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Lenovo Weldcenter

The control components and the wiring for the welding turntable are too delicate to leave exposed to the dust, metal chips and occasional flying tool around the shop. They have to go in a box. I could have drawn one up and had it fabricated along with the rest of the sheet metal parts for the bodywork, but (a) fabrication shops hate/love one-offs and charge accordingly and (b) a recently deceased Lenovo PC (born 2006, died 2019, R.I.P.) seemed like it might fit the bill.

At first glance, just a simple box.

Its apparent simplicity belies an extremely clever design that a lot of people thought long and hard about. It is also a masterclass in metal folding: the sophisticated locking(!) clamshell and double-pivot mechanisms are assembled from stamped and folded parts using only four screws. Very swish.

Having extolled the virtues of the Lenovo case I no longer need to feel guilty about cutting it up. Possibly voiding the warranty?

Time to start putting a few new things inside the now empty box. The heart of the controller is the stepper motor driver: a Geckodrive g203V. The literature states that the V stands for Vampire, as in unkillable. I have thus far failed to find the correct mixture of garlic and silver bullets required to prove them wrong. Other than an issue with making them play nicely with some common motion control boards that have a different electronic setup for their step and direction signals, these things are great, if not particularly cheap.

The heat sink from the GPU on the Lenovo motherboard is just the ticket for the stepper motor driver. It has a convenient spring-steel mounting clip that makes it easy to attach it to the opposing face of the motor mount.

A healthy application of thermal grease on all of the mating surfaces ensures the efficient transfer of heat from the driver to the sink.

Next, the new Weldcenter needs a face plate for the interface which will be made from a small scrap of 1/4″ acrylic. As usual, drawing up the cutouts and programming the CNC takes substantially longer than the actual cutting. Back surface first: a bunch of holes plus a relief pocket for the rotary pots that are designed for thinner material…

…and the front with engraved text for all of the various buttons, switches, sockets and dials.

Test fit of all the pre-wired controls including the LCD interface.

The front side, with residual laser-engraved tennis racket – the acrylic stock is a left-over from a sign project.

There were, of course, a couple of small, but in some cases mildly baffling, errors. The text at the bottom interferes with the mounting screws because I neglected to model them in CAD. Rather more inexplicable is the engraving of the “Gas” text which appears to have been outline, as opposed to single-line, engraved. Don’t know why, nor, as this is strictly a one-off will I spend any more time thinking about it. Much.

All the various bits and pieces stuffed into the box. Top left: the main cooling fan that used to be at the front of the PC. (For the ultra-observant, now you see why the fins of the heat sink below it are not oriented vertically the way they would be normally). Below the stepper controller is a solenoid for controlling the purge gas. Below that the microcontroller. The middle column is a DIN rail with a small (5 watt) 24 volt DC power supply and a bunch of terminal blocks for connecting everything together. The last column on the right is the other two power supplies. This is a bit of a kluge. There were only supposed to be two flavors of DC in the design: 5 volts for the microprocessor and 24 volts for the solenoid and motor and no fan. However, the 24 volt supply was very bulky so I swapped it for a much more compact 60 volt switching supply. The black box is a dual voltage (5 & 12) supply for an external hard drive of which I have many. So… four flavors: microprocessor 5 volt, fan 12 volt, solenoid 24 volt and stepper motor 60 volt. So much for simplicity. As always, the box is about 25% too small for all the stuff. There should really be cable tracks between each column and along the top and bottom. There aren’t so the resulting wiring is not exactly as neat as it might be.

The final piece of the puzzle is a foot control made from a couple of robust momentary switches (the kind used for guitar pedals), a nice metal case (ditto) and some three conductor wire (the extra green wire was spliced on).

The switches are wired in parallel with their corresponding button on the front panel of the interface. Pressing either the button or the foot switch triggers the control.

Finished foot controls. The throttle pedal, which is for an electric scooter and cost less than $10 (Canadian, including shipping), is extremely well made.

