Replicator vs Mojo

[Cymon]

I thought you guys might be interested in the head-to-head we had here at work between the Mojo they're renting and the Replicator I own:

http://joesmakerbot.blogspot.com/2012/10/makerbot-vs-mojo-showdown.html

[Zip Zap]

As you mentioned, Mojo has their own secret recipe filament or is it powder.  Mojo would have the same problem if using Makerbot filament.  It's like the difference between ABS and PLA on the same bot.  

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From: Cymon <joeal...@gmail.com>
To: make...@googlegroups.com
Sent: Thursday, October 4, 2012 10:38 AM
Subject: [MakerBot] Replicator vs Mojo

I thought you guys might be interested in the head-to-head we had here at work between the Mojo they're renting and the Replicator I own:

http://joesmakerbot.blogspot.com/2012/10/makerbot-vs-mojo-showdown.html

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[Cymon]

Well, the other thing Mojo does is fully enclose their filament from factory to you. Good for consistency, but bad for the consumer because you have to through them to do anything.

[Zip Zap]

Plus, I don't like the look of the Mojo printer.  It looks too claustrophobic.

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From: Cymon <joeal...@gmail.com>
To: make...@googlegroups.com

Cc: Zip Zap <zza...@yahoo.com>
Sent: Thursday, October 4, 2012 12:09 PM
Subject: Re: [MakerBot] Replicator vs Mojo

To view this discussion on the web visit https://groups.google.com/d/msg/makerbot/-/c71oZrYwdFcJ.

[PropellerScience]

We briefly looked at a Mojo, but it's 5" X 5" platform was too small
for what we need.

[Barry Schuler]

Very nice post.  I have experience with the closed systems like 3DSystems and several RepRap printers including Replicator and my view is that Rep2 will produce higher quality prints than $50K+ systems.  However, the industrial guys are far more experienced in the use of soluble support structures and their software front ends do a good job of generating clean support where needed.  Their Dual headed extruders are designed with the idea that one head is used for rafts and supports.  I have tried using PVA in the replicator but dual extrusion in the Rep is very quirky and the control over gcode generation lacking.  But these are very easy fixes and would expect that MB will address in MakerWare in time for the release of the dual headed Rep2.  That will be a Mojo killer...

[Have Blue]

Mojo can't use Makerbot filament anyhow - Mojo went to a 1.3mm filament diameter rather than the standard 1.75mm.  (the secret filament recipe isn't all that secret)

Additionally, there's no reason to try using different filament in the Mojo, as the print heads get replaced along with the filament spools (and are almost undoubtedly chipped to prevent them from being re-used).

[Have Blue]

One point, Barry - Makerbot and RepRap undoubtedly have kicked Stratasys's butt in terms of layer resolution - the best Stratasys can do is 127 microns, and that's only on their very highest-end Fortus machines (the Fortus 250mc at $45,000 can only do 178 micron).

However, resolution (which I believe is what you meant by 'quality') does not equal accuracy!  For industrial use, the Stratasys still has an edge, as you know that your print will be accurate to a stated level.  As Cymon notes, features on the Makerbot can be off by a bit, and that's not even considering potential part warping.

I'm not saying that a Makerbot can't make really good engineering prototypes, but settings and models will likely need adjustment, and produced parts should be double-checked with calipers.

[Barry Schuler]

Yes Blue you are correct.  Even the 3D Systems 3D Touch produces parts with more accuracy than Rep1 (in my tests).  It is clearly a far more robust from a mechanical point of view.  Sadly slow as hell.  Will be interesting to see how Rep2 does from bot resolution and accuracy point of view.

[hellphish]

I'm not sure if the accuracy of the commercial printers is due to mechanics or due to them controlling both the plastic and the slicing engine. Could be they have modeled the way their plastic behaves particularly well and can slice better because of it.  

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[Dan Newman]

On 6 Oct 2012 , at 6:08 PM, hellphish wrote:

> I'm not sure if the accuracy of the commercial printers is due to mechanics
> or due to them controlling both the plastic and the slicing engine. Could
> be they have modeled the way their plastic behaves particularly well and
> can slice better because of it.

It's likely two things

1. An plastic formulation which doesn't shrink as much after cooling, and
2. A factory calibration process

Indeed, 2 can compensate for 1 when you constrain the operation to a small
set of known plastics (as in the case of the Mojo).

Folks who assembled their own bots are familiar (or should be) with the
process of calibrating the bot's steps per mm in the x, y, z dimensions.
There's what it theoretically should be given the stepper motor, timing
belt, and pulley characteristics and then what you actually get in practice.
You make a few prints and tweak the steps per mm in the machine definition
file and then you get a very reasonable dimensional accuracy.

