Mendel90 vs Prusa i3 - which one to build

Hello everybody!

I'm new in the world of 3d printing and want to start building my first printer. After reading online for quite some time (and considering my passion for OpenSource projects) I decided I want a RepRap. So I started checking the models. At the beginning I thought Prusa i3 was the best option, then I read about the Mendel90 and doubts rose. Which one would you recommend?
If it's the Prusa, which variant? I read about Einstein, rework etc. but I can't understand the differences.
Do you think it is better to buy a kit or to source/build the parts all by myself? Consider I have no problem in building stuff and that I work with a CNC miller so I can machine everything is machinable!

Thanks a lot!

I went with the Mendel90 because I didn't like the use of threaded rod for the frame. I knew of others that had built Mendel printers and they always looked...imprecise. And that it could be a nightmare getting everything perfectly adjusted only to have something shift slightly if moved. Maybe my thoughts were unfounded, but I've liked my Mendel90. I did not buy a kit instead I purchased all the vitamins from my own sources or printed my parts. I probably ended up costing a lot of time and some money thinking I could do it better/cheaper in some areas.

Being new, if you want to get up to speed with a working printer going with a kit from a reputable source (if not from Nophead directly) of known good quality components is probably a good idea. If you don't want to go with a kit and want to make your own variations or tweaks, then going with a plastic parts kit but then sourcing your other vitamins may be a better option.

Thank you for the advice. Talking about the price a kit would be cheaper then? (I'm a student, so money is always short..)

Take a look at the P3Steel, it is imo the best Prusa i3 variant at the moment and it is much easier (and cheaper) to build than the Mendel 90 for approximately the same print volume.

I'm a Prusa i3 user. To me the Mendel90 is better for many reasons, the cheap and simple wood frame, less steel for the rods, wire management, and so on.

I didn't know the P3Steel. Interesting but why don't they rework the I3 for folded sheet metal technology ? Since you use steel sheets, it's cheaper, easyer and stiffer than using screws like on unfoldable materials. Unfortunately they stopped at half the way.

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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

I checked the P3Steel. It's built on the same idea of the Mendel90, I guess. But you don't need all those plastic parts to assemble the sheets. Do you know what's the print quality? It's an improvement compared to the Prusa i3 or to the Mendel90?

Have you looked into the Wilson TS?
It's a Prusa I3 variant and boasts these features:
Highlights of this kit
Open source design, the Wilson TS is a true RepRap printer similar to the Prusa i3 but built with a super strong Aluminum frame built from T-slotted extrusions.
All the parts you need are included
No soldering required! The hot end, heat bed, end stops, stepper motors, and even the fans are all prewired for you and plug-in ready.
No cutting of rods or beams needed! All the rods and T-slot frame extrusions have been cut to the precise lengths needed for you.
Print volume of the finished machine is 200mm^3
All high quality components, clearly labelled and carefully packed.
Arduino controller comes pre-programmed with Marlin 3D printer firmware for the Wilson printer configuration.
Assembly videos on youtube, community documentation at reprap.org/wiki/Wilson, and over 10 pages of assembly notes and pictures included with kit.
What's Included
Complete set of printed plastic parts for the Wilson TS, printed from the very latest models (this kit features parts printed in Black plastic)
Set of 6 precision aluminum extrusions, metric 2020 profile, precut
Set of 6 hardened chrome-finished steel rods, 8mm profile, precut
Five High torque (76 oz-inch) NEMA17 stepper motors, prewired for RAMPS connectors
Authentic J-Head hot end by Reifsnyder Precision Works – completely assembled and ready to use (for use with 1.75mm filament)
12V, 30A switching power supply, with professionally assembled line cord and RAMPS connector assembly.
All electronics, including Arduino Mega, RAMPS 1.4, cooling fans and A4988 stepper motor drivers.
SMART LCD controller with SD card interface and 4GB memory card included.
Heated bed (MK2a), completely wired up and ready for use, along with the MDF mounting sheet and glass.
Metric 5mm threaded rods
Every metric fastener (the nuts & bolts), spring, and bearing needed
Set of 52 t-slot nuts for frame assembly
12 LM8UU linear bearings
End stops, pre-wired and ready to plug in
MK7 stainless steel extruder drive gear
GT2 timing belt and aluminum 20-tooth pulleys
You can check it out here on the RepRap site at: [reprap.org]
The developer (Marty) sells kits on ebay (mjrice) for around $500 w/shipping in the US.

Ok so I checked your designs and in the end the Mendel90 is the one that I like the most. The reviews say it's great and like it for the simple reason that I also would like the process of milling the Dibond sheets by myself.
I think I'll start checking the cads to see if I want to modify something.
In the meantime, do you guys know where to buy the plastic parts for the Mendel90 in europe? I found them in the u.s. but considering shipping/taxes they become too expensive.
For plastic parts, is it better ABS or PLA?

