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CScottG
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Fri Sep 28, 2018 4:01 pm

-when it comes to watching youtube "watching" me - I don't care (..and sometimes the related recommended results to the side I find interesting, which can be useful). What I do care about is youtube (the service itself): wasting my time.

(..and conversely I do appreciate good Google results when shopping, and compare prices in its shopping function to other listings - generally decreasing my time spent shopping, by "watching" me.)
 
SecretSquirrel
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Fri Sep 28, 2018 4:29 pm

Chuckaluphagus wrote:
blitzy wrote:
wow that's really cool that you can print a flyable model, I initially thought it was just a display piece. Kinda surprised it's light enough, even with the skeletonization of the parts my 3d prints were still quite heavy (of the few I've done)

If I recall from looking at the model files and instructions (I believe this is the model that comes with the printer as one of the suggested prints), this prints with 0% infill, just shells. Would make it quite lightweight.


This are thin wall prints. Each wall is a single layer above the first 10 or so, which are double layer. I haven't weighed my full print set yet, but the manual puts the target print weight for the Spitfire at 432g and a flying weight of 840g for a 973mm wingspan. This is actually lighter than some EPO foam models of the same size. Dynam, for example, makes a 900mm EPO spitfire that has a listed flying weight of 980g.

Other than the fact that the wing ribs run an "odd" direction, these planes are constructed very similar to real aircraft. If you printed the just the shell, or just the ribs, they would bend and flex quite easily. Its the joining of them that makes for a stiff structure. It helps that one of the founders of the company is a professional architect and aircraft designer. It shows. Beyond being cool as RC models, they are incredibly beautiful to look at. It's the reason I printed this one in clear. It makes flying difficult, but being able to see the internal structure is really cool.

--SS
 
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Fri Sep 28, 2018 4:32 pm

I figured out when the initial print of the spinner did what it did, and it was "user error". I'll post more about it, with pictures, tonight. I'll also post some of my thoughts about the printer, after owning it for two weeks and keeping it printing for almost a week straight, as well as some general thoughts on getting a 3d printer, that apply to probably any printer.

Back to work now....

--SS
 
CScottG
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Fri Sep 28, 2018 5:58 pm

SecretSquirrel wrote:

This are thin wall prints. Each wall is a single layer above the first 10 or so, which are double layer. I haven't weighed my full print set yet, but the manual puts the target print weight for the Spitfire at 432g and a flying weight of 840g for a 973mm wingspan. If you printed the just the shell, or just the ribs, they would bend and flex quite easily. Its the joining of them that makes for a stiff structure.

..they are incredibly beautiful to look at. It's the reason I printed this one in clear. It makes flying difficult, but being able to see the internal structure is really cool.

--SS


It's those potential differences that I think the sla printer might be beneficial, perhaps even enabling a different internal structure that's lighter for added rigidity.

-and yeah, the print's look beautiful. :D Flying art.. a mobile mobile. :lol:
 
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Fri Sep 28, 2018 7:55 pm

I noted that I figured out why the spinner print failed. I reprinted it -- in silver since I ran out of clear -- to see if it had failed because something had hit the printer, or something like that.

Image

Nope. I actually watched as this one failed. Looking at the sliced model, it became obvious what was going on. The bottom edge tapers to a single layer. So each of the overhanging segments is being bonded to the bed by a single line of PLA. Once they get high enough, the slightest movement will topple them, even the natural vibration of the printer. I stopped that print and re-sliced the part, and added a single layer, 5mm brim.

Image

Successful print! Most of the brim broke off removing the part from the print bed. I haven't taken an X-Acto to the print to trim the rest yet.

I spent last night adjusting the bed leveling offsets -- printing lots of little squares. :)

The MK3 provides five offsets to account for variations in the print surface thickness -- a front, rear, left, and right, as well as a global that can be thought of as center. The printer does mesh leveling at nine points and it would have been nice if the firmware allowed adjustment at all nine points. To do the leveling, I made a 25mm, single layer square and replicated it in the slicer so I had nine of them. I placed one in the center and the rest around the perimeter , about 10mm from the edge of the print area. I picked a starting Z offset (center) of .700 and as each square was printed, I used the live Z adjust for the best print and made note of the value. It's not exact because you can't see the part well as the extruder tends to obscure it, but it gives you a good starting point. With all nine printed, I plugged the matrix of values into a spreadsheet and then normalized them to the center value. You subtract the middle from all the others and the result gives you calibration offsets for the other points. I set all four offsets and then printed again. Squares with holes get there offset lowered and squished gets them raised. I probably printed 10 series, homing in on the best values. As you do this, you can notice the difference when you are removing the squares. The effort to remove them becomes more and more even. When you initially start, some will be really hard to move, some will almost pop off on their own.

At this point, I think I have reached the limits of printer repeatability. They aren't identical, but I am also printing with a 0.15mm layer height, which is thinner than the recommended minimum. I will get an occasional gap in one of the squares that you can only detect by holding it up to the light. When placed in a tight grid, all the squares look pretty much identical. So now, its on to addressing oozing and stringing.

