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starter
30/07/2019 at 13:20
1

@papacorn In a broad sense bearings are simply rated by load and speed, so as long as they meet the desired criteria they will be fine. It is however worth considering that the spherical bearing housings commonly used, allow the bearing to change orientation a little and so make alignment and assembly much easier than a fixed rigid housing which generally requires accurate machining and perfect alignment.

 

With this type of machine it is always best to use ‘fuzzy logic’ so I would say that using some kind of  spherical bearing housings is pretty much a prerequisite

 

Square bar should be fine, however it is worth taking note that others have had issues with the hex bar set up and the original shredder design. So you might want to determine what sized bar would work best in your application.

 

With regards to the difference between a shredder and granulator, The PP design is a type of shredder, they are generally low speed, whereas granulators have high speed rotating blades. BTMetz posted a good photo of a DIY granulator early in the thread (I’ve attached it here for your convenience).

 

Google has heaps of good info on granulator design.

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In reply to: DIY Extruder Screw

starter
28/07/2019 at 05:43
0

Yes the RHS frame that the grinder is mounted to slides within the larger RHS mounted to the slide allowing for the grinder position to be adjusted.

The grinder can also pivot a little on its mounting bolt to compensate for any angular deviation between the wheel and workpiece as the grinder frame pivots.

In reply to: DIY Extruder Screw

starter
27/07/2019 at 14:37
1

I had some time to mount the grinder today (after I fixed my welder 🙁 ). I ended up having to raise the auger up from in-between the rails of the base as the cutting wheel did not engage deep enough into the workpiece. So I used this opportunity to simplify the ‘nut’ design. It is now a simple round bar sitting across the top of the auger. It works very well. No bearings, no complicated design. Much easier to build. The mechanism also still runs pretty smoothly, not as smoothly as the previous design, but I think that it is not important.

 

So for anyone who was having trouble visualising how the grinder was to be mounted, now it should be clearer to see 😀

 

Next step is to finish off the cam profiles and workholding and then I will be able to make some tests.

 

You can read more info and see some more photos here – https://deeemm.com/index.php/entry/general/diy-extruder-screw-making-machine-part-2-the-grinder

 

There’s also a sketchy video here – https://www.youtube.com/watch?v=kHPv1I7LjN0

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starter
27/07/2019 at 05:05
2

@antoinex Good work.

The CERN license is definitely more appropriate. Specifically the way in which it deals with derivative works. It’s very much like a GPL for Hardware.

I’m surprised it’s not more widely known / used.
/DM

starter
27/07/2019 at 03:45
3

Nice work. I’ve had some more progress on my own development that I will share…

 

The second cutting action on the underneath is very important and often overlooked. The first pass through from the top of the blade(s) cuts the plastic up, but it is the second blade underneath that cuts the shards to size so that it can fit through the screen. On the orignal PP design, there was no lower blade, the plastic had to return to the top blade to get cut to size. Essentially it had half the capability it should, which means half the throughput. Most dual blade shredders have this second blade (the plates to the outside of the blades.) Many commercial shredders / granulators have multiple static blades. Also, the clearance between blade tip and screen is usually about 1/8″ on commercial machines. No cutting takes place against the screen.

 

The size between the tip of the blade and the root of the rotor was very large on the original design, so the granule size was very large (it actually tore it into strips more than cut into granules). This also meant that to reduce the size of the strips they had to fit exactly in the right place on the blade and not between the blade tip and rotor root. This would then become more a game of chance than by design, which meant that the granules spent longer inside the shredder waiting to get cut to a size that fitted the screen.

 

My application is slightly different to yours in that I’m aiming for small (<6mm) size as I’m 3D printing direct from granules, so I’ve been focusing on the size, however, I think that the same principles apply to increased throughput.

 

If the size of the plastic after the first pass is small, then it will probably only have to be cut by the lower blades once to reduce to a suitable size to fit the screen. The key is to ensure that the space between the tip of the blade and the root of the rotor is small (like on your single blade machine or on my design – see photo.)

