3D Printer

Like all of my blog posts this article is not intended to be a how to tutorial but rather just my experience and observations in building a 3D printer.

A few months ago I decided that I wanted to have a 3D printer. There are a number of things I have in mind to make with the printer. One thing is to make patterns for metal casting. Both sand casting patterns and lost wax (plastic) patterns. Also some of my other future project could make use of printed parts and I will probably make some artistic things.

The prices for off the shelf printers are a bit more than I am willing to pay so I looked around for what is going on in DIY for 3D printers. I like building things anyway. After a lot of digging around on the WEB I decided on building a Prusa I3 which is in the reprap family of printers. This printer seems to be quite popular and there are lots of vendors selling parts for them. To get just what I wanted I ended ordering parts from quite a number of different vendors mostly on Ebay.

One of the concepts explored with the reprap printers is the idea of a self replicating printer so many of the parts for the printer are printed parts. Of course when starting out you don’t have a printer to make the parts so you have to buy them. As long as the printer does not completely break down you can then make spare parts or upgrades.

Surprisingly I had very little problems with parts not fitting or being defective. The metal frame had two holes that were not tapped for screws. That was an easy fix as I have to proper metric tap. The finish on the metal rods used for the carriage motion was not the best and the linear bearings fit a little tight. I mounted the rods in the lathe and sanded and polished them and got them to fit properly. I should have ordered chrome plated rods. I spotted two solder shorts on the electronics boards before I assembled them. Again an easy fix with a soldering iron. Another problem showed up when putting the X axis carriage together. The X axis guide rods tended to come out of the printed supports when the carriage moves back and forth. I drilled a hole in the support part and inserted a brass rod to retain the guide rods.

The rest of the problems I had were my own fault. I plugged the two circuit boards together wrong and burned up a trace on one of the boards, easily fixed with a jumper. Later on while testing the printer the carriage snagged a cable to a stepper motor and unplugged it. Unplugging a stepper motor with the power on almost always burns up the driver IC. Luckily I had a spare driver board.

3dprinter1

The basic frame of the printer going together.

I drilled and tapped a few more holes in the frame to mount the power supply and the processor board. After assembly it is necessary to make sure everything is square so that it will print correctly.

3dprinter2

What a mess and that is not even all the wires.

When I get it working I will gradually dress up the wiring so it looks a little better. I did not like the way the Z axis limit switches were supposed to mount so I made some metal brackets to hold them. They can be adjusted up and down by loosening a set screw. A metal bracket at the top holds the LCD at an appropriate angle. With the printer working I can print up a plastic case for the display. designs for several versions of a case can be found on Thingiverse.

cube1

First successful print a test cube.

It did not take too much to get it to print. Mostly fiddling around learning how to use the software. The cube was printed with PLA which is supposed to be the easiest to use.

ornament1

Christmas tree ornament.

After some test prints this is my first successful print using ABS plastic. It requires different setting for the printer and a heated bed. The bed had difficulty getting up to the 100° C temperature suggested for ABS so I bought a cork tile and glued it to the bottom of the heat bed.  Since it was Christmas time some ornaments were appropriate to try out the printer. The default settings in the printer driver software are set up for printing PLA and I did not find any good suggested settings for ABS so it too some experimenting to get it right.

ornament2

Yet another Christmas tree ornament.

I decided this ornament would be a good “stress” test of the printer as it has a lot of “printing on thin air” going on. It is not prefect, there is still some tinkering to do. The first time I tried printing this the extruder jammed about half way through the 3 hour print.

There are all kinds of suggestions out there for what to use to get the object to stick to the printing bed while printing. I am using a borosilicate glass bed with Aqua Net hair spray. So far this seems to work well. The above ornament stayed stuck during printing even though it only has a small base and came right off after the bed cooled down.

Still to do is learning how to use the whole software tool chain to design and print a part. I did design a test disk and used it to try out printer setting. But for anything more complicated I will have to better learn the CAD tools. My collection of software consists of Repetier-Host, Meshmixer, slic3r, openscad, FreeCAD, 123D design, netfabb and InkScape.

