Adventures in 3d printing Or "I Finally Built a RepRap!"

I've wanted a 3d printer for quite some time. A few years ago I stared building one that, to say the least, was poorly engineered and under constructed. It never actually worked at all. Some of the designs could have worked, especially in a large CNC machine, but were just not a good fit for a small 3d printer. I've been eyeing the RepRap i3 models for a while now, last week I bought a kit (less electronics).

RepRap i3 with cooling fans and filament spool.
Note spool is on backwards to allow for the sloped ceiling in my lab.

Assembly was quite straightforward, there is a partial guide, though it skips (or I missed) some key steps.

A few tips:

• Final alignment of the XZ (vertical) frame should be done after assembly. Just line it up so the extruder will reach the front and back of the Y frame and is square.
• I printed thumbnuts to fine tune the bed leveling, it makes it really easy to get it spot on. I used these "Easy Heated Bed Leveling Thumbnuts"
• The Z axis endstop was a pain, part of it was I used the wrong mount, but I printed this "Adjustable Z-Axis Endstop Arm" to make it easier

Fire in the Hole!

Everything I (and probably everyone else) build has some "teething" issues. I had (and am still having) a few. After I got it set up fairly good I started a print and it seemed to be working nicely, then the Sanguinololou literally caught fire (there were flames). The bug list for the Sanguinololou says the traces for the heated bed are too small, so I had reinforced them with wires before this point, it was the wires that caught fire. Turns out the mosFET shorted and the bed just stayed on continuously drawing ~16A. I salvaged the board and put a new mosFET (all I had on hand was a 12A logic level one) put it back together, set it to pwm at 50% and it lasted about 30 seconds before shorting too (I was watching this time). I swapped it again, added a reverse diode and ran it through an automotive relay (so the mosFET turns the relay on and off). That works really good.

Electronics, complete with rats nest

Now that the fires were out It was time to try some real prints. The filament won't stick to the bed. No matter what I do it won't stick. I tried cleaning really well, nope. gluestick helped, allowed me to print the upgrades I mentioned, but was hit or miss. I researched, tweaked settings, spent the better part of a day on it. Finally my brother was over and (looking on his tablet) said "they say here that Reprapper brand glossy black PLA won't stick to glass, use blue tape". Yep, I had Reprapper brand glossy black PLA filament, and yes, it sticks really well to blue tape.

A Sheep! Here's the first print that I took a picture of.

A few remain

Now I can print, I've still got a few issues left, mostly "dialing in" problems.

• Overhangs and bridging don't work quite right. I've been lowering the extrusion temperature and it really helps. I started at 200C and am down to 180C for the first layer and 175C after that. A box fan after ~5 layers helps even more.
• I printed some large parts and they warped, pulling the blue tape off the glass. The cooling fan bracket printed really nice with the 182C/177C and bed at 35C settings. this might be licked, but can't say yet. 
• The first layer of big parts will bunch up a bit during infill, leaving stuff sticking up that can catch the extruder. If it gets 3 layers or so it will bury the problem and will complete fine. I might still be a touch close on my z-axis start point or it might be something else.

Future plans

• Upgrade to optical endstop for Z-axis. It should be considerably more repeatable than a mechanical endstop, so I think it would be a big improvement. The X and Y axis are not nearly as critical, so I don't see any need to change those endstops.
• Upgrade the electronics so I don't need a computer hooked to it and add cooling fan support. I've got several options: MosFET board and sd adapter, MosFET board and android tablet, Panelolou (includes Mosfets on the interface board and SD on the panel). I'm leaning toward the tablet option. The software looks really cool. I need to try it sometime.

UPDATE: I printed a bracket to mount some 40mm cooling fans, but all my small fans are 50mm, so I printed a 50mm bracket. Seems I chose one bad fan (rattles) so I'll have to replace that at some point. It makes a huge difference. I'll do another post on integrating it with the electronics.

Links

http://www.thingiverse.com/thing:208137 - thumbscrews
http://www.thingiverse.com/thing:267927 - Z-Axis Endstop Arm

My Failed Fan Controller Design

I've spent all the time and resources I'm willing to on this project for now. I may complete it at a later date. It all works except the input voltage from the furnace transformer is too high after rectification (38-40v).  The 78M05 I'm using is 35v max and it doesn't tolerate any more. It doesn't seem to damage it, as even after testing as bad on the furnace it works fine on 18v (max on my lab PS) I tried to build a SMPS replacement based on Roman Black's design, that also worked fine on 18v and blew at least a zener diode when on the furnace. I used parts I had on hand, so sometime I will get precise values and try again. For now I'm ordering a snap-disk. Perhaps some of this design may be useful to someone for other purposes. It really sucks, as the controller works fine, I just can't get the voltage regulated to 5v. If you have any ideas feel free to comment. It's probably easy and I'm just not seeing it :)

My Dad's woodstove is ducted into his furnace. It works OK, but he has to manually turn the blower fan on to circulate the air through the house. This is OK when they're up and keep the fire going, but if they don't get up during the night the fire burns down and it circulates cold basement air. Brrrr

I realize I could just use a therm-o-disk, but what fun is that?

