Freesteel Blog » 2014 » April

Sunday, April 27th, 2014 at 3:09 pm - - Kayak Dive 1 Comment »

We went to Scotland over Easter with the Liverpool Canoe Club who rented the whole of the Blackwater Hostel. This meant folks didn’t have to be strict about washing up the pots and pans within seconds of using them for fear of pissing off the other guests.

By arriving early (having kipped in the woods near Lockerbie), there was time to walk up the the reservoir without a map (a map would have told us that it was too far to go). It took five hours in my normal shoes and I was cross and knackered by the end of it.


Saturday, April 26th, 2014 at 7:50 am - - Machining 2 Comments »

A mere 9 years after we first tried to use our own mini-machine tool — which Martin wants to make sure everyone understands he did get working (shortly before it broke) — it’s been brought out of the cupboard and fitted with some proper electronics in the form of an Arduino controller by the DoESLiverpool Italian intern, and is showing signs of life.

The part of this kit that gave me the most surprise was the GRBL G-code parser code that ran on the Arduino. Look at the amount of software crammed onto that thing! Watch out Hurco and Heidenhain, your days are numbered. Soon all your industrial equipment will be deader than a Vax VMS.

My favourite function in the GRBL code is report_realtime_status() which prints a line of the form

<idle WPos:10.999,-0.5,9.1>

Yes, it’s the current position of the tool while it is running.

I immediately wrote a threading Python program to drip tool motions into the Arduino interspersed with the “?” command to invoke this realtime status to find out where the position currently had got to. Eventually this could become the principle behind a combined probing, cutting and dynamically feed-backing CAM system — something that cannot be implemented on industrial machines today due to their batch-work nature and one-way post-processing valve filter. For more, see earlier post on the feedback in the cnc drive configuration.

While writing an internal rant about why it’s okay to machine triangles, when some CAM systems claim to be “more accurate” because they locate their cutter positions against the analytic geometric surfaces themselves, I came to an important observation: the point nodes of the toolpath as defined in the G-code file are of no significance to the total cutting process, which continues along the straight lines between the nodes. All these cutting positions on the lines between are never on the accurate surface, so getting the zero dimensional finite set of node positions exactly right doesn’t make a difference.

Saturday, April 12th, 2014 at 9:43 pm - - Hang-glide

What’s a blog post if it makes any sense the next year? It usually doesn’t when I go back over them to look up an important piece of information, like the date when something happened. I do have a separate logbook for the flying and things like that. Blogs don’t seem to work. Too whimsical and public and I tend to leave out names.

On Wednesday I took the DoESLiverpool intern down to Mach2014 as he is a mechanical engineering student when he’s home in Italy.

Lots of whizzy cutting machines and mechanical gadgets, mixed in with generally unfriendly software companies who deserve to be left for dust when the far more efficient open source methodology finally moves into this sector and the programmers can talk to one other freely and discover how to get things done. The best ideas can never all be inside one company. (You can forget about ideas that are the combinations of many other ideas). It’s just a question of persuading the market to raise X dollars for the programmers to do the work, rather than handing over 100 times X dollars to companies who own the dead capital and mismanage the software development process with their layers of management and high level strategy thinkers who have grown too lazy to do any programming themselves, yet still believe they have something to contribute.

You know the saying: “All politics is local”? Well, I’m beginning to believe that All programming is low-level. You either understand the software, or you don’t. There is no high level structure that you can be involved in without knowing about the code. Take, for example, another branch of engineering. It’s self-evidently ridiculous that you could have anything to say about the shape of the skyline of a petrochemical refinery if you have no idea about what the chemicals are doing, and what needs to be mixed with what. Is it unique to software that people who don’t program want to be in charge of the design? The one thing we do need from managers are specific performance targets to keep us from making excuses. Something like: “If I’ve got a 32 core machine, I want it to run 32 times faster on this example. Is there a theoretical reason why I can’t have that?”

Anyway, the picture on the left is a set of printed titanium parts for a bicycle frame that no one dared ride. The one on the right is of a mini-machine tool with a huge toolchanger system. There are no plans for a toolchanger on our triangular machine. I wonder if we’ll discover that this is a problem.

I spent all Friday at Llangollen for a 12 minute flight down the hill where I only barely cleared the fence into the landing field having taken an extra turn to bleed off height when I was stupid enough to think that I was going to overshoot. Something wrong with my judgement here. The guy I drove down with reckons the half-life for hang-gliding skills must be 6 months. Got a lift back to the top, set up again, then the wind changed, and we watched three paragliders soaring up to the clouds while we were grounded in a light, cold easterly cross-wind. Humph.

Time for something new. A month after seeing kitesurfing on the Wirral on a bike-ride with Francis, Becka and I were having a 4 hour lesson with a surfer dude in the same place near New Brighton.

This would have been last week, but after we’d got up at 6:30am, caught the train to Birkenhead where it broke down, and then cycled at a mad rush to the north coast through the morning rain, we met the man in the van who said there was not enough wind. He gave us a lift back over the water, and got the message that we were keen.

Still, compared to anything else I’ve tried to do, this is very close to instant gratification. We were kite body-dragging through the waves by the end of the fifth hour of the lesson. What a long day.

Tuesday, April 8th, 2014 at 9:56 am - - Cave

Weather was nasty over the weekend, I’m losing the plot when it comes to programming, and I enjoyed the physical activity I did last weekend, even though the flying was not successful.

I joined Becka and others on a “promising” dig in Gaping Gill beyond Hensler’s endless flat out crawls, and through the “blowhole”.

The dig was a tight wet inlet with pooling water, mud, and not enough room to turn over onto your back from your front. Clearly this had been subject to terminal worm-holing. There were a lot of digging tools to use with which I tried to widen the passage vertically at the front — though I didn’t pass much spoil back into the digging trays during the process. Tom took over after 90 minutes of me hogging the dig until he got too cold due to not wearing enough neoprene. We retreated and warmed ourselves up by chucking a heavy rock back and forth between us until our lower backs hurt. The remaining diggers complained that we’d used up all the air, so they couldn’t do any more. Never a good sign that a dig is heading towards big passages.

I got back-of-the-knees wetsuit rash walking up to the entrance, and we nearly got lost in the fog on the walk down. It was great. After a quiet night at Bull Pot Farm (all members were at the dinner/AGM), I got dumped at Clive’s house for a few hours while Becka went caving. This lead me wasting time on a couple of FOI requests to [1], [2], and flicking through the ACCU magazine to find an article about the First International Conference on Software Archaeology.

About time people started talking about software archaeology. It’s evidence of the dereliction of responsibility that the executives running our large moneyed software companies whose wealth depends on the functioning of decades old piles of buried and very crappy code are not properly funding this field of study, and leaving it up to a small number of visionary amateurs to do what little they can, while the executives cash out their share-options for yachts and corporate take-overs. I see no process within the corporate power structures that would result in those who control the money becoming aware of where the actual needs for investment lie. If it was seen that corporations devolved certain budgets to be disbursed by internal committees staffed by people who understood the challenges and were in a position that they did not need to get things signed off by senior officers who didn’t understand the challenges, maybe something positive would come out of it. After all, the public sphere exists as a system of quasi-autonomous organizations with their own budgets to get on with matters that central government are not always politically happy with, but which need to get done, so why is it not a viable option to consider such formal systems of operation within corporations?

Tuesday, April 1st, 2014 at 8:26 pm - - Hang-glide

Not cool! How did I end up holding my glider this way up in a bog at the foot of Whernside on Sunday?