 

It is also important to ensure that there are tight clearances between the fixed and rotating blades. If you are shredding milk carton and it is only 1mm thick, your blade clearance ideally needs to be much less, this prevents the material getting pulled through in between the blades and causing high loading to the motor. This action is not actually cutting the material it is stretching it – plastic is very strong in tension, It will stretch a long way before it yields, this is why the original PP design jams / trips – as the blade clearance is massive and plastic gets drawn in between the moving and static blades stretching the material. This effect is lessened with dual blades and both blades move and so the material does not have to stretch until it yields. The only issue with making a machine that has close blade tolerances, is that the manufacturing methods change and cost of the shredder increases. (Ground plate is required to control blade thickness).

 

There are also consideration to the feed object size relative to the desired output size. I cannot take a large plastic object and reduce it to a sub 6mm size. there is no way that a blade like this could deal with say an extruded beam and efficiently produce a sub 6mm output. Optimum blade characteristics lean towards larger granule sizes when dealing with larger input size, which is okay when used by larger machines. like the rest of the PP machines. There is probably an optimum ratio relating to input size, rotor size and required output size. I think that the ideal machine for household waste is not the same machine that you need for processing plastic beams, if the same design is used, there will be a tradeoff.

 

With all of this considered, I have actually come to the conclusion that a shredder is not appropriate for my specific application. My focus is now on a granulator design. In all of the plastics companies I have worked (injection molding / blow molding) none used shredders for reprocessing waste, all used granulators, and some processed large, thick material into a relatively small pellet size (from 800mm x 600mm x 15mm thick irregular shapes, down to 8mm – I think a much better ratio than a shredder can achieve). I think that it is also easier to make a granulator and requires less close tolerances and so are much easier to assemble. Additionally no gearboxes are required and there are less parts, so cost is most probably less.

 

I think shredders have an instant visual appeal and they have a definite attraction as they are very satisfying to watch, but I’m not 100% convinced that they are the most efficient / appropriate choice for this application. It’s funny, but having worked with granulators for many years I never really felt any excitement about using them for small scale recycling, but after seeing shredders in operation you get a bit excited at the prospect of making one. They are awesome / formidable bit of equipment and they get people excited, but I think a granulator is more appropriate. I am very surprised no one has tried to make one.

 

My granulator design is pretty much finished but is not formally documented. It will be released open source when it is done. I’m happy to collaborate / share with the PP team if they have the resources to take on another build. @davehakkens if you are interested, shoot me a PM to discuss.

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In reply to: DIY Extruder Screw

starter
25/07/2019 at 00:41
0

Yes, I think that any grinder could be made to work. It’s just a case of presenting the workpiece to the wheel in the correct orientation.

 

I’ll try and make some time this weekend to mount the grinder

starter
24/07/2019 at 16:13
2

Ahh cool, the post is fixed 🙂

Just noticed that the N/C contact on the first line is unmarked, it should be T1

 

 

 

 

In reply to: DIY Extruder Screw

starter
24/07/2019 at 03:04
0

My plan is to use an angle grinder – either 4 or 5 inch size – just a small hand held one. These are available everywhere. They also mostly all have screw mounts on the sides for the handle (also usually on both sides for left and right handed people), so it should be possible to make a mount that holds it. I plan to hold it in a vertical orientation.

 

I have also seen 3D printed mounts for similar tools. Worst case scenario is simply to use one or two large worm-drive universal clamps. I have done this before when I mounted a router to my plasma CNC. It works pretty good. Lots of options depending on what people may have available. For me I want to try to avoid using my 3D printer on this build as it is not tech that everyone has access to. Just basic tools.

In reply to: DIY Extruder Screw

starter
24/07/2019 at 02:34
0

Cool. One thing that I was planning when I get the time to make the rest of the device is to angle the grinder wheel so that it aligns with the angle of the flights, and also to choose a wheel that matches the width of the channel (if possible). If the wheel is narrower than the desired channel width then the wheel or workpiece will need to be reset.

Do you have a link to your video?

In reply to: Forum issues

starter
23/07/2019 at 15:14
1

Thanks for the clarification.

 

I’m going to comment on each of your points.

 

Recycling – PP is never going to fix the issue of plastics pollution on its own, it is just one contributor in amongst the many that are trying to do something rather than nothing. But why knock someone for trying? It’s a great idea, even if it’s little more than a curiosity or conversation starter, it’s still raising awareness and getting people involved. If you disagree with what they are doing, why do you have so much time and energy invested into it? It makes no sense. What is YOUR solution that is better? What is it that YOU are doing?

