He asked lots of questions and made a couple of videos of my answers for his blog, which you can see here.
I volunteered to print a set of Darwin parts to help get Factor e Farm up and running with 3D printing. I was confident that I would have my Darwin running in time to churn out the parts. However, because I spent a lot of time experimenting with extruder designs in an attempt to get something more reliable, I ran out of time and had to print the parts on HydraRaptor.
Here they are, all 109 of them: -
All the parts were printed with 0.5mm filament at 16mm/s with 32mm/s moves. Most were sliced with Skeinforge set to 25% fill and larger objects have double outlines to maintain strength.
Here are some stats: -
| Build time | Plastic volume | Quantity required | Total build time | Total plastic | Weight | Cost | Percentage of total | |||
| Corner bracket @ 90% | 02:44:44 | 29.1 cc | 8 | 21:57:49 | 233.1 cc | 291 g | $5.83 | 29% | ||
| Diagonal tie bracket-chris | 00:27:00 | 4.8 cc | 20 | 09:00:06 | 96.4 cc | 120 g | $2.41 | 12% | ||
| Bed corner | 01:32:06 | 15.5 cc | 4 | 06:08:25 | 62.1 cc | 78 g | $1.55 | 8% | ||
| Z-motor-bracket-chris | 01:23:12 | 14.6 cc | 4 | 05:32:47 | 58.2 cc | 73 g | $1.46 | 7% | ||
| X motor bracket | 03:56:35 | 37.2 cc | 1 | 03:56:35 | 37.2 cc | 46 g | $0.93 | 5% | ||
| X-carriage | 03:51:39 | 40.2 cc | 1 | 03:51:39 | 40.2 cc | 50 g | $1.00 | 5% | ||
| Y housing | 00:56:36 | 9.9 cc | 3 | 02:49:47 | 29.8 cc | 37 g | $0.74 | 4% | ||
| Extruder drive block | 02:30:44 | 26.5 cc | 1 | 02:30:44 | 26.5 cc | 33 g | $0.66 | 3% | ||
| X idler bracket | 02:28:06 | 25.4 cc | 1 | 02:28:06 | 25.4 cc | 32 g | $0.64 | 3% | ||
| Y motor bracket | 01:51:06 | 19.6 cc | 1 | 01:51:06 | 19.6 cc | 25 g | $0.49 | 2% | ||
| Bed constraint | 00:43:20 | 7.5 cc | 2 | 01:26:39 | 15.1 cc | 19 g | $0.38 | 2% | ||
| Bed clamp | 00:21:39 | 3.7 cc | 4 | 01:26:36 | 14.7 cc | 18 g | $0.37 | 2% | ||
| Extruder base | 01:13:19 | 13.1 cc | 1 | 01:13:19 | 13.1 cc | 16 g | $0.33 | 2% | ||
| Z-coupler-airpax | 00:14:21 | 2.6 cc | 4 | 00:57:26 | 10.2 cc | 13 g | $0.26 | 1% | ||
| Opto bracket @ 50% | 00:19:00 | 3.1 cc | 3 | 00:56:59 | 9.4 cc | 12 g | $0.23 | 1% | ||
| X-belt-clamp | 00:10:46 | 1.9 cc | 5 | 00:53:50 | 9.5 cc | 12 g | $0.24 | 1% | ||
| Wiper-diagonal-bracket | 00:43:50 | 7.6 cc | 1 | 00:43:50 | 7.6 cc | 9 g | $0.19 | 1% | ||
| Wiper-brace | 00:13:24 | 2.3 cc | 3 | 00:40:11 | 6.9 cc | 9 g | $0.17 | 1% | ||
| X-constraint-bracket | 00:38:10 | 6.6 cc | 1 | 00:38:10 | 6.6 cc | 8 g | $0.17 | 1% | ||
| Pulley | 00:12:35 | 2.2 cc | 3 | 00:37:44 | 6.7 cc | 8 g | $0.17 | 1% | ||
| Bolt plug | 00:04:36 | 0.8 cc | 7 | 00:32:11 | 5.8 cc | 7 g | $0.14 | 1% | ||
| Tall foot | 00:14:27 | 2.6 cc | 2 | 00:28:54 | 5.3 cc | 7 g | $0.13 | 1% | ||
| Y motor coupling | 00:25:02 | 4.5 cc | 1 | 00:25:02 | 4.5 cc | 6 g | $0.11 | 1% | ||
| Z-adjuster-housing | 00:24:12 | 4.1 cc | 1 | 00:24:12 | 4.1 cc | 5 g | $0.10 | 1% | ||
| Short foot | 00:11:21 | 2.1 cc | 2 | 00:22:42 | 4.2 cc | 5 g | $0.10 | 1% | ||
| Fan base | 00:22:29 | 4.0 cc | 1 | 00:22:29 | 4.0 cc | 5 g | $0.10 | 1% | ||
| Y belt clamp | 00:03:43 | 0.7 cc | 4 | 00:14:50 | 2.6 cc | 3 g | $0.07 | 0% | ||
| Fan-leg | 00:15:48 | 2.8 cc | 1 | 00:15:48 | 2.8 cc | 4 g | $0.07 | 0% | ||
| X-motor washer | 00:15:27 | 2.8 cc | 1 | 00:15:27 | 2.8 cc | 3 g | $0.07 | 0% | ||
