Category Archives: Miscellaneous

Workshop Upgrade: Laser cutter and engraver SCULPFUN S9

There are various laser engravers or cutters available in the market, so it is hard to make a choice. Finally I got a Sculpfun S9, which appears to be well-regarded in the community as a cost-effective and capable machine. I was also looking for something that is easily serviceable, not using custom controls or special motors – the Sculpfun S9 is built from all relatively standard components so it can have a very long service life even if I eventually need to fix the electronics or replace the controls altogether.

The machine ships as a kit, but there are good instructions for assembly, step-by-step, even the screws packaged for each step in a separate bag.

The machine is fairly portable, so you can also set it on the surface of large panels to do local engraving or similar.

Some first tests, works very well indeed! Just the smell of burned wood and plastic – it is really not a machine for an apartment, and the laser also seems no toy for kids. It is fairly strong and can be dangerous. This laser has a very sharp (maybe 0.1~0.2 mm beam) that cuts through several mm material in a single cut. No good idea to get your fingers in the way.

You can also cut foil. Maybe better to use a knife cutter (because of the smell and vapors), but for some once-off jobs, it is easy to use and also cuts uneven old foil very well in my test. Better use some magnets to push the foil down on a piece of sheet metal.

The main application that I am looking for is to cut custom seals from plain seal stock. The machine cuts well through 1 mm Elring Abil plate, and similar materials. Even thin rings can be cut, no problem (very hard to cut with a cutter knife or punch).

Next step will be to get the machine properly installed. This means, adding an air nozzle to assist with cutting (made from brass), a machine table, and an enclosure with exhaust fan to get rid of the toxic vapors.

The nozzle is made from a piece of brass (several of these pieces purchased at a scrap yard 25 years ago when I was still a kid).

The nozzle has a side inlet, and is designed for about 20 L/min with 1.5 mm diameter, so we are looking at 150~250 m/s linear velocity at the nozzle outlet.

The gas is fed through a 4 mm PU pneumatic tube.

To measure the air flow, we are using a very cheap Chinese gas flow meter. This has a needle valve, but it is not working well – the needle valve puts a spin on the gas, and the indication is incorrect (the sphere starts oscillating and spinning), so I use a separate needle valve (FESTO GR-QS-8) in the supply pipe.

The flow meters comes with flimsy plastic connectors, and these have 5/16″ UNF (24 TPI) tread… not a very common part in Germany to get a transition from 8 mm pneumatic tubing to 5/16″ UNF…

Fortunately, found a suitable thread cutter in my tool selection, so an adapter was made quite easily (from 5/15″ UNF to 1/4″ NPT, then us a 1/4″ NPT to 8 mm push-in tube connector).

The next step has been to make a suitable table, sure you can put the laser machine on some ordinary table, but it has quite some speed and movement and even relatively stable tables will be moving and there is some impairment of precision. So I wanted to give this machine a stable basis that doesn’t shape. It is all welded construction from about 1.5″ square steel pipe. The top is 18 mm waterproof plywood. There will be a piece of zinc-plated sheet metal on top, also to use magnets, and a open cutter support plate on top in case of heavy cuts.

To fabricate such a table, after the welding is done, grind off the scale (this is just plain steel), clean with acetone, and then roll-on some primer paint.

Finally, painted in a blue-gray color, and with the top plate mounted.

Next step, fabrication of an enclosure with a movable cover. All made from 15×15 mm (about 3/4″) square tube, all TIG welded…. looks easier as it is with all the parts and angles.

There will be two large windows, 40×60 cm, to observe the process. I selected GS-1C33-GT Plexiglas (acrylic glas) which is nicely transparent for visible light, but blue light of the laser can’t pass at all.

This is also confirmed by the spectrum, the laser is emitting at about 452 nm.

After some hours of work, the enclosure is ready for painting. It opens nicely and smoothly, also because of a gas spring (200 N, 535 mm total length, 220 mm travel).

It is one of the few occasions that I have use gas loaded springs in my design but it is working well. Just the design calculation is complicated and probably it is always a bit of experimentation to find the right gas spring size and force. But this time, successful at the first attempt. My recommendation, to rather use a slightly stronger spring (say, 200 N if 150 N is calculated) to allow for aging of the spring or other design uncertainties.

