Building a Mendel in 2021. What would you choose?
Posted by ComeWhatThey
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Building a Mendel in 2021. What would you choose? October 12, 2021 10:46AM |
Howdy! I've long been a fan of the reprap project, I remember first reading about Darwin when I was in high school and was inspired, even if actually building one was way out of reach for me. But now, some 13 years later, I find myself in a position where doing something like that actually does seem to make sense...
The why
I want to get some experience of DIY building, with an eye to eventually making something with a significantly larger build area for automotive parts, as well as multi material stuff and laser/CNC. I’ve learned that it’s often best to start small and build up, to get an idea of the sorts of issues you might run into with scaleability, and so that when you do get there you can concentrate on that rather than trying to learn the basics at the same time.
So for now I’m just looking for something on the smaller side, more of a low pressure project to play around with and get comfortable with. And while I’m aware that stuff has come along significantly in the past decade, I actually feel like going back to the beginning (to an extent) and getting that first hand look at how some of those developments occurred and what fuelled them could be really interesting and valuable.
I actually already have access to a 3D printer, my partner has an flsun delta, so I have no trouble getting printed parts. But also because of that, build area isn't too much of a concern right now; if there's anything larger I wanted to print I could always use that. Making my own is more about getting that build experience, and also having a bit more freedom to get to grips with the software side of things, and to experiment with different hardware and settings.
Speaking more philosophically for a second, I actually feel like reprap could be just as relevant now as ever, which makes it particularly sad to see the wiki in such a sorry state. The fact that home 3D printers are much more available and widespread than a decade ago, the fact that so many of the components have reduced in cost as a result, that should play directly into the hands of an open source DIY option, not against it.
Obviously not everyone can or should build their own, and the community is better off for there being so many affordable options to get straight into it. There’s more to print, more people to ask for help, more resources and easy to follow youtube videos. But it’s also way easier and cheaper to get the 3D printed parts you need to put your own together if you have a friend or family member you can ask.
I know there are practical and structural reasons why this isn’t the case, but a lot of the early hype around home 3D printers seemed to be around how they could “end mass production” of cheaply made, disposable parts that get shipped all over the world with massive environmental impact, just because it’s cheaper than producing things as they’re needed more locally. I can’t help but feel some sense of loss that home 3D printers themselves have largely become part of that system, with everyone seemingly rushing to cash in and produce the “next big thing” that you absolutely must buy from them, rather than taking a more sustainable approach to design.
As I say, I think the wider community is in a pretty healthy place, as much as can be expected. And I think this is more or less how things will continue unless and until there is a much bigger push to enshrine right to repair in law. I just wish that reprap builds and documentation had kept up more, to make the DIY option as easy as possible for those who may consider it. Anyway...
The what
I want to build a Mendel, or one of its close derivatives, for a few reasons. I’m aware that there’s been much discussion about the drawbacks of the design and there are good reasons why more modern designs have largely moved away from trapezoidal shapes. But the idea of putting one together using stuff from the hardware store has always appealed to me, and let’s not ignore the most important factor, they just look cool! xD
Despite all the drawbacks, clearly many people have managed to make well performing and reliable printers from these designs, and the process of getting to that point seems like a great opportunity for learning. I do think it strikes a good balance for my (admittedly niche) use case. They can be built fairly cheaply, heavily modified, have parts re-used and iterated, and because of the threaded rod construction, scaleability is fairly easy. I’m intrigued by the notes in the wiki about scaling to use standard lengths of 13” silver steel for the axis rods, and I guess that could apply just as much to scaling down a Mendel as it does to scaling up a Huxley.
As fun as it would be to build my own Gen7 board, for now I will be using a cheap RAMPS kit for the electronics. I can also find Nema 17 motors much cheaper and more available than Nema 14s, I assume there was a time when they were priced according to their capabilities but the economics of mass production seem to have changed that.
In the interests of keeping things simple I also want to start out with a geared extruder and without a heated print bed, as these are things I could fairly easily iterate later on. So, which design to build?
Sells Mendel
Controversy time! In the process of my research I came across this old comment on reddit:
[www.reddit.com]
I’m sure much of it is subjective, debatable or just incorrect. But something about this outlook really speaks to me. Obviously a 12 year old design will have downsides compared to a more modern printer. But this would be the epitome of a “back to basics” approach, allowing me to see where they all came from, what improvements were made, and what, if anything, was lost.
They are notoriously difficult to assemble and square, but I am experienced enough with complex builds that that doesn’t particularly turn me away. If anything, the main downside is the cost.
