Stratasys Mojo - Customizing print settings

[Enginwiz]

The Mojo Print Wizard is preset to a fixed slicing layer height of 0.178 mm.

A bit of digging in the program directory of the Mojo print wizzard and the

config file for the SOLO slicing engine together with the print profiles showed up:

There are already three profiles for predefined slicing heights on board:

The configuration and profiles are plain text files and easy to read.

Most of the parameters have well thought descriptive names.

Looks like the Mojo is as tweakable as the good old Replicators.

I switched from 0.007" to 0.005" layer height in the SOLO.TCL file.

The Mojo Print Wizard now starts up with a preset of 0.005" / 0.127 mm layer height instead of 0.007" / 0.178 mm.

And the model gets sliced at  0.005" / 0.127 mm layer height.

The T12 Nozzle of the Mojo print head has a 0.012" / 0.30 mm orifice

and prints in Stratasys ABS M-30 like the big industrial Fortus printers.

At a layer height of  0.005" / 0.127 mm the Mojo performs like a well tuned

Replicator 2 printing at 0.100 mm layer height. This is Wingcommanders

Deprime Test part printed on a Mojo at  0.127 mm layer height.

The layering is barely visible and the dimensions are within +/- 0,1 mm

of the CAD model.

I did not try out the 0.003" / 0.076 mm layer height. Printing in layer heights

less than 0,10 mm wastes a lot of time and in most of the cases the increase

in print quality is barely visible.

[Ryan Carlyle]

Nice!

[Kurt @ VR-FX]

+1

The question then becomes - why does StrataSys hide this layer height changing thing. Why not make it an option in the Mojo Print Wizard SW - instead defaulting 2 the standard print height!

:-(
-K-

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[Joseph Chiu]

Keeps people from unknowingly shooting themselves in the foot...

[Kurt @ VR-FX]

Yes - that's true - putting layer height too low - and building Bigger objects - will take INSANE # of Hours! TAke it from me...

:-)

[Jetguy]

Here is my request. I'd like to understand the entire profile of temps for chamber and print head during a print. As far as im

[Jetguy]

Oops hit send a bit early. Point is the process is what's most important to me. I already know the machine from looking at VRFX's.

[Enginwiz]

The profiles for higher resolutions are obviously hidden from the user on the Mojo.
You have to buy a high end Fortus 400 to 900 machine to print in layer heights
of 0.005 or 0.003 inch. Maybe they intentionally dumb down the Mojo to avoid
canibalizing their high end Fortus product line.

What really astonishes me is that Stratasys is officially specifies the print material
of the Mojo as low quality ABS plus and according to the print profiles ships
high end ABS-M30 in the Mojo cartridges. ABS-M30 or SABIC Cycolac MG94
as the polymer is called outside Stratasys is a high strenghts ABS used on the
Dimension and Fortus printers. It is also available as filament from other suppliers.
I use it on the Replicator 2 and the printed parts are very strong. Excellent
interlayer bonding makes it an ideal material for FDM printers.

[Jetguy]

Again, maybe it's something as simple as can be seen in the profile config but what is the chamber temp? Does it warm up for a while (presumably to stabilize the build plate temp) before starting a print?

What exact temp do they use for extrusion? What temp for the support material? Since you can get the ABS-M30 can you get the support material as well?

The reason I'm asking is while the machine is nice and yes, they patented the chamber- the facts of how they print the material are what really matters. In other words, if you can mimic the chamber temp and extrusion temp- equivalent mechanics should produce the same results. And 0.3mm nozzles are not that hard to find. 

[Enginwiz]

The Mojo preheats the build chamber for about 10 minutes before it starts to print. The problem with
the nozzle temperature settings is that Stratasys
cheated on the thermocouple wires like Flashforge.
Inside the extruder is a cold junction from Type K thermocouple to normal wire without compensation.

[Ryan Carlyle]

...Really? Wow. 

I guess if your chamber temp is controlled, and don't have variable motor heat soaking the TC junction like the Dreamer does, you could just set your print temp about 30-40C lower than nominal and call it good.

[Enginwiz]

Stratasys published the process of printing with ABS-M30 in patent US 20090295032 A1.

http://www.google.com/patents/US20090295032

 “CYCOLAC MG94-NA1000 ABS from General Electrics Co., Pittsfield, Mass." is their ABS-M30.