Workshop Upgrade: 3D Printer

Finally, I had to opportunity to acquire a long desired tool, a 3D printer. In recent years these have become fairly affordable, and also easy to use. So it is on longer needed to spend days with optimizing various settings. I am planning to print mostly in durable parts, so I am targeting PETG and ABS rather than PLA plastic materials. Mostly planning to use it for spare parts, or mold patters for aluminum casting.

The machine, it is an Artillery Sidewinder X2, a great product, all nicely arranged in a box.

It didn’t take long to set it up, maybe one hour, and then you can use the well known software packages to run the machine. I am using Freecad for modeling and Cura for processing.

All worked fine already for the first part… great!

A cylinder, and a space shuttle. All fairly robust.

So far, I can only praise the machine, it is working fast and precisely. Just printing low cost PETG material. Key point is to keep the bed rather hot to keep the parts sticking, and then just remove them after cool-down with no effort.

SMEG CS19ID-6 Range: another defect

It seems my SMEG kitchen range is getting older… at least it is again showing some issues. The right hand side front induction field is sometimes coming on, intermittently, only to shut off quickly again. Normal operation is no problem, but when it is switched off, it doesn’t remain fully switched off all the time. Could be dangerous if some pot is left on the induction field, and the range decides to switch it on by itself… a praise to all the old-fashioned switches that completely took power off the appliance.

First we need to find out the source of the issue, is the it controls electronics, or the switch? To test, I opened up the front panel (easy enough, it is just 8 screws…), and switched the cables going to two of the front panel switches. And, as it turns out, the issue also switched. So it is probably a defective switch rather than any issue with the electronics. That’s good news.

For about 35 EUR, I got a new switch, as it turns out, it is no switch put a potentiometer…

… and a quick exchange fixed the issue. Now let’s do some study of the old part.

Made by printing some conductive composite on a circuit board. Looking good. I can’t see any issue with it even under the microscope. Maybe just some contact issue, the contacts also don’t look clean.

So I will clean it all up thoroughly, bent the contacts a bit to give it slightly more force, and keep it as a spare.

These potentiometers aren’t cheap, at least the use good engineering plastics for it, like, glass fiber reinforced materials.

A Japanese hot pot: A hot spring without a hot spring

One of the most famous features of Japan is the availability of hot spring all around the country. If this is an advantage or disadvantage of my new living place in Germany remains yet to be seen, because the hot water close to the surface normally comes along with other earth activity including volcanos and earthquakes… Anyway, I have no source of hot water here other than by gas heating, so at least I wanted to have an outdoor bath resembling Japanese style.

The pot is handmade from high alumina clay, fired at about 1350°C, and shipped from famous Jingdezhen, Jiangxi China, within about 8 weeks. It is a heavy pot, about 350 kg. It resembles the Japanese made bath pots 1:1 but the price is much more competitive and a certain Ms. Wei of the pot company knows how to deal with foreign customers and can manage export of such items as a routine business… Transportation fees in Germany and customs duties, taxes turned out to be more costly than the pot itself.

The essential elements are, (1) the pot, (2) the piping system all made from DN40 glue-fitting PVC-U pipe, (3) a circulation pump (180 Watts, Wiltec 51554, including a filter/strainer), (4) a gas heater (fired by Propan), (5) hot water supply pipe – this is constructed such that it can be drained easily in winter after each use, so it is possible to have a bath also in freezing conditions, made from 18 mm copper pipe and fed by the main hot water system of the house (using natural gas), (6) a regulator system to keep stable temperature.

The water heater has a safety system to switch off the heater after 20 minutes of use, and it has a built-in electric ignition system powered by 2 batteries, 1.5 Volts each. In order to achieve temperature regulation without interfering with the internal circuit of the gas heater, I just switch on and off the 3 V power to the heater.

Normally the heater is only used to keep the water at constant temperature of about 42°C (Japanese baths are really hot…), which takes less than 20 min on-time, anyway, I decided to add a timer circuit that interrupts the heater ever 15 minutes for 30 seconds. So essentially, it can continuously heat the bath even when filling in cold water. Normally the bath is started with reasonably hot water from the house main supply.