While many parts of a 3D printer have dramatically reduced in cost over the past decade, fasteners are not one of them. And these make up a significant proportion of the materials cost for the printer, £42 out of around £180 total build cost. Is this just throwing money away relative to a design optimised to use less fasteners?
Huxley
These appeal to me largely because, as I say, I’m not too concerned about print area. Even with the reduced height that comes with using a geared extruder rather than a Bowden. Smaller shapes are generally stronger, and requiring less desk/storage space is always good. Most designs would require some modification to work with Nema 17s, which could be both a plus and a minus. I could build one for near half the cost of a Sells Mendel.
But unfortunately, the documentation seems a bit lacking in comparison. There’s a few different models and it’s not clear which one is being talked about at any given point on the wiki, or what the differences really are. Some use different electronics, some use push vs pull configurations for the Z axis, some of the printed parts seem slightly different. I was only able to find a BOM to use for pricing up by going to the page for the emaker model, on the original page the link is broken.
I’m sure I could piece one together, but given all this I wonder if it might be easier to just modify something else to be smaller if that’s what I want. It’d likely be over-engineered with 8mm rod in a smaller frame, but that’s rarely a bad thing...
Prusa Mendel i2
Sort of the other end of the scale to the Sells, and seemingly about as far as development got before moving to significantly different designs and custom fabricated frames. Drastically fewer fasteners than a Sells, and overall about 2/3rds of the cost. Some of the improvements make a lot of sense, and it’s better documented even than the Sells it seems.
Easier to assemble, less to go wrong, but also less to adjust and fine tune. Obviously this could be fairly easily converted into a Samuel if that’s where I decided to go.
I’ve really gone back and forth a few times on what would be best to build, so I welcome any input! And thanks a lot for reading
The why
I want to get some experience of DIY building, with an eye to eventually making something with a significantly larger build area for automotive parts, as well as multi material stuff and laser/CNC. I’ve learned that it’s often best to start small and build up, to get an idea of the sorts of issues you might run into with scaleability, and so that when you do get there you can concentrate on that rather than trying to learn the basics at the same time.
So for now I’m just looking for something on the smaller side, more of a low pressure project to play around with and get comfortable with. And while I’m aware that stuff has come along significantly in the past decade, I actually feel like going back to the beginning (to an extent) and getting that first hand look at how some of those developments occurred and what fuelled them could be really interesting and valuable.
I actually already have access to a 3D printer, my partner has an flsun delta, so I have no trouble getting printed parts. But also because of that, build area isn't too much of a concern right now; if there's anything larger I wanted to print I could always use that. Making my own is more about getting that build experience, and also having a bit more freedom to get to grips with the software side of things, and to experiment with different hardware and settings.
Speaking more philosophically for a second, I actually feel like reprap could be just as relevant now as ever, which makes it particularly sad to see the wiki in such a sorry state. The fact that home 3D printers are much more available and widespread than a decade ago, the fact that so many of the components have reduced in cost as a result, that should play directly into the hands of an open source DIY option, not against it.
Obviously not everyone can or should build their own, and the community is better off for there being so many affordable options to get straight into it. There’s more to print, more people to ask for help, more resources and easy to follow youtube videos. But it’s also way easier and cheaper to get the 3D printed parts you need to put your own together if you have a friend or family member you can ask.
I know there are practical and structural reasons why this isn’t the case, but a lot of the early hype around home 3D printers seemed to be around how they could “end mass production” of cheaply made, disposable parts that get shipped all over the world with massive environmental impact, just because it’s cheaper than producing things as they’re needed more locally. I can’t help but feel some sense of loss that home 3D printers themselves have largely become part of that system, with everyone seemingly rushing to cash in and produce the “next big thing” that you absolutely must buy from them, rather than taking a more sustainable approach to design.
As I say, I think the wider community is in a pretty healthy place, as much as can be expected. And I think this is more or less how things will continue unless and until there is a much bigger push to enshrine right to repair in law. I just wish that reprap builds and documentation had kept up more, to make the DIY option as easy as possible for those who may consider it. Anyway...