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vorac
I checked the P3Steel. It's built on the same idea of the Mendel90, I guess. But you don't need all those plastic parts to assemble the sheets. Do you know what's the print quality? It's an improvement compared to the Prusa i3 or to the Mendel90?

The P3Steel is definitely not built on the same idea as the Mendel 90. Did you check the wiki? [reprap.org]
The P3Steel uses a perfectly rigid steel frame assembled from laser-cut 3mm steel parts. The basic frame can be assembled in less than an hour (there are exactly 40 screws and nuts to tighten).
I built two of them and the print quality is as good as it gets.
Like most of those who have built and used a P3Steel, I have a hard time figuring out why people would build any other RepRap with a similar print volume, apart from availability of the laser-cut steel frame (which is hard to come by in the US and Asia).
The Wilson TS kit is a great choice in the US simply because Marty is such a perfectionist and a honest guy, apart from being a great RepRap designer, and his kit is super well priced.

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Zavashier
I'm a Prusa i3 user. To me the Mendel90 is better for many reasons, the cheap and simple wood frame, less steel for the rods, wire management, and so on.

I didn't know the P3Steel. Interesting but why don't they rework the I3 for folded sheet metal technology ? Since you use steel sheets, it's cheaper, easyer and stiffer than using screws like on unfoldable materials. Unfortunately they stopped at half the way.

Zavashier,

There would be nothing to be gained by going to folded steel sheet from laser cut 3mm steel, actually you would make the frame more expensive and more prone to vibrations. You would be surprised by how smooth running and almost silent the P3Steel is, specially when using 1/32 microstepping with DRV8825 drivers. Well, I know I was.

I just built a wilson ts... easy and solid. I love mine.

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AndrewBCN
Zavashier,
There would be nothing to be gained by going to folded steel sheet from laser cut 3mm steel, actually you would make the frame more expensive and more prone to vibrations. You would be surprised by how smooth running and almost silent the P3Steel is, specially when using 1/32 microstepping with DRV8825 drivers. Well, I know I was.

Opinion depends of the way you look at a piece. You can consider it stands at the top of the tops as it is, or you can appreciate it could be even better. My feeling about the P3Steel is the guy just attempt to swap i3's design out of steel instead of any traditional materials. I guess the inital thought was to reduce cost and get stiffness. But when you want to use a material, you want to use a technology that takes advantage of that material. As engineer I would say, there's no reason to get more vibrations with folded metal sheet. Hardware won't dump vibrations that much, it will work as a transmitter anyways. There's no reason it gets more expensive too. Quite the contrary, you'll need less hardware which have a cost, and the laser will be quicker if it does not cut all that pockets and holes. When you cut spare parts, you need to waste some material between the parts. With the folding technology, you reduce the number of the parts, so you reduce waste. At the same time your product will be more stiff, more precise, and easy to build. Just fold the sheet at the right angle and you're done. I hope this will help you to appreciate what sheet metal is all about

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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

Zavashier,,
To fold a structure like the frame for a Prusa i3 or P3Steel, you first need to laser cut the 1mm steel and then fold it. That's two industrial processes instead of one. Logically, it will cost you twice as much, perhaps even more depending on how many folding operations would be involved. And you'll still need holes to attach various things.
Irobri, the original designer of the P3Steel, has indicated he works for a company that laser cuts steels parts, and when I examined closely the DXF files he had created for the P3Steel, I could see that he knew what he was doing i.e. he had a clear understanding of how to laser cut steel and how to assemble a steel structure. I believe he took full advantage of the properties of steel, because when you assemble a P3Steel, and put it next to a classic Prusa i3, the difference in rigidity of the structure and in vibrations when printing is like day and night. 3mm structural steel is a very rigid material and you hardly excite any resonances in the P3 Steel structure when printing. This won't be the case with a 1mm steel folded structure.
Please note that I am not trying to convince you of anything, but I do recommend you take a look at a P3Steel by yourself next time you attend a Maker show where they have one.
Or take a look at some videos posted on the web; unfortunately I have not posted any video yet of my P3Steel with DRV8825 drivers, but I will do so soon.
Also, if you want to design a Prusa i3 frame using folded steel and get some quotes for its manufacturing with any industry in France, you'll certainly find out that it costs more than what the P3Steel frame costs right here in Spain - at the store. ;-)
But again, I am not challenging you to do it, it would really be a lot of work.

