[msimpson99]

I started working on some serious pyrography (wood burning) experiments with my CNC machines.

https://youtu.be/OHWT_tbI_TU

One of the problems when wood burning is that when the tip is raised off the surface of the stock it gets hotter. When the tip then touches the stock, it creates a darker mark.

The next step is to connect the pyrography controller start/stop relay to my M3 control relay on the CNC. With this I should be able to cycle controller enough to circumvent this.

[__Britt]

I'm wondering if a temperature controlled soldering station would be better for this? I can definitely say it makes a world of difference in soldering...

[CitizenOfDreams]

"Temperature control" was my first thought as well.

I would approach this with a T12 soldering iron cartridge. The entire kit - the heater, the handle and the temperature controller - is less than $20 shipped on eBay.

[__Britt]

Looks like there's custom, open-source firmware for that as well... so it might be possible to integrate it into the CNC such that it could be controlled from g-code...

https://www.ptdreamer.com/

[msimpson99]

I have several temperature controlled Irons, They just don't put enough watts to the tip. Even my HAKKO does not work very well.

I have even purchased some of those so called all in one burners/solderng irons from Amazon, and returned them all. I have a couple normal woodburner irons, and they take forever to heat up and loose their heat quickly if you travel too fast. This is why most high quality pyrography pens are a power source and resistance wire tip.

That's not to say there is not an iron out there that would work, I just have not found one.

Here is a video I did 8 years ago using a wood burner iron.
https://youtu.be/zGkC9HWWykE

I want to experiment with other power sources and temperature control, but the issue is getting a thermocouple near the tip. I made the tip I am using here so it may be possible to form the very tip around a high temperature thermocouple.

In any case for consistent burns, you need to quickly turn on and off the heat as needed. I just got my pyro controller hooked up to the M3 relay on my machine and have started working on my Mach3 config and Vectric post processor.

You dont need to change much in the Mach3 config file. Just make sure the spindle delays are turned off. Most of the work will be done in the post processor.

You need to set an initial delay so that the tip and get up to temperature. In this case its 1000 degrees. In my case it takes about 45 seconds at 15 Amps. This is easy for most post processors.

The real magic comes in at the actual point where the tip is moving into position. In all Vectric CAM software this is in the NEW_SEGMENT block. In SheetCAM its in the Pen Down block.

You need a M5, Dwell, M3 sequence. The dwell will be the value that needs to be in sync with the plunge rate at clearance height of the tip. With these things controlled, you should be able to get a tip down and burning without the initial scorch. Real pyrographers (not me ) use the landing (ramping) technique to keep from getting the initial scorch.

[msimpson99]

Another thing I might add; I feel the 20 Amps is not enough to do any real experimenting with. I just start research to build a 100 Amp controller.

I also attached the thermocoupler to the wire with some 24 gauge copper wire shown here. This should give me a little more consistency in my temperature measurements.

Attachment 428736

Eventually I will probably add a circuit that will close a relay when the temperature reaches a particular temperature. Kind of like ARC OK when plasma cutting on a CNC.

The end goal however, is to add a PID once I am happy with the wire to thermocouple interface.

[__Britt]

I'm still wondering if a T12 cartridge, perhaps run at a higher voltage so as to get the watts up, wouldn't work. It's got a temperature sensor built into it... Hmmm.....

[Mecanix]

Dunno why but I came here thinking it was a thread about machining titanium with a petroleum based coolant

Nice work! Creative, and result are looking good.

[msimpson99]

Im pushing 10 volts at 15 amps so its delivering 150 Watts. That's OK for MDF but real wood is going to need more. At 12V and 20 Amps (Max on my controller) that's 240 Watts. Which is the minimum for wood. Do you think the T12 cartridges can handle 240 to 300 watts. I know the handles that I have for them cant.

On a soldering iron the controller, will pulse the cartrige to get the temp where it should be. This OK for soldering but for a CNC the heat is being pulled away constantly. The solder controller would have to keep the power up almost constantly. That's a lot of heat.

Speaking of heat here is one of the problems I am having.
Attachment 428750

I am working on creating a dark chess board square. I increased the amps to 17 and did a run at darkening a square which took about 10 minutes. The problem I am having is the heat eventually destroys the terminal block. I need some sort of ceramic terminal block to hold the leads.

Please note that awhile back I added two copper sleeves over the ends of the resistance wire. Before I did this the terminal block would have a melt down in a matter of seconds. Now at 17 Amps it takes about 9 minutes. This is due to the resistance wire heat transferring to the copper via conduction to the copper then to the terminal.

