Model Engineering in the 21st Century

[Bazzer]

That is already available, the likes of Shapeways will take your 3D file

Or just go direct to metal by DMLS like this one that we had done a few months ago. 3D file to print bureau and part comes back two weeks later.

The printers are expensive at the moment but so were CNC's when they first came out !!

Superb properties as far as we can tell.

 

[timo_gross]

Or just go direct to metal by DMLS like this one that we had done a few months ago. 3D file to print bureau and part comes back two weeks later.

The printers are expensive at the moment but so were CNC's when they first came out !!

Superb properties as far as we can tell.

View attachment 152837View attachment 152838

I guess the machining stays. Due to the nature of processes.

The powder for certain alloys is a fire hazzard and or toxic, so I doubt that these machines will become "affordable", maybe easy to obtain an obsolete one in a few years, but..., nothing you put in your home workshop.
The complete powder must be kept away from Oxygen, so a protective gas is in the machine is necessary. (then you deal with a lot of technical gases, expensive and dangerous) "once a week" hobby user will probably not invest here. Tempting toy, but that needs to run its hours to justify the setup.

Would be curious how much a print like this costs, compared to 6061 bar stock?

Greetings Timo

 

[GreenTwin]

As for casting, more difficult part:

• neighbors that do not call the police, if they see sparks and fire ( I already got in trouble using an 100 mm angle grinder )
• convince the wife that it is not dangerous and the neighbours are in the wrong ("No honey the fumes are actually good for men, the neighbors Canary was already old, probably sick anyway!")
• have an idea about safety and risks,
• find the materials for casting

Getting started with casting is not easy. I think people need to be fairly persistent before the first good results are obtained.
My guess is before casting makes a big comeback, because of easier pattern making.

Machined parts ordered from the Internet, 2.5d machining (already available at reasonable invest) will replace casting even more than now.

Some old techniques do not disappear, they just become more a niche or hobby.

Noise, smoke, and flames can be a problem with foundry work in a neighborhood.
My diesel burner operates smoke-free, so smoke is not a problem.

The burner does make a lot of noise, and particularly a low-frequency rumble/roar, and it is acting a lot like a pulsajet I think, which is also a very noisy device. I put rubber under the wheels on my furnace, to miminize transmitting the low frequency rumble.
One person I know out west had a neighbor complain about furnace noise, and he added a stack that is about 8 feet long, on top of his furnace.
The stack is lined with lightweight ceramic insulation, and this solved his noise complaints from his neighbor.
The stack looks a bit odd on top the furnace lid, but is functional.

I had to overcome my own fear of getting burned alive, and then convince my wife that what I was doing was not going to burn me alive.
This took some serious conversation, but she knows I do my thing when doing whatever, and can do it safely.
Melting/casting aluminum is relatively easy and safe, and you don't need accurate burner adjustments, and don't need a high-output burner (assuming you avoid water and moisture).
Melting/casting gray iron is a whole new level, and while it can be done with relative ease once you are set up to do it, everything must be done in an exact fashion, and done consistently, else it is not going to work very well.

One of the main safety risks concerns avoiding inhalation of sand dust and ceramic blanket fibers; this is critical.
Many of the hobby furnaces for sale now do not have coated ceramic blanket interior insulation, and for a forced-air furnace, this is not safe.
The fire/heat dangers are just a matter of using leather everything, using heat shields in strategic locations, and understanding how to operate a burner.
I see so many folks online who build a burner and furnace, and then install a plastic 5 gallon fuel tank 24 inches from the furnace; this is a good way to burn yourself and your house down.

Finding the materials for backyard casting can be challenging, depending on what you are trying to do.
Many use Petrobond (tm), which is an oil-based molding sand. You have to know how to condition this sand to keep it usable.
Pottery stores generally have a lot of the materials needed to build a foundry.

The key to successful backyard foundry work in my opinion is the quality of the sand mold.
Your casting will be as good as your core/mold.
I think the mold is where many folks fail at backyard casting.

One does have to be persistant in order to learn backyard casting.
It is also important to research how to run a foundry, and how to make castings, and not just randomly try things, and not keep trying the same thing over and over again that does not work well.

.

 

[Bazzer]

I guess the machining stays. Due to the nature of processes.

The powder for certain alloys is a fire hazzard and or toxic, so I doubt that these machines will become "affordable", maybe easy to obtain an obsolete one in a few years, but..., nothing you put in your home workshop.
The complete powder must be kept away from Oxygen, so a protective gas is in the machine is necessary. (then you deal with a lot of technical gases, expensive and dangerous) "once a week" hobby user will probably not invest here. Tempting toy, but that needs to run its hours to justify the setup.

Would be curious how much a print like this costs, compared to 6061 bar stock?

Greetings Timo

A lot cheaper than using bar stock and lighter and with a better finish for heat dissipation.

