HydraRaptor

Back in March I had a visit from Marcin Jakubowski, the founder of Open Source Ecology. He was over here in Manchester presenting at a conference and asked if he could come and see HydraRaptor, as he wants to use RepRap machines on Factor e Farm. Like RepRap, his project also aims to change the world.

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.

About a year ago I blogged an alternative Z-axis for Darwin using four tin can steppers instead of one expensive stepper and a belt drive. The only thing missing was a source of cheap motors to make it economically viable. Some time ago Forrest Higgs pointed out a source of cheap 15° motors for $2.50 made by Airpax. I also found them available for $2 at Surplus Shed. That makes a z-axis for $8 possible, which is much cheaper than original motor, let alone the belt.

They are surplus stock, so when they are gone they are gone, but there does seem to be a lot of them around. Unfortunately it costs more than $40 to ship them from the US, so the economics don't look nearly so good this side of the pond.

They are 12V 0.4A per coil, so four wired in parallel will take 1.6A, well withing the 2A capability of the RepRap electronics. They are six wire unipolar motors, but they can also be driven from a bipolar drive by using the red and orange wires as one coil and the green and brown as the other.

The pull in rate seems to be about 200pps, which would give 200 × 15 × 1.25 / 360 = ~10 mm/s with M8×1.25 threaded rod.

The boss on the back of the motor is a bit bigger than the motors I used before so I have updated the bracket design accordingly. The motors come with a spiral drive screw on the shaft. I could not find a way of getting it off, so I made a new coupling piece that clamps over it. It has a pointer so that it is visually obvious if the motors get out of step with each other.