 

Open Source – When was PP ever a global open source project in the sense that you describe? Just because someone releases some plans under an open source license does not make them a global open source initiative. As I have said before, PP is NOT RepRap, it’s never been set up like this. PP is not what you think it is. I don’t believe that it ever has been.

Dave Hakkens is a serial entrepreneur, you can see this with the plethora of projects that he has tried to develop. It’s just that this particular project has grown legs and gone a little bit viral, which is a great thing and he is trying to do something with that momentum. Unfortunately due to the subject, a project like this also has the interest of of a bunch of people who seem to think that life should be free and that sentiment tarnishes what he is trying to achieve. Geesh, even if it was set up as a not-for-profit charity organisation, it is still a business, it is still allowed to make money. Else how does the fella make a living? How does this project sustain itself?

 

Sustainability – Disagree with you here. Plenty of people actually making a success out of this. It is a sustainable endeavor from a small business perspective. But as with all things, you only get out, what you put in. Of course this is no different from any business. If you’ve gone into a business only for it to fail, that is not the fault of the person selling you the machine. it just means that your business plan was no good and your market research bad. Please consider that not all people are cut out to run a business.

 

Community – This IS the community. it’s a bunch of people, just like you and me that are invested in the PP process. That’s what it is. Nothing more. We are here to talk about the PP process and machines, how to use them, improve them, share ideas, well you get the idea, all of that stuff.

Being a member of this forum does not make you part of the PP development team, it does not mean that anyone at PP has to take any notice of what you say about PP or its products, no matter how relevant you may think your contributions are. I keep saying it but it is not RepRap. They are not going to validate your opinion for you. Nor am I.

 

For the most part the community seems to be machine builders looking for a quick buck by selling someone else’s design and then complaining that this design is not what they thought is was, as they sold something without actually using it themselves, and without being aware of their obligations relating to warranty, merchantability, compliance and safety.  It’s comical that these same vendors then want to blame the designer for their lack of foresight (ironically the same lack of foresight that causes people to going into business without making a business plan). It’s just naivety.

 

The PP machines were designed to be built by the end user, not a middle man. The PP process is there to enable people to undertake the activities of building a machine and making / selling recycled items themselves. That’s the vision, same one it’s always been. PP ask for nothing in return. Nothing. NOTHING!. I look at this generosity and the fact that the design are given freely and I immediately think of the GPL terms and conditions, specifically those that say – “these designs are supplied as-is, with no warranty of any kind, either expressed or implied”.  And you know what? This is the same for ALL open source projects!!! By releasing the designs you admonish yourself of all liability.
So why is it that the machine builders complain that there are issues, and then try to blame PP for the problems they have with their machines? It’s simple. It’s because they just want to shift the blame for their lack of foresight, lack of experience, lack of business plan and the cost of their oversight somewhere else other than where it actually lies. They get an issue with a customers machine, the customer takes this issue up with the machine vendor (as they should) and the vendor is not set up to deal with it. They are not invested into their product as it’s not their design. They did not consider that they need to support it. They didn’t test the machine design or validate it.
The way I see these issues are that none of them are the fault of the designer. All of these issues fall squarely on the shoulders of the machine vendor.

If Joe Bloggs downloads the plans, builds a machine, but then has an issue with it, they seek help on the forum. The community help them to resolve the issue. They move on.

 

If Joe bloggs buys a machine from a vendor, but then has an issue with it, they don’t go to the forum to seek help, they go to the vendor. The vendor has a LEGAL

obligation to supply a machine that is fit for purpose, meets safety legislation, does what the vendor said it would do and is provided with a warranty. None of this has anything to do with the designer. Even if the vendor had engaged the designer specifically to design the machine as a paid job, it is still the responsibility of the vendor. If someone builds a machine exactly to the PP design, that they then sell to a customer, and that customer injures themselves on the machine, and the injury is the result of bad machine design, the vendor is 100% responsible. It has NOTHING to do with PP.

 

As a machine vendor the buck stops with you. You cannot blame anyone else. This is the law. Whether it is AS4024 / ISO12100 for machinery design or AS3000 / IEE 17th edition / BS7671 for electrical design, it is entirely down to the vendor to validate this. It has nothing to do with the designer. NOTHING.

