Metal 3D print

I was going to fabricate this part from brass but then started thinking about maybe a 3D print in stainless steel offered by PCBWAY. I first printed a few in PETG to get the fit just right then uploaded the STL file to their site. I deleted the through hole and mounting holes also adding some additional material to the upper flange just to be safe in case the printed size was off a little. The part took about about 10 days from placing the order and arrived today. I must say I was quite impressed! The material drills and grinds like tough stainless, no voids and the dimensional accuracy is excellent. Very happy with the result.

Crueby on MEM is using a 3D printed metal bucket in his RC cable shovel build.
RC cable shovel build

He expressed an almost identical opinion regarding the quality of his parts.

"SLM printing, laser melting of a metal powder".

Most interesting process.
Hard to keep up these days.
I saw a comic strip one time, and a hippy guy say "The times, they be a changin".
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Yet another new process (to me):

https://www.pcbway.com/rapid-prototyping/3d-printing/3d-printing-VC.html

I have used PCBway to print a Sugden Special crankcase. The accuracy and finish is generally good but there is evidence of what looks like post-print fettling which has left some minor marking in places. The only major issue is that the four radial mounting lugs have warped forwards so they may become rather fragile when machined flat. Price and delivery were good, about $30 and 10 days respectively.

As an experiment, Preso had some pieces through an online vendor made using the same process to create the raw center portion of some die holders he was making for a giveaway.



About 5 mins into the video he starts on the machining. Seems to go well but as the parts are stainless you have the usual annoyances.

That Sugden special crankcase looks to have come out quite well and the price is around what you might pay for a casting of an available design and less than a rare design that will attract a premium if one comes up for sale.

$30 is not at all out of line, and not really that deep of a bite into the pocketbook. Maybe you consider the 1st Sugden Special a practice run and have them print another? Only this time allowing extra material on the lugs for machining them flat, or anywhere else that you find needs it.

The accuracy of the selective laser melting (SLM) process is specified as plus and minus 0.3mm so I made the crankcase and cylinder bores well undersize to ensure there was plenty of meat to machine. The front housing is left solid so there was no danger of inaccuracy in a printed hole pushing a drill off line (probably an unnecessary precaution). I took pot luck on the exterior and used nominal dimensions figuring that something usable would emerge even if printed dimensions were a bit off in places. The warped lugs took me by surprise.

The SLM process guidelines mention that overhanging parts should be provided with support because the metal powered won't carry the weight. Not knowing how they would orient the part during printing I had hoped that their stl file checking process would pick this up and issue a warning, but there wasn't one. My expectation I suppose was that it would be printed with the backplate lugs supported on the baseplate so that there would be no possibility of droop. If it had been printed the other way up, crankshaft housing down, that might explain the effect. What little evidence there is of layering suggests it was printed in the normal upright orientation so droop wouldn't come into it.

I plan to print another one with a few minor variations to thicken up the lugs and add a chucking boss to make the early stages of machining easier. Hopefully PCBway can provide some information on how they orientate parts and design guidelines for support structures.

When you consider the alternative, pattern making and the task of finding a foundry willing to take on such a small job, $30 is a small miracle. No-one seems to offer cast iron printing, is it lack of demand for an old-fashioned material or something technical about high carbon steel?

At that price it would hardly be worth firing up even a home foundry.

PM me if you want the name of a UK foundry that will do one offs, though they mostly do iron they also do aluminium, couple of castings from my patterns that I machined the other day, flywheel is iron

f2cf1g said:

I have used PCBway to print a Sugden Special crankcase. The accuracy and finish is generally good but there is evidence of what looks like post-print fettling which has left some minor marking in places. The only major issue is that the four radial mounting lugs have warped forwards so they may become rather fragile when machined flat. Price and delivery were good, about $30 and 10 days respectively.

Click to expand...

