V4 BeyondPlastic – [MACHINE DEVELOPMENT]
For our prototyping so far, we used a 10t manual hydraulic press that cost us around 200€ in the beginning of V4. It enabled us to try out all kinds of things and to make the first bowls and containers from our biodegradable materials.
Moreover we moved some things around, added first portioning prototypes and upgraded it with a pneumatic motor, so we can use our air compressor to do the pressing. This automation was important to me, since I think it’s helpful when you are pressing a new thing every two minutes.
Since we now felt like we came to the end of that prototype and that it was time to start the actual building of a press from scratch, I came up with a few concepts.
I think the easiest thing is to just go through it and explain my thoughts and then you can commment, if you have better ideas:
In the beginning I really wanted to go for a C-frame press, since I like how easily accessible it is from the front, but after running some force simulations on fusion I realized how thick everything has to be to actually take the force of 10 tons. So I decided that it would be a liiiittle too heavy and look too scary looking for our purpose👻
So now the prototype I am going to build next is a simple build from threaded rod, steel profiles, which already a few DIY people out there made. Moreover I ordered a hydraulic jack with a pneumatic motor to take care of the automated pressing. (https://www.ebay.de/itm/Stempelwagenheber-hydraulisch-Stempelheber-Pneumatischer-Wagenheber-18000kg-18t/163639580393?hash=item2619add6e9:g:yuQAAOSw5gZcqwKq)
The threaded rod will be M20 and two on each side should be enough to take the force even at an angle. Additionally it’s cool, because it doesn’t require any welding, which might make it more accessible to some people.
You can see a screenshot of the CAD in the images.
I will keep you updated on the building. 👨🔧
Let me know what you think so far!
It looks like one of these https://www.harborfreight.com/12-ton-air-hydraulic-bottle-jack-94487.html or ebay/amazon equivalent.
It is funny, we were in a gardening store picking up some fertilizer and I saw they were selling a heated press for the errrrr…. cultivators…. I’m ignorant of that universe but these rosin presses are well finished heated presses that range from a few hundred https://www.rosineer.com/products/rosineer-rnr-mv2-manual-rosin-press-dab-machine-with-tools-for-best-plant-oil-extractions-dual-element-heating-plates-heat-plates-with-food-grade-stainless-steel-cover-easy-operation-with-manual?variant=40342718404 to a few thousand dollars. They look well capable of hot pressing things other than duckless duckweed.
If your plywood is handling the compression, why add the concrete? It would just add to the mass you are heating.
Unfortunately you are using the UNP in its weak direction. You have plenty of height, if you have more channel, you could turn the bottom one on its side and put another next to it to form an I beam. Basically copy this shop press design https://www.harborfreight.com/20-ton-shop-press-32879.html
So here’s a little update after working with the current press design for a while and trying out different moulds in it.
As I said earlier, we use the air compressor to control the force, but at some point turned it above the 8 tons, to see if one of the test we made would close with more pressure.Turned out we also tested the yield strength of the U-Profiles we used and permanently bent some of them.
Next mistake: I added another profile to counter the top part, but left the bottom one like it is.Now the top one seems to be able to hold the pressure, but the lower one is pretty bent still.In general I did realize in this process though, that the more stress we use, the better the products turn out. Moreover it feels a little bit like a waste, if we have a jack that can go up to 18tons and only use half of it. So it would be cool, to build the press strong enough, to hold the 18 tons.
Plus, that would also get rid of the problem of measuring the pressure, because you could just use as much, as you need to close the mould.
Now I have two ideas on how to change the design and would love some input from you girls and guys!
#1 To reinforce the press, I could just use bigger profiles and counter all of them. UNP profiles are easily accessible in 140mm width or higher everywhere. (the current one is 120mm wide)The bad thing about it is that the press would get more and more heavy and definitely less friendly in a way. Especially if you would want to make it mobile for workshops or stuff like that. And more material = more resources and energy spent in the process…
#2 I came across the second idea, when I saw this video by Lucy and her acrylic press.Her press uses heating elements made out of concrete and from my carpentry school I still remembered how we reinforce concrete with steel, because it can take a lot of pressure, but not a lot of tension, while steel is the opposite.So I am thinking now: Could I just fill my profiles with concrete to have a solid heating element, while at the same time, having a stronger profile?I have not too much experience with concrete, besides using it for table tops, so if you have any thoughts on this, I’m super duper interested! 🤓
Nice clean design. I wonder if you used an I-beam for the moving table and put the guide holes in the flanges, you could avoid the dreaded ” @pporg : yeah, I ended up welding anyhow” admission.
I wonder, when you add support feet to make it less likely to tip, you may be able to end support your bottom C-beam and then use a dial indicator on the center as your force measurement. Probably should run some numbers to make sure you don’t yield at 8 tons, though you could move the support points in as needed.
As far as using plywood as a isolator. It is not clear from your pictures how much is in contact with your hot plate but take a look at this page https://www.performancepanels.com/thermal-properties and see if the concerns apply.
Not sure what your temperature and force cycle timeline looks like but one option if you spend most of your time heating is to use some springs to support the hot plates and have the support transition to some lands (blocks) once you apply high pressure. I’m not sure about the concern of heated molds. The heaters are cheap and cable management should be doable.
So I finished building the press yesterday. After cutting the big U-Profiles it was actually pretty easy to build the frame. I used a wooden sheet to keep everything aligned while I fixed the threaded rods and added some spring washers to make sure the nuts won’t move when I’m going to apply pressure. For the moving part on top of the jack, I welded some steel tube to the U-Profile (@pporg: yeah, I ended up welding anyhow 😉)
In general I’m a little unsure which direction is the best way to use the profiles in. My logic tells me, that it makes most sense to press agains the walls and not the bottom (like between the top profile and the moving part), but the more I think about it, the less sure I am. Maybe someone has some input on it?