The Hall effect sensor inside it however, (the white stuff is silicon and isn’t as disgusting as it looks), is not. Either I killed it by miss-wiring it briefly while I was hooking everything up, or it was lousy to begin with (I lean towards the latter). Either way, a broken sensor means no throttle pedal which means the entire machine is about as useful as a third shoe. So I replaced the sensor with a brand-name version over-nighted from MagicKy (aka Digi-Key) – (which cost more than the entire pedal after shipping). Hall effect sensors work by measuring the flux of the magnetic field that passes through them. The stronger the magnetic field – i.e. the closer the magnet is to the sensor, the stronger the signal. The silver lining of replacing the sensor with a high quality part is that it has a bigger range – it detects lower strengths of the magnetic field and outputs lower minimum and higher maximum signal voltages, so the pedal response is far more sensitive. Coupled with a pseudo-logarithmic curve which is applied to the output from the sensor in software, the throttle pedal now allows very precise control at the lower end of the speed range where it is most important.

Et voila, the finished LenovoⒸ Weldcenter – running Windows Vista (ok, no it doesn’t).

The LED display shows the low and high RPM settings that are mapped to the throttle pedal output. The rewind amount is a fraction of a single rotation at high speed – a tap on the rewind button and the turntable reverses by that amount. In retrospect this turns out to possibly not have been the best way to do this as in practice the amount of rewind required changes too often. At some point I may (or possibly may not) add a mode where the rewind is active while the button/pedal switch is depressed. It also occurred to me too late that I could combine the two foot switches in a single cable and XLR jack, which means that I now have a spare jack for the ion cannon accessory.

A quick test with some scrap tubing before all the kinks with the code were worked out.

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Framework – 2

Ok, so I don’t have to climb a ladder quite that big to put the finishing touches on this frame. That is a lot of parts to design, fabricate and keep track of. Without computers. At once humbling and further proof, should any be required, that Zeppelins are insane.

Cross bars made from cold-rolled 1080 carbon steel. The small ones are for the top bar and the large ones for the bottom. These are rough-cut to length and squared and ground (sanded really) to just under their nominal finished length. These parts do not play a role in locating the sides of the frame (the laser-cut parts do that job), but they do locate the group and the taps so there can’t be too much play. In practice this translates to a length of within 0.2mm of, but always less than, nominal.

Drilled, countersunk, tapped and deburred.

The uprights are cut from lengths of rectangular tubing and are temporarily tagged and machined in pairs. This means that the left and right halves of each pair is the same length and, where necessary, hole placement is symmetrical. The baby 1″ clamps are made by Kant. The design with the central pivot eliminates twisting so the clamping force always remains axial between the jaws. Consequently, parts don’t slip out of alignment as the clamp distorts when they are tightened. Very clever, very useful.

The tops of the tubes will be filled with a coupon of 1/8th steel which is drilled and tapped for the ball studs that hold the cup warmer in place. This is the first time that all of the parts of this iteration of the design are being assembled so the coupons are left blank in order allow adjustment of the hole position, if necessary. Once I know that everything fits as it is supposed to the holes can be laser-cut the next time this part is ordered.

All of these things meet each other for the first time in the upright frame assembly. <digression> Interesting word thing. At some point in my education I learnt that the English word “thing“, along with its German and Dutch cousin “Ding/ding” and Scandinavian “ting“, original meant assembly, as in an assembly of people. A thing was a gathering of the populace to legislate, adjudicate and elect leaders. In other words, it is a precursor to our courts and parliaments rolled into a single time and place. For the Vikings, “Are you going to that thing on Friday night?” meant finding out how many pounds of salt cod your neighbor Leif owed you because his son Svend borrowed your longship without asking and crashed it. </digression>

The pieces are brought together in the jig along with an extra spacer-bar across the top that will not be welded in place. In this particular jig, the left side and bottom rails are installed permanently perpendicular to each other while the rest of the transverse parts are allowed to move slightly from right to left. This permits clamping and means that the frame can be removed from the jig despite the inevitable slight distortion to the thin walled tubing that occurs during the welding.

After beefing up all of the fragile tack welds, the sections of the frame can now finally be united with the words: with this TIG I thee weld. Though admittedly an actual three-way wedding would be a little weird. Front and upright.

Back, front and upright held in place against carefully aligned stops welded to the table.

Almost complete!

Now that the tubes are in their final place the end fillers can be located and fixed with a delicate weld. The gaps are left purposefully so that welds don’t have to be ground where they would interfere with other parts.