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Posted in Crafts, DIY, Electronics, Machine Shop, Metal Working | Tagged , , , , | 2 Comments

Fan Aspirated Temperature Sensor

The temperature sensor for my weather station is a commercial wireless temperature/humidity sensor that I have mounted in a commercial solar radiation shield. It has been in operation for a couple of years and seems to be reasonably accurate. The humidity sensor part did fail and the sensor had to be replaced. Despite being in the radiation shield the outdoor environment is hard on humidity sensors.

radshld1

Above is a picture of the commercial solar radiation shield with the wireless temperature/humidity sensor inside.

Another approach to protecting the sensor for solar radiation is to use a fan to provide a steady flow of external air. Essentially blowing away the hot air around the sensor. The processor that I am using to read the wireless weather sensors also has provisions for a wired temperature/humidity sensor which I have been using to monitor the conditions inside the instrument cabinet. I thought it would be interesting to compare the passive radiation shield with a fan aspirated shield.

I build a simple shield out of some 2″ PVC pipe and fittings.

fantemp1

The picture above shows the parts of the sensor. In the middle is the actual sensor mounted on a small PC board with a RJ11 connector. Above that is a 12VDC wall wart to power the fan. The 40 mm computer  fan to the left is mounted in a short section of 2″ PVC and glued in place. A length of telephone cable is used to connect the sensor to the processor. A PVC U fitting and a longer piece of PVC completes the sensor.

fantemp2

Above is a picture of the completed sensor mounted on my instrument platform. The fan draws air up the long tube and out the short tube. With both ends to the tube facing down it should help keep the rain and snow out.  The sensor is located near the middle of the U fitting.  It remains to be seen how long the fan and humidity sensor will last in this environment.

After it runs for a few days I will compare the performance of the two sensors.

6/22/2016 Comparison data between the two sensors shows that the fan aspirated sensor is affected by the sun more than the sensor in the shield. Next I will try a simple sun shade for the fan aspirated sensor.

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Chainsaw Lumber Mill

A rather large silver maple tree trunk came down in a wind storm recently. I have cut most of it up for firewood but there was a nice 4 foot section that I decided to make into some boards. Maple has a tendency to rot in the center but this piece was solid.tree2

A few years ago I built an attachment for my chainsaw to let me use it to cut boards from logs. It is based on the Granberg small log chainsaw mill. The Granberg mill is made of aluminum and mine is made of steel so it is a bit heavier but it is used sitting on the log or guide board so it is not too much of a problem being heavier.

saw1

To guide the mill for the first cuts a 2X6 is screwed to the log.

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The log after the first cut.

log3

It makes cutting the boards a lot easier if the log is squared up first. My saw bar is not long enough to cut through the center without taking the sides off. It took some doing to get the log rolled up onto the 4X4s. A peavey would have made things much easier. log10

After the log was squared up I cut it into boards. Here I stopped the cut part way in to take a picture.

board1

The boards now get stacked in the shed for a year to dry.

Posted in DIY, Metal Working, woodworking | Tagged , , , , , | 1 Comment

Tankless Water Heater

Here is more than you ever wanted to know about fixing my tankless water heater.

A few years ago I bought and installed a Poloma model RMTG-53DVP tankless water heater in my home. This exact same model is also sold under the brand names of Rheem, Ruud and Richmond. After operating for about a year it shutdown and started flashing error codes C7, 13 on the remote control. If I unplugged it for a while it would work again but would only run for about 3 minutes before shutting down again. Some digging around on the WEB indicated this was a oxygen sensor fault. In other words the oxygen sensor was telling the controller there was low oxygen. Never having worked on a tankless water heater before I called a plumber that advertized fixing tankless water heaters. He came out and we had a nice conversation and basically recommended I fix it myself. For this I paid for a service call. Apparently he was not familiar with that brand of heater and did not want to figure it out.

Now a tankless is way more complicated than a conventional water heater with a microcontroller and lots of sensors and valves.

heater

Here is my heater opened up. At the top is the copper coil assembly where the water gets heated. The plastic with the black lines on that is an electric heater that keeps the water from freezing if the temperature gets too low. Below that is where the burner assembly goes. The burner assembly and manifold is removed in this picture. Below the burner assembly is the controller, valve and fan. There is a whole bunch of screws that have to be removed to get thing apart.