Plus I get a bit more practice making boards. NOTE: I bumped the zone fill clearance from .020 to .025, that definitely helped me not bridge pins to ground. It's a simple board and I used mostly .025 traces with a few .012 and .080 ones as needed. I can etch .012 very consistently, even .008 fairly well, but I keep tearing pads off drilling. The extra copper seems to help considerably. Extra copper around pad make things much easier drilling and mounting. Essential for wire connections. My first board's traces got torn up where wires mounted (all .012 traces). Notice the pads across the top of the following image compared with the bottom of the board above:

 Requirements:

• Run off furnace power (28VAC)
• Switch fan on at approx 120F, off at 90f
• Make sure fan runs at least 10 minutes when turned on.
• Cheap, hopefully less than a $15 T-O-D

Specs:

• Controlled by a attiny85
• PCB was done for a full-bridge rectifier, but we may use a half-bridge to keep the voltage under control. (use 2 diodes instead of 4) (Note: Didn't Work)
• Used Salvaged Components where possible

Parts List:

• Attiny85 ($1.30) 
• lm335a Sensor ($1.00) (I had some of these, I would use a mcp9700-e/to($0.25) in the future. the board supports it, just omit the 2k resistor)
• lm7805 Regulator ($0.50)
• 2n7000 mosfet ($0.60)
• 2x 1n4007 diodes ($0.50x2)
• 330u 50v cap (salvage)
• 10u cap(salvage)
• 0.1u cap
• 10K resistor
• 2K Resistor (omit for mcp9700)
• RY5W-K Relay (salvage)(you can get ones with ~30ma coils for less than $2.50 and drop the mosfet, though a mosfet does make it more robust IMO) You could also try a solid state relay

Schematic

The 7805 was a bit close to the cap, that will be fixed in the linked files. I intended to use a to-92 regulator, but the one I had was rated for 100MA. I thought my relay was 150MA. It was a last minute change. As it turns out it uses about 9MA idle and 54MA with relay powered. I could have used the to-92 after all.Total cost was under $5, though to buy all the parts would be more like $10, the cheapest T-O-D I found was $8. If I have the wrong temp with this I just reflash the chip, with a T-O-D I buy a different one.

Code is in Arduino, you will need the attiny85 hardware files, a programmer or an arduino, some wires and bits. See this guide for more information. I may redo it in AVR C sometime, I just wanted it up and running. I didn't need to do anything special.

 /*  
  Fan Controller intended for a attiny85, but takes ~3k, change pins below for arduino and uncomment the serial for debugging on the arduino.  
  it's intended for a furnace, so no fancy pwm or anything, thought it wouldn't be hard to add.  
  Stephen Evans - stevesfixitshop.blogspot.com  
  */  
    
 #define INPIN 3  
 #define OUTPIN 2  
 #define ONTEMP 48  
 #define OFFTEMP 32  
 #define DEL 600000  
   
 unsigned long wait = 0;  
 int avread = 0;  
 int ain[10];  
 int i = 0;  
 void setup() {  
 // Serial.begin(9600);  
  pinMode(OUTPIN, OUTPUT);  
 }  
   
 void loop() {  
  //make 10 readings  
  while(i<=9){  
   ain[i] = analogRead(INPIN);  
   delay(10); // wait for adc to stabilise  
   i++;  
  }  
  i=0;  
    
  //average the readings  
  avread = 0;  
  while(i<=9){  
   avread = avread + ain[i];  
   i++;  
  }  
  i=0;  
  avread = avread / 10;  
    
  //Convert reading to degrees C  
  float sensorValue = ((avread*4.8)/10)-284.15;  
 // Serial.println(sensorValue);  
    
  // turn fan on  
  if(sensorValue >= ONTEMP){  
   digitalWrite(OUTPIN, HIGH);  
   wait = millis() + DEL;  
  }  
    
  // turn fan off if below set temp and delay has passed.  
  else if (sensorValue <= OFFTEMP && millis() >= wait){  
   digitalWrite(OUTPIN,LOW);  
  }  
  // every 50 days millis rolls over to 0, this makes sure it doesn't mess things up  
  else if (millis() <= (wait-DEL-50)){  
   wait = millis();  
  }  
    
 }