Unfortunately, the ignition system by high voltage causes the regulator to hang up. The high voltage sparks change the ground potential it seems, and even some attempts with protection and clean-up circuits (low pass filters) had no permanent effect, when powered from a single supply that is split to 12 V the regulator/timer, and 3 V for the heater. So I now powder the unit from two completely separate powder adapters, and two completely separated circuits, isolated by mechanical relay.

The voltage regulator for 3 V is a simple LM317 circuit, with some more capacitors and features to protect it from any surge voltages.

The temperature regulator and timer, sure you could build it yourself with some microcontroller, display, etc, but no need as the complete module is available for less than 3 EUR mail-order.

The water circuit has the circulation pump. Note that not all the water is passing through the heat, only a certain portion, and pressure is generated by an orifice in parallel with the heater. Temperature sensing is done in the circulation loop. In winter the circulation system can be completely drained and switched-off by appropriate ball valves. So you can still have a bath, but you just can’t heat it by the circulation system (rather need to add more hot water, or just limit the bath to 1 hour or so).

The heat loss seems to be about 1 kW, so we need to run the heater that is using about 1.2-1.4 kg of propane per hour of operation only for some minutes at a time (1 kg propane has about 14 kWh of energy, and we may assume an efficiency of 0.7). Experience shows that is this correct, the heater may switch on every 15-20 minutes of so for about 3 minutes.

Now the system is completely automatic. In normal usage there is no need to adjust any regulators. Just fill in water and switch the bath main switch to “ON”.

Lastly, the water is not just plain tap water but sure enough I am adding bath salts composed such that they resemble my favorite Yamaguchi prefecture hot spring pretty well!

Heating energy consumption: first evaluations, and total annual energy demand

In the meantime, I have collected enough consumption data for gas consumption (mostly heating, some little bits for hot water), and at various temperatures outdoors, including, very cold temperatures.

As it turns out, the gas consumption correlates well with the outside temperature (daily average temperature in 2 m height, as officially recorded close to my place by the weather authorities).

With datasets of daily temperatures for 2019 and 2020, we can then estimate the total gas consumption of these years.

The 2019 predicted consumption:

The 2020 predicted consumption:

For German standards, everything less than 100 kWh per m2 and year is quite reasonable. I need to admit that not all of the rooms are fully heated all the time, but well, it is not all that bad, comfortable, and affordable.

Here an energy rating chart – in German – around 100 is a good value, above 200 … there it is getting really bad, wasteful and expensive!

Christmas Time: Honigkuchen (honey based cookies)

It is a long time favorite, and easily stores for some months – honey based cookies. Here is a good recipe.

500 g Honey
125 g Sugar
150 g Water (you may just add some more Honey if you don’t like to add refined sugar, but it makes the dough easier workable)
1 kg wheat flour (can be some coarser type wheat flour)
60-80 g Spice including anise, clove etc., a ready purchased mixture. Adjust quantity to strength of spice and your taste
25 g Ammoniumbicarbonate (“Hirschhornsalz”)
Pottash can also be added, by I didn’t add it, it will make the cookies flat.

First, mix and melt honey, water, sugar, at low heat. Add the other ingredients and work firmly. Let it rest for 2 or 3 days in the fridge (cover to avoid drying out).

Then, prepare cookies, and bake at about 200 degC for 8-10 minutes. These need to be well baked. Underside can be dark brown, but don’t burn them to bitterness.

The Honigkuchen can be stored in a well-closed container for 2 or 3 months no problem.

A major move, and a defective CATV splitter

After returning from Japan to Germany early October, I decided to move to a new place, a larger property with ample workshop space and gardens.

Needless to say, a major effort with tons of heavy test equipment and other stuff piled up…

Apart from the heavy lifting, apart from tap water, electricity and a tight roof, a fast internet connection is the most essential thing. This took quite some more effort than expected. First, the grounding system of the house needed an upgrade (otherwise the internet cable company would refuse to install their amplifiers and cable modem), and, that done, there was not enough signal going in and out the house to allow for the 1 Gb/s connection…. first, they changed all the stuff inside of the house, a full upgrade, but to no avail, finally, they marked a spot on the sidewalk.

Only hours later, strong men showed up, digging up the ground in the search for the internet…


The connection here is delivered on CATV coaxial line for the last mile, so there is main line about 50 cm underneath the sidewalk, and there are taps/splitters, usually one splitter serving two houses.

