lost pla casting

4 Articles

Levitating Magnet In A Spherical Copper Cage

October 13, 2024 by 21 Comments

Lenz’s Law is one of those physics tricks that look like magic if you don’t understand what’s happening. [Seth Robinson] was inspired by the way eddy currents cause a cylindrical neodymium magnet to levitate inside a rotating copper tube, so he cast a spherical copper cage to levitate a magnetic sphere.

Metal casting is an art form that might seem simple at first, but is very easy to screw up. Fortunately [Seth] has significant experience in the field, especially lost-PLA metal casting. While the act of casting is quick, the vast majority of the work is in the preparation process. Video after the break.

[Seth] started by designing and 3D printing a truncated icosahedron (basically a low-poly sphere) in two interlocking halves and adding large sprues to each halve. Over a week, the PLA forms were repeatedly coated in layers of ceramic slurry and silica sand, creating a thick shell around them. The ceramic forms were then heated to melt and pour out the PLA and fired at 870°C/1600°F to achieve full hardness.

With the molds prepared, the molten copper is poured into them and allowed to cool. To avoid damaging the soft copper parts when breaking away the mold, [Seth] uses a sandblaster to cut it away sections. The quality of the cast parts is so good that 3D-printed layer lines are visible in the copper, but hours of cleanup and polishing are still required to turn them into shiny parts. Even without the physics trick, it’s a work of art. A 3d printed plug with a brass shaft was added on each side, allowing the assembly to spin on a 3D-printed stand.

[Seth] placed a 2″ N52 neodymium spherical magnet inside, and when spun at the right speed, the magnet levitated without touching the sides. Unfortunately, this effect doesn’t come across super clearly on video, but we have no doubt it would make for a fascinating display piece and conversation starter.

Using and abusing eddy currents makes for some very interesting projects, including hoverboards and magnetic torque transfer on a bicycle.

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Casting CNC Parts In Aluminium

April 16, 2019 by 19 Comments

When it comes to machining, particularly in metal, rigidity is everything. [Tailortech] had a homebuilt CNC machine with a spindle held in place by a plastic bracket. This just wasn’t up to the job, so the decision was made to cast a replacement.

[Tailortech] decided to use the lost PLA process – a popular choice amongst the maker crowd. The spindle holder was first sketched out, then modeled in Fusion 3D 360. This was then printed in PLA slightly oversized to account for shrinkage in the casting process.

The PLA part was then used to make a plaster mold. [Tailortech] explains the process, and how to avoid common pitfalls that can lead to problems. It’s important to properly heat the mold once the plaster has set to remove moisture, but care must be taken to avoid cracking or wall calcination. It’s then necessary to slowly heat the mold to even higher temperatures to melt out the PLA prior to casting. With the mold completed, it can be filled with molten aluminium to produce the final part. When it’s cooled off, it’s then machined to final tolerances and installed on the machine.

Lost PLA casting is a versatile process, and goes to show that not everything has to be CNC machined out of billet to do the job. It’s also readily accessible to any maker with a furnace and a 3D printer. If you’ve got a casting project of your own, be sure to let us know. Video after the break.

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Casting Car Emblems Via 3D Printing

March 28, 2019 by 10 Comments

Casting is a process that can be quite demanding for the first timer, but highly rewarding once the basic techniques are mastered. It then becomes possible to quickly and reliably produce metal parts en masse, and with impressive tolerances if the right method is chosen. [VegOilGuy] has been experimenting with lost PLA casting, and decided to see if it could be applied to car emblems. 

The process begins with 3D models of various car emblems, primarily sourced from Thingiverse. These are printed in PLA, with sprues added to assist with the casting process. The parts are sanded to avoid unsightly print lines on the finished product, and any voids filled with wax. The various emblems are then assembled onto a casting tree, with extra sprues added to improve metal flow with wax and further PLA parts.

The investment mold is then created with plaster, and baked to remove water and melt out the PLA. This is crucial, as any water left in the mold can react explosively with the molten aluminium bronze.  The mold is then filled with metal and then allowed to cool. The plaster mold is destroyed, and the parts can then be removed. Final processing involves a trip through a rock tumbler before final polish with sandpaper.

[VegOilGuy] gets impressive results, with the parts looking excellent in their bronze colour. This is an unconventional color for a car emblem, but it’s noted that this material is an excellent candidate for chrome plating to get a more OEM finish.

You might find your lost PLA casting experiments could benefit from the help of a microwave, too. Video after the break.

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Casting A 3D Printed Extruder Body In Aluminum

July 14, 2018 by 33 Comments

Creating 3D prints is great, but sometimes you need something more durable. [Myfordboy] printed a new 3D printer extruder in PLA and then used the lost PLA method to cast it in aluminum. You can see the results in the video below.

The same process has been used for many years with wax instead of PLA. The idea is to produce a model of what you want to make and surround it with a material called investment. Once the investment sets, heat melts the PLA (or wax) leaving a mold made of the investment material. Once you have the mold, you can place it in a frame and surround it with greensand. Another frame gets a half pipe placed and packed with greensand. The depression made by this pipe will provide a path for the metal to flow into the original mold. Another pipe will cut a feeder into the greensand over this pipe.

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