The polymer division of GE is now owned by Saudi Basic Industries aka SABIC. Here is the datasheet:

http://www.sabic-ip.com/gepapp/eng/weather/weatherhtml?sltRegionList=1002002000&sltPrd=1002003002&sltGrd=1002010283&sltUnit=0&sltModule=DATASHEETS&sltVersion=Internet&sltType=Online

CYCOLAC MG 94 is avaliable as filament under the brand 3DXmax Premium ABS  

http://pushplastic.com/collections/3dxmax-premium-abs

or even as pellets for filastruders on Etsy

https://www.etsy.com/de/listing/212314555/5-lbs-abs-plastic-pellets-cycolac-mg94?ref=market

Nozzle temperature should be in the range of 205 to 245 degrees Celsius.

On my not fully enclosed Replicator 2 with HBP I need at least 240°C

to get full interlayer strength.

[Jetguy]

No it's not just like the dreamer. I think the thermocouple amp is part of the termination board inside the head and thus might be compensated which makes a ton more sense. Again, inside the mojo print head there is a multipin contact board that mates to the socket. Things that are connected is the DC extruder motor, heater, thermocouple, and eeprom contains filament information.

[Jetguy]

Keep in mind, the blue head contains the filament drive, motor and thus termination board are outside the chamber bellows and likely has cold airflow directed in the upper chamber above the print chamber. So the claim the temps might be invalid are a stretch compared to the dreamer where the junction and amp are far apart.

[Enginwiz]

I already did a complete teardown on a Mojo extruder.

When I saw the chip on the PCB I thought: Yes, they do it properly and use a thermocouple to SPI converter.

But it is a AT88SC 25616C Crypto-Memory from Atmel.

http://www.atmel.com/Images/doc5211.pdf

By the way the complete Mojo extruder pinout to the hinge connector on the extruder carriage is:

 

1 - Motor wire black on internal  two pin connector

2 - Motor wire red on internal  two pin connector

3 - Heater cartridge black #2 on internal five pin connector

4 - Heater cartridge black #1 on internal  five pin connector

5 - Ground wire white to extruder barrel  #5 on internal  five pin connector

6 - Thermocouple red to extruder barrel  #3 on internal  five pin connector

7 - Thermocouple yellow to extruder barrel  #4 on internal  five pin connector

8 - Pin 8 on Atmel  AT88SC 25616C  Cryptomemory - VCC

9 - Pin 5 on Atmel  AT88SC 25616C Cryptomemory - SDA

10 - Pin 6 on Atmel  AT88SC 25616C Cryptomemory - SCL

So they simply connect the thermocouple to the PCB and accept several

cold junctions on the way to the controller board of the Mojo.

[Ryan Carlyle]

If the junctions are outside the heated chamber, it shouldn't add much error.

[Joseph Chiu]

Well, if the machine is preheated for 10 minutes as described, then as Jetguy already pointed out, it won't matter quite so much.

On Thu, Mar 5, 2015 at 10:17 AM, Ryan Carlyle <temp...@gmail.com> wrote:

If the junctions are outside the heated chamber, it shouldn't add much error.

[Jetguy]

To be honest, chamber temp is what I really want to know, plus an understanding if cooling air is used temp and CFM with some notes on direction angle etc.

[Enginwiz]

The setting for the oven temperature is 68 degrees celsius.

In the back center of the print chamber is a radial fan with
an open center air intake. There is a black plastic air duct
leading upwards, that covers the heating and blows hot
air towards the front just at the underside of the bellows.

The radial fan wheel has an outer diameter of around 70 mm
and runs at a low speed of aproximately 600 rpm.

There is no cold air supply to the build chamber or the extruder
assembly. The second fan sits inside a ATX power supply and
its air intake and exhaust are separated from the inside of
the Mojo plastic housing. The controller board and the servo
motors practically sit behind a big baking oven and are not
actively cooled by a fan. It gets pretty hot under the hood, where
the extruders with their PCB and flexstrip wiring are located.
I will try to put a temperature sensor under the hood during
the next print.

[Enginwiz]

This is a picture of the Mojo build chamber with fan and air duct.

Stratasys calls the build chamber "oven" and that is what it looks like.

 

[Enginwiz]

After tinkering around with the GUI settings in the solo.tcl

I found a way to unlock the dropdown list for the slicing layer height in

the Mojo Print Wizard 1.2. Now all preset profiles are available without

editing the solo.tcl each time.

The blue part in the solo.tcl unlocks the dropdown list in the Mojo Print Wizard

[Kurt @ VR-FX]

Holy Shit dude - that is Freakin' AWESOME!

I'm going to have to try doing that. Will be reporting back.

-K-