Thread: Mega prusa kit by Stuffmaker 3D user review

With the additional hotend and some filament (bad quality) almost 1200$.
Considering the obvious problems using the plans provided by the Reprap community and local suppliers a similar printer with proper hotends, extruder and print bed could be build for around 800-1100$ depending on supplies.
But this means you would have to go through all the initial firmware calibrations and modifications to even get to the first print.
Sadly I thought I could avoid that by buying a komplete kit that was claimed to work perfect within 10 hours of starting to built it....
If I take the cheap price in account that I paid for my Mega Arduino I would say the basic hardware for the printer and electronics can be sourced for about 400$ plus motors, cables and hotends.
In case someone got it wrong:
The printer itself is pretty well designed and some problems with printed parts won't appear since all plastic parts are extruded or machined.
With a proper extruder and hotend it will be a very good printer for large projects, but at the original state as bought I highly doubt anyone will be happy in the long run.
There is no real excuse for the limit to PLA except the lack of support for a heated print bed in the electronics and the bad hotends.
Since I already got two Mega Arduinos to play around with I will add the Ramps electronics at a later stage and try to get my own Marlin firmware working.
But the original circuit board won't go to waste as it will be still perfect to drive a CNC cutter or laser engraver

Edit:
Found a nice design for a hotend, although the original is used to quickly heat some fluid to a certain temp.
Instead of using a single resistor 90° to the filament flow this design opts for tow resistors parallel to the filament.
This results in a much larger melting zone and a more evenly distibuted heat along the element.
Just have to find a way to simplify the design so it can be used in a hotend for a 3D printer with parts readily available in our local stores.
My aim will be focussed on a relatively small build size with compatible measurements so the hotend can be used in many printers with only minor mods to it.
Considering hotends go for 50 to 100$ on Ebay and most of them can be serviced easily I think it is about time to develop something that anyone can built at home if has a basic toolset and a drill press at hand.
Was thinking of a hotend that allows a quick change of nozzles instead of replacing the whole hotend for different nozzle sizes.
After all it makes sense to have a spare hot end, but why have 3 or 4 diferent hotends just for different extrusion widths??
Will post an update once I got a prototype running

Well, if you consider the huge built volume the price is quite fair.
But I agree, you would expect a fully funcional system for that price and good support for problems related to the product.
If I would have known before that I only run into troubles I would have decided on a build from scratch, at least this would offered more ways of solving problems...
Considering the trend goes to multiple hotends these days it is hard to understand why anyone would produce a circuit board that is totally limited to what comes with the printer.
The main reason for postin was to make other people aware that buying a comlete kit is not really the easiest way to go.
For most people a printer like the Markerbot, Replicator or UP! will be more than they will ever need, but I needed a printer to go beyond the usual 12x12cm platform...
Now, after considering the overall costs for material including tests and misprints I have to say that a resin printer with a proper DLP projector would be cheaper in the long run.
Especially if you also consider the problems with support, overhangs and fine details...
I won't give up on the printer yet as I think a proper extruder and hotend will result in a printer that acually works but I'd like to warn everone considering buying a kit from Stuffmaker (or IPrint Technologies) that print speeds need to be reduced to a crawl if you want to finnish a big print.

I know most users will opt for a ready to go printer and only encounter problems when using some new filament, but I also like to offer my help for everyone trying to build a 3D printer or that is simply confused with all the settings you have to consider.
For example with an Up! you only select the STL file you want to print and all is done automatically.
Same for my printer except I had to find out the hard way what the limits are
I also noticed in other forums that people search for a simple was to modify existing STL files.
There are a lot of good programs out there but none are really capable of simple and easy changes to STL files as they all prefer their own format and only allow for the import of STL files.
In case you have a STL file that you simply can't edit I can offer to convert it into a format that can be used in most programs including 123D design.
Don't ask me why Adobe don't want to include the STL import for their programs....