A satisfying row of finished frames cooling with a vintage bicycle…

The next step is to cover them in a skin made of cotton painted with aluminum, put a gas bag made from cow intestines inside, fill them with hydrogen and fly them to New York. Perhaps not. (What were they thinking?)

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Very fine

August is very fine. People take holidays. In France and other places in Europe where the sun shines more than occasionally, things start slowing down in July and people “faire le pont” until sometime in late September when they finally remember they had a job. Trying to do anything other than sitting by the pool and taking four hours for lunch (i.e. an hour longer than usual) in August in Italy just isn’t worth attempting. Here in Montreal we are more organized; we like to do things together: along with Moving Day, July 1st, when everyone moves at the same time (Which is insane. Try to find moving truck on that day. I’m not making this up.) we also, as anyone who lives here can attest, tear up all of our roads and rebuild all our overpasses and bridges at the same time. It is more efficient to wait fifty years and then get it all done in one go, ripping-off-the-band-aid-style. Economies of scale you know. We also have this thing called the The Construction Holiday. Towards the end of July, once we are done ripping up the asphalt and putting out the traffic cones, we all go on our government mandated holiday for exactly two weeks. On the same day. We also all come home at the same time. Over the interchanges that we are rebuilding and along the roads we tore up before we all went on holiday. Sensible I call it.

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Welding the boiler together is a complicated set of procedures. Each type of weld requires a different setup and either a judicious application of inert welding gas, a custom heat-sink or both. Some operations render others either difficult, or in some cases impossible, so it is critical to get the assembly order right. To further complicate matters, each weld introduces some distortion in the parts: more or less depending on their geometry and the amount of heat that goes into the weld.

The HX tubes are easy. The size and fit of the parts makes for a simple weld that is almost invisible.

Ditto (once the heat-sink is made) for the bolt ring.

Just load your nine-shooter and fire away!

All the bolt rings were welded up in about an hour.

Fitting the HX tube in place requires a more complicated setup as both the inside of the boiler and the HX tube have to be purged with inert gas during the weld.

The group mounting flange and brew reservoir meet for the first time.

The end flanges are also done using the turntable (a.k.a. the Ouroboros machine).

A few welds later and after some clean-up: the first full-stainless diagonal heat-exchange boiler off the production line.

This one is now ready for a few tests before the rest are assembled. Mistakes at this point would be, ermm, disappointing.

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1 – MONTREAL, QUE.: AUGUST 21, 2014 — Construction cones line Rene Levesque Blvd east of Atwater Street in Montreal, on Thursday, August 21, 2014. (Dave Sidaway / THE GAZETTE) Web 4×3 ORG XMIT: POS1410031753473482

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Ouroboros – part II

At its simplest: A circle is a … closed curve that divides [a] plane into two regions: an interior and an exterior. But it is so much more than that. One of the more marvelous properties of the circle is that, by definition, all radii are perpendicular to the circumference. Though seemly obvious, this has the convenient side-effect of transferring pressure, which acts outwards equally (i.e. along all the radii simultaneously) over the surface area of its containing vessel, into two force vectors that are perpendicular to each radius and tangent to the circle at all points around the circumference. The net result is that the pressure is converted into pure tension: rather than bending, the circular ring just wants to get bigger, elongating the material. Because this happens to be the way in which metal is the strongest, it is also the most efficient way in which to use it, requiring the least amount of material to contain a given pressure. Which is, of course, the reason that pipes and other pressure vessels are round (or, more ideally, spherical, but don’t get me started on spheres).

In the interim, I caused the translocation of a low-quality 1″ bearing from its previous resting place to my doorstep in exchange for a small amount of the most widely-known social construct most often referred to as money. And I made a plan.

The shaft is made from the same cold-rolled steel stock that the lever handles were machined from.

The crown gears have grooved hubs so that they can be keyed to their shafts but I had no key stock on hand. I cut some out of a piece of scrap – which was only somewhat quicker than going all the way to the specialty hardware store – who may or may not have had any (“Did you say ‘metric’ key stock?”).

Milling the slot in the shaft is a lot easier than cutting the groove in the hubs 🙂

Ah yes. I love it when things fit first time.

