3D printed plastic burner experiments (photo heavy)

[ThomasPowers]

One of my grandkids likes those, Monster Hunter, ; so I read a couple I found at the used bookstore before sending them on. Always good to be able to talk about stuff with the folks who will be signing you up for the Soylent Green tour...

Currently reading "Black Blade Blues" J.A.Pitts about a lady smith who's involved with reenactment/SCA...just got started; sigh just hit my first big blooper on page 24 "I would temper the edge of the blade by dousing it in water. Oil would make a better edge; but I wanted the metal softer, prevent it from keeping a good edge."   got *that* backwards!

[Another FrankenBurner]

9 hours ago, John in Oly, WA said:

What temperature was your flask when you poured the aluminum?

The flask was at 600°C (1100°F).  We are experimenting with DIY investments.  That is probably still the problem.  Just to specify, by full vacuum, do you mean 29+ inches mercury?  We are using a healthy vacuum pump and I could not find much information on the commercial vacuum table capabilities.  

[Mikey98118]

one of  my favorite authors has a main character using tungsten carbide swords

[jlpservicesinc]

Deleted. was silly dribble in regards to tungsten sword.. 

[Mikey98118]

Yes, exactly; it was silly dribble. The author is a talented spinner of tales, but tidn't take the slightest effort to get his facts straight.

[JHCC]

When we were little, my brother proposed that we could make the world's sharpest sword by making a lead casting in a mold lined with razor blades....

[ThomasPowers]

I have a welder friend who can tig weld razor blades together to make you a blade...

[John in Oly, WA]

So what you're saying is..."Not only is the world my oyster, but..."

15 hours ago, Frosty said:

Have you read any of Larry Correia's books?

No, but now I'm going to have to. Just the titles are enough to pull me in. Ah, this is really going to cut into my forge time, or my sleep time. LOL

13 hours ago, Another FrankenBurner said:

We are experimenting with DIY investments.

Oh yeah, that could be part of the problem. Are you printing with PLA and using that for your mold pattern? I've heard that can expand quite a bit before it actually burns out of the investment. There are investments designed to withstand that. I've been using Certus Prestige Optima. It was created specifically for 3D printed materials. R & R Plasticast is good too.

[John in Oly, WA]

13 hours ago, Another FrankenBurner said:

Just to specify, by full vacuum, do you mean 29+ inches mercury?

Can't say exactly. I have a gauge on my vacuum system, but after the first time using it, it went well past the 30 mark and afterwards, the needle never came back to zero. But I'd guess that it's close. Doubt it's a perfect vacuum though.

[Buzzkill]

Nevermind.  Re-read what you wrote, and it's clear your gauge is no longer reading correctly.

[Another FrankenBurner]

1 hour ago, John in Oly, WA said:

Are you printing with PLA and using that for your mold pattern? I've heard that can expand quite a bit before it actually burns out of the investment.

Yes, PLA burnout.  Our investment withstood the burn out, it was inspected out of the kiln.  I heard it crack when vacuum was applied.  We are adding a bit more head to the investment the next go around, it was less then 3/8 inch thick.  

Do you turn on the vacuum prior to pouring or after?  I have read people do both ways but without explaining reasoning one way or the other.  

[John in Oly, WA]

I turn on the vacuum just before pouring. In my experience, the metal (brass in my case) goes in and starts to solidify so fast, if I turn the vacuum on after pouring, it has no effect. Before pouring, it helps pull the metal in.

6 hours ago, Buzzkill said:

Re-read what you wrote, and it's clear your gauge is no longer reading correctly.

That's what I said. But perhaps this part "But I'd guess that it's close." wasn't clear. I meant "I think I'm pulling close to a full vacuum", not "I think my gauge is reading accurately". Obviously my gauge is WAY off.

[Frosty]

9 hours ago, John in Oly, WA said:

No, but now I'm going to have to. Just the titles are enough to pull me in. Ah, this is really going to cut into my forge time, or my sleep time. LOL

That's one reason I like audio books I can listen while I: work, drive, sleep, etc. The trick is to take note of what page you're on when you turn it on so if you get distracted, doze off, etc. you can go back and catch what you missed. The other reason I listen to books on audio is arthritis is settling into my thumb joints and it's hard to hold a paperback open very long.