Anyway I hope that there will be more users jumping into 3D printing and designs so we can built up a little community outside the Reprap forums

Update:
The special bearings for the extruder arrived today and I was able to replace the pressure plate with a friction free mechanism now.
Initial tests showed no more jams on the test objects (same G-code use as before).
This means where in previous prints the infill failed, because I wanted to infill at least two layers at once,
all printed fine now.
Also the transport speed keeps steady now resulting in basically no dust and shavings coming out of the extruder - this means no clogging up of the hobbed bolt either
Best thing is that I now can print at much lower temps as now all force from the hobbed bolt goes onto the filament and is no longer wasted on friction on a pressure plate.
Will do a spped test tomorrow to see if can reach higher printing speeds now.
Judging by the current test prints with the .7mm nozzle quite a bit more speed should be possible.
Currently infilling at 30mm/s at .2mm layer height, .1mm @ 35mm/s for the perimeter.
I think I could pump it to about 50mm/s for the perimeters and and 40 for the infill.
Once the parts for my new nozzle are here I should be able to reach similar speeds with the .4mm nozzle.
12$ for the bearing, money saved on now finnishing prints - who knows...

Update: print results are much more reliable with so far only failed prints during the speed tests (apart from a few failed ABS parts peeling off the platform).
The result is quite good in terms of the extruder mod, if the print speed is set correctly for the job and not high during infills there is no chewing up at all.
Together with the hardened hobbed bolt a huge step in the right direction.
Also tried some of the available "all metal hotends" with very mixed results.
My electronics are designed for the standard 5.6Ohm heating resistor, but some hotends arrived with 40Watt ceramic heating elements, so I had to send them back.
Good thing about the others is that you don't have to worry about getting the temp so high the peek starts to go soft.
Also much easier to clean.
But their biggest drawcard, the exchangable nozzle tips is actually not that easy to use in real life.
To avoid damage and stress the hotend needs to be hot enough to at least have a soft filament inside - burnt fingers are a must have
Also the actual usage is quite complicated compared to the usual MK V designs.
You can say each hotend needs to be tweaked to it's own temp settings.
This is due to the type of heating used as well the location of the thermistor within the heating block.
One thing they all have in common is quite a big footprint

So after a quick but not final mod to the extruder is time to re-invent the wheel and to design a hotend with a very small footprint being able to print at over 240° celsius.
My initial thoughts and rough designs were based on the use of a ceramic nozzle block holder and a full metal, one piece heating block.
Turned out finding a source for the ingredients of a base ceramic with very low heat transfer that can be made in your kitchen furnace is impossible, at least for a reasonable price based on a small batch.
Corrent designs all use either a seperate heating block or a huge round heating element, I don't like that because
a) the bigger the whole nozzle/heating part and higher the mass, the longer it takes for temp changes to become effective.
b) some of the designs are simple ugly and too big
Since ceramic is out of the question and I want to go as small as possible I will try the impossible way.
A hand full of people succeeded, only a few tried, a lot of people failed, but I think I got a way of creating an all aluminum hotend with a stainless steel heat barrier that is less than 2cm in diameter!
Round bars are ordered, basic design is clear, but need some new drill bits between .2 and .7mm
My idea is to include the heating into a very small alu tube with the thermistor mounted into the the nozzle tip.
This way temp changes are very fast and the temp readings are for the actual nozzle instead of the block heating it.
Also, since the heat is applied along the whole melting chamber instead of heating a block it should be possible to go over the magig 280° mark for printing.
If I can really make it work it means I can print not just Nylon but even PP, PE and all other high temp plastics
Anyone has a 25 or 30amp battery charger that needs a free new home? Could need a stronger power supply for the anodising than the 14amp PC power supply
Still not sure how to solve the wiring problem in a neat and still vibration and handling proofe way, after all most thermistor fail due to stress on the connecting wires right at the glass base....