--SS
 
SecretSquirrel
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Sun Sep 30, 2018 2:09 pm

I had a nice big post written up yesterday and my web browser ate it because I let my login time out.... :evil: Completely my fault, but kinda ruined the mood.

So I've had the printer for two weeks now, and been printing for a week, almost nonstop. Overall, I've quite happy with it. The fit an finish it quite good, with one exception, which I'll get to in a minute. For a printer that has large structural and mechanical components composed of printed parts, the accuracy and repeatability is quite good. The mesh auto leveling does a great job of accounting for tilt in the bed. My bed has ~ 0.75mm of height offset from front to back.

Image

While I could pull the bed heater and install shims to bring it closer to level, that just provides an opportunity to screw something else up, and the software is handling the bed variation just fine. On the subject of bed leveling... this is one place where the printer firmware falls a little short. The mesh auto leveling takes nine measurement points. However, the firmware only allows for five points of compensation and they are not independent. The five points are live Z, front, rear, left, and right. Each point effects all three points along the perpendicular axis. So a -10um offset to the front will offset front-left, front-center, and front-right by -10um. Further, offsets are linearly interpolated across the bed. So that same -10um front offset will offset the center-left, center, and center-right points by -5um. This makes bed offset adjustment very difficult. I am not the only one to notice this and at least one person has developed a firmware patch that lets you supply independent offsets for all nine points via g-codes. I haven't made it far enough into the thread to see if this is being incorporated into the production firmware or not.

On the topic of firmware features, while I was typing the preceding paragraph, the printer was busy printing bed calibration squares and I got to test another feature of the firmware -- power loss detection and recovery. The printer is currently sitting in my home office and plugged into my UPS -- a cheap APC Back-UPS 750. The UPS is quite sufficient for my office workstation, but the transfer time is slow enough that the MK3 power loss detection will kick in before the UPS can transfer to battery. Twice during the last print, the UPS switched to battery and the MK3 power loss detection triggered. In both cases it was able to recover and continue printing where it left off. There are minor surface imperfections due to some ooze while the extruder was re-heating, but fall all but the most complex or detailed prints, it would have saved the print.

Oozing. With the stock I3 MK3 Slic3r profile, I get pretty significant oozing on print start up. Once the extruder comes to temp, residual pressure will cause filament to ooze out of the nozzle. If just pre-heat and let it set, I can get a 6cm string before it stops. Where this really becomes an issue is during mesh leveling. If there is any ooze on the nozzle, it can leave blobs at one or more of the measurement points. You can fine several version of custom start and finish g-codes to help address the ooze. I've got my own version that seems to almost completely fix it.

I mentioned one fit and finish issue. Actually, I came across two. One i mentioned earlier in the thread -- the heat bed screws having varying sizes of heads. The other is the power supply. If you go searching, you will find a number of threads on the MK3 power supply and failures of the supply, sometimes rather energetically. One of the PRusa forum threads is over 55 pages now. Most of the power supply issues have been reported by people with 120V AC grids, like me. A common report is that the power supply clicks when the bed heater is enabled and it is quite noticeable when the heat PID algorithm is holding it at temp. The bed power can be pulsed several times a second and the power supply clicks each time it is pulsed. Several people have reported that heating the bed and the extruder can pull right at the supplies rated 240W. Running the motors at the same time would exceed its rated capacity. This can obvious be avoided at the expense of extended start up time by sequentially heating the bed and extruder and keeping the motors off during that time. However we don't have any control over the PWM phases and rates during print so it is entirely possible that power draw exceeds the supplies rating routinely, for short durations, during a print. At least my power supply is audibly noisy beyond the clicks. With the printer at idle, when power draw is minimal, I can hear the distinct whine/hiss of the PWM circuits in the supply. A number of folks have ordered replacement 350W power supplies as an "upgrade" and I count myself in that group. I have a MEAN WELL LRS-350-24 arriving tomorrow. There are brackets to adapt the slightly different size MEAN WELL supplies to the MK3 mounts up on Thingiverse and I will be running a print of one over night tonight. As noted, the problems, including the click, seem to be mainly related to running from 120V AC. Prusa is aware of the clicking and states that it isn't anything to worry about and is mainly noticeable due to how quite the rest of the printer is. For me, $30 seemed a reasonable expenditure to remove the possibility of an energetic power supply failure, especially since I'm not monitoring the printer at all times. While I think the possibility of anything more than a pop, flash, and bad smell is incredibly low and I'm not really worried about that, I don't want to come home and find a failed power supply and have to wait for a replacement supply to show up. Should Prusa have addressed this from the beginning? That's kind of up to individual opinions. The included 240W supply is fanless and finding a 300-350W fanless supply is much harder. Likewise, the LRS-350-24 I ordered is not an auto-ranging, active PFC unit like the one that comes with the printer. Such a supply, is more like $75 instead of $30. Prusa made the choice they made, and based on the amount of testing they do, I am pretty certain they believed the included supply to be sufficient. However, it is certainly the weak point of the printer.

