One of the pieces I need to make is this discharge nozzle. Other than buying a MillRight I'm unsure how I could make this shape out of foam. 4mm thick. I do not need the feet or square bottom flange. Just the cone shape. I welcomme any and all suggestions.
It would be fun to experiment with a small hot wire cutting table for that. I used to use hardboard templates and a large hot wire bow cutter for my watersports projects. That was followed by an electric planer and copious amounts of sanding. The people cutting RC plane wings have it down to a science. Maybe work in two pieces, a cylinder and an oversized cone and glue them together after you've achieved the shapes and thicknesses.
What tools do you have and what precision do you need? Could be done as Tops suggests. Do you have a router and woodworking equipment or a hot wire? Could also be done with a spinning jig and router bit in a drill press. What is the major diameter and height? Best, Kelly
Hey Tops and Kelly, yes I think that using a hot wire would work great for the outer diameters of the funnel (4" on one end x 1-3/4" on the other end), overall height of the funnel is 3". I'm thinking that if I built a small hot wire rotary table for the outer diameter, and then used a sanding plug for inner diameter I could make this work. First sand out the inner diameter, which is the outer diameter less 4mm of thickness, then mount that foam onto a plug that fits the inner diameters draft, then set that up in the hot wire jig to cut the outer shape. I'm concerned about using the hot wire to cut the inner diameter. How do I get the wire through the center of the foam, and I don't want to cut through the wall of the funnel. If i built another jig that let me make the discharge nozzle, 1-3/4" ID with a wall thickness of 4mm, I can just glue that to the first piece. Kelly, I want to tell you that I have spent a great many hours watching your videos, and they have crystallized so much for me. Can't wait to finally pour some hot metal! Is there a group of guys that have pooled some $$ together to buy a batch of the Poly Cap 600? I'd like to try that but I don't need 10 5 gallon buckets - I'd never use that much. By the way, what is a spinning jig? I do have a Precision Matthews lather and mill, and a hand held router, but no router table.
This guy has one of the most complicated foam cutters I've ever seen. If you just have the ability to cut circles and angles, you should be able to make your part in sections and glue them up. Circular Cutting Board 2.0: Crafting Cylinders, Pillars and Domes - YouTube
You can see from the video Jammer posted there are a couple examples of circle jigs. There's really not much concern about piercing the wall to cut the ID of a cylinder. The kerf is so thin, just a little glue restores the cut. To make cones, you just need to be able to hold the circle jig at the desired angle and you get cones instead of cylinders. There are a lot of nuansce things to learn in hot wire cutting, but with practice, you can make pretty complex patterns of decent quality. A couple of things you will learn quickly; you cannot dwell while cutting, you need to keep the stock moving or the wire will locally melt deeper than the cut damaging the pattern. There is an optimal heat to operate the wire. Too hot and you will have to move the stock too fast for adequate control to avoid burn-in to the pattern. Too cool provides a lot of control but will create a lot of wire deflection, so dimmer switch control for heat and a little experimentation is very important. Also, It's helpful that the upper support arm is very stiff so it doesn't deflect under cutting load. It can be wood. A lowersupport eye and an adjustable upper support eye for the wire that can be adjusted to the stock height helps minimize wire deflection. Adjustable spring tension on the wire is also helpful. Here is mine: Hot Wire Build | The Home Foundry Best, Kelly
