Resin cast & 3D printer parts replication

I'm a huge proponent of 3D printing (additive manufacturing). Where it really shines is in recreating parts for which you don't have a master to mold from, or where the original was created with casting, machining, or molding processes which are not feasible to replicate for one or a small batch of parts. It really is a modern miracle in what you can do with it.

If you look in my thread here, you can see part of my process for creating a replica washer discharge spout for a Mustee Duratub 93 laundry sink.
www.automaticwasher.org/c...
I have some other washer-related parts I've 3D printed, but haven't shared yet...

That being said, 3D printing might not quite work the way you'd like for your projects. In particular, 3D printing tends to leave parts with "layer lines"... microscopic ridges... as part of the process, which makes the printed parts difficult or impossible to fully clean. There are ways around this, particularly with sanding or chemical treatments, or printing on higher caliber (commercial/industrial) machines that use different processes. In the end, for practicality, you may find that your 3D printed part becomes an ideal candidate as a "plug" or "buck" for mold making, with your "actual" parts then being produced from casts within those molds.

There are secondary issues with 3D printer materials. These are not dead-ends, but things to be aware of if someone says "Yes, my friend has a 3D printer! She could do that for you!".

The vast majority of 3D printers have an extrusion nozzle made of brass, which typically contains around 1-2% lead. Therefore, a printer printing items for food contact would need to have all of the brass components (nozzle, heat break, extruder drive gears, etc) replaced with alternate parts made from metals which do not contain lead, such as stainless steel. Stainless is not as good of a material in some of these applications, so it would be a special use case that makes someone switch to stainless.

The plastics used also must be selected carefully. Some plastics are definitely not food-safe, while others generally are. But those that are will come with documentation (MSDS), and will cost a fair amount more. Also, being food-safe is not a characteristic of the plastic type (Polyethylene, PLA, etc), but rather the specific batch you've received. Almost all 3D printing plastics (called "filament") contains additives to improve printability and mechanical properties, as well as to change the color, opacity, etc. So while the plastic type may be generally food safe, the resulting product might not be after the additives are mixed in.

So it's an amazing technology for all kinds of part reproductions - it just might not be a good match for your needs, since your parts will see direct and repeated food contact.


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Post# 1045160 9/17/2019 at 10:14 (1,682 days old) by sarahperdue (Alabama)
Checkrate/Likes Are any of you messing about with either of these methods for replacing missing parts? I'm going to attempt to cast my wall fridge missing and broken butter conditioner doors with clear poly resin from Abatron. I have no 3D printing experience, but it seems like a technology that would enable one to recreate more complicated parts--like the Americana auto fill ice cube trays. Thoughts? Ideas? Sarah

Post# 1045162 , Reply# 1 9/17/2019 at 10:21 (1,682 days old) by sfh074 ( )
Checkrate/Likes *I would suggest this ....* Used this for a clear washer knob and it worked well. Use a high grade platinum silicone to make your mold. Lots of good videos on this site as well. www.alumilite.com/store/p... Here it is from a couple of years back when I did it. www.automaticwasher.org/c... Bud - Atlanta

Post# 1045203 , Reply# 2 9/17/2019 at 18:09 (1,682 days old) by LowEfficiency (Iowa)
Checkrate/Likes 1 I'm a huge proponent of 3D printing (additive manufacturing). Where it really shines is in recreating parts for which you don't have a master to mold from, or where the original was created with casting, machining, or molding processes which are not feasible to replicate for one or a small batch of parts. It really is a modern miracle in what you can do with it. If you look in my thread here, you can see part of my process for creating a replica washer discharge spout for a Mustee Duratub 93 laundry sink. www.automaticwasher.org/c... I have some other washer-related parts I've 3D printed, but haven't shared yet... That being said, 3D printing might not quite work the way you'd like for your projects. In particular, 3D printing tends to leave parts with "layer lines"... microscopic ridges... as part of the process, which makes the printed parts difficult or impossible to fully clean. There are ways around this, particularly with sanding or chemical treatments, or printing on higher caliber (commercial/industrial) machines that use different processes. In the end, for practicality, you may find that your 3D printed part becomes an ideal candidate as a "plug" or "buck" for mold making, with your "actual" parts then being produced from casts within those molds. There are secondary issues with 3D printer materials. These are not dead-ends, but things to be aware of if someone says "Yes, my friend has a 3D printer! She could do that for you!". The vast majority of 3D printers have an extrusion nozzle made of brass, which typically contains around 1-2% lead. Therefore, a printer printing items for food contact would need to have all of the brass components (nozzle, heat break, extruder drive gears, etc) replaced with alternate parts made from metals which do not contain lead, such as stainless steel. Stainless is not as good of a material in some of these applications, so it would be a special use case that makes someone switch to stainless. The plastics used also must be selected carefully. Some plastics are definitely not food-safe, while others generally are. But those that are will come with documentation (MSDS), and will cost a fair amount more. Also, being food-safe is not a characteristic of the plastic type (Polyethylene, PLA, etc), but rather the specific batch you've received. Almost all 3D printing plastics (called "filament") contains additives to improve printability and mechanical properties, as well as to change the color, opacity, etc. So while the plastic type may be generally food safe, the resulting product might not be after the additives are mixed in. So it's an amazing technology for all kinds of part reproductions - it just might not be a good match for your needs, since your parts will see direct and repeated food contact.

Post# 1045277 , Reply# 3 9/18/2019 at 10:03 (1,681 days old) by sarahperdue (Alabama)
Checkrate/Likes *Thanks very much for the information* I've already ordered supplies to mold and cast my butter conditioner doors. Since they have no direct contact with the butter, I'm not terribly worried about food safety on these, but thanks for the reminder that it will matter with products that directly contact food like ice trays, butter dishes and the ice bin. I've used food grade silicone caulk to make food safe molds before (for my son's homemade gummy Lego bricks). It worked very well, but my, oh my, the vinegar smell!

Post# 1045286 , Reply# 4 9/18/2019 at 11:40 (1,681 days old) by kb0nes (Burnsville, MN)
Checkrate/Likes Consumer 3D printing that uses filament based FDM (Fused Deposition Modeling) will make parts with pretty lousy surface finish as the part is basically squirted out by something like a hot glue gun. There is also a variability in overall strength due to the fusing of the material, tends to be weaker in height or the "Z" axis of the part. Personally there aren't many finished reproduction parts that I would accept from a 3D printer, they just don't look good enough to me. New LASER fused Resin printers are starting to become available to consumers now, these will make a significant jump in part surface finish and possibly strength also. I don't have any hands on experience with these yet. 3D printing is indeed amazing technology, but I just don't see it making many end products unless you just don't care about the look, fit & finish and quality of the piece. They can hold pretty good dimensional tolerances though, +/- a few thousandths of an inch easily (note I manage a machine shop so I think that is pretty crude). The truth about 3D printing is that we are in the infancy of the development curve and it will only be getting better with time. High-end commercial printers of course produce far better parts then consumer models but they cost 5-10 times more. The other issue with using 3D printing to make repro parts is getting a suitable model to print, yes 3D scanning is getting better too. Resin molded parts could be excellent quality reproductions, its all down to having a good part to make a mold from and getting the process down. The photos are from a largish 3D print I had made to hold a 6" convex mirror that will be used for a high power infrared transmitter. You can see the ridges of the finish clearly in the photos. It is a fine part, but appearance is lacking. It also took over 30 hours of time to print. The printer that turned out this part was a $2000 class machine. Photos... < > Photo 1 of 3 View Full Size