Larry Correia's "Hard Magic" series is another excellent one. I have yet to read a bad story by him. 

Frosty The Lucky.

[D.Rotblatt]

Been lurking in the background.  I have a 3D printer and used to teach art Foundry(primarily shell molds and sand casting) and thought a Mold Making class.  Just an FYI: they make printer wire for burnout.  Here's one example.  Never used it, just know it exists.

https://www.machinablewax.com/product.php?product=52

Alternatively, have you thought about making a silicon mold of your successful "vortex injector?" and pulling waxes of it.  Could save your expansion problem.  Also, any foundry will cast a tree of waxes for not much money.  If you where doing 30 or 40 of them it could be cost effective if you thought to sell them.

Also, if you are sucking investment into the 3D print during vacuum investment, just spray the print with a couple of coats of shellac to seal any holes.  It will make it smoother too.

Really fun stuff you're doing!  I've been enjoying following it!

Dan R

[Mikey98118]

Thanks for the input, Dan.

[Another FrankenBurner]

I was aware of the machinable wax filament.  I have read it is difficult to use.  I would have to change the firmware on my machine to lower the minimum print temperature, convert to a direct extruder system instead of the Bowden system and it sounds like a fight with bed adhesion.  I might look into another machine as I still like the idea of using it.

I had thought to do a silicone mold to make wax forms but I didn't think I could with this design.  I don't know much about silicone molds.  There is a large void in the middle of the inducers so I don't know how I would get the print and the waxes out of the mold.  I would like to figure it out so that I don't have to reprint it each time but can't think of how to do it.

I don't suspect the investment is cracking due to expansion.  Once we started using the flask, the cast comes out of burnout without cracks.  The last one was cracked by the vacuum I suspect.  We are tinkerers and so we are still playing with DIY investments which is probably the problem.  We are also messing with the burnout schedule.  When we are tired of failing, we will get some proper investment and follow it's instructions.  

I don't think we are sucking investment into the print like I originally worried about.  To test though, we have an investment made which we pulled a deep vacuum on for several minutes.  We are going to burn it out and break the mold apart to see if there is any evidence of it.  I do like the idea of using shellac to smooth the print though.  The shellac will burnout ok without adding problems?

Thank you for the casting advice.  It is fun stuff.  Our favorite part is the moment of truth.  All that work buried in an investment and you don't know if it was successful.  

We now have a larger kiln and several flasks made up so we can start doing multiple experiments in one go.  That should speed things up.

 

 

[John in Oly, WA]

There are a LOT of variables in a LOT of different processes to get from start to finish in what you're doing. I'm in a similar process casting brass knife hardware. Hard to keep track of it all. Hard to change just one thing at a time when the process can take so long for each little test of a change.

I'm using an SLA/DLP resin printer and was told, with the resin and investment I'm using, I could put the flask in and take it straight to 800C and shorten the 15 hour burnout schedule considerably. Like down to 3 1/2 hours. I could even preheat to 600C, then put the flask in the oven and take it to 800C. Well, heating the flask from ambient temp to 800C as fast as possible worked, but the surface finish of the cast brass suffered, in my opinion, greatly. Adding the flask at 600C preheat and taking it to 800C, the investment shattered. Now I'm back to the ramping up in three steps to get to 800C and running the 15 hour schedule.

But you've got to experiment or what do you know. 

[D.Rotblatt]

7 hours ago, Another FrankenBurner said:

There is a large void in the middle of the inducers so I don't know how I would get the print and the waxes out of the mold.

I was thinking about this this morning.  I think you would have to print two halves with keys on each half.  Think of taking the cylinder and splitting it lengthwise, put two or more short posts (or 1/3 spheres or really any irregularity) on the edge of one side and matching holes on the other.  When you pull the wax halves, the posts/holes would key the two halves together so they match and you fuse them together with a hot knife in a few places.  Clean up the joints and spray with shellac.  It's a little wax work, but I know how long it takes to print 3D.  Don't know which is more efficient for you, since you don't have to be around when the 3D prints.

7 hours ago, Another FrankenBurner said:

The shellac will burnout ok without adding problems?

I was taught to paint my waxes with shellac as a way to fill pinholes and allow for a surface that the investment will stick to (helping to prevent bubbles). No difference between shellac or no shellac except less bubbles.  In short, it burns out fine.  

