Md/Lg Format Printer Platform for Precision?

[CCS86]

Hey guys,

I am planning to build a new printer in the near future and am researching my options. I have had my Ultimaker Original for about 8 years now, and have redesigned almost every component on it at this point. It is a great little printer, but it's time to step up a bit in size and hopefully in precision.

Budget: flexible (always looking for value though)

Size: 250 - 300mm cubed

Dual extrusion: I'm on the fence. I would probably be more inclined to run a larger and smaller nozzle with dual extrusion, than I would for multi material. Soluble supports would be cool, but I would be happy with single extrusion too.

Quality: This is one of my biggest goals. I do a lot of functional 3D prints and engineering prototypes. So, high precision, high geometric alignment (skew, perpendicular Z, etc), great extrusion control, and an absolute minimum of artifacts are prime objectives.

Materials: I most often print with high grade PLAs, so an enclosure is not necessary. Occasionally, I will print Nylon or flexibles.

Extruder Type: I think this printer should be direct drive. The 6mm rods on my UMO really limit its capacity to carry a DD extruder, so I have spent a lot of time trying to optimize its bowden. At this point, I want a motion system rigid enough for high speed printing with a DD extruder.

Axis Configuration: I would like to avoid deltas. I am fine with Z axis on the bed, but not X or Y.
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I am not opposed to a kit, but am happy to self-source as well. I have been looking at the Voron, RailCore, and HevORT. Any other suggestions would be appreciated!

[jens55]

I will be watching this thread with great interest. I too am looking at a step up from what I am currently running (CR10-S5).
One bit of input on the dual extruder thing - my thinking was the same as yours - dual extruders and I went ahead and modified my printer for that. As it turns out, this has been a great disappointment for me.
My current configuration is with one nozzle at 0.4 mm and one at 0.8 mm although I do run PLA on one and PETG on the other.
I have spent an enormous amount of time trying to get dual colours as well as dual materials to print and my conclusion is that it is just not worthwhile. This despite many examples on the web showing perfect multi colour prints .... Very frustrating.
I have consistent issues with one head drooling while the other is printing, there is the difficulty of aligning the nozzles to just the right height, there are issues with printing with just one head as the second (cold) nozzle will on occasion run into what the active head just laid down and on and on.
This is in addition to the enormous waste of time and filament as you switch between heads.

I am thinking about something with a tool changer now but I have severe doubts about this setup at this time. I believe it is too early for tool changers to have matured enough to make them useful on anything other than an experimental basis. A tool changer will also not be any faster or waste less filament than a dual nozzle printer. It would however offer more choice as to what filament and nozzle combination is loaded.

On a relatively small printer like you are looking at, I think you will find that a single nozzle size is a good compromise. When you go larger, like my 500 mm cubed printer, then print times can get excessive and you will want the option of a larger nozzle.

YMMV

[bot]

For multi-material-or-colour prints, IDEX or ToolChanger is essential. I wouldn't bother with multiple tools on one head, unless it's a mixing or multiple-input single hotend. Still, my preference would be for independent tools.

As for geometric accuracy, etc. You need to build the printer with precision methodologies. If you don't have measuring tools or reference tools that exceed the precision you are after, you'll never achieve it. IMO, a granite surface plate is essential. This gives us a reference plane to build off of.

Also, parts need to be made of metal. This helps with strength, but also with thermal expansion. Even aluminum, a metal with more thermal expansion than other metals, has less thermal expansion than ABS and other thermoplastics.

Parts also need to be big enough to resist deformation. Aluminum plates should be like 6 mm minimum, otherwise there will be no hope that they are flat (if they need to be flat...).

Z axis should be supremely precise. If your layers are not accurate, nothing else matters.

Extruders are important! Go for high resolution (relative to the size of parts you want to make) and direct drive. IMO, dual-drive wheels are good and an important aspect is to not mount the idler with spring tension. I've found that the spring tension allows too much variability. A rigidly mounted fixed-distance idler performs much better, from my experience.

This is just off the top of my head.

[CCS86]

@bot said in Md/Lg Format Printer Platform for Precision?:

For multi-material-or-colour prints, IDEX or ToolChanger is essential. I wouldn't bother with multiple tools on one head, unless it's a mixing or multiple-input single hotend. Still, my preference would be for independent tools.

As for geometric accuracy, etc. You need to build the printer with precision methodologies. If you don't have measuring tools or reference tools that exceed the precision you are after, you'll never achieve it. IMO, a granite surface plate is essential. This gives us a reference plane to build off of.

Also, parts need to be made of metal. This helps with strength, but also with thermal expansion. Even aluminum, a metal with more thermal expansion than other metals, has less thermal expansion than ABS and other thermoplastics.

Parts also need to be big enough to resist deformation. Aluminum plates should be like 6 mm minimum, otherwise there will be no hope that they are flat (if they need to be flat...).

Z axis should be supremely precise. If your layers are not accurate, nothing else matters.

Extruders are important! Go for high resolution (relative to the size of parts you want to make) and direct drive. IMO, dual-drive wheels are good and an important aspect is to not mount the idler with spring tension. I've found that the spring tension allows too much variability. A rigidly mounted fixed-distance idler performs much better, from my experience.

This is just off the top of my head.

Good thoughts. I agree.

I'm a mechanical engineer, and run a CNC manufacturing firm. So, I have access to precision equipment and practice these things every day. I have a small granite at home (used mostly for sanding things flat), but we have giant, qualified granites at my shop.

As I'm sure you know, while bad assembly technique can botch a good design; even good assembly technique can be thwarted by poor design. So, I'd definitely like a platform where some consideration has been given for maintaining (or even adjusting) geometry during/after the build. At the very least something that doesn't constrain the assembly in a way that guarantees distortion.

Dual drive gears are a must, for sure. I am running a custom extruder drive on my UM that uses the Bondtech gears. Interesting thought on your dislike of a spring loaded tensioner. I can see that how, especially in areas with multiple retractions, your effective drive ratio could shrink. Even areas where hardness of filament might vary a bit could cause variability too. Maybe I'll do a test with my current extruder, where I replace the spring with a spacer and set a fixed distance. There is another inherent flaw in the Bondtech gears, where the gear lash is tied to the filament size and amount of "bite" you dial in. I made my idler arm in a way that the idler gear axle bore is actually an obround, instead of a cylinder. Then I have a set screw feeding in at an angle to act on the axle itself. This lets me adjust my spring tension for bite into the filament, then dial in gear lash after the fact. With too much lash, what's the point of dual drive really?

I think I'm over the multi-extrusion altogether for the moment. Like @jens55 said, just not mature enough to justify the complications and compromises, for my current needs.

As goofy as the UM wooden chassis looks (better stained black), it does a pretty good job of being thermally stable and reducing resonance.

[martin7404]

I just finished building MULDEX 3d printer. It js a Rep Rap style project with 3 Z and 400x300 buildplate and kinematic coupling with . Corexyu kinematics, 2 independent dual extruders and duet wifi with duex and paneldue.

[deckingman]

@CCS86 Multi-colour - use a mixing hot end - multiple inlet but a single outlet. Multi-material - use a tool changer (or IDEX). A mixing hot end will get prints done much quicker, and with some creative gcode processing can negate the need to even purge between colour changes. But all filaments get heated to the same temperature so for multi material with different temperature requirements, that can be a problem.

[CCS86]

@martin7404 said in Md/Lg Format Printer Platform for Precision?:

MULDEX 3d printer

Looks interesting. Information for it is a bit sparse.