Shapeways will do that crankcase for around $750.00 you would get nowhere close to that price for a 5 axis billet machined case as a one off, and I paid nowhere near to $750.00 either !!

The DMLS machines are costing around $200K at the moment.

Every process has its place and I will still at some stage do some backyard casting.

 

[GreenTwin]

Making patterns from wood is an easy way to get into the backyard casting hobby.

If the pattern does not work as expected, it is easy enough to modify a wood pattern by cutting and or adding material, or even starting over with a new wood pattern.

The art of pattern making is not that difficult to learn.
You have to pay attention to draft angle, shrinkage, and machining allowances on the surfaces that need machining.

.

 

[Jasonb]

Barry, are the top 5 or so darker grey fins part of the liner? And what is the purpose of what looks like a series of vertical holes in the fins approx above the fuel barb?

What does it machine like, I have heard some of the sintered prints can be difficult particularly the stainless steel ones but hopefully your alloy will be easier.

A die cast crankcase would be cheaper until you figure in the cost of making the die, OK for bigger runs where the cost can be spread over 100s of engines. Home cast from a 3D pattern would need care to pull the fins, maybe home printed wax and investmet casting would handle the fins better buy you need a good setup for clean castings.

 

[GreenTwin]

The art-iron folks are creative about getting their iron castings made.
Art-iron folks make their patterns at home, and then travel to events that are held by non-profits of some type.
The non-profits operate a cupola/cupolet.

Everyone drives from around the country to the cupola operators site, and then they do a group operation of the cupola, and make their castings over several days.
You can get an idea of a typical art-iron event from castirongypsy's video below.

Basically the event provides the sand and binder for the molds at a cost-per-pound, and the folks running the event own the cupola.
There is no reason why hobby folks could not do something similar.
For that matter, there is no reason why model engine builders can't attend art-iron events and make engine castings there (I have done this).





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[GreenTwin]

Barry, are the top 5 or so darker grey fins part of the liner? And what is the purpose of what looks like a series of vertical holes in the fins approx above the fuel barb?

What does it machine like, I have heard some of the sintered prints can be difficult particularly the stainless steel ones but hopefully your alloy will be easier.

A die cast crankcase would be cheaper until you figure in the cost of making the die, OK for bigger runs where the cost can be spread over 100s of engines. Home cast from a 3D pattern would need care to pull the fins, maybe home printed wax and investmet casting would handle the fins better buy you need a good setup for clean castings.

A lost-filament/ceramic shell casting, using a high-quality 3D printer, and a filament designed to burn out cleanly, would easily rival lost-wax quality, and can be done in gray iron too.

I think the lost-filament castings are the most cost effective method for complex parts.

Here is an example, and I think this person used standard PLA filament.

 

[Bazzer]

Barry, are the top 5 or so darker grey fins part of the liner? And what is the purpose of what looks like a series of vertical holes in the fins approx above the fuel barb?

What does it machine like, I have heard some of the sintered prints can be difficult particularly the stainless steel ones but hopefully your alloy will be easier.

A die cast crankcase would be cheaper until you figure in the cost of making the die, OK for bigger runs where the cost can be spread over 100s of engines. Home cast from a 3D pattern would need care to pull the fins, maybe home printed wax and investmet casting would handle the fins better buy you need a good setup for clean castings.

Hello Jason

Yes the top 5 fins are part of the liner (same piece of metal) the liner below the fins looks like a conventional model cylinder and the ports are machined in.

The fins being part of the cylinder do two very advantageous things, 1) The heat dissipation is much better than a conventional setup of a complete drop in liner, these engines run for just about 60 seconds in the air and 15 seconds on the ground but even in the 15 second ground run the engine is very hot. 2) The fins very much help hold the top of the cylinder in shape.

The material is super to machine, very much like 6082 T6, it is completely free of voids.

Originally we were going to do 3D printed waxes and investment cast as per Peter Halmans advise in the following link, but then we latched onto the 3D DMLS process.

 

[Bazzer]

A lost-filament/ceramic shell casting, using a high-quality 3D printer, and a filament designed to burn out cleanly, would easily rival lost-wax quality, and can be done in gray iron too.

I think the lost-filament castings are the most cost effective method for complex parts.

Here is an example, and I think this person used standard PLA filament.

I guess my issue with lost PLA is that having run a lost was foundry I know the efforts that we went to stop the shells cracking, burning all the wax out and then firing the shells.

I will have to take a look at lost PLA but like I say I have reservations based upon experience of lost wax casting.

The results you show do look good.

 

[GreenTwin]

I guess my issue with lost PLA is that having run a lost was foundry I know the efforts that we went to stop the shells cracking, burning all the wax out and then firing the shells.

I will have to take a look at lost PLA but like I say I have reservations based upon experience of lost wax casting.