From what I can tell, it is a 2x 15 dB tap, a quite common part in the CATV network. It took the crew just about half an hour to install. Great job.

The part, here is a clean shot, it has the connectors already mounted, and in the field, the cables are merely inserted and heatshrink tubing applied.

There are now a few interesting left-behinds, an old CATV house connection box with filters, I will test it out once there is more time.

After the installation job had been done one the road, it took just another two visits of the cable company to get all up and running! At least, they managed to do all this in less than a week.

SMEG CS19ID-6 Range: cold food only….

Recently, big disaster. My cooking range failed, not quite completely, but the right two of 5 induction hobs. It is not just a plain range, but a high end version large range, made in Italy…

It took a while to figure out how to disassemble it, and at a first glance, nothing visible, so I put it back together, and started to investigate the professional repair services…. quotations ranging from 900 EUR minimum, to 1500 EUR average cost to fix the error “E-5” that is now showing on the display.
Before going forward with the repair, I got some single hot plate so that at least cooking can continue, while dealing with a potentially lengthy repair.

A proper repair is done in a workshop, so I took out the whole hob assembly.

Upon close inspection, the filter assembly has a blown trace. It is a PCB trace acting as a fuse…

The copper of the trace deposited on the plastic cover nearby.

Fortunatly, the manufacturer, E.G.O. (a very famous German enterprise that makes most of the European induction range drivers) provided already a fuse holder to fit a US type 20 Amp slow-blow fuse.

Checking around, the left two IGBTs, IXGR40N60C2D1 are completely short.

That’s the full assembly, 74.470.061, with capacitors, a rectifier, and 2 IGBTs per hob.

For the time being, waiting for spare parts (ordered several more spares, and several fuses, just in case….). The IGBTs desoldered nicely, and I also checked the rectifier and all the diodes around, nothing suspicious.

Delicious Apple Muffins

This a well time-proven recipe, and will yield 20 mid-size muffins.

500 g wheat flour
3/4 package baking powder (about 10 g will be sufficient)
165 g sugar
a little bit of salt
1 small and flat teaspoon of ground cinnamon

All the dry material, mix them well, and best pass all through a flour screener.

Cut two large apples into small pieces, or use 3 small apples. Don’t store them for a long time, as they will turn brown. Best use some firm apples, not overly ripe or soggy.

Heat up the oven to 180 degC.

To the dry mixture, add 250 mL milk, 90 g of neutral taste oil (also works with 90 g of soft margarine). 2 Eggs.

Mix the dough well. Then add the cut apples, and mix well again.

Fill the dough into muffin papers (in some holders of metal form), fill to almost full, but don’t spill the dough (use 2 spoons for best results).

Immediately bake in the pre-heated over, for about 30 minutes.

Let cool down. You may apply some heated/liquified jam or glazing, but I just eat these plain, and also kids like it that way.

Banana Muffin: sooo delicious, and we don’t add any chocolate

I use this blog for various purposes, including, not to forget the well-proven recipes and to make them available for your use, if you like.

This time, we have banana muffins. There are many recipes on the internet, but none that is really as easy as this one, and that works without a mixer or other equipment.

First of all, take about

5 bananas (large), or 6 bananas (middle size) – best some really ripe bananas.
120 g butter and/or margarine (I use 80 g margarine, and 40 g butter in Japan because butter is in short supply), unsalted butter of course.
4 eggs.

The bananas cut them up a bit and use a fork to make to uniform mass. Then mix well with the nearly molten (but not hot) butter and eggs.

Then, prepare a mixture of

300 g all purpose flour
1 package vanilin sugar, or some vanilla essence.
2/3 of a pack of baking powder, about 8 to 10 g
170 g sugar
1 little bit of salt

Mix all this well as a dry powder, or put it all through a sieve if you have.

Then mix the liquid mixture, and the dry mixture well and fill into muffin papers in their forms or trays. This will yield 20 pieces. Don’t overfill, form needs to be filled to about 6 mm below the surface only.

I am baking these in a professional deck oven, 180 degC upper, 175 degC lower temperature. For 25 minutes. Sure you can use other ovens at some similar heat.

After baking, you can enjoy these immediately after cooling. May apply some powdered sugar, icing sugar, as you like.

Oooh. So delicious.