Larger Ultimaker Designs?

[sydneydesigner 0]

Hi everyone,

First of all many thanks for all the contributions I've been reading over the past few months on this forum, Google Ultimaker Group and the Reprap forum....particularly from the regulars. I've found them very inspirational, if a bit daunting and bleeding edge at times! I'm a design engineer based in Sydney but I don't have a rapid prototyping machine yet.

I'd like to print larger parts, of about 1kg weight. They would fit within an envelope of about 100mm by 300mm by 500mm, and could be printed lying flat or perhaps standing up. I'd prefer not to print them in 4 pieces. So, I'm looking for your thoughts please on larger Ultimaker-style designs that could do this. Do you think larger X,Y,Z axes are practical give your experiences with the standard Ultimaker so far? I like the design of the Ultimaker and feel that it is probably the most upwardly scalable design out there, basically because it doesn't move the (heavier) part in the X or Y axes, and the extruder functions much the same independent of part size. Would you agree?

I know about the taller (i.e. Z axis only) Ultimaker+ but I've been told by Ultimaker that is not for sale for the next few months at least. Apparently there are some issues to sort out as printing with it becomes more challenging because the object itself has limited stiffness and becomes a large lever which exerts torque on the platform. Perhaps larger X and Y axes would be easier to implement - what do people think?

I think there are a few Ultimakers in Australia now......with a bit of luck, maybe someone is already working on a larger Ultimaker in/near Sydney!

I'd be very interested in your thoughts please.

[owen 19]

Hi

I live near Newcastle but aren't planning on making my UM bigger, though it would be good if it was bigger in X or Y for what I'm working on at the moment.

I'd say it's fairly doable.

For X and Y you need longer wood panels, longer shafts and longer bowden tube and you would suffer in accuracy and stringing as a result.

For Z you need taller wood panels and longer screw.

Basically I think you'd need to get it going reliably and maybe have backup power.

Good lusk.

[Daid 306]

I'm not sure where I read it, but if you increase the X/Y then you'll run into stability problems with the Z platform. It's only held at 1 side making it a big lever. You might need to use 2 threaded rods on both sides, with the added complexity.

[ddurant 0]

I think Martijn told me that it gets difficult to scale up the design, though I don't think he said what the limit was or if we were anywhere near it.

IIRC, one big issue is getting longer X/Y rods that are very straight. As they get longer, it gets harder to get ones that are as straight (and stay as straight) as we need. You can get around this by using thicker rods but then you're adding weight and potentially lots of other changes needed to support bigger rods..

Changing Z is a bit easier - there are a lot fewer bits that need replacing.

[sydneydesigner 0]

Interesting points thank you. Here are a couple more considerations....

Do you think there is much sideways force from the UM extruder on the object, that might flex (or even topple) objects as they get taller?

Do you think a longer Bowden tube would introduce more problems? (From the forums, quite a few people seem to be having problems with the current Bowden.) The Bowden would presumably need to increase by a similar amount to any z-axis increase, and only by some portion (due to the angles) of any X-axis and Y-axis increases.

[ddurant 0]

Do you think there is much sideways force from the UM extruder on the object, that might flex (or even topple) objects as they get taller?

In general, the nozzle shouldnt touch the object being printed - the only connection between the nozzle and the print should be a very small bit of liquidy plastic. In reality, this isn't always true because some bits of prints can curl up a little and cause (usually safe) contact with the nozzle. Large overhangs where you're printing onto air as much as onto plastic are notorious for doing this.

The real issue here is probably more about the normal vibrations of the machine. X/Y movements in one direction push the machine in the other direction and with the speed these things can run at, it can make for a bit of a bumpy ride. I think this usually isn't a problem (never has been for me anyway) but since the print is only connected to the machine via the first bottom layer, you could end up with that equaling a lot of force at the top of a tall object. You could use a raft or something to help anchor the print to the platform but that delays/lessens the problem rather than solving it.