I can't compare the I3 MK3 to another printer as I don't have one, though I do have prints from an Ultimaker 2+ from my local library. Time will tell whether I can get equivalent quality prints or not. The MK3 is certainly capable though. I haven't finished calibrating and adjusting yet and my printer still successfully printed one of the torture tests you can find on Thingiverse, including 80deg unsupported overhangs. The back side of the overhang tests gets rough at 60 degress and pretty ugly by 80 degrees, but the print was successful.

Image

Now, back to fine tuning my print bed. :)

--SS
 
CScottG
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Tue Oct 02, 2018 5:43 pm

..this link is interesting (from today's shortbread no less):

https://hackaday.com/2018/10/01/high-de ... sh-nozzle/

https://www.youtube.com/watch?v=cuw-UHO88K4


..that that point about heat close to the work-piece is interesting, probably depends on the material being printed. Might be interesting (once "dialed-in" for a particular material) for thin-wall print.
 
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Tue Oct 02, 2018 8:49 pm

Just some more thoughts on both the I3 Mk3, and 3d printing in general...

Prusa makes a quality kit for the most part. I've already commented about the power supply. I printed a mount for the replacement this afternoon. I had to reprint one part of it due to my first shifted layer. I'm pretty sure its my fault though, as it happened at about the point I got up and started using my office this morning. I also made a mistake in slicing. The spacer that had the shifted layer was printed on end instead of laying flat. Anyway, I reprinted it laying flat. So I'm replacing the power supply. The only other part I feel the need to update/replace are the Y rod holders. In the stock kit, they are a half round that holds the rods and then a zip-tie is passed through the holder and over the rod to lock it in place. I started tracking down the skew in my bed and found that I could cut it from > 0.7mm down to ~0.2mm by shimming the rods in the holders. I wasn't being particularly precise as I was using slivers of my calibration squares as my shims. I has 0.1mm shim washers on order, arriving tomorrow, but I want to get the rods as good as possible before I start shimming the bed. So, I'm printing a set of "upgraded" rod holders that fully capture the Y rods and will hopefully be a bit more precise.

So, those to things I've hit so far. Still, even as it is, it is turning out decent functional prints. Could they be better? Yep, but its a work in progress. This is a kit after all. I said it before, if you don't like tinkering, buy the pre-assembled version. I think even the pre-assembled version will require a good bit of tinkering. Some of it is just inherent to 3d printing. You have to tune your slicer setting to your printer and filament. Even a $3500 Ultimaker 3 won't get you away from that. You can have the best printer in the world and completely bodge a print due to bad setting in the slicer. So, this is a kit, hobbiest printer, even if you buy it pre-assembled and you will have to deal with some amount of fiddling. I obviously can't compare it to any other printer as this is my first one, but my impression is that the extra work and testing that Prusa puts in, the time you spend tinkering will be much more targeted and getting good prints, rather than just getting things functional. But, that's just my impression..

On 3d printing in general... expect to spend another couple hundred dollars on top of the cost of your printer. You are going to be buying several spools of different types and colors of filament. At ~$20/kg for basic PLA, it can get expensive fast, especially if you start getting into more exotic filaments. Order a roll of Ninja-Flex.... $$$$. I've got a spool of black PETG arriving tomorrow for printing parts for the printer. The power supply mount I printed today was done in PLA since that's what I had and there aren't any significant mechanical requirements, though I will probably re-print it in PETG later, once the print quality is increased.

As far as content goes. Obviously you can find all manner of things to print, online. If that's your goal, then not a problem. If you want to create your own models, I would highly recommend you start playing around with CAD software prior to plopping down ~$1k on a printer. I've been doing CSG since I was in college, here and there as needed, but it still takes me a significant amount of time to put something together. CAD programs aren't known for their user friendliness, though applications like Sketchup are making it easier, if you can work within their limitations.

I'll try and get some pictures soon too.

--SS
 
Chuckaluphagus
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Tue Oct 02, 2018 10:42 pm

SecretSquirrel, I'm really interested to see how you're analyzing your printer. You're going a good deal further than I have - I tend to just throw a spool of filament on and print whatever I'm going for. I'm curious, how did you do the analysis of the bed tilt?

With regard to the power supply, I'm running the one that came with the printer and haven't had any issues at all so far. I do get the clicking of the bed heater, but the PSU itself isn't making any appreciable noise, certainly not above the noise level of the motors themselves during printing.

I think you're spot-on in your comment about the cost of filament. I've printed lots of PLA (as well as "PLA+"), including wood-fill PLA and glow-in-the-dark PLA, as well as a little NinjaFlex. I've spent ... too much money on filament at this point, trying to get desired colors and effects. On the upside, I have yet to have any bad filament - all the regular PLA I've bought, from the $12 MicroCenter store-brand special to the Prusament silver that came with my printer kit, has given me strong prints with almost no blobbing or stringing.