The oxygen sensor work by monitoring a flame burning in a special chamber. There is a precision orifice that controls the amount of gas burning and a thermocouple to monitor the flame temperature. The controller waits for 3 minutes after the heater starts to check the flame temperature so that everything is stabilized. If the temperature is too low the controller shuts down the heater and sends an error code to the remote control.

burner

This is the burner assembly. On the left is a round brass hole. That is where the sensor flame burns.

So what could cause the problem? Obviously there is plenty of oxygen and nothing blocking the air flow into the heater. The thermocouple could be bad but those thing are very reliable. The controller board could be bad (horrors). After a bit of poking around and inspection I discovered that there was some crud deposits around the precision orifice.

hole

It did not seem like the orifice was blocked that much but since I could not find any other problems I cleaned the orifice and reassembled the heater. That solved the problem.

Since then I have had to clean the orifice about once a year. Something in the propane  is forming the crud.  They also recommend cleaning the water lines by running vinegar through the heater with a pump for about an hour. I have done that once. It did not seem like there was very much lime build up though.

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Soapstone Stove Restoration

Many years ago we bought a soapstone stove at a garage sale for $25. It was not in the best shape with numerous stones broken. I brought it home and dismantled it so I could move it. The complete stove weighs around 700 pounds. I stored the pieces in the barn. Now that I am retired, with a little more time on my hands I decided to fix it up and install it in the house. I have a lot of wood and it would be nice to have a backup for the propane heat we have.

The stove is a Hearthstone I made by the Hearthstone stove company of Vermont. I believe that the Hearthstone I is the first model made by the company and is no longer in production. I did learn from an online dealer that the Equinox 8000 stove replaced the H1. It looks similar but the innards have been modernized.

Replacing the stones

The first task was to see if it was even possible to replace the broken stones. A few years ago I visited the local Hearthstone dealer and asked about getting replacement stones. They said I should talk to the factory. I contacted the factory and they were kind enough to send me an owners manual for the stove but said I had to go through the dealer to get part. The old run around. The factory would probably have had to make the stones and that would be and expensive way to get the stones. I did find an online dealer that had some of the stones but they are quite expensive. One valuable thing I got from the online dealer was a chart showing the layout of the stones in the stove. That leaves me with getting some soapstone and making the stones myself. It turns out the stones are 30 mm thick which is the same thickness as the soapstone slabs used for kitchen counter tops and the like. There does not seem to be any soapstone counter top dealers nearby so I have been contacting soapstone suppliers. I got samples from three suppliers, Finnish soapstone, Brazilian soapstone and Virginia soap stone. I wanted  to match the look of the old stones. Shipping turned out to be quite expensive for the stone so I finally found a dealer a few hours drive away in Wisconsin. The slab I purchased there does not match the stones of the stove but arranging the new stones symmetrically it will look OK.

brokenstones

The picture above shows the broken stones. I used this to estimate the amount of new stone I needed to purchase. After I got the slab of new stone I realized that I actually needed more stone as I wanted to move the flue outlet from the back of the stove to the top. This requires a few different stones, which I have to make. To compensate for this I decided to glue the stones with simple breaks and no missing parts. This is a stove and the stones get quite hot so you can’t use just any glue. I have a gallon of sodium silicate which can be used as a glue. Sodium silicate when dry is essentially glass and can withstand high temperatures. This worked quite well and after refinishing the stones the breaks are hardly noticeable.

cuttingstone

The picture above shows the method I used to cut the new soapstone slab into the sizes for the stove. I put a diamond tile saw blade in my circular saw and cut the stone wet with a clamped on guide. This produced a nice smooth cut. I was careful not to get the electrical part of the saw wet and it is plugged into a GFI outlet.

I planned on cutting the grooves  and bevels for the stones on my table saw with just an ordinary carbide wood cutting blade. I tried cutting some of the broken stones to see if this would work and they cut quite nicely. When I went to cut the new stones they promptly ruined the carbide blade. The new stone was much harder than the original soap stone in the stove.  A 10″ diamond blade for the table saw solved that problem.

Each stone has a decorative beveled edge and grooves in the edges. Flat metal strips fit into the grooves to hold the stones in place.