The other motivation for using the big cast iron face plate from the lathe is that has the same mounting system as all the other lathe chucks. So rather than mounting the face plate directly to the shaft, I am making a back or adapter plate from some mic6 aluminum (that has been patiently and unknowingly waiting for this day) so that all the other chucks will fit the turn-table.

Test fitting the back plate to the shaft.

Things are coming together.

Now we just need a nice neat control system, which I absolutely promise to clean up and put in a proper box very very soon.

But for now, I can’t wait to give it a test drive.

And so we return to where we started; It always comes back around. Ouroboros: the snake that eats its tail.

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Ouroboros – part I

Ouroboros – It always comes back around – part I

The Early alchemical ouroboros illustration with the words ἓν τὸ πᾶν (“The All is One”) from the work of Cleopatra the Alchemist in MS Marciana gr. Z. 299. (10th Century) – 1
It always comes back around – Michael Kiwanuka

Ouroboros: the snake eating its tail signifying infinity and the eternal renewal. Across cultures and throughout recorded history, the circle has always been associated with perfection and the divine. Euclidean geometry, the intersection of Platonist thought (the theory that ideas have an independent, “perfect” existence outside of the physical world) with logic (a process of systematized reasoning where each thought is linked to the next in a chain of validity) could be considered to be the headwater of the river of technological progress. From Euclid’s circle comes the wheel, the foundation of machinery, from the wheel comes the gear and from gear it is just a short leap of imagination to the steam train and its aesthetic and cultural off-shoot (and, many would maintain, the logical endpoint of progress): the espresso machine. Today’s post is all about round things (not run-on sentences, just read it again, it makes sense)…

… specifically, turning this lot of rotational miscellany into a welding turn table. The large wheel is a faceplate that has been languishing in a cabinet under my lathe since I bought it ten years ago. It still has the original grease/ear wax stuff from the factory on it so obviously the previous owner also found it useful. The blue cast iron bracket thingy used to serve as the lower bearing mount and hand crank for raising and lowering the head of the mill before it was converted to CNC. The shaft and the crown gears were also parts from the hand crank.

The casting from the mill is not particularly high quality and needs to be cleaned up and properly squared before it can be used. The surface above the bearing mount pocket wasn’t a precision surface in the original design and therefore wasn’t machined – which is fair enough. The little bits cast iron and grit that aren’t actually attached to the casting because it wasn’t even sand-blasted, a bit less so…

After the cleanup, I add a trio of tapped holes to attach a retaining ring to keep the bearing in place. This could also be done more simply with an internal cir-clip, but I don’t have any on hand, nor do I have convenient tooling to cut the internal groove.

I’m making the retaining ring itself from a piece a (presumably cold-rolled) steel from the scrap bin. This came from a completely weird and baffling machine that I bought surplus just for the nice black anodized aluminum base plate that became my primary work surface (you may recognize it as a backdrop in quite a few photos). I have absolutely no idea what it was for (miniature seismic simulations??) but it came with all sorts of esoteric bearings, pulleys, springs and custom fittings. This piece is part of a matched pair of beautiful adjustable counterweights. Apologies to the designer and fabricator of this beautifully made mystery device, but I’m cutting it up.

Sizing the internal bore and the external diameters to their required dimensions on the lathe.

The finished retaining ring – the pair of slightly larger holes were from the original part. Presumably they are threaded to receive the divining rod attachments.

Now we need some structure to attach everything to. I don’t have anything nearly big enough for this on hand and it really should be made from steel, but the size requirements and the stock available means that these heavy aluminum angles are going to have to do.

The new welder makes welding aluminum really, really easy by comparison with the old machine. I haven’t investigated the science behind the ‘why’, but the AC balance setting allows the arc to “clean” the metal, removing the surface aluminum oxide in front of the weld. Magic. Suffice it to say that if I can put that bead down, anyone can weld aluminum.

The two sides are notched and spacers are added to make room for the bearing mount.

More to come….