The what
I want to build a Mendel, or one of its close derivatives, for a few reasons. I’m aware that there’s been much discussion about the drawbacks of the design and there are good reasons why more modern designs have largely moved away from trapezoidal shapes. But the idea of putting one together using stuff from the hardware store has always appealed to me, and let’s not ignore the most important factor, they just look cool! xD
Despite all the drawbacks, clearly many people have managed to make well performing and reliable printers from these designs, and the process of getting to that point seems like a great opportunity for learning. I do think it strikes a good balance for my (admittedly niche) use case. They can be built fairly cheaply, heavily modified, have parts re-used and iterated, and because of the threaded rod construction, scaleability is fairly easy. I’m intrigued by the notes in the wiki about scaling to use standard lengths of 13” silver steel for the axis rods, and I guess that could apply just as much to scaling down a Mendel as it does to scaling up a Huxley.
As fun as it would be to build my own Gen7 board, for now I will be using a cheap RAMPS kit for the electronics. I can also find Nema 17 motors much cheaper and more available than Nema 14s, I assume there was a time when they were priced according to their capabilities but the economics of mass production seem to have changed that.
In the interests of keeping things simple I also want to start out with a geared extruder and without a heated print bed, as these are things I could fairly easily iterate later on. So, which design to build?
Sells Mendel
Controversy time! In the process of my research I came across this old comment on reddit:
[www.reddit.com]
I’m sure much of it is subjective, debatable or just incorrect. But something about this outlook really speaks to me. Obviously a 12 year old design will have downsides compared to a more modern printer. But this would be the epitome of a “back to basics” approach, allowing me to see where they all came from, what improvements were made, and what, if anything, was lost.
They are notoriously difficult to assemble and square, but I am experienced enough with complex builds that that doesn’t particularly turn me away. If anything, the main downside is the cost.
While many parts of a 3D printer have dramatically reduced in cost over the past decade, fasteners are not one of them. And these make up a significant proportion of the materials cost for the printer, £42 out of around £180 total build cost. Is this just throwing money away relative to a design optimised to use less fasteners?
Huxley
These appeal to me largely because, as I say, I’m not too concerned about print area. Even with the reduced height that comes with using a geared extruder rather than a Bowden. Smaller shapes are generally stronger, and requiring less desk/storage space is always good. Most designs would require some modification to work with Nema 17s, which could be both a plus and a minus. I could build one for near half the cost of a Sells Mendel.
But unfortunately, the documentation seems a bit lacking in comparison. There’s a few different models and it’s not clear which one is being talked about at any given point on the wiki, or what the differences really are. Some use different electronics, some use push vs pull configurations for the Z axis, some of the printed parts seem slightly different. I was only able to find a BOM to use for pricing up by going to the page for the emaker model, on the original page the link is broken.
I’m sure I could piece one together, but given all this I wonder if it might be easier to just modify something else to be smaller if that’s what I want. It’d likely be over-engineered with 8mm rod in a smaller frame, but that’s rarely a bad thing...
Prusa Mendel i2
Sort of the other end of the scale to the Sells, and seemingly about as far as development got before moving to significantly different designs and custom fabricated frames. Drastically fewer fasteners than a Sells, and overall about 2/3rds of the cost. Some of the improvements make a lot of sense, and it’s better documented even than the Sells it seems.
Easier to assemble, less to go wrong, but also less to adjust and fine tune. Obviously this could be fairly easily converted into a Samuel if that’s where I decided to go.
I’ve really gone back and forth a few times on what would be best to build, so I welcome any input! And thanks a lot for reading
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Re: Building a Mendel in 2021. What would you choose? October 12, 2021 11:21AM |
... good luck with your project! 
I'm following RepRap since 2007 -- and every now try to "inject" some new/alternative options and ideas, which were partially accepted, but some not so (or waiting).
For now I'm focussed on Laser-applications and some aspects of "laser assisted 3D-fabbing" too, but not so meant for common use, but more for high-tech "niches" aimed on accuracy/resolution and mixed materials ... will still need some years until my "target" will reach maturity state, but actually already near to some partly aspects, like materials, laser-types and -powers
Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]
Call for the project "garbage-free seas" - [reprap.org]
I'm following RepRap since 2007 -- and every now try to "inject" some new/alternative options and ideas, which were partially accepted, but some not so (or waiting).
For now I'm focussed on Laser-applications and some aspects of "laser assisted 3D-fabbing" too, but not so meant for common use, but more for high-tech "niches" aimed on accuracy/resolution and mixed materials ... will still need some years until my "target" will reach maturity state, but actually already near to some partly aspects, like materials, laser-types and -powers
Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]
Call for the project "garbage-free seas" - [reprap.org]
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Re: Building a Mendel in 2021. What would you choose? October 12, 2021 07:05PM |
... one of the R&D-projects, I was involved in, was started to develop a "all-in-one" machine for CNC, plasma, laser and 3D-printing (my part was the 3D-printing and some aspects of high-power IR-diode-lasers).
