Thoughts from the last podcast - PEI & PETG and Testors glue on PLA

[Bryan Eckert]

After listening to this week's show I must say I am amazed at the amount of people I run into who refuse to believe you need to use a release agent when printing PETG on PEI - especially smooth PEI. A quick search turns up all kinds of posts from when we had PEI stickers (mentioned in the show) being completely destroyed by PETG.

Also, I have tried using Testors glue on PLA before - to absolutely zero result. HOWEVER there are different Testors glues... which one were you using?

I have some PLA Gloop I recently bought that I haven't used yet. I plan to finally put together the Corellean Corvette model I printed 3 years ago on my X1C (it's humongous over 3 feet long and took 4 complete rolls of filament to print). 

[Bryan Eckert]

Some more thoughts on that - I often see posts by people saying their PEI bed doesn't stick anymore and I ask if they've printed PETG, and did they use a release agent. Usually the answer is no, so they don't realize they've been slowly destroying the bed. I also agree with you PEI isn't the end all miracle print bed like people think. I prefer my G10 garolite plates, especially printing with Nylon. It holds like a vice grip, then when cooled off the model picks up as if you had sat it down on a table.

[3D Printing Tips and Tricks]

Its Testors Model Cement for Plastic. There are only a couple of different types but they vary only in how thick it runs. Otherwise they are the same.

I've been using it for DECADES with 100% effectiveness. If you've had problems with it it's simply because you are doing it completely wrong. It's only good for PLA and ABS. It does not work with PETG. You do not use it like CA glue. It does not instantly bond which is why I prefer it. If you are using it without some form of clamping then yeah it won't work for you at all!

A thin coating on both surfaces that will come into contact. Give it about 30 seconds, then bring them into contact. You then have at least 15 min of time to adjust and clamp before it starts to set. The surfaces then melt and fuse together into a bond that is thicker than the layers and as such way stronger. Testors is the stuff used by old school model makers for more than 60 years.

[Bryan Eckert]

Thanks, I e used Testors forever as I’m one of those old school model makers, which has translated over into my 3D printing. 

I’ve always used the orange tube, but I think I used the thin liquid when I tried it. 

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[Ray Price]

+1 for the Testors Model Cement for Plastic (the standard red and white metal tube). I did try the Testors glass bottle which applies with a brush, and that didn't work nearly as well. I think I picked up the Testors tip from Andy on a previous podcast, and it has been a great solution for me, for much of what Andy mentioned above.  Long set time, strong bond, etc.  Previously I had used some ultrafast gel-like glue from HD which I think was CA based, and while it worked, I had real issues with the bottle tip drying out or being impossible to open.  Moving to Testors has been a great solution.  I do only PLA, so that also tracks with Andy's comments.

On to a couple other things from this episode.

For the flexible build plate.  I'm a big user of Wham Bam's PEX plate.  While they don't cover the N2 explicitly, they do have something close - Flexi Plate with PEX - QIDI TECH X-Max 3 - 330 x 330 – Wham Bam Systems.  The PEX has been great for both PLA and PETG.  PETG you have to be a little careful with and let the bed cool completely before removal.  The PEX surface is a solid sheet, and I've been using the same surface for 3+ years.  Occasionally, I scrub the plate with fine steel wool and acetone followed by wipe down with 91% ISP, but other than that it has been great.

Lastly, on the tramming issue.  I have had some dips in my creality beds using the flex plates, and my solution has been to use strips / fragments of metal flashing tape applied directly to the magnetic surface.  It's an iterative approach of measure, apply tape, measure, but it has really helped getting my bed "more" flat.  The metal tape is thin and has held up fine with the heat of the bed.

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[Bryan Eckert]

Thanks Ray I will pick up a tube for a try. I checked and what I have was the thin liquid in the bottle and no, it did not work AT ALL. As in, all it basically did was make the PLA wet. It did not melt the PLA like it would polystyrene. The PLA did not soften at all, I had both parts wet and clamped. The next morning when I removed the clamp, they simply fell apart. The stuff works so well on polystyrene, it bonds it near instantly.

I see all kinds of differing information out there, but there are so many formulations of PLA now with all kinds of differing additives it may just be a crap shoot.

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[3D Printing Tips and Tricks]

I’ve been thinking about trying some kind of tape on the magnet on the n2 to try to get the flex plate flat before I give up on it. Good tip on the. Metal tape.

[Ed Street]

What may be good for that N2 would be to toss Klipper on there, add something like TAP, cartographer, edy, etc., and run a bed mesh.

One test you can try is to put that straight edge directly on the mag sheet and see how true it is.  We go out of our way to get stupidly flat build plates only to put low-quality magnetic sheets that vary in thickness.

You can also forgo the mag sheet and put the build plate directly on the bed, use clips to hold it in place.

[Bryan Eckert]

Ed your comment made me remember something - they questioned if the Bambus could print an entire bed full of ABS - which the answer is a resounding yes BUT - you have to clip the print plate down because the magnet doesn't have enough force to keep the bed from curling up. So on larger parts clip the bed down and it'll be fine.

[Ed Street]

I have been giving this a ton of thought.  I may have a solution for the build plate issue.  

First and foremost, powder coating is not uniform on many surfaces.  Depends on how it was put down and the grounding used; this means the edges of the plate could be thicker than the middle.  Using the textured plate *MAY* be the issue.

Textured plates are very coarse, while smooth plates are flatter.  If the textured plate shows as uneven with a ruler, what would a smooth or semi-smooth plate show?  You said on the podcast that the bed was flat, but the sheet was not.  This could also make the magnetic sheet not flat, in which case you could add something to smooth it out, like a leveling compound. Which, in turn, would make the build plate flat.  Depending on the amount and volume used, this may affect the magnetic part, but you can add it to key areas to build up.

It is also not unheard of to use build plates that are smaller or larger than the bed, provided clearance permits it.

So, 

Some build plates are not the same thickness throughout. I have a thickness gauge for powder coating that also reads anodizing.  Since you probably don't have one, put the build plate on a flat surface (make sure the ruler reads flat on that surface first), then put just the flex plate on it and read it to find the low spots, and mark them to fill in later. One possibility is that the build plate itself is not flat.

If the sheet is flat, it must be the magnetic foam sheet; in that case, you could sand the high spots and/or fill the low spots.  You can use a variety of materials, such as filament, tape, and resin, to make it flat.

Since I do powder coating, I am including some PEI powder from my shop for reference on how it looks before spraying and baking.