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3D Printing - "It's all about design and quality output. Not how fast the printer can run."

LWC Flask Covers

One of my most rewarding activities is designing jewelry and then creating the design using the process of Lost Wax Casting (LWC). This requires embedding the carved wax design in a plaster like material called “investment” within a metal cylinder called a “flask’.

This flask with the investment (which hardens on its own in about 15 minutes) and embedded wax master are fired in a kiln to 1350 degrees over a 12 hour period.


When the wax master is first put into the flask and before the investment is poured in, I like to cover the open end to keep out dust and any other foreign material. The investment is usually added to the flask several hours before going into the kiln. The goal is to have the investment hard, but not dried out (It is mixed with water like plaster.)

Sometimes the invested wax needs to be held longer than a few hours before being fired so a cover is useful to keep the water from evaporating after the investment hardens. The heat of the kiln does three things. It drives out the moisture, melts out the wax (the “lost wax” part) and turns the investment into a ceramic like mold material like a bisque.

The silver is introduced into the mold cavity while the investment is still about 800 degrees.

Ok, so I need a way to cover the open end of the flask at certain stages of the process because there may be delays. If Lost Wax Casts could be done in one continuous flow, the covers would not be needed.

I used to use whatever was handy to cover the open flask. But now I have 3D printing and custom plastic covers can be a reality.

I made a quick sketch and a few measurement notes to identify the major dimensions. This is never very high quality artwork. It doesn’t have to be. Quality drawing is what CAD does. I jumped into my trusty RhinoCAD program and created the cover design I had sketched.

From there I exported the design as an object file and looked at it in 3D Builder which is now supplied free with Windows 10. It is a designed-for 3D printing software. It permits adding and changing a few things outside of Rhino. It also does a better job than Rhino of creating .STL files that are suitable for 3D printers.

I print with either Cura or Simplify 3D. Simplify 3D is my favorite. Either will create excellent prints but I like all the options available in Simplify 3D. There are always options in software but I find it best to stay with one and become expert rather than dabble in everything available. At least as long as I can do what I want with what I have.

In the pictures, you can see the infill is 35%. I want the finished cover to be strong and the 35% also provides a good base for the solid cover that becomes the inside face of the cover.

The large cover is less than 34 grams, about $0.55 worth of ABS plastic. Run time was about an hour and twenty minutes.

It was a no problem to print out eight of these covers, four in 64mm ID and four in 77mm. My flasks are 2.5 inch and 3 inch. Also a no-brainer to make each size a different color.

They fit their flask well and are an example of designing simple 3D printed objects from scratch. It is so enjoyable for me to take and idea and turn it into reality and a useful product.

I added the KautzCraft name just because I could and it was fun building it into the CAD drawing. It doesn’t always print as sharp as I would like, but it does get the message across. If I ever sell or give some away, it will have my mark on it.

These could be made for pennies in a mass production commercial injected mold effort. I have never seen them offered by any casting suppliers. The market is so small, I can’t say there is a market. I am sure there already exists plastic caps this size made for something else that could be re-purposed. It’s just more fun to make my own. For me, that’s what 3D printing is all about. Why buy it when I can make it!

This is the simple sketch just to nail the dimensions  This is a Rhino graphic output. Showing here the inside of the cover. Nicer than my sketch :)
 This shows the design of the KautzCraft label. Note the rounded fillet on all edges.  Just finished the 2nd layer of the cap.
 The core of the cap is 35% fill. Good strength and provides support for printing the solid layers in the inside of the cap  The eight caps printed and how they fit on the casting flasks. They hold snug and will not fall off.
 The black rubber base comes off as well as the cap when the flask is put into the kiln. 1250 degrees burns up everything except the steel flask and the investment material.
 There is a lost wax carving inside this flask. The cover keeps debris out until the investment is added right up to the top...  

The Author

Ramblin' Dan Kautz

dankautzThere is no doubt one of my hobbies is writing about my hobbies. I read somewhere a long time ago, the best things to write about are the things you know very well. I have been writing and publishing long before the personal computer became the tool of choice.  My first printed and published club newsletter was created in the late 60's.

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Our Mission

The intention of this web site and “Ramblin’ Dan’s 3D Print Design Studio” is to promote creative design thinking and demonstrate how ideas can be changed to tangible creations through the proper application and use of Three-Dimensional Printing systems.

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