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veryken

versus Stratasys Mojo

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I'm trying to decide whether to purchase the Ultimaker 2 or the Stratasys Mojo. Anybody familiar with the Mojo?

There are many outrageous differences including price, which may shock many people into not even considering the comparison of the two (or deriding me for suggesting it). But bear with me. I don't want to discuss all the various differences except for the ABS output.

I need parts that are somewhat structural and functional. My parts are mechanical in nature but shaped and designed for the consumer (for household use). They will ultimately, hopefully, to be manufactured in clear polycarbonate. But first I need reiterative prototype testing.

How does the ABS output compare in quality, accuracy, strength, etc between the UM2 and Mojo? Anybody here use the UM2 for similar mechanical-part prototype testing?

For example, scrolling through the Layers View mode in Cura makes me think that the UM2 prints large solids in hollow-core at every opportunity. In other words, does the print software introduce ribbing (shown in yellow) for the actual output?

K4i5UMT.jpg

 

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Hi, I can answer your question partially. At 3PS our core market is prototyping in the mechanical engineering area, although so far we have also done manufacturing a lot more than we originally envisaged –my early view, due to the poorer surface finish from FDM printing, was that manufacturing would not be required but clearly ultimately it depends on what the part is to be used for as we are doing a considerable amount of manufacturing.

The Mojo was on our short list last year, primarily as being the cheapest “professional” printer available.

We decided against pursuing it in detail for two reasons, firstly the small build plate area and secondly, at the time, I am sure the filament was only available in one colour; I think it is now available in 7 or 8 colours.

It will almost certainly be far easier to use support with the Mojo as it prints support in a soluble material and optionally you can buy a self-contained washer to remove the material. You can though do the same thing with a dual extruder RepRap printer by using HIPS for support.

In the end we bought a 3ntr printer as it had dual extruders and a heated bed. It is very similar to the UM in overall mechanics/architecture although clearly it has a more reliable drive system.

I am inclined to think that the Mojo, especially for difficult intricate items, will produce a better job. I do note that its resolution goes “only” to .17mm layers whereas the UM will go lower than 0.05mm layers.

What you are referring to as a “hollow core” on the UM is a misunderstanding. You are looking at a layer map for a piece that has been setup to print with something like 20% infill. If you setup with 100% infill you get a solid piece. The Mojo has a similar function called sparse infill. Most of our pieces are produced with 100% infill for the same reasons you need it. This is all done by the slicing software not the printer.

So far we have not used ABS for prototyping, we use PLA and Nylon. I would assume the strength of ABS parts between the Mojo and the UM would be very similar. The key element will be layer adhesion and as long as the UM is setup properly I doubt it would be disadvantaged.

Accuracy could be a different thing. The only way I think to really determine that is to take an appropriate part and have it printed by both printers. We tend not to print assemblies but do print parts that have to fit existing assemblies, so accuracy is often very important for us. For most geometries we will hit 100 microns accuracy and sometimes will go down to 20/30 microns – the UM ought to be similar. My personal view is that manufacturer quoted accuracies are not actually accurate as I do not believe they take into account material shrinkage.

My gut tells me that the Mojo is a more plug ‘n play printer than a RepRap and if you are OK with the smaller build plate, more limited material types and colours then it could be a very good printer for you.

But equally for prototyping a RepRap style printer, if it is a good one such as the UM or 3ntr, is extremely capable. I think the only real drawback is when you have to use supporting material. Unless you use a soluble material (needs dual extrusion) you can end up with the supported face being very rough unless you have time/cost to spend in smoothing it, which can be very tricky on smaller items. I must say that so far for us we have been able to work around the supporting point and have not been defeated by a design given to us.

And do not forget that good product design takes into account the manufacturing environment. What is easy to produce on a CNC machine may not be easy on a 3D printer – and the reverse – we designed and prototyped a part that was to be injection moulded, only to find that the injection moulders could not produce it.

HTH

 

 

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We have two Stratasys printers at work, one uPrint SE and one Dimension Elite.

I have compared prints, and even printed the same object, with my Ultimaker 2.

The Stratasys machines has the advantage of a heated chamber, which makes large components easier to print.

For the Ultimaker, large ABS things are always a bit tricky to print (they want to bend and come off the platform).

With some experience you can mostly get it to work, but some designs are almost "unprintable" in ABS without a heated chamber.

For the print quality, the Stratasys machines seems as accurate as the Ultimaker in the X-Y-plane, BUT they offer considerably lower surface quality in the Z-direction I would say.

This is partly because the rather thick layers (0.254 mm for uPrint and 0,178 mm for Dimension Elite) but also the surface quality of the top layer always seems much worse on the Stratasys machines for some reason.

For what I do, the rather thick layers of the Stratasys-machines prevents me form printing certain things, like fine pitch threads, which I find very convenient being able to print on the Ultimaker.

I would say that for reliably printing rather large prototypes in ABS, Stratasys is a good choice.

When it comes to strength, one could assume that the heated chamber makes layer adhesion better on the Stratasys out of the box.

This sometimes seems valid for small components, but I have not done destructive testing on Stratasys prints to compare yet.

Playing with the settings on the Ultimaker can probably get you quite far too though. My printed sway bar link is still working fine for exampel: http://umforum.ultimaker.com/index.php?/topic/7240-examples-of-truly-practicaluseful-prints/?p=70778

For what I am doing though, the Ultimaker is a way more flexible machine which, can archive better quality at a much lower cost than the Stratasys-machines.

Things printed on the Stratasys machines typically looks like good prototypes (accurate and robust, but not very fancy).

The Ultimaker prints can go beyond that, to a point where your fist reaction is that you could probably sell them for a reasonable amount of money just because they look beautiful.

When I bought the Ultimaker 2, one of my demands was that I would not immediately be able to tell that the object was 3D-printed if held on an arm length distance. I would say that the Ultimaker 2 can do that but the Stratasys machines we have can not.

But that is probably just because Ultimaker and Stratasys are focusing on different customers which will use the printers for different purposes.

 

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I can answer your simple question:

"For example, scrolling through the Layers View mode in Cura makes me think that the UM2 prints large solids in hollow-core at every opportunity. In other words, does the print software introduce ribbing (shown in yellow) for the actual output?"

This is the fill setting. By default it is 20%. You can set it to 100% and get a solid part. Also you can control the shell thickness. When the fill is < 100%, you can increase the strength by using a thicker shell while the part is still somewhat hollow. This results in a stronger part that is lighter and use less material and therefore prints faster (usually). However, it is not as strong as a part with 100% fill. The shell setting can be used even with 100% fill to change our the outer surface of the part is built.

BTW what you see in Cura and the printer's capabilities are two different things. You can use other slicers to get different results. What I described above is how the Cura software works and is NOT an inherent property of the UM printers. A different slicer might produce different infill or use different methods for finishing the shell.

Also, PLA seems to be pretty strong. There is also nylon filament that makes strong parts.

 

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For example, scrolling through the Layers View mode in Cura makes me think that the UM2 prints large solids in hollow-core at every opportunity. In other words, does the print software introduce ribbing (shown in yellow) for the actual output?

 

I think you have a key difference here. Not the hollow bit, most printers can do that. It's the level of customization. With the Mojo, it will do right what it's told to do. But nothing else. Little room to tweak. While with the UM2, the default output might not be exactly as you want it, but you can tweak the hell out of it.

Depending on what you're looking for this might be good or bad.

(Also the rips are just on the inside, you can only see this on transparent prints, as the top/bottom/outsides will be printed solid. And you can adjust all this, in every way you want. You could even print only the ribs... yes, you can... not sure why)

 

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