I found eSun wood-fill PLA to be amazingly stringy by comparison, at every temperature I tried from 180 to 230, but it still produced a good print otherwise.

I've done only a little printing with glow-in-the-dark PLA (Inland, MicroCenter's house brand again), since it requires swapping in a hardened steel nozzle instead of the stock brass. I find swapping nozzles on the Prusa MK3 to be straightforward, which is good, because the steel nozzle simply does not work as well as the brass. I think the steel is supposed to be a poorer conductor of heat as well, so I needed to slow down the printing movement to 33% (using the on-device interface) in order to get results I wanted. This, of course, meant that the printing was that much slower, but I was happy with the final result.

Oh, I did just get a nice spool of green AmazonBasics PLA, since they just started offering their own brand and I wanted to give it a shot. It prints very well, and I think the color is excellent, a nice, rich green.

I'm currently consistently sleep-deprived right now, so I may have rambled some in this post. If anything's not clear, or you'd like any more detail, just point out the gibberish and I'll try to follow up soon.
 
SecretSquirrel
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Wed Oct 03, 2018 7:12 am

Chuckaluphagus wrote:
SecretSquirrel, I'm really interested to see how you're analyzing your printer. You're going a good deal further than I have - I tend to just throw a spool of filament on and print whatever I'm going for. I'm curious, how did you do the analysis of the bed tilt?


If you connect your printer to you computer via USB and fire up Pronterface, you can dump the last set of mesh calibration values using the G81 gcode. If there aren't any, G80 will trigger mesh bed leveling. If you have an octoprint enabled printer, there is a plugin that will do this and present a heatmap as well. There are also online visualizers though I have found them not particularly helpful other than making pretty pictures for posting on forums. For me, the most useful thing was to just paste the matrix into a spread sheet and do some basic math to calculate relating offsets from the highest point.

What pointed me at shimming the Y axis rails was that the reported values were relatively linear in any given direction, but there was a distinct diagonal tilt to the plane of the bed. Now, if you go read online, you will find people agonizing over getting the bed level down to 10 microns or less, but I suspect there is enough variation in the PINDA probe readings that its really just a combination of internet competition and OCD driving that. I have seen at least one person mount a dial indicator gauge on the print head. That would give you absolute value and take probe variation out of the picture. The mesh bed correction was working pretty good even with my > 700 micron variation. It was only with large prints that I would see first layer issues. One thing to note. If you are shimming the rods, the end you shim is opposite of the end you need to raise. If you are trying to raise the back left corner of the bed, you need to shim the front left end of the rail.

--SS
 
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Thu Oct 04, 2018 6:56 am

On the left is the improperly plated spacer. On the right is the one printed laying down. You can see the point about half way up the left on, where the layer shift occurs.

Image

Closer shot of the layer shift. Despite the bad print orientation, and rather rough surface finish, I would have just used this spacer, except for the layer shift.

Image

Reprint, laying on the bed. This takes almost the full length of the bed to print. There is some variation of the bottom surface finish, but overall its quite smooth. Smooth black PLA shows finger prints... Just FYI.

Image

Top surface. The discontinuities around the holes are artifacts from the slicer and hold it laid out the infill. I was also printing at high speed which may make them a bit more prominent. The waviness is something I'll have to work on tuning out. Could be ringing the Y axis. Could be a byproduct of high print speed, Not super worried about it at the moment as this doesn't have to look perfect and that face will be hidden against a power supply. Plus, it looks much worse in the picture than in person.

--SS

*edit*

I forgot the new Y axis rod holders.

Image
 
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Thu Oct 04, 2018 7:11 am

So the printer is upstairs on the workbench, with the power supply removed.

I have another airplane I want to print, but I figured I'd take care of a few tweaks before I do. First up is swapping out the power supply for the new MEAN WELL. But, before I do, I want to take some measurements from the existing supply. I picked up a 100mV/20A current shunt so I can take some more accurate current measurements. I plan on taking voltage and current measurements on both the DC and AC side of the supply. When I print upstairs in the hobby room, the overhead lights will pulse slightly with the PWM of the bed heater so I'm curious what the AC current and voltage waveforms look like. The pulsing isn't unique to the printer. Running my hot air gun will do it as well. It's a variable temp/variable speed unit and the heating element is almost certainly PWM controlled. The light is a large 4000 lumen integrated LED unit and I suspect the LED driver is somewhat susceptible to fluctuations elsewhere on the circuit.

Once I get the power readings and the power supply swapped, I might re-print the Y rod holders in PETG, along with a Y idler and Y motor mount to get a better alignment on the Y belt. Or maybe I'll just put in the PLA Y rod holders for now. From there, it will be fine tuning the bed. I ordered a set of 5mm spaces (the stock are 6mm) and a set of 2.5mm compression wave springs. With that I should be able to get the bed pretty darn level.

At that point it will be time to do a bunch of calibration prints and measure and tweak.

