My TIG welding frustration suffered more than usual the other day .
I have an ESAB Warrior Tech helmet which works really well when welding but it would not stay flipped up when I wanted to see things in daylight. Every time I leaned forward the helmet would drop down over my eyes and thump me on the chest. Added to the fact I was trying to TIG some thin wall tubing I was no in no mood for distractions.
Before the helmet joined the happy hunting ground over the neighbours fence I took it apart to see why the latch up action was not working. Inspection revealed that the backing plate had cracked around the latching cam.
I could have bought a completely new head band assembly but the part in question might just be 3D printable. The Fusion 360 sketch ended up being very complicated based on eyeball guesses on curves and centres but on the second version I had a printed replacement which did the job …. for the time being anyway.
If anyone is suffering from a bruised chest let me know and I will forward the Fusion file.
You know how I keep on going on about how solutions to problems are often solved by coming at them from different and often unconventional directions, by utilising and marrying available resources ? It was a philosophy that I encouraged in my team while running my business and it has carried over into my way of working in retirement. A recent job brought his home to me.
A client had a very old clock that had had a new barrel wheel made and fitted but the clock would not run for more than a few minutes. There appeared to be an incompatibility either between the modulus of the new wheel and its mating pinion or the shape of the original pinion did not match the shape of the new wheel.
If you spun the barrel wheel you could feel the resistance build up as the synchronisation between the two profiles drifted out. Adding extra weight to the barrel helped but did not solve the problem.
So what to do ?
The barrel wheel was serious engineering and I did not fancy making a new one. The existing mating pinion was a seven leaf format and its leaves were what you might call pear drop shaped rather than the expected profile. The pinion arbor had a 72 tooth wheel driving the next part of the clock train but we did have a spare one of these to hand from the minute dial.
Calculations from the geometry of the barrel wheel resulted in a modulus figure of 1.86. A rather large value and not one that conventional cutters are readily available for. The pinion was perhaps something that could be drawn in Fusion 360 and then made on my Tormach CNC PCNC440 milling machine. The only snag was that the profile needed on the pinion would likely be weird and the world’s supply of brass could diminish rapidly while getting the profile correct.
Using Gearwheel Designer I created what would be the expected profile for a 7 leaf pinion with a modulus of 1.86. This was exported as a DXF line drawing into Fusion 360. This outline was extruded in Fusion into a 3D design and a boss was added to mount the 72 tooth wheel.
The design was 3D printed on my Sindoh 3DWOX printer and was mounted on a 6mm silver steel arbor. I added a driving disc that interlocked with the printed pinion and the crossings on the wheel to drive the assembly. Surprise surprise it didn’t run but it did mirror the regular pattern of stiffness of the original pinion.
I now had the test bed for quickly making and testing different pinion profiles. There followed a number of hours watching the engagement progression of the profile of the pinion into the barrel wheel and then trying to conceive a profile for the pinion that might run.
Fusion 360 made this process so easy and round 10 printed test profiles later I had success with a clock that now ran. The driving weight on the barrel was around 11kg and it looked to be worthwhile wasting some brass making a ‘proper’ one.
I took the 3D design and produced CAM code in Fusion. This would cut the profile ‘on end’ using an adaptive first cut with a 4mm end mill followed by rest machining the remaining material with a 2mm end mill.
The resulting brass pinion was mounted on the arbor and the clock ran with a strong beat. As expected the brass pinion gave less surface to surface resistance than the 3D printed part and the barrel driving weight was now able to be reduced down to 6.25kg.
I ran my Microset Timer on the clock overnight and had a first off timing error of 5 minutes per day which was fixable with a pendulum tweak. The movement had an instability of a few seconds per day which was quite astonishing.
The conclusion of the experience is that at first glance this seemed like a conventional pinion cutting exercise …. but M1.86 cutters are not readily available. If a cutter could have been found at less than a King’s Ransom it is likely that the resulting conventional profile would have been wrong to match the barrel wheel.
The alternative route that was taken of Gearwheel Designer to Fusion to 3D print to Fusion CAM to CNC machining solved the problem albeit with a final weird profile. The purists and traditionalists will groan. There will be a gnashing of teeth and a pulling out of hair.
