Low-Budget Hydroformer Puts the Squeeze on Sheet Metal Parts

Between manufacturing technologies like 3D-printing, CNC routers, lost-whatever metal casting, and laser and plasma cutters, professional quality parts are making their way into even the most modest of DIY projects. But stamping has largely eluded the home-gamer, what with the need for an enormous hydraulic press and massive machined dies. There’s more than one way to stamp parts, though, and the budget-conscious shop might want to check out this low-end hydroforming method for turning sheet metal into quality parts.

If hydroforming sounds familiar, it might be because we covered [Colin Furze]’s attempt, which used a cheap pressure washer to inflate sheet metal bubbles with high-pressure water. The video below shows a hydroformer that [Rainbow Aviation] uses (with considerably less screaming) to make stamped aluminum parts for home-brew aircraft. The kicker with this build is that there is no fluid — at least not until the 40,000-pound hydraulic press semi-liquifies the thick neoprene rubber pad placed over the sheet metal blank and die. The pressure squeezes the metal into and around the die, forming some pretty complex shapes in a single operation. We especially like the pro-tip of using Corian solid-surface countertop material offcuts to make the dies, since they’re available for a pittance from cabinet fabricators.

It’s always a treat to see hacks from the home-brew aviation world. They always seem to have plenty of tricks and tips to share, like this pressure-formed light cowling we saw a while back.

Thanks for the tip, [Noah Orr].

19 thoughts on “Low-Budget Hydroformer Puts the Squeeze on Sheet Metal Parts

  1. I just looked on eBay for rubber blocks – apparently you can get a 4″ x 4″ x 0.75″ block for about $9 with free shipping.

    It’s called a “jeweler’s block”, and two of those might work for a smaller system.

    Does anyone know where you can get big pieces of rubber (that might work in this application) cheaply?

      1. Derek Anderson: I think this is a dead end – “old” tires don’t have a lot of rubber left outside the belts, and don’t have a whole lot of rubber on the inside, either. And the belts themselves would keep the rubber from flowing the way it needs to for this to work.

  2. I’m always excited to learn new ways to make parts, especially parts that can’t be made with just a band saw and drill press. This opens up some possibilities.
    Now all I need is a similarly easy way to cut the sheet metal blanks to the pre-formed shape, that’s just as simple.

    1. Rule die. It’s a thin strip of hardened metal (e.g. a scrap bandsaw blade) bent to shape and secured by a matrix (e.g. epoxy resin). The rule needs to clear the matrix by the thickness of the metal sheet to be cut. Make sure the edge of the rule is square. For simple shapes use strips of hardened ground stock.

      The other option is to make a silhouette of the desired shape of thin ground stock and harden.

      In both cases place the sheet stock on top and proceed as with shape forming. This is primarily a soft metal forming process.

      1. Reg: thanks for the tip. I’ve seen dies made for cutting paper or cardboard that have structures like you describe, and I can see how these could be used for materials like aluminum and brass sheet, but I’m just not sure how to make the dies. I can see using hacksaw blades or something similar, but it seems like it would be difficult to bend the steel strip into the desired shape, so I’m wondering if there’s a way to “grow” a die using something like plating and/or etching operations to get the precise shape desired, of a material hard enough to be used for cutting blanks. Just casting about for ideas, here.

    1. It is commonly called a hydroformer. They made them during WW II the size of a couple bowling alley lanes. In one operation they could form a huge quantity of parts such as wing ribs. Preferred die material at the time was micarta. The book I have showing the giant press is MIA at the moment or I’d supply a citation.

      You can do VERY much more sophisticated things. Search on “Bonney Doon Press” and you should be able to find some spectacular examples of bracelets and other jewelry made with them.

    1. Or for that matter, whether a solid slab of an appropriate hardness of urethane would be cheaper than rubber, and whether it would work as well.

      But your point is well taken. I think it would work, and probably better than rubber. The disadvantage is that a given urethane negative would only be good for making that particular part. Might be good for a high-volume run, since it would probably outlast a block of rubber, but you have to be making enough copies to make it worth the price of the urethane.

    2. Urethane work very well. As you move toward harder durometer’s though, you can begin to get some cracking on thinner urethane sheets. We use urethane pads (aka – wear pads) that help set details into parts and they also protect the Bladder in hydroform presses.

  3. A further comment, slightly off topic. Short run hydraulic press work is often done using Kirksite (a trade name for a zinc alloy aka “pot metal”) dies. Die life is dependent upon shape and size. Common life is 10,000-15,000 parts. The neat thing about Kirksite dies is the metal can be cast using carved plaster of paris molds. Carve the male side, place release agent on the face and pour the female die. This was widely used for aircraft parts like fuel tanks during WW II. A single die set would last the entire production run.

    YOU HAVE TO DRY OUT THE PLASTER OF PARIS IN AN OVEN AT 250 F FOR 24-36 HOURS BEFORE POURING METAL!!!!!

    Probably longer if it’s a big die. Get a die design book or two if you want to try this and start small. There’s a lot of fine print to doing this.

    1. It’s not off topic at all, since part of the process is making the die, and the original video shows an example of die-making by carving Corian. This sounds like a good idea. You can carve a positive model out of wood, wax, or clay, your preference, then a negative of plaster, then a positive of zinc or zinc alloy. Or lead, or solder, or some other low-melt alloy. The good part is that the metal positive is easily melted down again for later projects. You keep the plaster negatives, of course, because you can make a new positive every time you need to produce more parts. Zinc can be melted on a hotplate, as can lead. Just don’t melt zinc with tools that have ever been used for melting lead, as this will lead to “zinc rot” (https://en.wikipedia.org/wiki/Zinc_pest).

  4. I am the Technical Sales Manager for the Beckwood/Triform press company in Fenton MO. We build Hydroform’s, both Deep Draw and Fluid Cel models. We didn’t invent the process but we did re-invent the way it works for our customers. I have been involved with Hydroforming for over 45 years now and having owned them, purchased them for companies I have run, consulted with Verson on their design after they purchased the product line from Cincinnati (the creators of Hydroform’s) and co-designed a new model for a company that I was running Deep Drawn lighting products for at that time. What you are describing above is a rubber pad press. We build them at Beckwood in any size bed/box our customers might need. The real problem with a rubber pad press is, the rubber makes all its pressure on the top of the part while the pressure quickly diminishes as it begins to form over the sides of the tool and part. This leaves the parts needing hand work as you alluded to. The real Hydroform process, has a bladder made of urethan, neoprene or rubber. The bladder contains oil behind it and once it engulfs the part and material, it make equal pressure at every point over the entire surface of the product being formed. This leads to completely formed part in most cases. To my knowledge, there is no Aerospace end users, that will allow suppliers to form fully hardened aluminum alloys as the material grain structures are compromised during the forming process. To add to that problem, hand working afterward, would compromise the material even more.
    We recommend 3D printed tools to our customers and Ultem material can withstand up to 10,000 psi for thousands of parts. We also use epoxies and basically anything the can’t be compressed to form on with the real hydroform process. Very inexpensive tooling.

    I must say that this is a great way to form parts in your garage and I salute you for you innovative approach at recreating the rubber pad press but … this is not a Hydroform process. And, I would not use it to form parts in any type of aircraft that I needed to fly in! Just my humble opinion. Please see the videos attached in the links below.

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