MakerBot Stepstruder MK7

by MakerBot, published

MakerBot Stepstruder MK7 by MakerBot Sep 20, 2011

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MakerBot Stepstruder MK7 by MakerBot is licensed under the GNU - GPL license.

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MakerBot® is offering our first dedicated 1.75mm filament extruder! It's a huge leap forward for personal manufacturing- you will be amazed by the improvement in your print quality, and the reliability of use obtained with the MakerBot® StepStruder MK7.

Designed from scratch, the StepStruder® MK7 contains a number of newly created custom manufactured parts. The MK7 redesign rolls in all the innovations and user experience from the MakerBot® Plastruder MK5, StepStruder® MK6, and StepStruder® MK6 Plus into one cutting edge, pint size device! The StepStruder® MK7 is compatible for use with MakerBot® Generation 4 Electronics and the MakerBot Thing-O-Matic® 3D Printer.


Smaller format, lighter, more gumption! The MK7 uses our tried and true NEMA 17 motor to drive it- a lighter extruder with tons of torque and reliable stepper performance. The extruder design has been carefully refined, and the assembly process is faster and requires fewer pieces than ever. The StepStruder® MK7 represents major advances in the design, functionality, reliability, ease of use, and print quality for desktop 3D Printer extruders. We've trimmed as much from the design as we could, and what's left is a tightly functioning device that has only one reason to exist- to extrude endlessly!


Our most compact extruder yet, the StepStruder® MK7 is less than half the weight of our previous extruder. The MK6 Plus extruder was a sturdy 1.8lbs, and the MK7 is only 0.8 lbs! The inside of your MakerBot® Thing-O-Matic® will feel positively spacious with an MK7 in place- spacious enough you could mount a second MK7 right next to it!

We've also shrunk the filament as well, and the StepStruder® MK7 is exclusively for use with our 1.75mm stock from the MakerBot® plastics selection. No more big 3mm filament here! All MakerBot® ABS colors and PLA are available in 1.75mm- now is the time to switch filament sizes if you haven't. Do you want cleaner prints, with less stringing, finer detail, and faster start-up? Drop in the MK7 extruder and you're off and running with 1.75mm. Really easy!


We're proud of what we can offer you with the StepStruder® MK7- the shortest build time of any of our extruders. Our assembler Colin, who has built more MK7's than anyone, reports that it takes less than half of the time to build a MK7 than any of our previous extruders.

The MK7 is still fully modular, and any component can be replaced or worked on without replacing the entire unit. We're trading up for easier, faster assembly so you can get back to the business at hand- printing! The lasercut acrylic pieces from previous designs have been removed in favor of precision-milled aluminum and high strength injection-molded plastic components.The extruder heats up faster too- knocking minutes off start up time, and saving hours of your time throughout it's use.


The MakerBot Stepstruder® MK7 is an all-new extruder which was designed from the ground up exclusively for 1.75 mm filament. We have eliminated all PTFE tube components from the design, allowing the extruder to work with higher-temperature materials, and dissipate heat more effectively than ever. A custom aluminum heat sink and fan keep heat from spreading from the cartridge heater.

It's our most compact and reliable extruder to date, and the simplest to assemble! The stock 0.4 mm nozzle allows printing at a layer height of between 0.32 and 0.27 mm right out of the box, for the most detailed prints you've ever seen from your MakerBot®. Even better, the compact design allows us to stack two complete extruders next to each other for an EXPERIMENTAL dual-extruder setup! The design and software for the MK7 are fully open source, so get involved and become a leader in Dualstrusion™! Keep in mind Dualstrusion™ is strictly experimental and not for the faint of heart! It's an open source challenge to our users to take EXPERIMENTAL dual extrusion to the next level!

Buy it: http://store.makerbot.com/stepstruder-mk7-complete-stepper.html

Stepstruder MK7 is tracked on Github: https://github.com/makerbot/Stepstruder-MK7.

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I've had these files re done as dxf and stl, so they are now veiwable without needing soldiworks,

I agree with some of the people below. Please could you upload a stp file aswell? It would give everyone more freedom to import the parts!

solidworks viewer 1) requires OSX/Windows and 2) doesn't let you export in a 3d format (at least in OSX).

Anyone got a part/vendor for the cooling fan? Mine is effectively DOA.

The new MK7 works like a charm! I'm using it with PLA and it just does it's job!

Great work, thank you!

No you can download the Solidworks eDrawings 2012 viewer it is on the solidwork web site

Bummer. Solidworks files! Posting all these files that are unreadable unless you own a $4000 program is hardly open source hardware. Can't you use a non-proprietary file format, or release 2D drawings in dxf?