--SS
 
Chuckaluphagus
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Thu Oct 04, 2018 12:17 pm

SecretSquirrel wrote:
Chuckaluphagus wrote:
SecretSquirrel, I'm really interested to see how you're analyzing your printer. You're going a good deal further than I have - I tend to just throw a spool of filament on and print whatever I'm going for. I'm curious, how did you do the analysis of the bed tilt?


If you connect your printer to you computer via USB and fire up Pronterface, you can dump the last set of mesh calibration values using the G81 gcode. If there aren't any, G80 will trigger mesh bed leveling. If you have an octoprint enabled printer, there is a plugin that will do this and present a heatmap as well. There are also online visualizers though I have found them not particularly helpful other than making pretty pictures for posting on forums. For me, the most useful thing was to just paste the matrix into a spread sheet and do some basic math to calculate relating offsets from the highest point.

What pointed me at shimming the Y axis rails was that the reported values were relatively linear in any given direction, but there was a distinct diagonal tilt to the plane of the bed. Now, if you go read online, you will find people agonizing over getting the bed level down to 10 microns or less, but I suspect there is enough variation in the PINDA probe readings that its really just a combination of internet competition and OCD driving that. I have seen at least one person mount a dial indicator gauge on the print head. That would give you absolute value and take probe variation out of the picture. The mesh bed correction was working pretty good even with my > 700 micron variation. It was only with large prints that I would see first layer issues. One thing to note. If you are shimming the rods, the end you shim is opposite of the end you need to raise. If you are trying to raise the back left corner of the bed, you need to shim the front left end of the rail.

--SS

Thank you!

Right now, I'm just running my MK3 standalone, loading files onto the SD card and walking it across the room as needed. I used Octoprint on a Pi3 with my previous 3D printer (a Monoprice Mini Delta), but in-between printers I repurposed that Pi and need to either get a new one, or try installing a Pi Zero W in the provided header location on the MK3's mainboard. Once that's done, I'll generate a heatmap and post it for comparison.
 
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Thu Oct 04, 2018 1:18 pm

While I greatly appreciate this thread, I have to say it's discouraging me from getting a 3D printer for a bit longer. I think it comes down to the fact that I don't want a new hobby, I just want a printer that works. FWIW, that's the opposite of how I felt about 3D printing until about a year and a half ago when when our second daughter was born, heh. I think I'll keep watching and waiting for another couple years.
 
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Thu Oct 04, 2018 2:20 pm

drfish wrote:
While I greatly appreciate this thread, I have to say it's discouraging me from getting a 3D printer for a bit longer. I think it comes down to the fact that I don't want a new hobby, I just want a printer that works. FWIW, that's the opposite of how I felt about 3D printing until about a year and a half ago when when our second daughter was born, heh. I think I'll keep watching and waiting for another couple years.


I wish I had a few thousand dollars to plop down for one of the high end systems to see how much fiddling is needed to get them printing, out of the box. In some ways, even if the general print quality is good from the beginning, I still don't think it will ever reach the "just works" point for anything but canned prints. So much of the resulting print quality and results comes from understanding how the printer works and what to do in the slicer to work with the printer mechanics and/or around the physical limitations of the printer, that expecting your average Jane/John Doe to be able to slice and print something successfully may be a stretch.

I liken it to photography in a way. We've reached the point where anybody can take a picture. And, the cameras in phones and point-n-shoots have gotten so good that, on occasion people get really lucky and get an outstanding picture, both from a technical and artistic point of view. However, the vast majority of the pictures are mediocre at best -- which is fine since the meet the need and are sufficient for the expected use. To reliably produce high quality photos requires lots of experimenting and studying to understand the camera, its configuration settings, and its operation in different settings. Then you have the artistic nature of the pictures themselves. Some people have inherently good compositional and framing skills, some practice and study and hone their skills over time, some just never make it. I think that's where we are at with 3d printing.

Doing nothing other than calibrating the Z axis as described in the documentation, the printer produced prints of a quality that would meet about 70% of what I wanted to do with it. The were ok, probably above mediocre. I was able to print a full airplane with enough accuracy that I could glue it together, in some places joining 0.5mm surfaces on end, and it is mechanically stable and should fly once I get to putting all the electronics in. I suspect that had I shelled out $3.5K for an Ultimaker 3 or something similar, it would have been capable of doing 95% of what I would ever need, out of the box. I, on the other hand, would still have had all the learning that I need to do, regardless of whether it's a $700 Prusa I3 MK3, $3.5K Ultimaker 3, or a $189.99 Monoprice MP Select Mini.

--SS
 
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Thu Oct 04, 2018 9:53 pm

So, I spent some time with the o'scope and my printer this evening. Max measured power draw -- 10.7A, from a 10A supply. :o

Now, I should point out that I don't have a hall effect current probe, so the measurements are pretty noisy. I'm using a 20A/100mv current shunt in the DC ground. Since the scope is on a 50mV/div setting with an unshielded shunt, I get all sorts of high frequency noise. I'm having to rely on the scope averaging to get a reasonable reading.