Do you think a longer Bowden tube would introduce more problems? (From the forums, quite a few people seem to be having problems with the current Bowden.) The Bowden would presumably need to increase by a similar amount to any z-axis increase, and only by some portion (due to the angles) of any X-axis and Y-axis increases.

Nope - don't need a longer bowden if you're just increasing Z.. X and Y only/always move at just the top layer - you can add more space at the bottom (Z) without having to make any changes to X/Y.

[sydneydesigner 0]

Thank you, this is very useful.

It's sounding like increasing Z is easier than increasing X and/or Y. As you point out, increasing Z doesn't increase the Bowden length (assuming the extruder stepper is mounted the same distance down from the top of the UM).

I'm wary of straying too far from the norm and forum expertise (at least for my first printer). Reorientating my objects to print in a taller UM like Ultimaker+ will give me overhangs.....but maybe that is OK given the pretty impressive Yoda ears seen clearly on Florian's useful website

http://techwall.net/20-microns#more

.

In general, the nozzle shouldnt touch the object being printed - the only connection between the nozzle and the print should be a very small bit of liquidy plastic. In reality, this isn't always true because some bits of prints can curl up a little and cause (usually safe) contact with the nozzle. Large overhangs where you're printing onto air as much as onto plastic are notorious for doing this.

What minimum overhang angle (from the horizontal) can be reliably achieved with a standard Ultimaker (and what are the tricks to achieving this)? Do you think this can be translated to similar overhang capability for a taller Ultimaker?

[ddurant 0]

What minimum overhang angle (from the horizontal) can be reliably achieved with a standard Ultimaker (and what are the tricks to achieving this)? Do you think this can be translated to similar overhang capability for a taller Ultimaker?

I think 60 degrees (so.. 2:00 with noon being a vertical wall) is the number people usually quote. Where on the print this happens (sorta) doesn't really matter - could be right near the start or could be near the top as the issue is about putting plastic onto thin air.

There are a number of things you can do to help push the limit but you'll never (with FDM) be able to just print on air. My favorite things that help are lowering the temperature and having a high width:height ratio.

[sydneydesigner 0]

Thank you for this guidance.

Basically, what it seems to boil down to is this.

1. A taller Ultimaker+ (more Z, same X and Y) will perform identically to the standard Ultimaker up to an object height of 22cm - am I correct?

2. Thereafter, as the Ultimaker+ platform steps lower and the object gets taller, the only extra issue to consider over the standard Ultimaker is the potential vibration-induced sideways leverage forces, which would tend to get worse for taller objects but would probably not be so much of an issue for broader based objects - is this right?

The real issue here is probably more about the normal vibrations of the machine. X/Y movements in one direction push the machine in the other direction and with the speed these things can run at, it can make for a bit of a bumpy ride. I think this usually isn't a problem (never has been for me anyway) but since the print is only connected to the machine via the first bottom layer, you could end up with that equaling a lot of force at the top of a tall object. You could use a raft or something to help anchor the print to the platform but that delays/lessens the problem rather than solving it.

[konrad 0]

I'm not sure where I read it, but if you increase the X/Y then you'll run into stability problems with the Z platform. It's only held at 1 side making it a big lever. You might need to use 2 threaded rods on both sides, with the added complexity.

That is very true - with bigger building platform AND more mass on it you will need more Z shafts to keep it strictly horizontal. I imagine that having 2 or more Z shafts would requie belt(s) to connect them (just like X/Y shafts are connected now).

While increasing envelope size at some point it might be more feasible to vertically move the whole extruder X/Y system with 3 motors, shafts and everything rather than building platform. That's what those guys did: http://lebigrep.org/ But that would require a major redesign.

I wonder how long would it take to extrude 1kg of plastic. Weeks? A bigger nozzle diameter might help a bit here but still it would take several days depending on layer height. Just remember to count into the budget cost of a UPS unit

[sydneydesigner 0]

Thanks for all your ideas.

There is a parallel discussion on this topic in the Ultimaker Google Group which people may be interested in:

https://groups.google.com/forum/#!topic ... 9eprnjA1bQ