Metal Parts

After sitting in the barn for years it was impossible to remember how all the pieces of the stove fit together. It was a jigsaw puzzle type of challenge to sort out the stones and metal parts. The metal parts had become quite rusted.

stovedoor

As can be seen in this picture of one of the stove doors. All the metal parts got sandblasted and the cast iron parts repainted with flat black high temperature stove paint. Some parts like the screen for the doors had to be replaced. I replaced the screen and all the nuts and bolts with stainless steel. I also had to replace some of the steel strips that hold the stones in place because I changed the vent from the back to the top of the stove. This requires some different length strips. The ugly bolts in the door handles were replace with some stainless steel rod and some nice brass acorn nuts.

Reassembly

Because the complete stove weighs somewhere around 700 pounds there was no way I was going to assemble it and then move it into place.

stovebase

In the picture above the base of the stove is placed along with some of the internal workings. There are cast iron plates and a channel around the bottom that supplies air around the base of the fire. The incoming air is regulated by a thermostatically controlled damper on the back of the stove. The 400 pound water filled cast iron radiator behind the stove provides and excellent radiation shield to protect the wall behind it from the stove heat. Not seen in this picture is another metal radiation shield on the right wall.

stoveinside

Above is another view of the stove being assembled. The three stones in the back with the fiberglass screen on them are some of the replacement stones. The original stones were shorter to allow for the vent in the back. You can also see the ends of the steel strips that hold the stones in place. Because of the way the temperature of the stove is regulated by controlling the incoming air it is important that the stove be airtight. The rope gaskets for the doors were replaced. New ceramic fiber paper gaskets between the door frames and the stone were installed. When assembling the stones into the stove each stone mortared with furnace cement to seal all the joints between the stones and between the stones and the cast iron frame.

Heating

stovefirst

Above is a picture of the completed stove with a nice fire going. Normally I use the side door for ash removal, loading wood and starting. This winter I have been using the stove daily. It will keep the downstairs part of the house warm without any additional input from the propane heat even on below zero days. When the temperature is in the 40’s it is easy to get the house a bit overheated. Because of the way the air is regulated I believe you are supposed to be able to load the stove up with wood and have it burn most of the day. I prefer to keep only a small amount of wood in the stove and add a piece every hour or so during the day. This way if it gets too warm I can just stop feeding it wood.

warmdinner

Since the stove is in the dining room it can be used to keep food warm. Here it is keeping thanksgiving dinner warm.

The dining room gets a bit warmer than the rest of the downstairs so I have a fan to help circulate the air to the other rooms.

References:

Hearthstone stove manufacturer http://www.hearthstonestoves.com/

Soapstone supplier http://www.elegantstoneproducts.com/

Posted in Alternate Energy, DIY | Tagged , , , | 11 Comments

Solar Power

I have wanted to put up a solar power system for some time and last month I finally got around to getting one installed. When I first started looking at solar power the panels were small and expensive. The inverters were fairly primitive and not too reliable. All that has changed in the past few years. Now when I drive around, particularly in rural areas I frequently see solar panels. It is still hard to find installers so when I saw a sign for a business along the road in the next county I called then and asked for a quote. In the past I would have probably done the installation myself but I am getting a bit old to be scampering around on a roof carrying big solar panels. It would have taken me all summer to get the job done. They got the hardware all installed in two days. After that it was a two week wait for all the paperwork to get done and approved.

solarroof1

This building looked to be the ideal place to put the panels. The house is not suitable due to trees and not facing south. The building next to this one has a shallower roof angle and is shaded more by some trees. The solar array I wanted consists of 21 270 watt panels. When we first looked at putting the panels on this building it looked like 21 panels would not fit. The panels are normally installed in portrait because that uses the least amount of racking. In that orientation they would not fit. I decided to spend a bit more on the extra racking to get the panels on this building.  As can be seen in the picture above the 21 panels just fit in the landscape orientation. The tilt angle of the roof on this building is 35 degrees which appears to be a good compromise. The panels are wired in three strings of seven panels each.