But with the Replicators, MBI has not seemed to call attention to this
particular process which users might do themselves. (Indeed, when the
accelerated firmware was first introduced, the axes lengths and steps per mm
were hard coded in the firmware. That's recently changed and from
looking at github, RepG can now transmit that info from the machine
definition to the bot's firmware. Hmmmm. Really good idea. Why didn't
we think of that for the Jetty Firmware ;) ;)

Anyhow, circling back: a Replicator 1 or 2 or even a ToM or a Cupcake
can produce reasonable dimensional accuracy. However, you have to take
the time to do some calibration prints to get their. I know for a fact
that doing that is part of routine maintenance on some of the big, high end
commerical 3D printers -- I've seen it in the manuals. They may do an
initial in-factory calibration on the Mojo's.

Dan

[Elbot]

replicator wins, mojo is run by nazis who believe in confiscation. i heard that they confiscated someone's leased printer because they didn't like what they were doing with it, claiming illegal activity, but they hadn't finished printing their model yet, so how can they have done something illegal if they hadn't finished yet? What is this Stalinism? Your thoughts are policed?

[Elbot]

This is what I'm referring to: http://defensedistributed.com/
I've emailed those guys in austin and told them to rent a replicator for $100 a month. There's a hackerspace membership in austin for $100 a month and they have replicators.

[Have Blue]

The shrinkage amount for ABS is pretty standard - I don't think Stratasys' P400 ABS (Dow AG700) shrinks any more than PA-747.  However, when using different materials, the Stratasys software does compensate for differing shrink values.  As well, a heated build envelope (versus just a heated bed) ensures that the entire part will shrink equally.

There's no dimensional calibration that needs to be done on a Stratasys - the only calibration done is to extrude a square of support material onto a square of model material to ensure that the offset between the two tips is fully dialed out during material changes.  Newer machines that don't use a foam build tray also have a calibration cycle that adjusts for an out-of-level build surface.  Anything beyond that generally gets handled with a service call...

[Elbot]

So when making stuff yhat requires dimensional accurscy, I should print out a large calibration cube to see how much the top shrinks vs the bottom. Cuz top shrinks more but bottom shrinks less due to hot bed? Then, design my large models with compensation in mind?

[Dan Newman]

On 8 Oct 2012 , at 3:36 PM, Elbot wrote:

> So when making stuff yhat requires dimensional accurscy, I should print out a large calibration cube to see how much the top shrinks vs the bottom. Cuz top shrinks more but bottom shrinks less due to hot bed? Then, design my large models with compensation in mind?

Use 100% fill for the cube. MAKE SURE YOU ARE NOT USING HEXAGONAL FILL WITH SF 50 owing to
a bug which will make 100% fill be closer to 50% fill.

Print cube.

If too little plastic on top (indented, concave), then too little plastic is being extruded; decrease stated diameter of filament in
print-o-matic or increase stepspermm setting in .xml file for RepG

If too much plastic on top (convex), then too much plastic is being extruded; increase stated diameter of filament in
print-o-matic or decrease stepspermm setting in .xml file for RepG.

Dan

[PropellerScience]

On Oct 8, 5:41 pm, Dan Newman <dan.new...@mtbaldy.us> wrote:
> On 8 Oct 2012 , at 3:36 PM, Elbot wrote:

> Use 100% fill for the cube.  MAKE SURE YOU ARE NOT USING HEXAGONAL FILL WITH SF 50 owing to
> a bug which will make 100% fill be closer to 50% fill.

So that's why my 100% infill isn't really 100%. I never knew...

[Dan Newman]

Doesn't exist in SF 35. I don't recall it existing in SF 47, but I didn't use
SF 47 much. Definitely is there in SF 35 and can be seen in gcode viewers such
as Pleasant3d.

Dan

[Dan Newman]

… bug is definitely there in SF *50* and can be seen in gcode viewers such as Pleasant3d.

Dan

[Elbot]

dnewman, i don't know what you mean by "make sure you're not using hexagonal fill". I mean, isn't it all automatic how the fill will be calculated? So, there's no control over this? That's why I always type in 99% fill so that it won't be 100% and incur the 100% fill bug. Please advise. Thanks.

[Doogiekr]

If you edit your slicing profile... there is a fill section in SF that gives you several options... see image (look near the bottom)

[Elbot]

so, you're saying i should type in "line, circle, or rectangle" instead of "hexagonal" in the repg settings? that way, i won't incur the 100% is really 50% fill bug?

What about just simply typing in 99%? Will that work? I mean, will 98% really be 99% fill as opposed to really being 50%?

Thanks.

[hellphish]

It's a radio button. In repG you hit ctrl-R to edit a slicing profile. Choose your profile from the list, hit edit, then go to fill and select a fill pattern.

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[Have Blue]

All Fortus/Dimension/uPrint filament is 0.070" (1.778 mm) in diameter - the Mojo is the first Stratasys product to have deviated from that.

Layer thickness depends on the machine and what it's set at - the smallest layer thickness that any Stratasys model can do is 178 microns (and that's only on higher-end models).


On Saturday, October 13, 2012 1:59:05 AM UTC-5, Alex Czech wrote:

Do you know the layer thickness of the Fortus ABS-M30i by any chance? I've been searching everywhere and I can't find out. Then I came across your post and you knew the layer thickness of the Mojo filament so I thought you might know the Fortus ABS filament diameter. 

Thanks