The results you show do look good.

The reasons you note are the reasons I don't do shell casting, including but not limited to purchasing some short-shelf-life slurry that must not be allowed to freeze in storage.

The investment process is a big and involved step above sand-mold casting work.

The way I get around shell castings is to use an intermediate step up, which is resin-bound sand molds (or sodium silicate bound molds).
Resin-bound molds that are sprayed with ceramic mold coat will give basically ceramic shell quality, without the complexity of the ceramic shell method.
The caveat is that the ceramic shell process will work on very intricate parts that have a lot of fine detail, such as a model airplane engine with fins, and the bound sand mold often won't work in these situation.

The lost-filament method works well with iron, as you can see from the video above, and that is a big deal if one is making iron castings.
I have not seen anyone successfully use the lost-foam method with iron.
I am not a fan of the lost foam method that is generally seen in a backyard setting, basically because the foam used is generally not the correct type, and the foam pattern is burned up in the process, requiring a new pattern to be created with every casting.
Commercial lost-foam castings use a permanent metal mold, that can be reused many times.

The benefit I seen of the lost-filament process is you dispense with wax, and dispense with having to make a mold in which to cast the wax.

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[Bazzer]

The reasons you note are the reasons I don't do shell casting, including but not limited to purchasing some short-shelf-life slurry that must not be allowed to freeze in storage.

The investment process is a big and involved step above sand-mold casting work.

The way I get around shell castings is to use an intermediate step up, which is resin-bound sand molds (or sodium silicate bound molds).
Resin-bound molds that are sprayed with ceramic mold coat will give basically ceramic shell quality, without the complexity of the ceramic shell method.
The caveat is that the ceramic shell process will work on very intricate parts that have a lot of fine detail, such as a model airplane engine with fins, and the bound sand mold often won't work in these situation.

The lost-filament method works well with iron, as you can see from the video above, and that is a big deal if one is making iron castings.
I have not seen anyone successfully use the lost-foam method with iron.
I am not a fan of the lost foam method that is generally seen in a backyard setting, basically because the foam used is generally not the correct type, and the foam pattern is burned up in the process, requiring a new pattern to be created with every casting.
Commercial lost-foam castings use a permanent metal mold, that can be reused many times.

The benefit I seen of the lost-filament process is you dispense with wax, and dispense with having to make a mold in which to cast the wax.

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I guess that the high temperatures involved in iron casting maybe does away with my worries of deposits of PLA being left in the mould as I guess it just get obliterated. I am not sure that aluminium with the lower casting temps will handle this so well but stand to be proven wrong.

 

[GreenTwin]

In the video above with the lost-PLA, he does burn out the filament in a kiln prior to pouring the mold.

Many folks say that to get a clean burn-out of the filament, you must use a special filament, but his castings clearly show that you can cleanly burn out PLA, at least with molds of the complexity that he is using.

A more complex pattern may require a special easy-burnout filament.

I think aluminum would work well too using the lost-PLA method in the video above.
I think the bottom line is that the kiln burns out pretty much all of the PLA filament.

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[Bazzer]

I will watch the video out of interest this evening.

You can see from the progress that we have made that we will be fairly wedded to the DMLS process and to beat it all I have found out an organisation who will do the DMLS printing for free !!

 

[GreenTwin]

I don't know much about the DMLS method, but I can see that it has a tremendous amount of potential in both the hobby and larger world.

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[Jasonb]

I have found out an organisation who will do the DMLS printing for free !!

Little point in trying other methods in that case, look forward to seeing a finished one.

 

[Bazzer]

Little point in trying other methods in that case, look forward to seeing a finished one.

We have done a deal with a University that majors in additive manufacturing, the NB40 will be used as part of the additive manufacturing course work and in return we get a number of FOC crankcases.

The crankcase is not the hold up now, rather getting the aluminium cylinder chromed commercially in the UK and manufacturing the crankshaft to the required spec is our challenge now.

Having said the above, there will be times when other techniques will be applicable, I am interested in those as well.

 

[GreenTwin]

Little point in trying other methods in that case, look forward to seeing a finished one.

For larger engine castings, I think some sort of sand casting method will be necessary, but I am not sure exactly how large the DMLS method spans, or how the costs may ramp up with size.

And for those who like to make their own castings just because they enjoy that process, of course backyard casting is the way to go.

Playing with fire and molten metal can be dangerous, but it can also be a LOT of fun, in spite of what the wife may advise.

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[Jasonb]

Interesting to see the dies for the waxes in that video Barry, My first IC was an Irvine Sport 40 in one of Jim Morley's Bell 47G choppers.

 

[peterl95124]

model engineering in the 21st century is this: iron lathes and mills made in the 19th century still work perfectly well, anything with a computer over 10 years old is obsolete, unmaintainable or unrepairable, and is pretty much useless.