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1 – By Unknown – Chrysopoea of Cleopatra (Codex Marcianus graecus 299 fol. 188v), Public Domain, https://commons.wikimedia.org/w/index.php?curid=36915535

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Chinchillin

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It seems like the weather is always a theme in Montreal: crazy winters, crazy summers and no spring. After about two weeks of enjoyable temperatures, the mercury has shot up to the mid thirties by late morning and the sub-tropical humidity makes it feel like it is well over forty (that is a Floridian 105 for those south of the border). Seems a like the right time to make a chiller. But not for me, not for the cold-brew or the iced coffee – for the welder!

The new production welder came with two torches: one air-cooled for work below 120 amps and a second water-cooled version in the same form-factor for up to 250 amperes.

It is pretty simple really: cold water goes in one hose, flows through the torch nozzle picking up heat as it goes and comes back on another line. Now, I could have just hooked the cold side up to the tap and dumped the returning hot water down the drain, but a) that would be wasteful, b) there was neither a convenient drain, nor a supply line in the vicinity of the welder and c), if you have been following since this project started, you will know that that just isn’t how we roll :). Besides, it turns out that welding chillers have rather a lot in common with espresso machines. Wait, what?

Above are the essential components of a welding chiller: a heater core from a car, some specialized quick-connectors, a couple of computer fans plus a power supply and a motor and pump from a coffee machine that I just happened to have on the shelf. Chillers, also like espresso machines, are somewhat specialized pieces of gear and, despite their relative simplicity, tend to have a rather hefty price tag. Total cost of the build so far (for the connectors and the heater core): about $45 Canadian.

The first job was to cut off the crimped ends of the inlet and outlet on the heater core and to tap the tubes. I’m not sure what this thing is made of, possibly an amalgamation of aluminum dust and recycled chewing gum, but they actually took enough of a thread to stay leak-free at the very low pressures involved here. Hmm – might not be a good idea to run the pump with the valves closed.

I mounted the fans on a simple wooden flange in an attempt to increase the air through-put and fixed the heater core (aka a radiator) to the opposite side.

As seems to be case with most projects, it is actually the box that is the most work. To speed things up, I chose a material called Alupanel which is a laminate sandwich of plastic inside two thin sheets of aluminum. Because it is mostly plastic, it is very easy to cut, but the ductile aluminum skin allows it to take and maintain a fold. The front panel cutouts:

The flip side is scored on the table saw with about a 1/4″ of saw kerf .

Thirty seconds afterwards, the part is folded up without any tools.

A second panel is cut for the rest of the front and the pump and radiator assembly are mounted on a plywood base board.

The remaining work is really just about hooking everything up. I used a bit of DIN rail that does double duty as cable-guide and structure to connect the front and back panels. The “reservoir” is an 8L plastic jug that the distilled water I bought to fill the machine came in – I was researching 8L containers for camping etc., but then I thought: wait a minute! The plumbing connections are a first draft in this photo. The pump is on the “cold” side of the circuit, so pretty much any kind of material will do for the piping runs – I used 6 and 8mm pneumatic fittings and hose because they are convenient and were on hand. The return side will probably be above the rated temperatures for pneumatic hose, so those are made from slightly sterner stuff – fiber-reinforced vinyl I think.

The hot water return runs through the radiator and dumps back into the top of the reservoir (through a hole in the cap – why make things complicated?).

The supply side, specifically the tiny channels inside the torch, is protected with a simple filter made from a scrap of fine plastic mesh and a few o-rings.

The cover is cut from another piece of Alupanel and, rather than drilling a million holes by hand for air circulation, I riveted some stainless perforated sheet metal (surplace drip trays!) into cutouts on opposite sides.

The tall, rounded slot on the front panel is a sight-gauge for checking the level of the water in the reservoir. The hole on the top, which was supposed to be round but isn’t because my father borrowed the hole-saw kit, is for topping it up with more distilled water. Almost everything here was made with surplus parts and materials (even the Alupanel was actually an old sign), and while it isn’t perhaps the prettiest thing ever and the case took way longer to make than it should have, it might possibly win the “oh I could make one of those” prize for diy/new cost ratio. Actual cash outlay: (quick connectors, the heater core and a couple of plumbing fittings) about $75 CAD (maybe $350 total if you had to buy all the parts). A quick check online for a brand-name version of a similar device: $2600. Now we’re chillin.

1 – image: National Geographic