3D Printing Stainless Steel Nozzle

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So at my school they got a Markforged Metal X printer earlier this year. So naturally I wanted to try and print a nozzle for my 29mm motors. Motor details will be left out, but it is for sugar motors. I'm not sure when I'll be able to static fire this but I will post the results. I'm posting the thread now to see if anyone else has heard of an amateur/hobbiest using a 3D printed nozzle? I know there are companies doing it on a sub-orbital/orbital scale.

This is as is after the wash and sinter. Due to issues with the wash and the sinter it has been a process of 5 months from when this part was first printed till it was finished.

And this is the nozzle as it stands with the bottom raft and support removed. Despite what Markforged claims, the support does not just pop off and I am going to have to take this thing to a lathe to get the o-ring groove cleaned up. I was hoping to be able to print nozzles and use them as is but that isn't the case. As for dimensions, it'll also need to be cleaned up to fit the casing due to a ridge from where it contacts support material.

Plan is to machine it tomorrow and then I'll post pictures of the final product as I will use it in a motor. Also I will compare its weight to a turned nozzle to see if there is a difference with this having a supposed 30% infill. I don't expect much of a difference as this part is so small and is likely mostly just perimeters.

 

[Hobie1dog]

cool stuff

 

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At 40.92grams the nozzle is ~91% of the calculated/modeled weight. There is a small amount of infill in the thicker portion of it though most of it is perimeters. The support material was a pain to remove from the o-ring groove but I got it out. Next nozzle with have some changes and will be printed at a larger throat size.


I love this photo because you can see how nicely the edge cleaned up on the lathe versus the raw printed convergent section. One future change will be adding a fillet to the edge of the throat so that it isn't a sharp transition.

This macro shot of the side is also pretty good. The inside of the o-ring groove isn't great because of the difficulty in getting the support out. I basically was turning it until it finally popped out. The rest of the surfaces you see are turned. There are marks from the chuck. The support had breaks in it that were supposed to allow it to pop apart, instead those gaps caught on the grooving tool and snapped two inserts before I found a working feedrate (aka VERY slow).

Likely won't get to casting grains until Thanksgiving break (thanks senior design), but I should have the time to make at least 3 motors for this nozzle. Testing might not happen till after the semester ends in December though as there are issues with the local field. Most of the test data will be posted in the research sections, but I will update this thread with the condition of the nozzle.

 

[alexzogh]

Curious - given you have access to a lathe, which process would you find easier? I know which is cheaper!

 

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Curious - given you have access to a lathe, which process would you find easier? I know which is cheaper!

When I had my lathe I would say it was easier due to how well it was maintained. The one I have access to isn't in as great of shape and I don't think I could make a nozzle from a stock and have it come out with the tolerances I like because flipping things in the chuck adds too much runout compared to what my lathe had. The printed one is faster in terms of my time since I can just pop it on and clean it up (in theory if the support comes off). With the new nozzles printing we will see but I likely would only need to do maybe 5 mins of machining vs close to an hour per nozzle (making multiple as once was faster but for 1 at a time I would take close to an hour including polishing the converging and diverging sections).

Right now printing is cheaper, easier, and less of my time, but thats cause I simply submit the file and it gets printed for me for free.

 

[dhbarr]

When I had my lathe I would say it was easier due to how well it was maintained. The one I have access to isn't in as great of shape and I don't think I could make a nozzle from a stock and have it come out with the tolerances I like because flipping things in the chuck adds too much runout compared to what my lathe had. The printed one is faster in terms of my time since I can just pop it on and clean it up (in theory if the support comes off). With the new nozzles printing we will see but I likely would only need to do maybe 5 mins of machining vs close to an hour per nozzle (making multiple as once was faster but for 1 at a time I would take close to an hour including polishing the converging and diverging sections).

Right now printing is cheaper, easier, and less of my time, but thats cause I simply submit the file and it gets printed for me for free.

I really appreciate how thoroughly you've considered your time tradeoffs here.

 

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I really appreciate how thoroughly you've considered your time tradeoffs here.

Thanks. With classes taking as much time as they do I really have been learning how to value my time better.

 

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So an update for this. I had two more nozzles printed. I'll post pictures later but they have already been cleaned up on the lathe. These are only 27 grams due to infill and I'm excited to see if they hold up. I am making a new set of casting hardware and plan on getting grains made before the end of the year. Static fire information will be in the research forum but I will post pictures here of the nozzles afterwards. Plan is for mid January hopefully right before classes start. Only snag may be that I will have to travel due to the uncertainty around our local field again. If I can't fire there then I will likely reach out to another club, either Culpeper or ROCC.

 

[kramer714]

Are you concerned thatthe weight is 91% of modeled? Can that be due to porosity?

 

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Are you concerned thatthe weight is 91% of modeled? Can that be due to porosity?

It's water tight, but also I realize that I weighed it post machining so I likely removed a bit of weight there. Also not sure how accurately Inventor calculates the weight from density.

 

[kramer714]

You should be able to get the volume exactly from any cad system. Should calculate the weight exactly (assuming the density is correct). Did you do a quick check of the OD and length to see if the shrink factor after sintering is right? Just to calibrate the final part dimensions to the cad model for a weight / volume / destiny calculation.

Not sure what alloy you used, Inconel 625 has a SG of 8.4. SLS Inconel parts that I have used in the 'day job' had to be HIP (Hot isostatic Press) to remove porosity, I forget the number but porosity was well under .5% SLS is different than what you used, I'm not sure what the shrink factors and processing is like on parts made the way you did. MarkForge claims 96% density of Wrought alloy for Inconel. 91% seems really low. Not sure how that would affect the application as a nozzle....

BTW - Cool that you are trying this!

 

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Second nozzle I printed, after two burns now. This one had a radius in the o-ring groove for better printing, and a radius on the convergent side where it meets the throat. Also is a larger throat than the other one. The first one has been fired once and will be fire two more times tomorrow and then I will post pics of it. Interesting to note that it didn't smooth the layer lines like I anticipated. The motors it experienced peaked at 250psi first and then 500psi for the first and second burn. Last two are the highest pressure motors so we will see what they do to the layer lines.

 

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First nozzle that was printed. This one did not originally have a fillet. Peak pressure it experienced was 1150psi on its third burn.