 

7 hours ago, Another FrankenBurner said:

To test though, we have an investment made which we pulled a deep vacuum on for several minutes.  We are going to burn it out and break the mold apart to see if there is any evidence of it. 

Sounds good.  I'd just paint with shellac to make sure.  That one may have no pinholes in it, but another one might.  If investment gets inside the model...well, the casting will be full of  bits of investment which will probably break off inside the mold during pouring leaving pits etc.  You'll probably see a lot of bubbling from the model when you vacuum the investment if there is a pinhole to the inside cavity.

Dan R

[Another FrankenBurner]

Another fun Saturday.  We finally played with the 3/4 burner.  He ended up getting the 045 jet.  This flame is at 4 psi and the nozzle ends at 1.5 inch.  It's a big slow flame.  The orange is from the kast o lite nozzle.  

.  

Here is 10 psi:

Here is the 3/4 guy:

It still needs some tinkering, more nozzle experiments, and the mix tube is too long.  When the nozzle matches the inducer, the final FAM stream is slowed, the jet size is increased, and the induction volume curve matches the fuel volume curve through fuel pressure range.  We 3D printed a thin form for the kast o lite to make this nozzle.  A 1:12 taper after a step.

We made 4 more flasks and 3D printed bottoms which include the funnel/sprues for the inducer.  

We had obtained a dilapidated larger kiln and rebuilt it, so today we poured 5 experimental investment mix flasks.  We ran the furnace with the ugly salvaged 1/2 inch burner from the last pour.  We are happy with how it runs.  

We have pulled out working burners but they are not good enough yet.  Investment still needs work.  The burners have porosity problems.  A good learning day.

 

[Frosty]

0.045 mig tip jet on a 3/4" mixing tube? Oh MY. 

Frosty The Lucky.

[Mikey98118]

Yes, Frosty. I noticed to. It seems the young scamp will end up with the best parts of your flame, and the best parts of mine

[Frosty]

It exceeds my best attempts for sure, I've always pushed for the most fuel air I could force into the forge per second I could. The limiting factor has always been inducing enough combustion air. 

The only thing that takes it out of my design parameters being these aren't minimum equipment and skills home builds.

I want at least one once Curtis is ready to share. 

Frosty The Lucky.

[Mikey98118]

I have waited twenty years for the next big leap in burners; its time to see it--finally.

'course now he faces the big one; coming up with a catchy name before some wag can hang something on his burner first

[D.Rotblatt]

20 hours ago, Another FrankenBurner said:

The burners have porosity problems

Possibly sprue size or too small a button.  also looking at your casting, I'm betting you are sprueing into the end.  The spiral "fins" may be freezing off before the downstream portion is solid causing porosity if the downstream section.  I'm more familiar with bronze casting then aluminum though.  Do you have closer pics showing the porosity problems and a description of how you sprue it?  Maybe I can help.  

Dan R

[Another FrankenBurner]

I'm glad you both like them.  It is exciting.  I think I have the inducer ratio's tuned in to a point I am happy.  I have scaled to the 3/8" and the 3/4" with the exact same ratios and they both do very well.  More air can be induced but then the mix tube velocity starts to scream and the induction volume and fuel volume curves don't match as well.  I think I have found a nice balance for a stable, well ranged, versatile burner.  

The gentle nudges in Burners 101 were not lost on me, I will be scaling to the 1/4", just for Mikey.  I will have to change up the jet assembly for that small.   

I am also starting to tinker in the NARB side of things.  I am as excited about playing with NARBs as I was about playing with inducers.  I know almost nothing about their dynamics and look forward to becoming acquainted.  

Catchy name?  I kind of like Frosty's "Twisted Gizmo."  Others have referred to them as vortex injectors or vortex inducers.  I'm up for suggestions, I didn't put much mind to it.  

We are getting close to aluminum inducers.  A few poured yesterday are now functioning burners.  Just ugly.  One total failure is now a burner shaped candle holder.  Big flames coming out of that one.  

I don't have any pictures of the sprues and the porosity problems currently, but I will get some.  I appreciate the help.  We are going to get some proper investment so that we can know how it functions and what we are aiming for with the DIY investment experiments.