Update:
Got an Email today stating my thermistors will be delayed another week, same for the bloody drill bits - will never learn not to order from Ebay to save a few bucks
But at least the aluminum rods are confirmed to arrive this week, so I can start with the new nozzle design.
Will post the next update once I something to report on the new nozzle

Short update:
Started to anodise some test parts and was able to create a nice scratch resistant surface,
however the coloring did not go too as it was hard Aluminium with a high content in added additves.
Tests with an old clamp from the scooter worked really well altough I still have problems getting a nice shiny surface.
Although the optical part is not that important for a nozzle I'd like to have different colors for the different nozzle sizes

Update: the last parts finally arrived yesterday and after breaking 2 drills I found a way to use these tiny things properly, takes time though
Completely re-designed my hotend again to make it shorter, without the heat barrier and wires it is just under 2cm long now and under 12mm in diameter.
Will try to solve the connecting problem over the weekend and upload some pics if I'm happy with the outcome.
This "short" hotend will be mainly for PLA, a longer hotend with a longer melting zone for ABS and Nylon will follow.
Still working on the ideal length to give the plastic enough time to melt properly.
One thing I noticed, and that's pretty much totally against all current design rules, is that a longer nozzle hole works better that the usual "as-thin-as-possible" approach.
However, this might only be because my hotend is heated all the way down to the nozzle, and not like standard designs with the nozzle poking out of the heated area.
Especially at lower temps the stream of plastic is very straight with a constant width.
I assume due to the length the pressure inside the fine channel has more time to equalize, as where a standard nozzle only provides a "hole in the bottom".
Hoping all works out with the connections I should be able to do some speed- and quality tests by the end of next week.
Stay tuned

Originally Posted by Downunder35m

One thing I noticed, and that's pretty much totally against all current design rules, is that a longer nozzle hole works better that the usual "as-thin-as-possible" approach.
However, this might only be because my hotend is heated all the way down to the nozzle, and not like standard designs with the nozzle poking out of the heated area.
Especially at lower temps the stream of plastic is very straight with a constant width.
I assume due to the length the pressure inside the fine channel has more time to equalize, as where a standard nozzle only provides a "hole in the bottom".

As you are aware, i am very much of the opinion the current design "rules" on hot-ends are wrong (for ABS).
Having seen how injection moulding works (I occasionally work on robots in the factory), they pre-melt the entire injection..... so where did the reprap community get these "rules"?
Keep going where your going, as mentioned i'm building mine for extra long heating tube and 2 elements to do it, I'm convinced every printer is doing it wrong.
Until proven otherwise.

edit, i now realise your talking about the nozzle, not heating tube..... misread, but here i will side with everone else, resistance becomes the issue, forcing you to higher temps, yes, i feel shorter is better.
Again, until proven otherwise!

I know what you mean and the same thoughts made me us a longer bore for the actual nozzle outlet.
Did not do any injection mouldind myself, but was the sparky for them over a period of 3 years.
Compared to 3D printing it would seem in the moulding business they do almost everything wrong, but if that's the case why are most machines at least twice as old as the oldest 3D printer??
The inital design for the MK nozzles used brass and a very complicated milling process.
Only minor changes have been made, and Alu was/is used too.
But you will also find designs in stainless steel and everyone will tell you that is one of the worst heat tranmitter out there, usually used as a thermal barrier.
One company took it even further and made a hotend out of Titanium - again a very bad heat transmitter.
Compared to real injection moulding a little step forward if the the original MK design rules would not have been (mis)used.

I think there two option to overcome the basic problem we all face with our hotends:
a) use much longer melting chambers to allow the plastic to fully melt before it is forced through the outlet
b) use a hotend design that allows for a more direct heating along the melting zone