Moreover I build a new version of the heating elements, which I want to connect permanently to the press, so we don’t have any cables on the mould and it’s easier to clean. Since it’s quite hard to find insulation material that doesn’t cave under all the pressure, I came up with the idea of insulating it with vertical plywood and use different heights to build air chambers. It might look a little complicated, but it actually wasn’t too much work, when you can cut stuff with the table saw. In general I’m wondering though, how much insulation really makes a difference in the end and if there isn’t an easier solution out there. If you have an idea, let me know! 🙂
So next I’ll add the heating elements to the press and see how everything behaves under 8 tons of pressure. Wish me luck! 💪
ah, sorry forgot to add : not sure what the specs of your machine are but for down-scaled version I can recommend the composition below. It can be archived mostly with machine shop cut offs / scrap – yard stuff and enables height adjustments as well re-configuration for plastic injection.
btw, let us know the link to your book; happy to promote it 🙂
Hahahaha, @pex12: Thank you for recognizing my welding talents. If you want to find out more about the art of welding, you can read my soon to be published book “weld it like it’s hot – weldcome to my weld” 🤓.
@s2019: Good thoughts! I made some modifications to the file, but now I’m a little scared about the strength, in case a mould is filled unevenly. Because the sides of the U seem so weak to me. Or is that just in my head?
And the concrete idea is just because I wouldn’t need aluminium blocks then and I thought it could make the structure stonger. But maybe I’m just wrong…
Anyways, here’s a screenshot of the changed frame. Let me know what you think!:)
well, other than that I am happy to see PP Eindhoven recognizes their role in the DIY world and shows better examples using ecological and recycle friendly welds 🙂 Stan is right about; those presses are stupid cheap and easy to mod; for machine builders there is also some basic work done to get this legally sold.
Oh and one more thing I’m still wondering how to do best: There is no pressure gauge on the hydraulic jack and it’s quite a messy process to put one in. (good example: https://www.youtube.com/watch?v=ZBmxkWK_OFA)
I already tested limiting the jack’s force by limiting the air compressors pressure. Testing the actual force in combination with the other press and it’s pressure gauge gave me pretty precise numbers on how much air pressure will lead to how much hydraulic pressure with the jack I’m using (e.g. 4.5 bar gave 8 tons with our jack). More over you could put in a pressure release valve in front of the hydraulic jack in case you don’t want to lower the main pressure on the compressor. So I could provide a table with a conversion rate for this exact jack and the air compressor I’m using, but I’m sceptical if a hack like this is a good (and safe) way or if it would be better to include the process of adding the gauge to the jack in the how-to for the press.
Ooooor maybe someone has a better idea on how to messure and limit the force in general? I’d love to get some more input on it 🙂
I’ll post an update about the progress of the press next, but to answer your questions first: @s2019 yes, it’s pretty much a hydraulic jack like the one at harborfreight. That’s the exact one we got: https://www.ebay.de/itm/163639580393
The one I chose is a little stronger, so I can actually test the limits of my frame at some point and also give some info of when it might break. Hopefully not too soon 😉
And about the rosin presses (from a pun-lover: props for the duckless duckweed pun ✊)
They also came up in my research and the heating is super nice to have, buuuut the work area is pretty small for most of them, so it would be hard to fit bigger moulds or objects. That’s why I decided to build one from scratch. Not to reinvent the wheel or anything like that 🙂
And @donald: The air pump of the jack works with a normal compressor at 8-9.5 bar. I also already tested a bit with limiting the pressure from the compressor to limit the pressure of the jack. But I’ll write more about it later on. But I’m super interested in the duckweed topic! Just started reading frogfalls paper. Did you manage to grow some in here in the Netherlands?
really neat, l like this design is close to what is in the shelf 🙂
just one thing about your welding notice, someone who can drill 20 mm holes through cast iron also has a welder, I bet my nasty little cat on it !
Other than that, no complain from my side; something which is always good to keep in mind is that ‘machine builders’ working for the bazar have it easy to turn this into a ‘pro’ machine. for instance, distances should be always chosen in a way that somebody can wrap this up with sheet metal (safety, aesthetics,..), and bolt it on support material (smaller cut offs); in a way he can do it him self or order it from special vendors (CNC metal bender machines, often equipped with laser cutters).
Actually, the way you have the threaded rod attached, you may locally bend the flange of the beam you assemble. What you can do is form the I beam shape from your UNP pieces and then just set it on top of your existing piece. You can either make it shorter so it fits inside of your threaded rod and use some small retaining screws to keep it in place, or you can make it full width and cut your large holes, they would be just clearance holes. In this approach your existing bottom piece is serving as the cross pin in the shop press design.
I’m not sure what you mean by mold filled unevenly.
If the top assembly is not bending, you could leave that as is.
On the bottom you could bolt the two webs of the UNP together just to give you more front-back stability or if you don’t feel like drilling holes, just weld them together at the ends. If you have a box beam, that would work as well but your threaded rods may not be in the right place. Of course, if you have access to one, an I beam works as well.
If you are interested there are plenty of online calculators for section moment of inertia and the resulting beam stiffness and strength.
Of course, if it was me, I would have been lazy and I would have bought the shop press as my frame work.
As far as the aluminum blocks, I thought that’s how you are heating the molds, or have you added mold heaters to the molds themselves?
Make the moulds round and get band heater around then to head them up
@pporg thanks! You might be right about the drilling/welding part;)
But maybe being able to disassamble the press might also come in handy at some point.
And if you are down to share a few of your machine builder tips about the distances and how to turn it into a “pro” machine, I’d be very open to already let them go into the design right now!
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