The infamous Dual-Wield Extruders! The hit to your armor-class is well worth the extra damage and higher crit' potential!

The new parts made with the MK7 are turning out great. I haven't had to do any clean up at all! I should have switched to 1.75mm filament a long time ago.

Can I use an A/B-like switch to have a easy switcheroo from MK7 to MK6+ and back?

I'm thinking as I wait for my MK7 to arrive today that I'd like to put a spare stepper board in my TOM in that "fifth place" and have it be for the MK7.

Then I'd like to have it tuned, voltage-wise, for the MK7, and keep the MK6+ board as is.

Then I'd make some sort of 6P switch labeled 1.75mm
and 3mm to change between the two boards going to the MB.

I'd keep a connector for the MK6+ stepper free up top of the TOM, and also a connector for the thermostat and fan. (My board for that is hidden down in the e-bay.)

I likely don't need connectors for the heater or thermocouple since they are
both very easy to unscrew.

This setup would allow a quick and easy change to either extruder without opening up the bottom.

What kind of switch would be right for the 6-conductor ribbon?

That's really great !! I can't wait to try out the MK7.

Now MBI need to work on :

1) Upgrading the firmware for the Gen4 Interface Board to control the extruder and platform heater temperature and the extruder stepper motor.

2) Implement accelerated platform movement ( e.g. http://www.thingiverse.com/thing:10294http://www.thingiverse.com/thi... ) to increase printer speed and decrea
se printer vibration.

3) Figure out how to create a thicker first layer (but not a raft), so that the filament sticks better to the platform, especially for objects with large base areas.

4) Come up with better solutions to minimize warping. I have tried most of the suggestions listed at http://w
http://ww.makerbot.com/blog/tag/warping/ww.makerbot.com/blog/tag/warpi... and still have significant problems.

5) Allow the platform calibration script and parameters to be stored on the TOM and work with the Gcode (or S3G code), so that the object doesn't have to be continually re-skeined if the platform calibration parameters change. C
reate an automated method to check the leveling on the four corners of the platform, perhaps using a simple laser, which would also prevent accidental extruder crashes into the platform.

Perhaps MBI could come up with a prize for the best solutions to improve TOM usability, print quality and speed.

Just my 2 cents.

Thing-O-Matic Accelerated Custom Firmware


Glad to see my firmware made #2 on your list. You might be happy to know it's even better than accelerated; it's got lookahead now so it won't even slow down in-between moves unless it has to (generally, some minor bugs to work out).

As far as Makerbot's dual extruder goes, I'm excited tha
t finally people will be making models for 2 color/material prints. I only published a working dual extruder design for ToM about 7 months ago, so maybe in 7 months MBI will have caught up with my firmware advancements as well.



Dual Extruder / Dual Material Makerbot

According to the "dual extruder" tag up here, there have been designs predating yours (but nothing successful posted). Adrian Bower also had functional multiple heads before that! This is not a pissing contest, and things have been evolving in parallel.

MakerBot loves to be "first" in the press, because they can make a credible claim about having the first-to-market in DIY printers.


Your 'pissing contest' comment makes me think you misjudged my tone. If you actually examine my dual extruder design, you'll see I give plenty of credit to MBI for having things almost ready for it at that time. I also very specifically welcome other people to take the basic idea and expand on
it. That's what sharing these designs is all about.

The brilliant thing about the open-source community is that a guy like me can help push the entire industry forward. If SJFW never ever gets used by another human being than myself, that's OK, because it still brings certain ideas to the tabl
e that other people will pick up and run with.

That's what I really meant with my 7 months comment. Yes, I'm poking some fun too, but I sincerely hope the the MBI guys put out a firmware that makes mine look silly and primitive, much like they've done for the dual-extruder setup.

Anyway, it only cools the extruders down (but it is good for putting out PVA fires).

On a lighter note, ScribbleJ I'm sorry to have neglected your need for 2 colour designs. I have however posted some now... Wanna give one a go and let me know if any of them work? :)

For 3, just change operating nozzle lift on first layer in raft. You have to have raft enabled, just put raft and interface to 0.

Thanks for the suggestion on 3). I'll give it a try.

Does anyone have an estimate of this things maximum effective flowrate (without acceleration)?

Can you 3D print the injected molded parts?

What temperature does it need to handle?

What kind of detail do you need?

Thanks in advance :)

And it does look like an up extruder but it's cheaper and doesn't use milled parts

Yes, the original design for the MK7 was based on printed parts, but we didn't have the botfarm capacity to scale it up. instead we switched to 1.75mm. There should even be an old one-piece design kicking around in the Solidworks file.

