pronterface instead. After the fun I had with sprinter, I was expecting to have some trouble with Pronterface, but was pleasantly surprised. The install guide is concise, but it works perfectly. Printerface needs almost no configuration, and is very quick - I like it! Comes with built in skienforge support too, which is nice. Infact I then went off and got Sfact too, as the pair seem to go together well (pronterface has some sfact-exclusive options).

More recently I have added the endstops to the axes. I'm using microswitches, and they had arms on them:

I popped them into the vice, and sawed off the arms - careful to avoid sawing off the switch!

I decided on locations for the endstops. They are configured as being at the minimum end of the axis in firmware, and so this translates to Y being at the front, the X being at the left, and the Z at the bottom. I played around with locations for a while before marking up the brackets.

I attached the endstops to the brackets with hot glue, as the screwholes were in the wrong places. Each bracket was then fitted to the axis with an M3x25 screw, with a couple of plain washers and a spring washer.  I added some insulating tape to the Y axis terminal, so that it didn't short to the frame.

Once the endstops were installed, I wired them to the plugs and routed the cables along the frame.

I powered on the machine, and tested the endstops. I moved the axis out a long way, and then told it to return. As it was moving I activated the switch. All 3 axes worked ok, stopping the moment the switch was pressed. I then told Pronterface to "Home" the axes. It was pretty scary to watch, as the axes drove themselves into the stops:

In other news, I ordered some filament from Faberdashery. When I tried to load it into the extruder, disaster struck! The hobbed section of my bolt is too narrow, and the filament is too rigid to come into contact with it, regardless of how much pressure is applied by the idler.

I have to hobb a new bolt. I have ordered some M8 by 60 shoulder bolts from ebay, and will hobb the shoulder with an M6 tap - if I can work out a way to do it.

Next up: not sure. Maybe the hot end.

Chapter 18 - In which my alternate spring source is validated

One quiet Sunday, I sat down to build my extruder. I had already hobbed the bolt, and so now only needed to build up the extruder body.

I had a little trouble fitting the bearings into the extruder body, but a little work with a file ensured that they sat flush:

I had a peice of threaded rod left over from cutting the frame bars down, so I cut it to 50mm and used it to mount the idler bearing. The bearing seems a little loose though, so I may have to change it out in the future.

I fitted M4 by 50mm bolts through the extruder body, and fitted a pair of washers to each one. I had to file out the screw holes a little to make the bolts fit.

I fitted the idler block over the bolts - this was harder that I had thought it would be, due to having to keep the block square or the bolts would bind up.

Now, time for the all important springs. As I mentioned here, I had found a source of springs in a certain shape of clothes peg. I had ordered some after scouring ebay for the right type. Unfortunately when they arrived they were the traditional, sideways-action spring type. I got in touch with the company, whoi were able to find some of the kind their listing showed. Lesson learned by me - some photos on ebay are for illustrative purposes only. Once I had the new, correct, pegs in hand, I set about de-springing them.

Having removed 4 springs, I was faced with another problem - they are too long for the bolts. After failing to compress them enough to get a nut onto the thread, I took them to the garage and took a hacksaw to them.  I cut them down to just the right length to allow them to be fastened on, with only a little compression.

The motor mount on the extruder is thinner then that of the Y axis, so I though I could use the same trick of doubling-up the washers as I did on the x-end-motor. However, This made the Screw heads stick out too far, and they interfered with the gears. I opted for the solution below, with one set of spring washers between the motor and the extruder, and the other next to the screw heads:

I fitted up the hobbed bot and large gear. I had to use 4 M8 washers to space the bolt correctly, because the hobbing had drifted to one side.

I had used a couple of M8 halfnuts that I found to hold the hobbed bolt in place, but have subsequently moved to one half nut and one full nut as I had problems getting the tension right and the locking tight enough.

Because of the extra washers spacing the big gear, I had to mount the small gear in reverse. This is actually suggested in some of the instructions, and won't cause any trouble due to the grub screw still being securely on the shaft.

Next up: talking to the machine

Chapter 12 - In which I finish the X axis, and have a good idea

I wasn't happy with how the X carriage was travelling, and so I loosened off the smooth rods and rotated them (one at a time) until the carriage moved much more freely. I then fitted the belt clamps.

As you can see, the suggested M3 by 25mm screws are very long. In fact the back pair are so long they interfere with the smooth rods, and the carriage binds (this is probably due to how the carriage sits on its bushings). I replaced the rear screws with a pair of 12mm ones taken from the X axis ends (which were too long in the X ends anyway, and were replaced with some M3x6 screws I had found in a draw earlier).

I fitted the X belt in the same orientation as the Y, namely with the teeth facing downwards in the clamps. It was only when I threaded the rest of the belt around the idler and back that I noticed that it was wrong - the teeth should face upwards, and the belt travel above the carriage rather than under it. I reassembled it and tightened everything up. The carriage now moves very smoothly, seemingly with no backlash.

I cut the belt off leaving a little for adjustment later if needed.

And that's as far as I can go today. Next I will build the electronics, but I need a PSU before we have any movement. I can also build the extruder once I get a few more bits delivered.

Whilst in the draw that yielded the earlier M3x6 screws, I also found the solution to the spring problem. I had previously been unable to find a cheap source for the springs needed to tension Wade's idler bearing in the extruder. I found this clothes peg, the spring from which is perfect:

I scoured ebay and picked up a pack of 24 for £2.50 - that's just over 10 pence each, a marked improvement on the £1 or £2 each I had previously seen springs going for.

Next up: Electronics build