inverter

The DC wiring is run underground to the adjacent building because it has power and is a better place overall to mount the inverter. This inverter is an impressive bit of technology. It is rated at 6 Kw and is capable of  MPPT on two independent  circuits. One of the seven panel string is wired to one of the MPPT inputs and the other two strings are wired in parallel to the other MPPT input.  The inverter is fully weather proof and capable of being mounted outside. Although I am much happier that it is inside a nice building. When you turn the inverter on it boots up and goes through a list of self checks before it connects to the grid.  A variety of information is available on the LCD and internal settings can be changed after entering a password. It keeps track of things like total energy produced, peak power for the day and overall and even the value of the energy produced if you enter the cost per Kwh. For some reason the default is in euros rather than dollars. The inverter is capable of being remotely monitored and controlled. This is done by RS485 signalling . This is a good choice overall but I would rather not bury a cable all the way back to the house for monitoring. Also I plan to have my shop in this building and want internet for the shop. So I am arranging to bring internet to the building via a wireless link. the open box on the left in the picture above is a place to mount the RS485 to Ethernet converter and the power supply for the wireless link. When that is all hooked up I will be able to monitor and log data from the inverter in the house and even put the data on the web.

inverter

I took the above picture during testing around noon on a sunny December day. The power output is about 1 Kw less than the rated power of the array. I don’t really expect to ever see the full rated power but it will be more in the summer when the sun is higher and more square with panels.  I got permission from the utility company to go online and switched the system on. So far the weather has been foggy and cloudy. It still makes 400 or so watts at noon on a foggy overcast day. The utility company came out and installed a digital watt hour meter that keeps track of coming and going power. This size array is expected to provide about 40% of my annual energy consumption. Time will tell.

Technical Details:

The solar panels are Suniva OPT270-60-4-100. These panels have 60 6″ mono crystalline cells. The 21 panels are wired in three strings of 7 panels. This gives a maximum open circuit voltage of 269.5 Volts for each string.

The inverter is an ABB PVI-6000-OUTD-US-A. This is a transformer-less inverter rated at 6Kw. It provides 240 volts to the grid when operating. The inverter manufacturer was formerly Power One. This caused me some difficulty  when looking for the users manual and monitoring software online as many of the web pages are still under the Power One name.

Performance:

I was planning on comparing the monthly electricity usage with the solar panels with the month from the previous year. The electric company has nice online access to the information. Only one small problem, you get an new account number when you set up for solar and the information from the old account is not available. I should have saved the usage information before the account switched. The first two months on the solar system December and January have the shortest days and are generally dark and cloudy. Despite this the overall bill from January was less than half of what I remember for a typical bill for this time of year. Based on this I suspect there will be months this spring and fall, when I am not using the AC that the solar system will make more than I use for that month.

References:

Green Transitions http://greentransitionsllc.com/

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PC Problems

A while back the computer that runs my instrument platform died. I don’t know what happened but I ended up replacing the internal power supply, motherboard and memory stick to get it working again. The front panel USB board was also dead but I don’t use that so I did not replace it. After repairing the computer everything worked except the computer would not communicate with the Arduino that runs the weather instruments.  At first I thought the Arduino was dead also but it would work if plugged into a different computer.  A different Arduino not programmed with the weather instrument software would work on the computer. Finally after a lot of digging around in the windows registry and playing with the device manager I got it to work. Here is what I think happened.

When I replaced the motherboard and started the computer windows booted up and found that there were two new serial ports (the ones on the new motherboard) since COM1 and COM2 were assigned to the serial ports on the old motherboard windows assigned COM3 and COM4 to the new ports. Now with the old motherboard the weather Arduino was assigned to COM4 and windows remembering that left the Arduino assigned to COM4 even though COM4 was also assigned to a motherboard port. So when I tried to communicate with the Arduino I was actually trying to talk to the motherboard COM port even though the device manager said COM4 was assigned to the Arduino. Using the device manager application assigning the Arduino to an unused COM port made thing work. I still have windows saying there are 4 motherboard COM ports. There are probably only two. All sorts of deleting registry keys and playing with the device manager have not been able to get rid of the extra ports. I probably should have reinstalled windows when I replaced the motherboard but that requires so much putting thing back together that I will leave it the way it is unless some other problem shows up.

The computer is a really nice little machine I built up with parts from MiniBox. It is small about the size of a 2 inch thick book and uses an Intel Atom processor. It only draws about 15 watts, which is real nice for something that runs 24/7.

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