The machine-base was designed for 1x1m with 4 combined heat-beds, 500x500mm each with cooling and heating by fluid through bores below the print-bed surface.
This project was progressing until roughly 50%, when the corona lockdown crumbled down the involved companies enough, so two resigned and the project was canceled (I've got most of "my components" for free, so tinkering with them in my basement now).
Don't expect an easy way, when developing an "oversized" 3D-printer -- the related part in the project was calculated for around 150k€ (but too, combined with other aspects, needed for plasma- and laser-welding/cutting) ... if building/developing this on your own, a 500x500mm printbed and the enclosure for lets say 60degC ambient temps will need some thousand USD in components and "experience" (or wrecked/incapable prototypes), until you'll get first results (have a friend in a company with this experience).
But again -- no need to give up! - good luck with your own aims!!
Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]
Call for the project "garbage-free seas" - [reprap.org]
The machine-base was designed for 1x1m with 4 combined heat-beds, 500x500mm each with cooling and heating by fluid through bores below the print-bed surface.
This project was progressing until roughly 50%, when the corona lockdown crumbled down the involved companies enough, so two resigned and the project was canceled (I've got most of "my components" for free, so tinkering with them in my basement now).
Don't expect an easy way, when developing an "oversized" 3D-printer -- the related part in the project was calculated for around 150k€ (but too, combined with other aspects, needed for plasma- and laser-welding/cutting) ... if building/developing this on your own, a 500x500mm printbed and the enclosure for lets say 60degC ambient temps will need some thousand USD in components and "experience" (or wrecked/incapable prototypes), until you'll get first results (have a friend in a company with this experience).
But again -- no need to give up! - good luck with your own aims!!
Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]
Call for the project "garbage-free seas" - [reprap.org]
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Re: Building a Mendel in 2021. What would you choose? October 13, 2021 04:43AM |
... if for delta - one of my smaller prototypes, presented 2007 in the RepRap builder blogs (a pity, the thread was lost in a server failure or such) was a pretty small delta (building envelope around 50x50x50mm), meant for high precision pick'n'place/microassembly -- it was made from only 12 parts and partially "self-aligning" with the ball-magnets.
Here some of the related images, I could still find - the first sketch and the assembled prototype:
Here a "mature" version (not from me) with more common ball-joints:
And here a "benchmark" for a "one-sheet-delta" (milled from a sheet of PEEK) sitting on a PZT-actuator-arrangement:
Edited 3 time(s). Last edit at 10/13/2021 04:48AM by VDX.
Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]
Call for the project "garbage-free seas" - [reprap.org]
Here some of the related images, I could still find - the first sketch and the assembled prototype:
Here a "mature" version (not from me) with more common ball-joints:
And here a "benchmark" for a "one-sheet-delta" (milled from a sheet of PEEK) sitting on a PZT-actuator-arrangement:
Edited 3 time(s). Last edit at 10/13/2021 04:48AM by VDX.
Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]
Call for the project "garbage-free seas" - [reprap.org]
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Re: Building a Mendel in 2021. What would you choose? October 16, 2021 06:07PM |
Yeah thanks for that! I can't say I know too much about belt layouts, I guess other corexy printers do seem to do it the way you describe? Looking at Hypercube/Smartrapcore. I did wonder why it uses pairs of flanged bearings too, instead of toothless idler pulleys. But those wouldn't fit within the printed parts as they're designed.
The Legacy actually does have a front cross member, it's just moved down slightly to make it level with the print bed in the zero position. I had assumed this was done to avoid interference or have better airflow or something, but looking closer I guess it's so that you get a better view of the print and/or can take cool videos. The 0 doesn't have one at all, but clearly it's small enough that it doesn't particularly matter - at the speeds those things print at, any instability would definitely have been picked up. And the 2.4 is a standard cube, but then it has the entire XY mechanism on a gantry and the print bed is just static.
As I understand it the Legacy isn't specifically designed to be enclosed, but there's a few ways it could be done. Could add a "top hat" style enclosure or put it in something larger. Either way there's no real need for it to be structural, so it could be added later. I will consider lengthening the frame but will have to see if it works out, from what I can see the cheapest 2020 I can get is in packs of 1m lengths.