 

To be honest, I’m getting a little tired of reading about this ‘us and them’ diatribe. I don’t mean to cause offense to anyone about this, but why beat a drum that just continually pokes sticks at what PP is trying to achieve. If people don’t agree with the way PP do things, or even think that the overall idea of PP is viable why are they even here? If they are not on board with what PP are doing, why don’t they go and do their own thing? Surely with all of that advice they have to give, they can do a better job.

 

But then, you said it yourself best… it’s all about selling machines to innocent users for big $$, and PP is where there are 1000 potential customers.

 

In reply to: Forum issues

starter
23/07/2019 at 04:23
2

This is interesting.

This popped up as the advert at the beginning of the PP video when I watched it.

https://4ocean.com/

These guys sell plastic bracelets and invest that money into actual plastics cleanup. How is it that this is possible? Just look at the infrastructure these guys have. Boats, cars, ocean vessels, geesh, that’s a lot of infrastructure to own and maintain from just selling bracelets.

Why aren’t PP doing something like this? I mean, they don’t even have to outsource manufacture, they have that aspect covered. They already have an online store, they already have a marketing department (go Madeska!!)
I think it’s simply because they are completely focused on making machines.

PP could also leverage their brand in each of those 350 workspaces and in turn each of the 1000 potential workspaces when they come online. Kind of like a franchise without a buy-in, where the cost of entry is a percentage of profit in exchange for being able to use the branding, be listed in a PP directory, being able to say that whatever % of each sale goes back into fighting the global plastics problem, be included in PP marketing and advertising. And fees for those workspaces that are not simply boutiques this could be waived. Of course if you want to the the PP machine designs there’s nothing from stopping you setting up without using the PP brand, but the most valuable asset that PP has, is their brand and they are not using it to its full potential.

If PP start generating a revenue from this kind of income, instead of just investing in these machines, they could invest in some of the other problems facing plastics. What about plastics recovery from beaches / the ocean / rivers / etc. People are already doing this, but it’s still not an accessible technology. Why not mobilise shredders and then post-sort the plastics using other means? PP are very good at making this kind of tech accessible. And this is the stuff that could really make a difference on the front line. It could even help people like 4ocean be more efficient in what they do.

In reply to: Forum issues

starter
23/07/2019 at 03:53
2

If you’d build that stuff for their users you may start understanding

Not sure what you mean.  I sense a lot of contempt in the way you talk about the PP project, but I am yet to understand why.

After watching the video and reading the comments there’s a few things that stand out to me…

 

– I think that they have done quite a lot with the 150K so far. Given the infrastructure that they have to support, and workforce they have to both house and manage simply managing to survive for 6 months is a fair achievement. Running any business is hard, hats off to them. The transparency of they are doing is also good.
But. I think that there are two aspects that they have invested in that are not wise choices:
1. One army. This is a distraction. whilst it *may* solve the forum issues (I refer to my previous comments) it is not actually necessary to address the forum issues, and so is completely superfluous.  The ‘how-to’ part of one army that they discuss should be a hard coded part of the PP site – they already have this with the tutorials, most of which are in video format, you cannot really improve on that. Dave correctly identifies PP community as the valuable asset in all of this, but creating these collaborative spaces is simply a case of creating another sub-forum, it doesn’t need three or more guys working on dedicated code to leverage the power of the community. I think that onearmy is a new vision for Dave, but it’s a little misguided and only tenuously related to PP, which is what has given him the capital for it in the first place. I would be very interested to know how much this particular aspect has cost, both in monetary terms and also in taking away key resources from other more relevant PP tasks. But with that said, if Dave thinks it will help move the business forwards then he is within his rights to invest in it. Speculation and forward investment is a part of business.

2. Robotic sorting. This is actually my background – I’m an industrial controls engineer by profession. I’ve spent the past 30 odd years designing, programming and installing special purpose machinery for clients all over the world, predominantly robot based. What they are doing is a cool project, and the guys working on it are probably pretty smart, but it’s another white elephant. You can pretty much put a standard price on single cell automation – it’s 250k euros. Thats the average price for your average single robot cell, with full safety and basic tooling. And that’s the budget version too. Who is going to invest in that? No one, that’s who. Running my own business, I can actually say that you have enough trouble getting established businesses with multi million turnovers investing in this kind of equipment. You will definitely not get a startup plastics recycling business to invest in this kind of tech, it’s too expensive. It’s also way outside of the PP demographic, if they have the cash and inclination to invest in robotic sorting solutions, I can guarantee that they won’t be buying PP machines for their business, they’ll buy commercial solutions. But, that said, I’m also having a hard time seeing where this has a commercial application, it will never be fast enough to sort plastics on a commercial scale.