I only see two ways to solve this:
1. Make some sort of ceramic terminal block
2. Use a small fan directed on the terminal block to keep it cool.

I'm kind of dead in the water until I can solve this issue.

[msimpson99]

I did get the Vectric post processor tuned as well as it could be as they don't have a lot of capability. For instance there is no pen down segment. I have to use the rapid move segment to cool the pen down. This kind of works, but there are multiple individual rapids that take place. One when the Z moves up, and another when it moves into position.

Here is an example:
Attachment 428752
As you can see the shading really looks much better here, some burning where a lot of points come together an a little at the touch downs, not near as much as I used to get before the post processor work.

I may just move to SheetCam for this as they have a lot more segments to use, as well as rules. Much more control.

I just need to get the heat buildup issues solved.

Keep in mind I could just slow the CNC down to 10IPM or so and drop the Amps. If I do this I might as well be using a $10 wood burner.

I think I will probably just go the ceramic rout. I have the clay and kiln to do it, but I dont like firing the kiln up unless its winter, as I dont like runing a 2000 degree oven for several hours, even as insulated as they are, they still put out a lot of heat.

[philba]

Out of curiosity, why not run at a higher voltage? 12V seems kind of low to me for pushing that kind of power.

Also, Altech makes ceramic terminal blocks.

Finally, an idle thought but metal changes resistance with temperature - perhaps by measuring the current flowing through the element you could determine the temperature. Might require some experimentation.

[msimpson99]

Im using 12V because I had a 12V 30A one and all the larger ones 24V, 36V, and 48V were much larger. The 12V 30Amp seemed to be a good choice for my first round of experiments. I think on my next build I will be moving to something in the 60Amp to 100Amp range. I will look at what is available for a reasonable price.

Getting the temperature is no problem. I have thermocouple rated to abut 1300 degrees strapped to the resistance wire. Seems to be working fine, for now. By the way that is kind of how the temperature sensors work on soldering irons. They literal attach a dissimilar metal to one of the electrodes on or in the cartridge.

My big obstacle right now is coming up with a mounting method and controlling the heat it puts out. I am going to start with a small fan pointed directly at the terminal block. It is not that big of a deal, as I already have a 12V accessory plug for my Z axis. Once I get the fan setup, I will start with the same 10 minute test and work my way up.

[__Britt]

Do you think the T12 cartridges can handle 240 to 300 watts.

Cartridges? I think so... they are used typically at temperatures between 300 to 400 Celsius; and their innards are metal and ceramic. With a properly shaped tip (i.e, large like a chisel or hoof shape, not a tiny pointed tip), I think there should be enough thermal conductivity to get the heat from the heater element to the wood.

One way to find out, though... get one and try it. Hmm...

I did get the Vectric post processor tuned as well as it could be as they don't have a lot of capability.

Perhaps a post-post-processor? Some script written in your favorite language should be able to pattern match the Z moves, and insert whatever code is needed.

Also, Altech makes ceramic terminal blocks.

There's a whole bunch of them on Amazon, eBay, etc... just search for "ceramic terminal block".

[msimpson99]

I have several T12 and T15 cartridges. Pretty much the same and I can use them interchangeably on a couple stations I own. I have my doubts but my eventually try them, but the soldering station power source will not work. Just not enough power to keep up with wood burning.

Does anyone know the connections for the terminals on the T12 cartriges. Also the voltage used to energize the cartridge would give me a starting point.



I have purchased several Ceramic terminal blocks. The problem is that in all I have tested, the actual terminals inside ceramic float. IE they are not held down. This may be to keep the ceramic from cracking when the metal gets hot. These wont work as the tip must stay stationary.

[msimpson99]

I attached a small fan with speed control to the front of the floating head shown here:

Attachment 429016

I started a new series of tests. MDF is the easiest and most consistent medium to burn, so I will start with it.

Shown here are three runs I made:

Attachment 429018

Test 1
This is where I dialed in the amperage to get the shade I wanted. The test consists of a very fine run in one direction then another at 90 degrees. I then burn an outline on the outside edge.


Test 2
A fresh test at 12.5 Amps. I did get some banding which was caused by an air conditioner that was cycling on and off. Another was caused by a carbon buildup, probably from the last test coming off and causing the tip to get better contact with the stock. I will need some method of cleaning the tip between burning large objects.

Test 3
I turned off the AC unit and ran the test again. As you can see the shading is much more consistent.

Each test took a little over 9 minutes so the machine ran 27 minutes with no heat build up on the plastic terminal block.

Where do I go from here? I need to test various wood types to see what kind of results I can achieve. I think I'm going to need a larger controller and thicker wire to the floating head.