The new carriage should take in account the dimensions of the MGN12 rolling block and the clearance between the fixation holes. When upgrading the X-axis of my Reality CR-10 printer to MGN12, I decided to build a carriage for light direct extruder.
It is a geared extruder with ratio 3:1, that delivers constant extrusion pressure whatever the filament. Final configuration of the print head mounted on MGN12H linear rail with BMG dual drive extruder, 23 mm pancake stepper with heat sink and radial part cooling fan.
To keep things this way, we finance it through advertising and shopping links. I would like to design yet another printer model with standard printing dimensions (200×200 mm), but without using steel rods nor linear ball bearings.
There are really many designs out there, and most of them use steel rods to drive the moving parts, while very few exploit aluminum profiles for the job (not talking about the structure of the printer, of course). It is obvious that stainless steel lasts much longer and is sturdier than aluminum, but I would like to know your experience in this respect, in particular negative ones if you have some.
Is V-slot (or some other) a “must” or any (straight) aluminum profile can work reasonably well, all things considered? Can be easily tensioned between featherlight operation and rock solid stability. I'd think most extrusion will be (reasonably) straight.
It can be lighter, cheaper, easier to machine, and harder surface than stainless steel. Stainless steels advantage is its corrosion resistance which as long as you take care of your printer, really isn't a concern unless you're printing next to an ocean.
If you can use extrusion that is Good Enough™ for both structural support and linear movement, you kill two birds with one stone. Quote CDU Short answer is reduced cost (hopefully) and complexity.
If you can use extrusion that is Good Enough™ for both structural support and linear movement, you kill two birds with one stone. You're going to have a hard time building for less than that yourself, and you'll end up spending many hours chasing ever cheaper parts and figuring out how to incorporate them.
If you can use extrusion that is Good Enough™ for both structural support and linear movement, you kill two birds with one stone. Good linear bearings are expensive, so maybe some Gus bushings or printed Berlin or nylon.
The change in profile direction provides measurable strength and flatness. We're only looking at what is directly a component of the linear movement constraint, not belts, motors, pulleys, etc or other parts that attach to brackets or the carriages that serve functions other than linear movement.
The Rostock has: 2 linear rods 2 linear bearings 2 zip ties to attach the linear bearings to the carriage 10 screws (4 top brackets, 6 bottom) 10 washers (4 top brackets, 6 bottom) 10 nuts (4 top brackets, 6 bottom) Total: 36 Plus I'm willing to venture that the overall rigidity of the Cherry Pi III with extrusion is greater than the Rostock design.
You're going to have a hard time building for less than that yourself, and you'll end up spending many hours chasing ever cheaper parts and figuring out how to incorporate them. And that's what I've done with my personal printer when I made my Mendel90 (although I must admit some of my initial attempts at “improvements” weren't so much).
Seemed is a semi-local company to me and have very strong presence at the Midwest Rewrap Festival with their commercial delta printers, all of which use extrusion in their designs. Honestly I'm not sure that their designs would be improved upon much if they switched to linear rail or rod arrangement.
I think I would have very little standing to go up to one of their designers or engineers and tell them that they are doing it wrong and that they should use the “right” part for linear movement. I think it's bad engineering to just accept the status quo rather than to innovate and find a better way (or even a just-as-good way) for a lower price. Cheaper is a worthy goal, so long the quality of the final product is still “good enough”.
It can change the entire paradigm (e.g. Henry Ford producing cheap cars). I would like to thank you all for your replies, I read your experiences, advices and comments (and encouragements) with great interest.
You answered many of my unwritten questions and gave me a lot to think about, so that new questions arise. As I think many other newbies, I am torn between having a good printer, saving money and having fun in creating and building something “new”. Reality is complex, many needs/constraints have to be taken into account and compromises are unavoidable (if one has a limited budget) in relation to printing volume, speed, precision (repeatability), accuracy, local availability and cost of parts and possibility to machine them on one's own, filaments that may be used... And I am also aware of the 1000 printer models and kits that have already been developed, not only the cheap ones: I considered many of them, and still I have not found the model that would fit perfectly my needs, although some printers are not that far.
My concern is: how can I optimize my design and purchases to obtain the highest printing “quality” with my budget? To come back to the topic, after reading some of your replies I tried to get a sense of the precision and robustness of cheap aluminum profiles from a local hardware store.
Robustness is indeed quite poor, they bend very easily, but I agree that this may be overcome with proper countermeasures. So, even if it has to be aluminum rail, it will not be the cheap one from the local hardware store, I guess.
But here is another question then: how do you measure the precision of parts, if the vendor is not providing already this information? Measuring distances and diameters is easy in most of the cases, with a good caliper.
One obvious reply would be to buy from vendors that give information about tolerances. However, thanks to your replies I think I almost made up my mind about the kind of printer I want to build.
And is there a more efficient (in terms of cheap, good, soon) way to get what you want than trying to straighten out a crooked aluminum extrusion? The “right” way to measure the things you ask about would be a to start with a known flat plane, like a granite surface plate.
If you're getting into 3D printing thinking you can just push a button and receive your part you've been drinking too much of the marketing dept Kool-Aid. Most people don't know what problems need to be fixed until they get a printer and find out all the things that can go wrong.
It would be better to look at these forums before buying/building a printer /kit and pay attention to the problems people report and use that to inform your decision. For most that would probably inform a decision now to bother... Back in the early days of computing, people put up with a lot of horrible/stupid stuff because there were few alternatives.
It's happening already- you don't see many machines made using laser cut plywood anymore, so clearly people are learning. My unused 8020 is waiting for my next project- that stuff is so useful you'll never throw it away, even pieces that are a few cm long can be put to good use.
Quote Cristian But here is another question then: how do you measure the precision of parts, if the vendor is not providing already this information? Measuring distances and diameters is easy in most of the cases, with a good caliper.
If you want an actual number for what the tolerance is, I can't help you any more than what koko76 said with a dial indicator and a surface plate. Ideally you don't want any light to shine through, indicating that the piece is at least as flat as the surface it's on.
I'd use a feeler gauge on a glass table, I suspect most countertops/desks will be less flat than the extrusion. Technically a dial gauge will measure the width/height of the extrusion as well as its straightness, so you may overestimate the error.
As I mentioned, the official tolerances are awful but in practice they seem to be pretty damn straight. Quote 691175002 Technically a dial gauge will measure the width/height of the extrusion as well as its straightness, so you may overestimate the error.
Actually I don't need a printer so precise that it can print Kim Kardashian: not sure suitable filaments have been invented for that yet, but I am confident that people smarter than me will manage sooner or later. For sure, the most valuable thing I want from all this is to learn new stuff, as I have been constantly doing since I bought my first printer kit (definitely sweat, tears, blood but also some surprising results). Besides that, I would like a printer that can exploit the whole surface of the bed for big pieces (as my current printer cannot do, despite a miraculous ho tend that never clogs even if I let the nozzle scrape the bed for ages), but that can also print smaller pieces at 0.05 mm layer thickness with a 0.3 mm nozzle (or even 0.2 mm maybe?).
But as you know already if tolerances are bad, printing quality (in particular for visible surfaces) will not improve: it will get worse. I started attending the local Maker space some weeks ago, it is indeed and interesting place to exchange not only parts but also knowledge.