Patent troll Stratasys wins suit claiming purge/prime towers unpatentable

[Bryan Eckert]

Bambu challenged Stratasys patent on purge towers claiming prior art. Court disagrees.

PDF of decision:

https://s3-us-west-1.amazonaws.com/ptab-filings%2FIPR2025-00321%2F36

[Gary Myles]

What the heck?

https://patents.google.com/patent/US9421713B2/en

Patent filed in 2013

Pretty darn sure we had purge towers even as back as skeinforge in 2009

But can't find any mention of it

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[Joseph Larson]

I don't know why they're not claiming prior art in any of these making the patents invalid. Unless they don't want to take that tact for fear that someone will do that to them in the future. Honor among thieves 'n all.

[Bryan Eckert]

That's the thing Joseph. Bambu did sue on claims of prior art to invalidate the patent. The court, despite agreeing with them that previous examples existed - said it wasn't "widespread" enough.

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[3D Printing Tips and Tricks]

I don’t have explicit info on it, but to me it makes sense that there actually is no prior art. Think about it… Stratasys was selling FDM for years before the folks at Bath in the UK started doing open source designs. When Stratasys started selling machines there were no others.

[Bryan Eckert]

The patent was filed in 2013. 

There are videos of using purge/prime towers previous to that. The court actually agreed with Bambu on that point. However they said it was not “widespread” enough even though the videos were available on YouTube and would not invalidate the patent. 

Seems like this won’t be the end of this suit.

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[Bryan Eckert]

FYI, here is the article brought up by Bambu, published late October, 2012:

https://www.okob.net/wp/index.php/2012/10/29/dual-extruder-pla-printing/

And here is the video (also linked in the article):

https://www.youtube.com/watch?v=ZAafPtKjZSc

Which only has ~1K views. Regardless, it does predate the patent filing by half a year.

[3D Printing Tips and Tricks]

The 1st Stratasys 3d printer, the 3d modeler, was released in 1992. That’s the same year as the initial patents. Whether or not these patents included a prime/purge pillar, I’ve no idea. 
Regardless, that’s 20 years before the article Bambu cited.

[Bryan Eckert]

The patent that is being challenged is  US 9.421,713 B2 

The patent was filed for in March 2013, and was awarded in August of 2016. 

The court agreed with Bambu that public use prior art existed. What they said was it wasn't widespread enough to invalidate the patent.The13B9421713B2US94

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[Bryan Eckert]

I should also add that a European court has already deemed that Bambu's prime tower does not fall within the scope of the patent protection, as it prints multiple color/material on a single layer in a single tower, whereas Stratasys wrote the patent to print different materials per layer, or in separate towers (as it was for IDEX printing). Which I would assume is good news for Prusa, Snapmaker, etc.

[Ed Street]

Stratasys did not introduce purge towers until much later, when the F123 series (F170/F270/F370) began printing a “purge part” on the build tray around 2017. Older Fortus/Dimension machines continued to use purge buckets; same with the modeler.

From 1991 through roughly 2012, Stratasys FDM systems consistently used:

• A purge bucket/waste bin

• A metal or ceramic wiper bar

• A stationary purge chute

• A nozzle brush or scraper

When it comes to prime towers, Stratsys was late to the party. Ultimaker (2013) / MakerBot (2014) / BCN3D Sigma 2015) / Raise3D (2015) / LulzBot (2015) / Prusa (2016) were all using prime towers from 2013 to 2017, BEFORE Stratasys introduced the F123 series in 2017.

Perhaps this is where/how things have been soft on enforcement for these companies getting away with infringement :)  It also helps when you buy out your competition.

In light of this, I really have to question the listing of " The court agreed with Bambu that public use prior art existed.  What they said was it wasn't widespread enough to invalidate the patent.  "  Did they actually look at and consider these other companies' use before Stratasys made the patent? 

[Bryan Eckert]

Ed you don't have to question anything. I posted the link to the court's ruling. Go read it, it's in there:

"2. Prior-Art Status of Boyer
Patent Owner argues that the inventors of the ’713 patent both
conceived of the invention and actually reduced it to practice before the July
31, 2012 effective date of Boyer. PO Resp. 9–39; Sur-reply 2–9. Petitioner
disagrees, arguing that Patent Owner “has failed to demonstrate an actual
reduction to practice of the claims” on a date early enough to antedate
Boyer. Reply 2–12. On the record developed at trial, we agree with
Petitioner for the same reasons discussed above with respect to Patent
Owner’s argument for antedating the RepRap references. See supra
§ II.D.4

They agree with Bambu that the Rep Rap video (among others like KISSlicer) came first.

"In addition, we are not persuaded that RepRap Video has been proven
to have been sufficiently accessible to interested members of the public just
because it was posted on YouTube, which Petitioner alleges is “a ‘well-
known, reputable compiler and publisher.’”

There it is - not widespread enough to have been common knowledge. Which, honestly I looked at the video which came out 15 years ago - it has roughly 1000 views - and how many of those views were by Bambu folks and their lawyers?

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