Hot end PWM:
Image

Bed PWM -- note, the yellow trace is channel 2, which is the DC output -- I moved the offset accidentally:
Image

Combined PWM:
Image

So, we have >9A current swings on a relatively high frequency PWM, and, during initial heating, a sustained period of pulling over 10A from the supply. If you are printing ABS, you could have a couple of minutes of running at >100% of the rated capacity. I'm not power expert, but its no wonder the silly thing ticks. Since this is a auto-ranging/active PFC supply, there is a front end likely has a boost converter that has to work a good bit on a 120V grid. I haven't taken the lid off yet, but I plan too. I expect the components are just enough for the rated capacity and at 120-130% over rated input capacity, some number of them are just giving up the ghost....

I'd really like to see the AC current waveform, but I'm not sure it's worth the $65 for a current probe...

--SS
 
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Fri Oct 05, 2018 7:08 am

Curious about the Monoprice MP Select Mini since you've mentioned it. Really how good or bad is it? I'm guessing 3d printers are "You get what you pay for" type of deal.
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Fri Oct 05, 2018 8:05 am

tanker27 wrote:
Curious about the Monoprice MP Select Mini since you've mentioned it. Really how good or bad is it? I'm guessing 3d printers are "You get what you pay for" type of deal.


I'm curious too, honestly. It's got a small build area and limited material support (PLA and ABS only). The Maker Select 3D V2 has a larger build area and full material support and is only $80 more. Absolutely no clue how good they are though.

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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Fri Oct 05, 2018 8:46 am

tanker27 wrote:
Curious about the Monoprice MP Select Mini since you've mentioned it. Really how good or bad is it? I'm guessing 3d printers are "You get what you pay for" type of deal.

My first 3D printer was a Monoprice MP Delta Mini, not a Select Mini, but that might be close enough to be relevant.

The Mini Delta is remarkably cheap ($160 when I bought it) and way, way better than you would expect for that price. It prints very cleanly, with good detail. But there were a slate of reasons I didn't stick with it:

  • It's inscrutable. If everything is working correctly, it produces excellent quality prints. If something isn't working, it can be very difficult to figure out why. Documentation is nearly non-existent. Customer support is slow and lacking. The best resources are a Facebook group and its partner wiki. Both of those are fantastic, but there's a lot of noise in there obscuring signal, and it was very difficult and confusing as a complete newbie in 3D printing.
  • Poor customer support. I had my heater block at the extruder fail after just three weeks of ownership, and customer support told me to ship it back for repair. I did, but it took six weeks to be returned to me, with no communication from Monoprice despite numerous e-mails from me just to get a status update.
  • Printing is inconsistent. Sometimes a print would turn out perfectly. The next time, under identical conditions, it would turn into a mess of spaghetti filament half-way through a print. The third time, fine again. No obvious reason.
  • Lack of dimensional accuracy (apparently a common problem of delta printers, not just the MP, but it's a definite problem). It just cannot consistently produce proper right angles and straight lines of a set length. There were all sorts of minutely detailed guides to working on solving this problem with the MP Mini Delta, and I tried some of them, but it was Sisyphean. The outcome of this is that the Delta is perfect for printing, say, model figurines, but not so much for producing a replacement part or an ersatz Lego block. I could print a beautiful Benchy, but not an accurate 20 mm calibration cube.
  • The user interface has issues. The actual screen interface and buttons are clear and work well. The integrated web interface loads a screen, but otherwise doesn't actually do anything - I've never heard of anyone being able to print that way, despite it being a touted feature. And the miniSD card slot for loading prints is apparently cursed, you might as well sacrifice a chicken and turn thrice widdershins for luck before trying to load up a file and print anything from a card that wasn't a supplied sample file on the card that came with the printer. I ended up setting up OctoPrint on a Raspberry Pi, connecting via a USB cable, and using that setup to control the printer, and it was a fantastic improvement.
  • No active development. This annoyed me. Had the MP Mini Delta not had obvious and weird bugs (nozzle crashing into build plate at random, for instance), it would have been just a minor nuisance. Monoprice doesn't appear to have any interest in supporting the printer after purchase, aside from making repairs under warranty, so I quickly realized that bugs weren't going to be fixed. The printer would benefit greatly from an actively developed 3rd party community firmware, but last I checked there wasn't anything available. There was an updated beta firmware floating around that supposedly fixed a bunch of problems. But that was released and then pulled, because flashing it also stood a good chance of bricking the printer.
  • Very small build area. This is an obvious and clear aspect of the Mini Delta, so I can't really complain about it too much. Where it came to bite me was in combination with the lack of dimensional accuracy: if I had to print something in two parts, the parts wouldn't mate.
So I set the MP Mini Delta off to the side and ordered myself a Prusa MK3 as a present to myself. It remedies every single problem I listed above, most importantly (for me) being the reproducibility and the dimensional accuracy. Unless I'm trying to change something up (swapping in a different nozzle, working with exotic filaments), I never need to tweak the settings to get a good result. Even then, tweaking has been as simple as re-running the first layer Z-axis calibration a few times to get the height right, or slowing down the printing speed. I print something nearly every single day (lots of toys and gewgaws, every once in a while something useful), and I've learned a ton about 3D printing in the process. Yes, the Prusa MK3 costs $750 (I built the kit) as opposed to $160 for the Mini Delta, but I'm willing to pay the difference for the quality improvements, the excellent documentation, and the active development and support. That's also why I went with an official Prusa instead of a clone - I have too little free time to spend it reading through Facebook posts for answers to my questions. :P

Personally, I wouldn't purchase a Monoprice 3D printer right now. Hardware quality on mine was good, but support and development were nonexistent, and I'm not prepared to spend the time on those myself.
 