| Z-flag-slider | 00:13:00 | 2.3 cc | 1 | 00:13:00 | 2.3 cc | 3 g | $0.06 | 0% | ||
| Bearing 360 run | 00:02:47 | 0.5 cc | 4 | 00:11:09 | 2.0 cc | 3 g | $0.05 | 0% | HDPE | |
| Extruder PCB holder | 00:09:45 | 1.7 cc | 1 | 00:09:45 | 1.7 cc | 2 g | $0.04 | 0% | ||
| Z-opto-flag | 00:08:45 | 1.6 cc | 1 | 00:08:45 | 1.6 cc | 2 g | $0.04 | 0% | Black ABS | |
| X-carriage-bearing | 00:08:39 | 1.1 cc | 1 | 00:08:39 | 1.1 cc | 1 g | $0.03 | 0% | HDPE | |
| Y-opto-flag | 00:07:43 | 1.4 cc | 1 | 00:07:43 | 1.4 cc | 2 g | $0.03 | 0% | Black ABS | |
| Bearing 360 jam | 00:02:49 | 0.5 cc | 2 | 00:05:38 | 1.0 cc | 1 g | $0.03 | 0% | Black ABS | |
| X-opto-flag | 00:04:43 | 0.8 cc | 1 | 00:04:43 | 0.8 cc | 1 g | $0.02 | 0% | Black ABS | |
| Wiper-lever | 00:04:26 | 0.7 cc | 1 | 00:04:26 | 0.7 cc | 1 g | $0.02 | 0% | ||
| Z-flag-clamp | 00:03:20 | 0.6 cc | 1 | 00:03:20 | 0.6 cc | 1 g | $0.01 | 0% | ||
| Circlip | 00:01:26 | 0.3 cc | 2 | 00:02:53 | 0.5 cc | 1 g | $0.01 | 0% | ||
| Bearing 180-x | 00:02:38 | 0.5 cc | 1 | 00:02:38 | 0.5 cc | 1 g | $0.01 | 0% | HDPE | |
| Bearing 180-z | 00:02:03 | 0.4 cc | 1 | 00:02:03 | 0.4 cc | 0 g | $0.01 | 0% | ABS | |
| 109 | 74:28:04 | 778 cc | 973 g | $19.47 | 100.00% |
The times and weights are calculated, and don't include the raft time, which is significant, or the time waiting for temperature changes and raft cooling. I weighed the parts on kitchen scales and they came out at 931g, so pretty close to the calculation. The cost shown is on the basis of ABS at $20 / Kg.
I save all the rafts for the day when we get recycling working. I weighed them in at ~ 200g, that is about 20% wastage and will bring the actual printing time up to about 100 hours.
I also wasted 150g in failed prints, for silly reasons, more on that later. It gives a measure of the reliability I am achieving at the moment, i.e. 8 parts failed out of 117 prints so 93% success rate. Of course the bigger the part is, the more chance something will go wrong, so by weight and time it is much worse .
I used plain ABS for most of the parts because it seems to bond better than coloured. I used black for the opto tabs. No guarantee that they will be opaque to IR, but I think black ABS usually is. The green parts are just ones I had left over from experiments.
I made some of the bearings in HDPE as that should be a better bearing material than ABS, lower friction and longer lasting. The black ones are "jam" bearings so I left them in ABS as they want maximum friction.
Some of the parts are my own design. Most significant are the z-axis parts described in the previous post. Here is a list of the other design tweaks, with links to the article describing them:- simplified diagonal tie brackets, X-motor washer, x-carriage bearing and the feet.
Some parts I had never printed before. The Pinch wheel extruder: -
The nozzle wiper assembly has appeared in the latest Darwin release but I can't find any assembly instructions. I leave it as a puzzle for Edward Miller, the guy who is actually going to build this machine.
Similarly the new adjustable z-opto flag assembly: -
I aimed to print these parts over the course of a week, three batches a day, but the machine had other plans and it actually took me two weeks. I will give more details tomorrow.
