V4 BeyondPlastic – [PROCESS] Heatable Mould
I think a lot of biodegradable materials work the same: They need heat, pressure and a way for water to evaporate. So the plan is to build a stand-alone machine that is able to process a lot different raw materials. A heatable mould might be an important part for this machine.
Building a Heatable Mould
Designing a mould that can be heated up by itself allows us to keep it hot throughout the time we are producing stuff with it. That’s handy, since biomaterials don’t need to cool down to harden and enables us to produce many objects in a short time (The bowls take around 2 minutes for example). Moreover it saves energy by only heating up what really needs to be hot and nothing else.
We designed our moulds in Fusion360 (a free program for students and small businesses), got used aluminium blocks from the scrapyard (cost us 3€/kg) and CNC-cut them with the great help of @friedrich and his self-built CNC.
In addition to the two parts of the mould, we also cut some aluminium cases to attach a old kitchen stove hotplate to each side, as our heating elements. You might be able to make these from other materials than aluminium as well though.
Moreover we changed the hotplates a little bit by taking them apart and cutting a hole in the middle. We did this to transport the pressure through the hotplate onto the mould, rather than squeezing the hotplate while pressing it. Since most hotplates have a thinner steel part in the center, it wasn’t to hard to cut this part out.After drilling holes through the cases and tapping threats into the mould, we attached the hotplates to the mould parts. Moreover we attached the insulation to the mould which you can find out more about here.
Last we connected everything to a PID Controller like in most of the other machines, hooked the sensor up to one half of the mould and connected it to the power.
Designing a Mould
While trying out different mould shapes, materials and processes, we figured out a few rough guidelines on how to design a functional mould for biomaterials.
You can find and download our CAD/CAM files here.
– Slanted walls help the material to spread from the bottom of the mould up to the top. Thus it helps to put the walls at an angle lower than 90 degree, more towards 70/60 degrees.
– Round edges help to create an easier material flow throughout the mould.– Giving the bottom of the mould a slight angle and a center point also helps to avoid material getting stuck.
– Little details like embossed or engraved imprints transport quite well, while little sticking out parts (like the pins in the take-away-container) are weak and chip off very easily.
– Add L-Profiles or supporting walls, in order to keep long walls straight while the material is drying (like you can see on the sides of the take-away container)
Insulating the Mould
Insulation helps to keep the mould warm throughout the use. So far we have tried out three different ways:
– Bend metal sheets + stone/glass wool
– CNC cut wood covers with air pockets from MDF
– A low-tech version of the MDF one with wood covers and air pockets from coated plywood.
The combination of wood and air pockets inside seems to work very well, since it is apparently hard for the heat to go from a solid material into air and back into the material. But MDF is sensible to water and steam and starts to fall apart a little bit after a while (even though we covered it in paint), so it is important to choose something more waterrestistant like fir example coated plywood.
Have you considered using cartridge heaters directly in the mold? They are very cheap https://www.ebay.com/bhp/cartridge-heater so each mold could have a dedicated heater. This gives you more direct heating and reduces the energy wasted on heating things other than your final product. I use one of these in my desktop injection machine and it works very well.
Thanks for taking this approach. It probably should be considered for many of the plastic press applications as well and replace the need for the oven. Should provide faster process flow and less energy.
@s2019, thanks for the suggestion!
I didn’t know about cartridge heaters, but it seems like a great option. When I started thinking about the heatable mould I was actually thinking about putting a hot wire into it, but it seemed like a lot of work, so I chose the hotplates instead. But these heaters look even easier.
How much heat do they create? How many do you use for your injection machine ( which looks amazing btw!!)?
The heater I use is 300 W and I only need one for the machine. There is a description of it about half way down this page https://davehakkens.nl/community/forums/topic/portable-desktop-injection-machine/
This is very similar to one I built: https://www.youtube.com/watch?v=m4uGuTAm5jI
I used 2x 120W cartridge heaters, they are only 6mm diameter and 50mm long. I only put them in the bottom half of the mould, since the top part goes completely inside the bottom half and it is well insulated this is all that is needed, though I do get a slightly better surface finish on the plastic in direct contact with the heated half. (You can also get much bigger cartridge heaters, I have some 1kW and more).
Pressure is from a spring and is only around 100kg, seems to be plenty for this size. I intended this machine to be used off grid run from batteries/solar. I plan to build a scaled up one almost exactly the same design which can do larger objects the size of plates/bowls etc. (one day, when I get time!)
One thing I noticed with this machine, moulding slowly at a lower temperature, I get almost no noticeable fumes/smell compared to injection moulding.
@andyn That is one clean, simple, well thought out design. It really should be part of the PP toolkit as an alternative to the oven based designs. It looks to be significantly more efficient, and with the low cost of cartridge heaters, each mold can have a dedicated heater and thermocouple.
Thanks for the video
@s2019 Thanks for the Information!
And @andyn, that looks like a really nice and low tech setup! 🙂
I will definitely give the cartridge heaters a shot, as soon as I’m working on the machine again. The amount of energy used by the two hotplates was bugging me a bit already. Looking forward to the next version of your machine!
@dasjannis Thanks for sharing
May I ask if I could use the Compression machine (the one to make plastic bowl) to do this edible bowl instead , as I’m not really good as this and I think it similar (not sure 🙂
I am planning to use the argicultural waste (sugarcane bagasse , corn husk, pineapple leaves, tea leaves, coffee grounds,…) and starch (corn starch, potato starch, tapioca starch,…) from my country – Vietnam to make the biodegradable tableware
I watched from youtube (links below) and wanna to make the machine like them
but not sure how
Would you mind to give some advices regarding the making machines,
I dont know why the links not working
Bio-lutions – Agricultural Waste to Biodegradable Cartons & Tableware
This zero-waste packaging is made from bamboo
hope it works
Oh, wow. Is this your output?
It’s absolutely gorgeous.
@huyennguyen: thanks for the links. super interesting! 🙂
About the compression machine: We tried using it in the beginning and it helped us quite a bit with testing our materials, but the pressure from it is not strong enough to make the materials really bind enough and spread throughout the mould. In the new press, that I’m developing right now (you can read more about it here), we can use much stronger forces, leading to way better material properties.
But the good news: the moulds in the videos look a lot like the ones we are developing, so hopefully soon, we’ll have a nice open-source solution for it 💪
And @msnmck: In this team we are only working with biodegradable materials and no plastic, so no, we didn’t make those bowls 😉
@dasjannis: thanks for your information
I was about to make compression machine for biodegradable , now I will focus on heatable mould instead , it would save me time and money, thank you so much 🙂 waiting for your new press, super excited 🙂 as this will help us to save the argicultural waste and making useful tableware to replace plastic
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