Madeska? The girl who does the visual marketing stuff. She is the linchpin to the entire PP success. The reason that the community get behind PP is that it is branded correctly. Yes more than anything PP is actually a brand – it is not known for it’s plastics recycling capabilities, it’s known for its ideals and being an enabler. It is the brand that builds trust and confidence, this is why people get on board. There’s lots of talk about how the PP machines are not what they are ‘sold’ to be, why do you think that this is? It’s because the PP brand is super successful in convincing people that these machines are the answer to global plastics pollution. If PP want to grow, it is investment in the brand that will make happen.

– The Bazaar. Lots of complaints about the Bazaar here in the forums. The youtube comments about capitalism also made me laugh. Why shouldn’t PP be monetised? If it doesn’t self sustain it will die. It’s simple economics. The interesting stats for me were that globally there are 250 machine builders 350 workspaces and 1000 potential workspaces, and that the Bazaar has a gross turnover of 20k per month. This echoes exactly what I noticed about the Bazaar. There are more people making and selling machines than there are making and selling plastic items. To me this simply says that at this stage PP is a community of machine makers, not a community of recyclers. I think that this is also echoed here in the forums where most of the discussion revolves around the machines.

– Business plans. Again lots of negativity about the business side of PP, but if they are not sustainable by the time that the rest of the 300k runs out, they will go the same way as makerspace. I think they are going about it the right way, it’s never easy trying to analyse how to monetise something like PP, especially where its success is based on moral and ethical righteousness.

 

/DM

In reply to: Forum issues

starter
23/07/2019 at 01:48
1

I have yet to watch the video where they explain what they have done with the first half of their funding, Maybe I should. Maybe that would cause me to judge (I’m sure I will have an opinion lol).
Of course everyone has perfect clarity of vision in hindsight. It is very easy to be critical of the work of others, but the truth is that given the opportunity most people would not be able to do any better.
Going to watch that video now…

In reply to: Forum issues

starter
22/07/2019 at 12:28
1

Managing any project is easy, if you know how. It just takes a few simple tools and a few basic management strategies, but project direction does need some vision & direction to set the path, and this usually comes from above.
I actually think that the project direction for PP is not too bad, they are trying to overcome the shortcomings with a redesign of current equipment and also trying to increase the scale of what it is possible to make. Both of which are logical pathways to take. They are also putting some more product design ideas out there, as the community is not contributing in this respect. This is obviously going to increase appeal. The work they are doing with creating large sheets is really going to attract a different type of end user. It’s all good and positive.

Best of all they have investment from volunteers too, although some of these seem to have been given too much of a free reign with what they are doing. But this is not necessarily wrong or bad, sometimes good things come from the leftfield. Often it’s good not to place restraints on what people are allowed to do just because you are too close to something. It’s actually good that Dave has let go and letting people take the reins from a design perspective.

I guess we will all see where it ends up when V4 is released.

In reply to: Forum issues

starter
22/07/2019 at 11:39
1

Yeah I’m just ranting. It’s not my project, they can do as they please. But it is a shame to see so much energy being wasted on something that is essentially unnecessary. Seems like a lot of misplaced effort to me.

I don’t really see the value in these project kamp / one army / phoneblox / story hopper / etc projects. PP has really struck a chord with people, it is this that has got people engaged. But this other stuff, it’s just going to end up losing people’s interest. The stats are right there in post counts. People come here for PP not this other stuff. They should concentrate on their customer-base. Better to do one thing well, rather than lots of things only half well.

Having taken a look at the OneArmy code I can see that the forums are not going to get fixed any time soon. Guess I’ll see how frustrated I get posting there.

In reply to: Forum issues

starter
22/07/2019 at 03:33
1

Actually, I’ve just taken a look at the GitHub repo for OneArmy. They are indeed trying to fix this issue, but the solution is basically scratch writing an entire platform. That path is folly. Been there. Done that. The amount of time that is needed to maintain a custom platform like that is immense. It’s a full time job and a management nightmare, especially when key people move on, which when you are not paying them is inevitable. Softies cost big $$$’s. Good ones cost even more.