These examples are quite encouraging. I assume this (link) is the alloy of your crankcase? Have you printed test pieces or progressed on actual engines to see how certain typical model engine features might be more challenging, or at least 'different'? I'm thinking our typical fine threaded holes, or fragility of thin sections like cooling fins, operating temp heat & cool down cycles.... things like that.

https://www.pcbway.com/rapid-prototyping/3d-printing/metal/aluminum/Aluminum-0/

Yes, that must be the alloy, they only offer one for SLM printing I think. As to test pieces, this is it. My only motivation was to get a Sugden Special crankcase to work on so I haven't considered any other experimentation. The design was done in Fusion and the stl file sent off to PCBway without further ado. It was my first attempt at any form of 3D printing and the simplicity of the process is impressive.

As to the sort of finer detail you refer to, the web site has several warnings about accuracy of dimensions and quality of surface finish to be expected and, if I remember rightly, a minimum wall thickness constraint of 1mm. The only part that could be called fine detail is the venturi. The trumpet and its outer edge have come out well but the needle valve bosses are less precise. I haven't done any machining so the quality/fragility of the material is yet to be determined but the case feels solid and strong.

Jason, thanks for the offer, those castings are impressive!

Jasonb said:

At that price it would hardly be worth firing up even a home foundry.

Click to expand...

But you don't get a chance to play with fire......

I call it the "fire-fun-factor" (FFF = 10 out of 10).

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Looking at the picture of the Sugden casting I assumed that it was printed with the rear of the case down and that the lugs has warped toward the nose. I guess I never thought that it might have been printed in some other orientation. Does the casting give any hints which way it was printed?

Pat you do get to have your part if time is limited rather than only being able to play with fire once or twice a decade

I had a play with the PCBWay website but could not get anything to happen when I clicked to say the part included threads, would like to have seen the cost change. The example shown is possibly the best way for most of us, treat the print as a casting and do the final machining from there.

I also put a few other STP files into the online pricing form, one which was a sole plate for a small steam engine would have cost about 10 times what an Iron casting would cost me. Retail costings for castings would be a bit closer. Infact the price they gave to CNC cut it from 6061 was cheaper than the ali print.

I have farmed out 3D prints, before I purchased a Prusa.
It all depends on what works out best for the individual, or how involved someone wants to get in the hobby.

I am a big proponent of backyard casting, and wish everyone could learn it and use that process.
It is unfortunate that backyard casting can be someone tricky to do.
Finding good molding sand, and making good molds seems to be the biggest drawback I see.

And I had high hopes for those small electric furnaces, but from the videos I have seen, crucible life may be problematic.

I have seen some very promising hobby castings posted here, and that is exciting.

I am going to go out in the backyard right now and burn some wood or sticks, just for fun, so I can imagine having time to do castings.

As far as I am concerned, making your own engine castings is the holy grail of modeldom.
Its a high adrenaline sport. Sort of like going CNC; once you cross over, there is no going back.
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Instead of burning sticks why not spend the time filling and sanding some of your prints, at least that way you will be one step closer to casting them.

I am traveling, so I will have to settle for burning sticks.

Edit:
I hope to get dual foundries set up one day, so I can cast wherever I am.
That is coming; I have a 2nd shop set up; just need to move one of my furnaces.

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Re the print orientation, as mentioned it in my first post, it seems to have been printed with the cylinder bore upright but its not very clear. I'd like to know more about the process.

This 3d metal printing is both encouraging and discouraging, for me, at least.
It is encouraging because of the seemingly limitless possibilities that are available right NOW, and for the new ones that will be developed in the future. The new processes are being developed sooooo fast.

And at the same time, it is discouraging because the new processes are being developed sooooo fast! LOL. I can not keep up. I actually bought an Alibre 3d package years ago but have not learned to use it. Still stuck on 2d autocad. I think it will take a boot print in my butt to make me learn the Alibre package. It is such a paradigm shift from 2d. I feel like if I could set down with someone for a day or two I would be well on my way. But at 73, I don't know if I will learn it in my lifetime. But I really do want to, but I already stay busy all waking hours of the day. Yes, I know, adjust my priorities.
Sigh.

But this process surely does look sooooo cooool.

Lloyd

Come on Lloyd, I learnt Fusion to a useful level a couple of years ago, at the age of 77. It's nowhere near too late. I suspect there are plenty of teaching videos on Youtube. Going back to Autosketch is like stepping back into the dark ages!