Does it really matter if the result is new life for what could have become a heap of scrap metal ?
A new idea for keeping PCB material flat while milling artworks
The vacuum plate mentioned elsewhere on my blog serves me well when milling printed circuit boards on the Tormach PCNC440. It keeps the PCB material flat and makes the cut widths repeatable when using V cutters.
Idle hands and brain during social distancing has produced a possible solution that might be of interest and stimulation to others. It consists of a circular pressure ring that sits around the spindle chuck and tool. There is a second ring that sits on the spindle body connected to the lower ring with rods which have coaxial springs pushing down on the lower ring. The magic is to use mini ball transfer units on the lower ring to press down on the PCB and glide friction free around the PCB as the cutter does its stuff. The assembly is held in place on the spindle with 3 gripping screws. The downward pressure is adjusted by 3 screws that press against the spindle mounting frame.
The prototype was made using 3D printed rings. There is an image below. Apologies for the yellow PLA but finding any PLA at a decent price is very difficult in the present circumstances.
The idea seems to work and has produced some good consistent quality PCB prints. It does have disadvantages in that you need to have a larger PCB blank to allow for the larger footprint of the pressure ring. It is probably only of practical use for PCB milling but then the problem of flatness is less critical in drilling the board and routing the profile.
Lots of activity to be documented and posted but let’s start off with a short note. Not earth shattering but might help someone somewhere.
I had the bright idea of using Micro USBs as a connecting medium on a couple of projects. This was driven by the need for a 5 wire connection. The design was finished and I dug out the Micro USB to Micro USB cable that had been bought in for the project and connected things together. All the LEDs went out on my project circuit board. Gloom.
After buzzing the cable through I found that on a standard Micro USB cable the Sense pin is linked to the Ground pin. There are not 5 independent and isolated cores as you would expect. Just four. What to do ?
By chance I had some Micro USB connector ends with solder tabs but no shells. I did not have any flexible small diameter cable with 5 cores. After some discussions with my other half she offered to plait 5 independent cables together for me as a cable form. These were soldered to the Micro USB ends. Two small end caps were quickly designed in Fusion 360 and took 10 minutes to print on the 3D printer. Job complete and project back up and running.
We got the electric bill for last winter and there was a sharp intake of breath … maybe the fan heater had been on too much in the workshop and maybe I did forgot to switch it off once or twice when going to bed … something had to change.
I did some research on diesel heaters as used in motor homes and commercial vehicles and the concept looked like it would meet my needs. I did some calculations on the workshop volume I needed to heat as an empty shell. With my insulation and window content this came to a figure of 3kW. Searching on EBay revealed lots of kits and ready built units so my first thought was to order a ready built one. This duly arrived and I decided to run it up to see what happened.
Actually nothing really happened.
The fan came on ran for a few seconds and then the unit shut down. The controller was showing a severe droop on the supply volts even thought the PSU was rated at 10A. More web reading and comparing notes with other users revealed these units take a serious current surge at switch on while the glow plug is warming up. If it sees a voltage droop it thinks it is in a vehicle and switches off to protect the vehicle supply.
Bigger power supply acquired and plugged in. Still no joy. I then realised I needed to prime the fuel line. Quite a few clicks of the pump later I had a full pipe feeding the device and finally it ran up. The fan was flat out and the pump was clicking like a French grenouille on heat.
And what a stink it made. I guess it was burning off all the manufacturing oils but it was pretty acrid. Finally the fog cleared and I could see the neighbours house and we had heat. Quite a lot of heat. Fiddling with the pump rate brought the heat and the fan rate down and all seemed good. But it was noisy.
There now followed some serious navel contemplation. Did I really want this fire breathing Smaug inside the workshop ? Not really. So how to solve the installation ?
Immediate thought was to mount the unit external on the side wall and feed the warm air from the unit into the workshop and take in air from the outside to warm. The smelly exhaust inlet and outlet would also then be outside. Not a good idea taking outside air and warming it unless I wanted a very rust rich environment.