I think that this choice is misguided. You don’t need a new platform to fix these issues and you also don’t need a new platform to unite people in a common cause. It’s not the platform that unites people, it is the shared ideals, shared ethics and common goals that brings people together.

Why reinvent the wheel? The solution will not be any better than what is already freely available. It’s not going to be taken up by third parties and if it is, then you need to invest resources supporting it, all the time this takes resources away from where they are better used. And when the wheels fall off down the track, as they inevitably will, you are right there back at step one, with a broken forum, wondering what to do. If wordpress cannot manage to provide a stable solution with all of the resources they have at their disposal, and all of the development time they have invested, what makes you think that you can do any better in such a short space of time? < (rhetorical question)

What happens when the code that you are using needs to be updated? or becomes obsolete? Things move pretty fast in this world. If you use a third party solution, all of that hard work maintaining and updating the core code is taken care of by others, it therefore has little impact on your resources, all you need is a basic webmin to take care of things. Anyone can do this.

So why embark on such a resource intensive activity? You’ve just stopped being a serial entrepreneur and become a cat herder. (as that’s pretty much what managing software engineers is akin to). Softies will always want to do this kind of work as it feed their egos. The big issue is that unless they have previously managed a project like this, they have no actual idea of the amount of work involved to get a working stable platform. And even if they do, they have probably never had to maintain such a platform. Contributing to an existing project and creating a new one are very different animals. What happens when they go back to whatever it was they were doing before this?

Looking at some of the pathway tasks you still have to complete, there is stuff like user avatars outstanding. This is basic stuff that should be part of a pre-canned user management framework. If you still have stuff like this outstanding and you are currently supposed to be in beta, then your have no hope in hell of meeting a 2020 launch, if it ever gets completed at all. By the time you have it working, it will all need updating again. Just take a look at ANY open source software project. Take a look at their resources. Take a look at their roadmap and history. And then consider the amount of work involved.

Much better to adopt an existing solution and extend it to do what you need. The reality is that what you are doing is not new, there are a bunch of solutions already out there that will pretty much do what you need out of the box.

Sorry if I come across as cynical, but I’ve been right there. Both as a softie and as a project manager. You need to consider that if you cannot manage a simple wordpress site and fix these issues with the help and assistance of the wordpress community (massive), how are you going to manage and maintain a custom platform that has basically no support community. (another rhetorical question).

I think you are lining yourself up to fail.

My advice is this. Stick to hardware. Tangible solutions. That’s what you are good at. I understand the lure of what you are doing, but rest assured. It is a white elephant.

/DM

In reply to: Forum issues

starter
22/07/2019 at 02:20
2

s2019

creating offline and pasting in any significant content is what I’ll do going forward.

I already do this, it’s force of habit, the issue is when it doesn’t post correctly. WordPress detects your second attempt at trying to post the same content as a duplicate post and refuses to post it. It is a ‘feature’.

plastichub
Not sure I understand. But in essence noone should be writing any PHP for this forum. It’s pretty basic stuff and there are a plethora of free solutions already out there. I run a bunch of community sites also with thousands of users and have none of these issues, simply as I use the right tools for the job. Don’t waste your time trying to fix WordPress so that it acts something like phpBB, it is a complete waste of resources. Just use a proprietary forum solution instead. It can still be made to look the same as it currently does with simple CSS overrides. Any basic webmin should be able to do this work.

 

These issues are as a result of reaching the limitations of WordPress and trying to make it do something it was never intended to do. Fixing this issue by hacking the code just pushes the inevitable down the road a bit further, it also makes maintaining the site that little bit harder as you also have to maintain the hacks at each update. By the time you have half a dozen of these hacks, on top of any mods you might have carried out, the site simply becomes unmanageable, the wheels fall off and things snowball out of control.

 

WordPress is great for blogs, managing posts from one user, it’s basically a glorified dear-diary. However, it falls down when this functionality is bent into trying to be a forum. It will always be a compromise.

 

I also notice that the devs are busy trying to recreate Inventables with One Army, Personally I’m not sure on the wisdom of this move but I guess time will tell, I understand why. I only hope that they are not trying to do it with WordPress. If they are it will be fraught with the same issues as this forum. (It actually looks like it is using StackIdeas EasyDiscuss which is good).