Don't get me wrong, I don't say the P3Steel can't be any good. Just seems to me that half the way is done. I don't know about Irobri, his skills and diplomas. If I deliver the same reworking of an I3 at work, my boss will probably gently ask me if I'm tired, and to go back to work. The original Prusa I3 design is not very stiff, it's not difficult to do better. Of course, except if you want to provide a (half)mounted printer, the final user is meant to fold the sheets. It's easy if the sheets are prestressed (I don't know if it's the proper word), which does not cost more. Folded sheet metal allows to reduce drasticly the number of parts, and accordingly the mounting holes. On a carthesian printer, you don't realy need to have spare parts for YZ motor or guides mounts for example. You don't realy need a thick frame too if you use folded straighteners. Nothing personal, nobody can be an expert on everything, I'm an average electronics. You seems to be not very aware about sheet metal prices and process, It's what I do everyday for living. Maybe I know a bit what I'm talking about too. If you don't trust me, ask any engineer, or request for quotations

I know salaries are very low in Spain and that makes cheap production process. In France, we need to push the design a step further to do better and stay competitive. That's why I've got a well payed job.

Anyways, it was just a thought. I won't argue any more. Whatever the P3Steel design is, buy it, use it, be delighted with it, it's fine to me.

Edited 3 time(s). Last edit at 03/10/2015 07:03AM by Zavashier.

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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

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Zavashier
Don't get me wrong, I don't say the P3Steel can't be any good. Just seems to me that half the way is done ...
...

You would probably think differently if you had built one or two...

Basically you are saying that you could design a folded steel sheet cartesian printer frame that you could demonstrate is as rigid as the laser cut P3Steel frame and would cost less to manufacture; why don't you ? ;-)

I'll spend maybe 200 hours on the whole process. Do you want a quotation ?

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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

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Zavashier
I'll spend maybe 200 hours on the whole process. Do you want a quotation ?

Nope, and I don't think that's the point here.

For mendel90 printed parts (UK) :

[forums.reprap.org]

Edited 1 time(s). Last edit at 03/10/2015 09:13AM by Ralph.Hilton.

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Ralph.Hilton
For mendel90 printed parts (UK) :

[forums.reprap.org]

What he said. You're buying from THE source and zero chance you're getting some random piece of crap from someone looking to make a quick buck with inferior printed parts.

I decided I want to source everything I can. Do you know a good online store to buy fasteners? I dont want one where I have to buy at least 25 or 100 pieces, I already found those. I know stores where you can buy even 1 bolt exist but can't find them!

I built the "sturdy" version of the Mendel90, and I am quite pleased with it. Nice thing about it (besides the heavier-duty threaded and smooth rods: 8mm and 10mm, respectively) is that I was able to make the frame myself from 1/2" MDF (specs call for 12mm, but there's not all that much difference, functionally - you just have to open up the notches in the spool holder brackets a bit). Nophead is great at answering technical questions, and his service - even over-seas - is top notch!

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vorac
I decided I want to source everything I can. Do you know a good online store to buy fasteners? I dont want one where I have to buy at least 25 or 100 pieces, I already found those. I know stores where you can buy even 1 bolt exist but can't find them!

I think you would spend less getting a fasteners set from the link I posted above.

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vorac
I decided I want to source everything I can. Do you know a good online store to buy fasteners? I dont want one where I have to buy at least 25 or 100 pieces, I already found those. I know stores where you can buy even 1 bolt exist but can't find them!

I purchased almost all my bolts/screws from boltdepot.com.

While if you only need 1 of a bolt it is cheaper to buy just that one, don't just automatically dismissed buying a box of 25 or 100 (or whatever your source might have them as) if you only need less than a full box of them. The Mendel90 dibond BOM calls for 67 4mm x 16mm socket screws. I can buy those for .09 each, or $6.01 for a box of 100. If I bought exactly what I needed I would have paid .02 more and would have 33 less screws.

Also, when building my printer with the nyloc nuts, I had more than a couple twist off on me so it won't hurt to have some additional on hand.

OK so in the end, considering the price of Mendel90, I had to stay on my budget and go for the P3Steel. I'm sourcing all the parts and I've chosen everything. The only thing I'm still missing is the hotend. The plastic parts set I've bought has a Wade's Greg extruder. Will any hotend fit in it?
Basically I saw that the two most used hotends are E3D and J-Head. Which one would you recommend?

Thanks again

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vorac
The plastic parts set I've bought has a Wade's Greg extruder. Will any hotend fit in it?

The extruder could have been printed out to be used with one of several different styles of hot ends. The "J-Head" mount is probably the most likely.

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Basically I saw that the two most used hotends are E3D and J-Head. Which one would you recommend?

What do you plan on printing? If you are going with just PLA, J-Head. If want ABS, either. If you want PLA or ABS, but also don't want to exclude other higher temp plastics like nylon or polycarbonate, then E3D. Some people say they have more difficulties with PLA and a E3D.

My acrylic i3 had 1 mm difference in teh parralel x bars from teh 3d printed sockets being different, and 1mm on the z bars from the acrylic of the 2 top z holders. I will adjust it but it's going fine for the moment. the rest is fairly ajusteable, and those 2 elements need a bit of fiddling to get straight. i3 is nice, i would prefer something as simple with adjusteable fine tuning on the bars.