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Post by don on Jan 1, 2021 20:13:35 GMT
I decided to try making a makeshift replacement blue knob to replace the one missing from the machine I gave my daughter. After +$20 in materials and several attemps I am going to stop with this version. I am sure others can improve on this experiment.
I tried making a mold from pure silicone but it never hardened. Children's play dough worked but was only good for one time. I tried two part epoxies and hot glue gun glue for the knob material. Durham water putty worked the best as it can be mixed with enough water so it pours and sets up hard over time.
I learned from an internet search that silicone hardens from exposure to water vapor and others have created molds using GENERAL ELECTRIC SILICONE #1 in a caulking tube and mixing it with corn starch that has been exposed to air that has absorbed moisture. They stressed that other versions of silicone will not work.
I lined a 1/4 measuring cup with plastic food wrap and mixed 2 ounces of GE #1 caulking gun silicone with 2-3 teaspoons of corn starch that had been exposed to air and placed my original FEA knob into the mixture to create a mold. The mold started to harden within five minutes. I added 2 TABLESPOONS of Durham water putty powder to a sandwich baggie and mixed it with enuf water so it was pourable. -2-3 teaspoons?- By cutting a corner off of the baggie the pourable mixture can be squeezed into the mold. I learned that you need to run a tooth pick along the perimeter edges to loosen up any air bubbles that are trapped.
I cut a 3/8" copper coupling in half and swaged it to fit tight in the hole of a steel washer and soft soldered it in place. The washer assembly was then epoxied to the back of the fascimilie FEA knob. A short piece of hardwood 3/8" dowel was used to extend from the copper coupling.
I plan on this being good enuf for my daughter's machine and am planning to spray paint it with white epoxy paint.
drive.google.com/drive/folders/1aymlkJzdsjk3kWT5rPi8f0H6MfuAAmgz
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Post by coldspaces on Jan 1, 2021 21:34:41 GMT
That looks pretty good. Thanks for sharing your methods.
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Post by turbokinetic on Jan 2, 2021 1:40:41 GMT
I decided to try making a makeshift replacement blue knob to replace the one missing from the machine I gave my daughter. After +$20 in materials and several attemps I am going to stop with this version. I am sure others can improve on this experiment.
I tried making a mold from pure silicone but it never hardened. Children's play dough worked but was only good for one time. I tried two part epoxies and hot glue gun glue for the knob material. Durham water putty worked the best as it can be mixed with enough water so it pours and sets up hard over time.
I learned from an internet search that silicone hardens from exposure to water vapor and others have created molds using GENERAL ELECTRIC SILICONE #1 in a caulking tube and mixing it with corn starch that has been exposed to air that has absorbed moisture. They stressed that other versions of silicone will not work.
I lined a 1/4 measuring cup with plastic food wrap and mixed 2 ounces of GE #1 caulking gun silicone with 2-3 teaspoons of corn starch that had been exposed to air and placed my original FEA knob into the mixture to create a mold. The mold started to harden within five minutes. I added 2 TABLESPOONS of Durham water putty powder to a sandwich baggie and mixed it with enuf water so it was pourable. -2-3 teaspoons?- By cutting a corner off of the baggie the pourable mixture can be squeezed into the mold. I learned that you need to run a tooth pick along the perimeter edges to loosen up any air bubbles that are trapped.
I cut a 3/8" copper coupling in half and swaged it to fit tight in the hole of a steel washer and soft soldered it in place. The washer assembly was then epoxied to the back of the fascimilie FEA knob. A short piece of hardwood 3/8" dowel was used to extend from the copper coupling.
I plan on this being good enuf for my daughter's machine and am planning to spray paint it with white epoxy paint.