 

I like the idea of https://precious-plastic.org/ but I’m not sure if I am invested in it (at this time). I’m trying to undertake some projects of my own. They do align with PP and the PP philosophy and could augment it, but for the time being I’m developing them outside of the PP framework.

 

Some questions: Who owns precious-plastic.org? I assume it’s you plastichub. What is your affiliation with PP? Where does this site fit into the PP framework? Is it ‘authorised’? I do not see any links to it on PP. Does this not simply replicate the information already available at preciousplastic.com? If so what is its purpose? Why not simply contribute to preciousplastic.com, those guys always seem to be calling out for help.

 

Which brings me back to this… I am happy to share some of my results here and impart some of my knowledge, which is why I am here, posting it. But if I keep having these issues then I will simply stop. I am sure I am not alone.

 

/DM

starter
21/07/2019 at 15:49
2


Most inverters have programmable outputs. You can use this with simple relays to create automatic reverse function. There should be the possibility to trigger an output at a defined torque or current level. You can use this to monitor if the motor has stalled.

Here is how to make it work…

Program inverter output to switch at defined torque or current level.

When activated this output activates a relayThe relay latches itself and swaps the fwd / rev control signal to the inverter which reverses the direction of the motorThe relay also also activates a second relay, the second relay is a delay-on timer relay.After a pre-defined time (eg 5 seconds) the second relay activates cancelling the latch on the first relay,The first relay de-energises allowing inverter to run forwards again.

 

Some caveats:

 

The inverter normally has several different control profiles eg how fwd / rev / run are connected. You need to choose the profile where applying a fwd signal causes inverter to run forwards and applying a rev signal causes inverter to run backwards, and removal of the signal causes it to stop. If your inverter does not have this kind of profile and requires an additional run / enable signal you will need to provide additional wiring to activate this. This may require additional an relay.

Most inverters have limited on board low voltage power supplies (24v), which means that they will most likely not create enough power to be able to drive the relays, so an external PSU may be required.

 

I’ve attached a simple schematic of the wiring.

Attachments:

In reply to: DIY Extruder Screw

starter
21/07/2019 at 05:38
0

Is delrin a thermoplastic? could be a good way to create the nut if it can be molded.

In reply to: DIY Extruder Screw

starter
20/07/2019 at 07:12
0

s2019 Sorry I missed your comment on making a nut from plastic.
Yes, I think that this could also work. I don’t think ‘drilling’ through the block would work, but I bet you could make the nut in two halves and press them together around the auger – much like the split nut on a screw cutting lathe. These two halves could then be mounted into a casing.
3D printing is another alternative, although some consideration of the design would need to be made.
An issue with trying to make a single design to suit all augers is that I think that no two augers are probably the same. Not only would the size differ (obviously) but I would imagine augers from different manufacturers would all be slightly different too.

In reply to: DIY Extruder Screw

starter
20/07/2019 at 06:56
0

Is there a way to embed videos?

https://www.youtube.com/watch?v=3FFFDuHzDP0&feature=youtu.be

In reply to: DIY Extruder Screw

starter
20/07/2019 at 06:55
1

OK. Some progress.

I’ve made the basic machine with moving table / carriage. This has proven the concept of using the auger bit as a lead screw. The results are quite good and should easily be good enough for stage 2 which is to develop the tool and workholding.
I have  (for the most part) followed the philosophy of readily available parts and construction with hand tools.
If you are interested in a step-by-step explanation take a look at the write up at the following link – https://deeemm.com/index.php/entry/general/diy-extruder-auger-machine-part-1 There’s also some learnings and caveats that are worth considering if you want to make your own version of this.
Here’s a short video showing the operation of the carriage.
https://youtu.be/3FFFDuHzDP0

Attachments:
starter
20/07/2019 at 06:45
1

Ahh yes, I can see the rest now. Ideally they need a force from both the back and from above to stop the bar from trying to climb upwards as the bar flexes. I can actually imagine the chatter from the photos, can be scary stuff.

 

Yes I agree, always good to take the route of less risk for students. Screw cutting can be complex and easy to mess up.

 

Great work.

starter
19/07/2019 at 18:14
0

BTW. I’m never really a fan of grinding on a lathe – the abrasive gets into everything and has a tendency to cause wear & damage.

starter
19/07/2019 at 18:12
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Good work. Results look good.