So air would have to circulate from the workshop, get heated and blown back inside. This means two 80mm holes in the workshop wall plus a power and controller wiring duct of say 20mm. A plan was forming and I could see where the two air ducts could be located.
Next problem the (I have to say very horrible) enclosure my ready made heater came in would not protect the contents nor would it last very long sat in the outside air.
Much Fusion 360 playing later I had a design based on a 20mm angle iron frame and aluminium sheet covering.
The angle iron and sheet were ordered from Aluminium Warehouse and came very quickly. I was now going to have to grasp the nettle and refresh my TIG welding knowledge to create my first major TIG construction. (I only have TIG as MIG scares the **** out of me).
Even though I say it myself I was pretty chuffed with the frame that resulted. Some of the welds were far from ticketable but my angle grinder and Hammerite paint soon covered up my ineptitude.
The aluminium covers also stretched my resources as I don’t have a formal metal bender but I do have some very long lengths of angle iron and a robust vice. Two side walls, a front panel and drop on top cover resulted without any serious clangs. Loving it.
The return air inlet needed an interface of some sort so a Fusion model was created and printed (6 hour print …).
With the enclosure complete, I mounted all the components and ran it up again. The new power supply also failed to do the biz so I decided to go with a meatier version inside the workshop rather than inside the external cabinet.
Installation day loomed. I was very ably assisted by Dave who is a long time friend. We are both cut from the same engineering mould and we usually end up with an interactive plan of action.
First job was to cut the hot air duct hole in the workshop wall. We had a long pilot drill, an EBay 80mm cutter and a SDS drill. Serious grief. The workshop outside brickwork seemed to have a Titanium content. We finally broke through into the cavity and thereafter the inner Thermalite block was like cutting chocolate cake in comparison. First hole finished and more to the point in the correct position.
We now offered the unit to the wall to match the routing of the hot air outlet pipe of the heater. We put a car jack under the unit to keep it in position while we drilled the mounting holes. Holes drilled, we then mounted it on the wall and drilled the cable duct and lined it with a piece of uPVC water pipe.
The circulating return air from the workshop was to come through the workshop wall and back to the heater from just over a meter away. I had a suitable length of 80mm spiral metal ducting for the air return and a mating right angle joint to route this through the wall. We marked off the duct hole position and drilled out a second 80mm hole (more grief, less dust as we damped it down, and hammer and chisel when we got fed up with the useless 80mm cutter).
The Cunning Plan
I didn’t want the metal spiral ducting exposed to the elements and also saw it as a source of heat loss. There is no point in heating up the workshop and then send the warmer air outside to lose heat on its way back to the heater. The solution was to buy a standard 1m length of 110mm soil pipe and a right angle joint with two mounting clips from Wickes. We wrapped the 80mm spiral duct in bubble wrap (quite a few turns) to fill the space inside the 110mm soil pipe to make a coaxial structure. As luck would have it the spacing to the wall of the soil pipe was pretty much ideal to use the standard pipe clips. We did however have to cut down the right angle soil pipe connector to get it flush to the wall. It then got a dose of squirty foam to seal it.
We were both very pleased with the result. As Dave commented it looked better than a professional install would have done.
This was the bulk of outside work done apart from mounting the exhaust inlet and outlet pipes. Inside we had the hot in wall vent grill to fix and the controller wiring.
I still haven’t decided where to route the outward air duct but currently it sits sucking air from under the Myford Super 7 cabinet. I am not comfortable with this (the location rather than the potential draft around my ankles) as it will tend to suck up workshop dust and particles. Some form of filter will be needed. As yet I haven’t mounted the new power supply on the inside wall.
We ran it up and I can describe it as toasty warm. At least one good reason to look forward to winter, probably the only one.
Finally thanks to Dave for helping. Also thanks to Steve Niebel for detailing his experiences with a similar unit.
If you want to know more about the heaters then the best source I found on YouTube was Dave McK 47
Anyone wanting a very basic indoor housing for their heater components should send me a message ….. and soon …. otherwise it is going in a skip (but I might save the handles).