drive.google.com/drive/folders/1aymlkJzdsjk3kWT5rPi8f0H6MfuAAmgz
Wow. That actually turned out very nicely! I like the silicone and starch mold idea. Will have to try that one for sure. Once the silicone and starch was mixed, how long did it take before it was fully cured, approximately? You mentioned 5 minutes for it to start hardening, but wondering how long before you could take the pattern knob out without messing it up? Have you every used casting resins? They are a lot more flowable and release air bubbles a lot better than regular 2-part epoxy. That might be one way to improve the detail of the knob markings, as opposed to water putty. Not saying it would be better, just curious if you've used both. I haven't used water putty. This is what worked well for me: www.hobbylobby.com/Crafts-Hobbies/Clay-Molding-Sculpting/Casting/EasyCast-Casting-Epoxy/p/27003 I needed to re-cast the lens in a control switch for a non-fridge project and used some of the casting epoxy, with a blue tint dye. It turned out amazing. |
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Post by don on Jan 2, 2021 2:37:06 GMT
I tried keeping the cost down for this experiment. Casting resins might be the cats meow especially if a shaft can be embedded on the back. Might need a jig for that. The lettering and arrows might need to be deepened on a created knob and then that knob used as the source knob for the best result. For my purpose the one I created is as far as I am going to go. www.instructables.com/How-To-Make-Your-Own-Sugru-Substitute/"It turns out that corn starch is highly absorbent and when sitting around in an open box it will absorb moisture from the air. It is an extremely fine powder that diffuses evenly in mixtures. By adding the right amount of corn starch, the sticky silicone is somewhat stiffened and very quickly starts to set up from the inside out. While it still sets up faster on the surface than in the middle, the whole thing will set up in five minutes to 2 hours no matter what the thickness. The actual curing time depends on the temperature, the humidity, the amount of corn starch added, and the speed at which it was mixed." |
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gmacy
New Member
Posts: 39
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Post by gmacy on Jan 2, 2021 3:12:17 GMT
I would live to borrow a knob for someone so I can scan an image of it and 3D print one ... I am a dentist and we have a digital scanner that creates a 3D stl file that I can export and ultimately print a knob
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Post by don on Jan 2, 2021 21:55:19 GMT
What area of the US are you located in? Others on this forum have said they would print one out but I have not seen any further communications from them. It would be nice to know if it were possible. Thanks
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Post by Travis on Jan 3, 2021 3:34:30 GMT
The folks that have done some 3D printing here have been busy. It’s always been my desire to see this knob reproduced, though admittedly after reproducing some DR parts I’d like to have.
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Post by Travis on Jan 3, 2021 3:37:43 GMT
I’ve always been interested in creating knobs as they’re frequently missing. I found this on YouTube awhile back. youtu.be/aNBHtlhlHF4 |
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gmacy
New Member
Posts: 39
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Post by gmacy on Jan 13, 2021 17:11:25 GMT
What area of the US are you located in? Others on this forum have said they would print one out but I have not seen any further communications from them. It would be nice to know if it were possible. Thanks Hi Don I am sorry for delay in replying... I am in East Texas ... an hour east of Dallas |
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mach
7 Cubic Foot
Posts: 135
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Post by mach on Jan 13, 2021 20:51:35 GMT
Can I borrow or buy one of these knobs from someone? I've got the casting materials to do this. Color matching would be trial and error but there's nothing complex about. If no one has a spare knob, can you measure and post the dimensions?
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Post by don on Jan 14, 2021 13:42:00 GMT
What area of the US are you located in? Others on this forum have said they would print one out but I have not seen any further communications from them. It would be nice to know if it were possible. Thanks Hi Don I am sorry for delay in replying... I am in East Texas ... an hour east of Dallas The reason I decided to come up with a home made FEA knob is that the one original knob I do own is attached to a refrigerator I have for sale at a fair price. For the price I am asking the new owner will receive the knob. I have talked with acquaintenances that have access to printers that say they use their CAD experience to program the printer to complete a project. Your access to a 3d scanner is unique and is new to me. I was hoping you were in the Minnesota area so I could deliver the knob so it could be scanned. Hopefully your offer being posted on this forum will find a knob owner in the Dallas area that can work with you. Thanks Don |
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mach
7 Cubic Foot
Posts: 135
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Post by mach on Jan 14, 2021 16:09:21 GMT
Do you (or anyone else reading) have a digital caliper that you can take measurements of the knob? I can CAD it with measurements, 3d scan an actual knob or cast it directly. I'm willing to give it a go.
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Post by coldspaces on Jan 15, 2021 4:12:14 GMT
Can I borrow or buy one of these knobs from someone? I've got the casting materials to do this. Color matching would be trial and error but there's nothing complex about. If no one has a spare knob, can you measure and post the dimensions? I have one I can send you. |
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mach
7 Cubic Foot
Posts: 135
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Post by mach on Jan 15, 2021 20:01:10 GMT
Thanks Coldspaces, I sent you a PM.
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