Time and moodswings limit how fast I can fork out prototypes for testing but so far I can say:
1. it does not really matter what material is used for the hotend as long the melting zone and outlet get the right temp - if easier to handle ceramic would be good too!
2. don't be fooled by new and expensive designs, when it comes to small nozzle diameters speed must go down too - you will never reach the print speeds (with the same layer height) of a big nozzle!
3. correct temp settings are a misconception Too many variables affect a tolerance free true reading in your print software - find your own temps that work best for you and your filament, note it on the roll!
4. more power does not always mean more speed!! I'll try to explain:
Some hotends offer 40W heater cartridges instead of the standard 25W resistor.
It is claimed that those cartridges get the hotent to temp faster and also allow for much higher printing speeds.
The big problem with that is that you need a suitable circuit board/driver to handle this much power.
That's close to 4Amps that need to get to the heater! So bigger cables are recommended to start with.
For me the major downside with the more power aproach is that it will tempt users to also use higher print temps to get higher print speeds.
At first thought this is the right way to go considering more heat means the filament melts faster and during printing all is fine - if well adjusted.
On the other end you also have a lot of non print mooves, during that time the filament can sometimes reach boiling point in the melt chamber!
You might see the result of this when you see deformed areas at the starting points or when overhangs start to curl down instead of up.
My aproach to a "perfect" hotend goes against all design rules you can find for 3D print nozzles/hotends.
Firstly I use a stainless steel heat barrier combined with an all Aluminium heater/nozzle.
Secondly the nozzle outlet is 4mm long instead of the ususal "as-thin-as-possible" designs.
Thirdly no heater cartridge or ceramic resistor is added, instead the heater wire is wound directly onto the melting chamber and covered with an additional Aluminium casing.
Last but not least the thermstor is mounted as close to the outlet as possible.
I evolved to this design to avoid any additional insulators and the use of thermal cement.
If you check normal heating elements they try to prevent the use of additional fillers and glues, so I guess I could be right too
Biggest downsides so far:
Machining is not the easiest bit but can be done in about 3 hours on your personal lathe.
Drilling stainless steel for a heat barrier needs special tools.
Avoiding the use of additional insulators on an Aluminium hotend means a lot of work for the correct preparation of the Aluminium, after all one short on the heater can cause the electronics to fry.
Creating suitable connectors for the heating wire that still fit inside this tiny barrel is the worst bit.

Once I'm really satisfied with my design I could think of publishing the design but I doubt it will find much use in the general community.
So I might as well wait until Im able to combine 4 nozzles into one print head.
My next printer shall be bigger, faster and equipped with a 4-head system.
This way I can easily change colors during the print or use dedicated nozzles for infills and soft-touch perimeter material.
Current designs are bulky and usually use heater with more than 40W for more speed.
I hope to come up with something that has a footprint smaller than 5 by 5 cm

I got my printer basically to replace the old tiny one and if I would have know the problems that are to come I would have kept the old one as a spare
But I also see it as a hobby and the only real problems with the printer are the extruder and the hotends - I simply don't like the MK design, not matter which version number.
Not having a heated bed and no option for it in the hardware can be a downer, but again I knew this a problem to be dealt with later.
With the big print size finding a suitable heatbed is next to impossible, so that will be the next design once the hotends work the way I want them to.
Skeinfoge is something to look into at a later stage as current designs work just fine in Slic3r if you accept the limitations.
Failed prints due to the code happened but I don't count them as in the original design it was easier to count the finnished prints.
Would like to work with the manufactorer to get a proper design, but as I mentioned they still did not sent the corrected manual and refuse to hand out and code to work with. - Nothing anyone would call support....
But they advertise heavily and people buy their printers.
If their high end models perfom better I still can't understand why they stick to long outdated designs copied from other developers....

Printing in PLA might be good for some things but not for anything the has to last or is subjected to temperatures above 70° celsius.
Ready-to-printers like the UP or Markerbot are nice for everyone that needs results fast and without major complications.
But I need something bigger and sometimes I like a good challenge, especially if it involves using skills I learned over 20 years ago and never really used
My system for the heater wire worked nicely but getting tiny crimp connectors seems to be impossible.
The smallest I could find was for 0.25mm cable, that is a bit over 0.5mm in diameter.
Will check the local suppliers next week and in the meantime enjoy my half finnished print head ROFL

Sometimes getting the right idea just needs a few cold beer and a few mates that are even more drunk
For the heater wire connection I now substituted the sensor pipe of a broken fridge.
Only needed to trim down the outer diameter a bit on the lathe and got perfect tiny crimp connectors in return.
Next step is to get the tiny thermistor in place, for the time being Kapton tape has to do for the insulation.
Since I will leave these wires on the outside there should be no temp problem.
Will upload some pics before connecting the wires to the circuit board.
If all works out a video showing the failure or success will come next - to be continued

Finally Only the wiring is left, so here are some pics of my new hotend:




For size comparison I added the SD card to the pic.
The heat barrier is M6 stainless steel.
Top mount made from Teflon.
As you can see the hotend is pretty tiny, thanks to the full metal design the built-in heating instead of a heater cartridge or bulky resistor.
Not much time the next few days but I will try to get some live test done over the weekend.