Wow. The Cupcake/TOM sure grows fast.

Looks like a copy of the UP to me, 10 million dollar investment into makerbot and they copy the UP. :-$

NOBODY has come up with new designs. 3d printing has been around for some 30 years. It is interesting to see the convergence of hardware. In full disclosure I too own an UP!. Works great when it's not down. :)

Direct drive extruders have been around since the reprap darwin.

And they had the direct drive extruder before the UP was even out!

The UP! copied reprap originally. And Makerbot is openly a derivative of reprap... So they didn't copy anyone without giving notice. Part of the point of Makerbot is that they contribute to the community and the community contributes back to Makerbot. Its not a traditional business model, but it works.

Anyone care to make some measured drawings from all these SolidWorks files?

The thermal barrier and mounting plate have PDF drawings. If there is a specific part for which you would like a drawing, I'd be happy to make it. I would rather not make detailed drawings for all parts. I should probably also upload STLs for the two plastic parts.

So what is the MK7 Stainless Steel Thermal Barrier Tube actually? Is is Teflon coated on the inside?

Just stainless steel. No PTFE. This allows for higher temperature without PTFE breaking down.

So what is the max temp this can be run at now?

With the fan active, the extruder should not be able to exceed 300
ºC, and the safety cutoff should kick in and kill power before that point as well. Minus fan and without the cutoff, the nozzle can reach upwards of 400ºC, possibly as high as 500ºC; well above temperatures needed for printing with ABS.

During testing I connected the extruder directly to 12 V and it exceeded 500 C. It could probably have gone higher, but it was emitting a strong odor and. Please to not run the machine at these high temperatures or without a safety cutoff. After this test the extruder was cooled down and extruded fine at normal operating temperatures.

WOW, who bought the UP! and took apart their design and copied it? =-X

Meh, so what if they did? If it's a good design, it's a good design! Pretty much every human invention is a copy of an earlier one; why start complaining now?

I don't think it's complaining about good design.... It's just disingenuous to say "Designed from scratch." MBI bought the Up! about a year ago. It's okay to admit that someone else implemented better design and we're going to integrate it into our own design - but let's own up to it.

From their solidworks CAD - they seem to have copied some of the flaws that are in the Up! extruder design. Luckily, these things are very minor.

seems like someones filtering my posts. Makerbot own thingiverse O:-)

Direct drive stepper extruders have been around since the reprap Darwin -- the UP was the first to skip 3mm and use 1.75, allowing a smaller stepper.

It is just me or is this stepstuder enhanceable by removing the fixed plunger, adding two motorized plungers, and a second hot end (possibly with a unified dual heater block) to support two filaments?

Clockwise + plunger a = filament 1
Counter-clockwise + plunger b = filament 2

Possibly with having both plungers activated to withdraw the one filament and prime the other?

This would be awesome on a gantry based extruder as the head could move off the build area to clear/prime filaments.

Add t
wo of these stepstruders and you have 4 filament support all within the existing TOM/Cupcake package size!!! (Think 1 dissolvable and 3 colors)

I thought the same thing. Dimension printers do something similar except the head toggles to apple pressure to the central filament drive gear.

Craziness; the potential of this extruder is killing me, every time I hear newer possibilities over this... it's... like a tease! ACHHH (*throws his arms in the air)

Ack, i was mixing concepts! I started letting the notion of filament mixing get into the more simple approach of two nozzles for one extruder. This eliminates the need for clearing/priming and works better on the existing Cupcake/TOM platform. So all told, 2 extruders = 4 filaments and 4 nozzles...

The clearing/priming notion i've been tinkering with on a 7 color extruder and technically 7 isn't any special limit, just the colors I have laying around.

Definitely not just you, it's a really interesting concept. Two extruders could provide the CMYK needed for overlapping filaments to represent a full range of color (if there were ever software to support it).

I've thought about CMYK possibilities, as well... but I'm also thinking it's next to impossible without first being able to mix the melted CMYK filament combinations in precise measurements before extruding.

All I need to do is use up all my 3mm filament now :(

I'm putting together a mk7 3mm today! Possibly using pieces from the mk6+. Measure twice drill and tap once! :) In all seriousness, I have a shit-ton of 3mm myself and plan to sue it all.

Or just keep using 3mm filament like a sane person...

or drill the nozzle to 1.75 and extrude it to size :-D :-D :-D :-D

Great work, guys! Looking forward to seeing it in action, and seeing more complex designs with support material start to take shape with the dual head capability.