Thanks for that vid, 40s in is a highlight
I certainly wasn't planning on using the afterburner print head, for cost reasons as much as anything.It actually does have two motors for the Y axis, but there's an inductive proximity sensor on the print head that lets you run a macro in firmware to sort out the tilt for you. You can see it here at 20 seconds. Over complicated? Possibly. But again, these machines seem to be designed for speed.
And yes, we have a roll of PETG on the way which should hopefully do most of the printed parts, don't worry about that
The Legacy actually does have a front cross member, it's just moved down slightly to make it level with the print bed in the zero position. I had assumed this was done to avoid interference or have better airflow or something, but looking closer I guess it's so that you get a better view of the print and/or can take cool videos. The 0 doesn't have one at all, but clearly it's small enough that it doesn't particularly matter - at the speeds those things print at, any instability would definitely have been picked up. And the 2.4 is a standard cube, but then it has the entire XY mechanism on a gantry and the print bed is just static.
As I understand it the Legacy isn't specifically designed to be enclosed, but there's a few ways it could be done. Could add a "top hat" style enclosure or put it in something larger. Either way there's no real need for it to be structural, so it could be added later. I will consider lengthening the frame but will have to see if it works out, from what I can see the cheapest 2020 I can get is in packs of 1m lengths.
Thanks for that vid, 40s in is a highlight
I certainly wasn't planning on using the afterburner print head, for cost reasons as much as anything.It actually does have two motors for the Y axis, but there's an inductive proximity sensor on the print head that lets you run a macro in firmware to sort out the tilt for you. You can see it here at 20 seconds. Over complicated? Possibly. But again, these machines seem to be designed for speed.
And yes, we have a roll of PETG on the way which should hopefully do most of the printed parts, don't worry about that
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Re: Building a Mendel in 2021. What would you choose? October 19, 2021 08:07AM |
Twists in the belts are only needed if the pulleys are small or you want quiet operation at very high speeds. The stacked F625s used in that design are still a little small to have the belt teeth hitting them- they could cause print quality problems (as well as making zipping noise at high speed). Gates recommends a minimum of 9 teeth in contact with a smooth pulley surface, and since the belts are wrapped at 90 degrees on the pulleys, that would be a pulley diameter equivalent of 36 teeth. Belt pitch is 2 mm (a little less when bent around a pulley), so pulley circumference of 72 mm (approximately). 72/ pi = 23 mm (approximately) in diameter. F608 bearings are 22 mm in diameter (close enough!). I used stacked F608 bearings and 9mm wide belts in my corexy machine and prints are great.
This is the minimal pulley count belt layout for corexy::
I used larger pulleys in the corners to provide extra clearance for the belt when the X axis is near the corner pulleys. It isn't strictly necessary. The most important thing about this diagram is that belt segments labeled A-H must all be positioned parallel to the guide rails (in every corexy mechanism, no exceptions!). Otherwise belt tension will vary as the extruder carriage moves and prints will be distorted. There are a lot of bad designs out there! If you see a clothespin spring belt tensioner, beware! The layout is probably wrong.
See: [drmrehorst.blogspot.com]
Edited 5 time(s). Last edit at 10/19/2021 11:12AM by the_digital_dentist.
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
This is the minimal pulley count belt layout for corexy::
I used larger pulleys in the corners to provide extra clearance for the belt when the X axis is near the corner pulleys. It isn't strictly necessary. The most important thing about this diagram is that belt segments labeled A-H must all be positioned parallel to the guide rails (in every corexy mechanism, no exceptions!). Otherwise belt tension will vary as the extruder carriage moves and prints will be distorted. There are a lot of bad designs out there! If you see a clothespin spring belt tensioner, beware! The layout is probably wrong.
See: [drmrehorst.blogspot.com]
Edited 5 time(s). Last edit at 10/19/2021 11:12AM by the_digital_dentist.
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
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Re: Building a Mendel in 2021. What would you choose? October 26, 2021 12:05PM |
If you are building a CoreXY, you might want to consider the MaybeCube. It's a linear rails design that supports a high level of customisation. It's also fully enclosable. I took a lot of steps to keep the costs down (for example using standard extrusion lengths, so no custom cutting required, hidden joints are used as they are the most rigid (and self-align) and also keep the fastener count down). It also addresses most of the points that the_digital_dentist raises, since I read most of his blog while I was designing it (it does however use a 7 pulley CoreXY design, since using a 5 pulley variant would have significantly reduced the build volume for a given extrusion length).
Or if you are looking for something smaller, you might want to consider the BabyCube
Or if you are looking for something smaller, you might want to consider the BabyCube
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