 

You should look at using a travelling steady on the lathe. It will allow a much larger depth of cut and reduce your machining time considerably. Not too hard to make if you don’t have one, especially as you do not need to make it adjustable – just tailor it for this job.

Also I notice that you are reversing the lathe to return to the start of the cut. If you use a thread dial you can leave the lathe running, disengage from the lead screw and manually return to the start while the machine is running, it is much faster. Again, you can easily make a thread dial if you don’t have one.

 

/DM

 

starter
18/07/2019 at 16:59
1

sharma-sagar Ahh ok I understand. 🙂

I personally think if you have a complete design for something then it is better to create your own repository (GitHub or Sourceforge etc) and release it under a license that aligns with your particular beliefs. This way you have control.

But as I mentioned earlier in the topic, in my experience there will always be someone who wants to take advantage of your designs for their own gain and this is in a way unescapable once your design is in the public domain. The only real way to beat this is to provide the same service for less money.
I see you are from India, I get some manufacturing undertaken there and can say that you are in a very good position to be able to do this, as your manufacturing costs are much lower than elsewhere. If you ship parts instead of complete machines you also do not need to meet any CE requirements. You can easily beat those vendors at their own game.

Of course you can also consider that for every machine that a vendor sells there are probably multiple machines built by DIYers. It’s all about balance.
Then there is the big picture stuff, that all machines built, whether built and sold by a vendor or by someone making it DIY are all helping to reduce the plastics problem, so no matter where they come from they are all positively contributing towards the overall goal.

starter
18/07/2019 at 16:09
3

I dunno, it seems to me from where I am standing that everyone has the wrong end of the stick. No disrespect but PP is NOT RepRap, no matter how passionately people might want it to be. It could be, but it isn’t and never has been.

sharma-sagar I’m all for constructive criticism, but swearing and shouting at people because they do not agree with your opinion is not polite conversation. Passive-aggression like that is not on.

It’s funny how aggressive people get when they think they are being wronged.

starter
18/07/2019 at 15:41
0

then there are other who are basically doing mental gymnastics and bringing in laws and copyright practices etc to justify the parasitic behavior that “some” makers on bazar are doing.

Are you referring to my input into this discussion?

starter
18/07/2019 at 11:32
2

I seem to have stepped into a pre-existing argument here.

sharma-sagar The moral aspect is clearly defined in the project license. There is actually NO requirement to share derivative works. There are other more suitable licenses that could have been used if this was the case.

Whether the MIT license has been specifically selected for this reason, or if it is simply an oversight, only the licensee would know, but given that this conversation is happening, it will be interesting to see what license the V4 designs are released under. There is now an opportunity the change things with the V4 release should the license not follow the project ethos.

plastichub is correct – all of the risk of selling a pre-built machine is worn by the vendor. It is they that go to court if someone is injured by a machine, not PP. This liability costs money, liability insurance is not cheap. Nor is the risk of losing your house / car / business / savings if you choose to operate without it.

If vendors choose to modify their products to get an edge in the market then good for them, there is currently no requirement for them to share such refinements. If this does not follow the ethos of the project then the license should be changed. However it should be considered that vendors have embarked on machine supply under the current terms, and there is therefore no moral issue with vendors protecting their intellectual property as it is their right to do so under the current license.

I can see that you feel passionately about sharing design changes but I think that you need to talk to the licensee about this as the vendors are doing nothing wrong, not from a legal perspective, nor from a moral perspective.

In reply to: DIY Extruder Screw

starter
18/07/2019 at 05:16
0

Yes, I agree. I think that the finish will require several stages with final hand finishing / polishing. This method will take a long time and will never replace other faster manufacturing methods, but it does offer an opportunity for people without access to a machine shop to be able to produce a better extruder screw.
Adding a radius to the root of the spiral is easy, it’s just a case of shaping the grinding wheel. In fact if you look at the ideal profile for the spiral, it is non-symmetrical. The pressure side of the flute is squarer.
I think that another factor will be changes in diameter to the abrasive wheel. it will wear as the job progresses which will affect the finished dimensions. So as with any dimensional grinding, the grinding wheel will need to be dressed / replaced / reset as the job progresses.

@s2019 I think that the air is simply pushed back up towards the hopper / load end as this is effectively a lower pressure area within the extruder.

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