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Fri Oct 05, 2018 9:07 am

That was the greatest review ever. And Thank you for it. :wink:
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Fri Oct 05, 2018 9:19 am

tanker27 wrote:
That was the greatest review ever. And Thank you for it. :wink:

You're welcome! (I think that was directed to me.)

I realize that I come off as not liking the MP Mini Delta, but it's a little more complicated than that. When it works right, it produces really excellent prints, almost as good as the Prusa. It comes ready-to-print right out of the box, you just plug in the power and the miniSD card and go. But when it doesn't work right, I was left with little clue as to how to proceed. From the Facebook group, it appears that there are a lot of people quite happily purchasing it specifically to modify it, extend the build height etc. If the goal is to have a 3D printer project, it's pretty much ideal. I just wanted to have a working 3D printer instead.
 
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Fri Oct 05, 2018 9:49 am

Chuckaluphagus wrote:
tanker27 wrote:
That was the greatest review ever. And Thank you for it. :wink:

You're welcome! (I think that was directed to me.)

I realize that I come off as not liking the MP Mini Delta, but it's a little more complicated than that. When it works right, it produces really excellent prints, almost as good as the Prusa. It comes ready-to-print right out of the box, you just plug in the power and the miniSD card and go. But when it doesn't work right, I was left with little clue as to how to proceed. From the Facebook group, it appears that there are a lot of people quite happily purchasing it specifically to modify it, extend the build height etc. If the goal is to have a 3D printer project, it's pretty much ideal. I just wanted to have a working 3D printer instead.


No, I think you just described the situation with all the various cheap Chinese clones. It's not that they are necessarily cheap from a manufacturing standpoint. Some of them might be, and quality control might be iffy at times, but lots of times you are getting the same parts that you will get in a more expensive printer. It costs a lot to maintain a company with active development and customer support. Product development (not cloning) is expensive and that NRE has to be spread across the units you sell. On a low volume product like a 3d printer, recouping development costs can be a significant percentage of the sales price. If done right, the open source model can help offset that cost since some of the development expense is borne by the community. However, you also have to continually innovate, or the cloners will eat your lunch. You also have to be true to, and respectful of, your community -- for nerds are a fickle bunch! :lol:

On another note, I ordered a current probe. It will be here tomorrow. I've had enough other situations in the last six months where I've wished I had one that I could reasonably justify going ahead.

--SS
 
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Fri Oct 05, 2018 1:46 pm

SecretSquirrel wrote:
On another note, I ordered a current probe. It will be here tomorrow. I've had enough other situations in the last six months where I've wished I had one that I could reasonably justify going ahead.

I'm not sure that even your upgrade is going to be ideal, my limited experience with MeanWell supplies left me a little leary of the build quality.

A TDK Lambda with the right ratings is not quite as cheap, but given that you've got about $1k riding behind it...
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Sat Oct 06, 2018 11:36 am

Spent some time last night installing the new Y axis rod holders. This morning I installed the new bed spacers and springs. Started at about 250mils of variation across the bed. After a number of passes, I'm now at 19mils of variation across the bed. I'm sure I could keep chasing 0, but I figure I've pretty well reached the point of diminishing returns. I haven't printed any first layer calibration prints yet. That will be later today. By the sound of it, I have an Amazon delivery at the front door. Hopefully its my new current probe.

--SS
 
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Sat Oct 06, 2018 12:08 pm

SecretSquirrel wrote:
By the sound of it, I have an Amazon delivery at the front door. Hopefully its my new current probe.

I love the "your package is 6 stops away message". I find something to do on the front porch just so I can get my new toy ASAP.
 
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Sat Oct 06, 2018 2:29 pm

Usacomp2k3 wrote:
SecretSquirrel wrote:
By the sound of it, I have an Amazon delivery at the front door. Hopefully its my new current probe.

I love the "your package is 6 stops away message". I find something to do on the front porch just so I can get my new toy ASAP.


I ended up getting sent the 650A model rather than the 65A model which is what I was trying to order. However, I think I'm going to keep it as it seems to do a pretty good job even on the lower currents and I do have occasions where measuring 100-200A will be useful. It has actually been pretty cool measuring the power supply. I'll post pictures later, once I get them all sorted.

