Gary_Ash Posted June 24, 2023 Share Posted June 24, 2023 My 1963 Studebaker Wagonaire station wagon needs new rubber seals for the rear quarter windows. The glass is almost 4 ft long, has a corner with a 1" radius. The factory seals are no longer available but Steele Rubber has some standard extrusions that can be used for 95% of the seal. They are a bit taller than the originals, but close enough. The originals also used stock extrusions with two molded corner pieces vulcanized or glued together. I ordered copies of the original drawings of the extrusions and seal from the Studebaker National Museum archives. Using those, I drew the piece for the sharp corner in my TurboCAD Pro program. Then I drew a rectangular block and "subtracted" the rubber part from the interior of the block, then "sliced" the block from top to bottom. I added two alignment pins and sockets in the two halves of the mold. The two mold pieces were then printed out on my Creality Ender 3 printer in PLA plastic. On the advice of Studerex, I ordered some liquid urethane casting material (PMC-121/30 "Dry") and black pigment from Smooth-On. With 12 grams of Part A in one small cup and 12 grams of Part B plus 4 drops of black pigment in a second cup, I stirred it up, and poured the Part B into the Part A cup, more stirring. The mold halves got coated with Butcher's Paste Wax as a mold release. I didn't want to use silicone mold release because adhesive might not stick to the parts later. I clamped the mold halves tightly together and poured in the liquid urethane. It was about the consistency of maple syrup. After 16 hours of curing, I unclamped the mold and tried to slide the part out. One side of the mold captured the rubber very tightly, so I had to pull and push quite a while to get the part out - a different mold design next time! But, once out, the part is very good. It got cooked in a small toaster oven at 150 °F for 6 hours to complete the cure and toughen it up. The part is the right size and shape, about the hardness I wanted and very flexible, and fits the corner of the glass. Now I have to order about 20 ft of the extruded materials from Steele Rubber. It isn't cheap but it is available. Then I'll miter two corners and glue the cast part in with black weatherstrip adhesive to make the two gaskets I need. The 1963 Studebaker Wagonaire Standard in progress. The tight corner on the rear quarter seal. Mitered corner at bottom left. CAD model of the corner piece. The 3D printed mold for the corner. The mold halves together. Liquid urethane rubber poured into mold. Test fit of cast corner on glass with Steele Rubber extrusion. Old seal in back. 23 1 Link to comment Share on other sites More sharing options...
37_Roadmaster_C Posted June 25, 2023 Share Posted June 25, 2023 This is a REAL and PRACTICAL use for 3D printing. GREAT work Gary!! I am just starting with 3D printing and enjoy seeing things like this. I hope to see more. 3 Link to comment Share on other sites More sharing options...
60ch Posted June 25, 2023 Share Posted June 25, 2023 Thank you for this post! It is great to hear about a challenge and how it was overcome with available technology. I'm sure that there are many in this group that have obsolete rubber seal issues. Terry Link to comment Share on other sites More sharing options...
nickelroadster Posted June 26, 2023 Share Posted June 26, 2023 When there is a will there has to be a way. I have cast some parts in urethane rubber but none quite so complicated as this. Impressive! Link to comment Share on other sites More sharing options...
Buffalowed Bill Posted July 5, 2023 Share Posted July 5, 2023 I'm just curious whether the molds that you produced are reusable, and what earlier wagons the parts might fit? Link to comment Share on other sites More sharing options...
Gary_Ash Posted July 5, 2023 Author Share Posted July 5, 2023 Yes, the molds can be reused. I actually made 4 parts, only need two. The corner fits ‘63-‘66 Wagonaires. Link to comment Share on other sites More sharing options...
bryankazmer Posted July 5, 2023 Share Posted July 5, 2023 Nice work! My only suggestion is to add about 2 degrees draft angle to help the release. Shouldn't impact part function. Link to comment Share on other sites More sharing options...
Gary_Ash Posted July 6, 2023 Author Share Posted July 6, 2023 3 hours ago, bryankazmer said: My only suggestion is to add about 2 degrees draft angle to help the release. Shouldn't impact part function. Pouring in the liquid urethane completely fills any cavity so draft angle doesn't help when casting. I should have made the mold in 3 or more pieces to separate the mold parts from the rubber when I disassembled the mold. As it was, 5 to 10 minutes of pushing and pulling got the cast part out of the mold without tearing the rubber but it wasn't easy. When I laid out the 3D print for the mold, I had not realized that a recent upgrade of my CAD software allowed me to "slice" with a curved surface or the extrusion of any complex line. The trick seems to be to lay out a complex line to be used as a slicer and extrude it as a zero-thickness surface, then subtract it from the solid. That leaves two parts that still mesh together with nothing missing. With the mold parts in 3 or 4 pieces, it will still need alignment pins. Using some other slippery mold release beyond the Butcher's Wax might also help. Link to comment Share on other sites More sharing options...
bryankazmer Posted July 6, 2023 Share Posted July 6, 2023 The draft will still help after the first movement of the part away from the bottom of the cavity, but this part wants to stick. You've already got the parting line in the best spot. A metal soap like a stearate would be a possible mold release, as these are also common ingredients in the EPDM or fPVC that the extrusion is likely made of. It won't be as slippery as a silicone (I agree, don't!) or a paraffinic wax, but less of a risk for later adhesion. I'd still clean the surfaces with iso propyl alcohol before bonding. The typical commercial process uses a primer on the extrusions, which are held in the mold for either reaction injection of urethane or regular injection of PVC. If you have adhesion problems getting a sample of the primer might help. I recall one supplier was Lord, later bought by Dow. The other major supplier is eluding me. Again, great job Link to comment Share on other sites More sharing options...
jp1gt Posted July 8, 2023 Share Posted July 8, 2023 I appreciate your posts. Gives me incentive that I can always do more-- Link to comment Share on other sites More sharing options...
DavidTaylor Posted September 6, 2023 Share Posted September 6, 2023 Casting rubber parts in a 3D printed mold involves using a mold created through 3D printing technology to shape and form rubber materials into specific designs. This process starts with the 3D printing of a customized rubber mold, which is then used as a cavity into which liquid or molten rubber is poured or injected. Once the rubber cools and solidifies within the mold, it takes on the mold's shape and details, resulting in the desired rubber part. This method is particularly useful for producing small to medium quantities of rubber components with intricate or custom shapes, offering flexibility and cost-effectiveness in production. Link to comment Share on other sites More sharing options...
californiamilleghia Posted September 6, 2023 Share Posted September 6, 2023 Thanks for posting this , I need to kick off the dust from my 3D printer and make some stuff Link to comment Share on other sites More sharing options...
Gary_Ash Posted September 7, 2023 Author Share Posted September 7, 2023 David Taylor, are you an AI bot? 2 1 Link to comment Share on other sites More sharing options...
Littlestown Mike Posted September 9, 2023 Share Posted September 9, 2023 Glad to see this! What an ancouragement for others who are stuck with small parts that are NLA! Link to comment Share on other sites More sharing options...
dodge28 Posted September 10, 2023 Share Posted September 10, 2023 Congratulation, Nice work. Link to comment Share on other sites More sharing options...
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