--SS
 
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Sat Oct 06, 2018 7:16 pm

I re-checked my DC measurements using the current probe and the came out reasonable the same as using the shunt resistor. I couldn't use the shunt resistor to measure the AC as there was enough offset between ground and neutral that it would trip the GFCI breaker. It was only about 0.4VAC, but those things are pretty sensitive. So, on to the current probe measurements. These were at 1mV/100mA ratio on the probe.

Here is the AC side during bed and extruder heating. DC output will be about 10.5A.
Image

So its pulling 2.8A RMS on the AC side. If I am doing my math right, thats 75% efficiency

Once the bed and extruder are at temp and go into PWM regulation, this is what AC input looks like.
Image

A single cycle.
Image

Input current is peaking at 3.36A RMS.

I did notice how nicely lined up current and voltage are. This supply has active PFC, and it shows. Especially when you look at the waveforms from the MEAN WELL.

Speaking of the MEAN WELL, here it is under full load (bed and extruder heating).
Image

RMS doesn't apply here due to the current waveform. Input current is 8.4A. Notice the waveform. The supply does not have PFC correction.

Once the bed and extruder are in PWM management.
Image

I haven't taken apart the stock Prusa supply, but there is nothing in the external measurements that hints at it misbehaving. It just looks like its running at or beyond its max specs.

--SS

*edit* corrected stupid math errors
Last edited by SecretSquirrel on Sun Oct 07, 2018 10:17 am, edited 1 time in total.
 
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Sun Oct 07, 2018 10:15 am

SecretSquirrel wrote:
Here is the AC side during bed and extruder heating. DC output will be about 10.5A.
Image

So its pulling 5.6A RMS on the AC side. If I am doing my math right, thats like 37.5% efficiency :o


Quoting myself to point out that I did make a math error. It's pulling 2.8A RMS for 75% efficiency. :oops:

--SS
 
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Mon Oct 08, 2018 6:47 am

First, the MEAN WELL supply is significantly louder than the Prusa supply. As it has a cooling fan, its not unexpected and several people have replaced the cooling fan with something quieter. It is also louder at low load, when the fan isn't running and all you can hear is the switching noise. The sound profiles are different, obviously, but it will certainly vary from person to person as to which is more objectionable -- whoosh of a fan, or the clicks of the Prusa supply.

Took some pictures of the new supply installed.

Image

Image

One thing I should note and, looking back, this is a "well duh". If you are going to modify the printer, do so before you carefully level the bed, or expect to re-level afterwards. I didn't take the bed off or anything, but turning the printer over, as well as just bolting the new supply in place, is enough to knock things out of alignment by a few hundred microns.

Springs to the rescue.

Image

Yes, the spring isn't perfectly centered under the spacer, but i'm not unscrewing everything to fix it right now. I'll fix it next time I need to do maintenance. I re-leveled the bed and ended up about 17 microns before I started just chasing the light point around the bed. I'm guessing I hit the limits of the PINDA probe accuracy. Be careful if you have any OCD tendencies -- bed leveling can be a rabbit hole. :D

I finally got a chance to print a first layer calibration and after four or five passes of adjusting the Z offset...

Image

I didn't take a picture, but a nine square print turned out equally uniform. All with no mesh leveling compensation, they are all zeros. Quite pleased actually. So now it was on to print quality. I have half a dozen 20mm XYZ cubes sitting on my desk now.

Image

Image

http://www.kovarindustries.com/coppermi ... 059_v1.jpg

Image

Image

To the comment drfish made about tweaking and such, the changes I made in the while printing calibration cubes were all in the slicer settings and are things that you have to do with any printer. There is just too much variation in filament and individual printers for things to be finely tuned globally. There is still a bit more tuning I could do, but I'm pretty happy with the cube.

I printed the mount for the static prop for the Spitfire and couldn't help but smile when I popped it off the printer.

Image

The print was done on my modified version of the 0.2mm "fast" settings for the MK3. Admittedly its a pretty simple shape, but it's also one of the nicest prints I've produced, to date.

--SS
 
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Re: My thoughts on the Prusa I3 MK3 3d printer kit

Sat Oct 13, 2018 7:01 pm

So, I've moved past tinkering with the printer. I have a little bit on ringing, probably in the X axis, but correcting that would require dis-assembling the X axis. I'm worried that it would take a long time to get back to where I am now, and its just not worth it. I've moved on to learning the slicers. Even with a well configured printer, the quality of your print depends as much on the slicer settings and your understanding of what the print needs, as it does on the printer. I'll post some pictures after a bit.

I will say that I will probably buy another printer in the spring when I have a bit more free cash. And, despite earlier comments, I will likely buy another kit. My reasoning is that I have enough modifications that I'd like to make that I'd rather make them as I build the second printer, rather than having to take it apart. Having two printers lets me adjust one without being unable to print and if both are good to go, it lets me use one for test and draft prints while the other is turning out high-quality, final prints. Since someone will ask, if I built another kit, I'd used the modified Y rod holders, springs on the print bed, and cable chains on the print bed and X carriage.

--SS

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