Model Railroading > New 3D Printer (Part 5) – The Wedge of Death

This is Part 5 of a series on my recent experience with a Phrozen “Mini 4K” 3D printer.  (Parts 1 thru 4 were posted earlier.)
 
The very first layers of resin deposited on the Build Plate are called the Bottom Layers.  They are particularly critical, because if they do not adhere to the Build Plate tightly, Game Over.  You can tell if the Bottom Layers are adhering well when you go to scrape the part off of the Build Plate.  You want it to put up a fight (within reason) to let you know it won’t separate mid-print and cause the part to fail.
 
FAIL
There are multiple levels of a part failure that range from minor to catastrophic.  If a part has “soft” or muddy details, then it is a failure.  It may have printed fine, but still ends up on the reject pile.  Other times there is a feature that does not have a Support at the right spot and the feature ends up as a blob on the FEP.   Again, onto the reject pile. 
 
The Wedge of Death
The most feared failure is the part separating completely from the Built Plate during printing.  The best outcome is the part lands in the Vat, and it is a disappointment.  Worse-case scenario is the part lands in the Vat, tilts, and creates a wedge between the Build Plate and the FEP.  The printer doesn’t know the part has created this nightmare, and continues to cycle normally.  The Build Plate will raise up, allow the part to create the wedge, then the Build Plate will come down, pile-driving the part into the FEP.  If the part is thin and/or flexible, the FEP just dimples, and I have dodged a bullet.  However, if the part is thick or solid, more than likely the FEP will tear, and resin will go EVERYWHERE.  If the part is particularly stout, there will be enough pressure on the LCD screen to crack it.  (Time to get out the credit card.)  Needless to say, this is NOT what I want to find when I come to retrieve the finished part.
 
Fortunately, I have yet to experience a cracked LCD screen, but have had my share of dimples in the FEP.  The closest I have come to a part detaching from the Build Plate is having the layers not bond properly to the Bottom Layers.  Here is what it looked like:
 
 

---

Pretty scary to see an air gap under nearly half of the part!  :-0
 
It is a miracle it didn’t completely detach.  What causes that?  Not enough exposure time to bond the layers. 
 
Defaults
The default in the Slicer (Chitubox) is 4 Bottom Layers @ 50 seconds (for each layer) of exposure time.  The Bottom Layers bonded fine to the Build Plate, but the next layer was only given 2 seconds to cure, and that wasn’t enough time for all of the layer to bond.  Once a layer forms, and doesn’t bond to the previous layers, it creates a “skin” and the air gap will be permanent.  (I was amazed that the part actually came out decent, despite the Supports being deformed by the air gap.)  Being a newbie, it is difficult to gain the confidence to change a default setting.  I mean those default settings were established by folks much smarter than I, so why change them?  They wrote the software, so they would know what is best, right?  Well, yes and no.  They are making an educated guess for most printers and resins out there.  For example, the default for the exposure per layer is 5 seconds.  It wasn’t until I finally changed it to 2 seconds that I started getting decent parts. 
 
Initially I resisted changing the number of Bottom Layers.  I assumed the resin had been allowed to settle in the Vat and it needed to be mixed right before starting the print run.  That didn’t help.  Preheated the resin and printer for 1 hour, before pressing the Start button.  Nope.  I rotated the part on the Build Plate.  The air gap merely changed to the other side of the part.  If this kept up, I knew I was flirting with disaster.    I decided to increase the number of Bottom Layers from 4 to 8.  The air gap was reduced.  It was incrementally increased by 4 until it reached 16, which completely closed the air gap. 
 
I tried to reduce the height of the Raft, but wasn’t successful.  (The theory was that if the Raft had fewer layers, then the number of Bottom Layers could be reduced.)  As long as the dreaded air gap is eliminated, I can live with 16 Bottom Layers.
 
Boom!
I’m no longer afraid to change the default settings.  However, I only change one at a time, and not by a lot.  Then, print the part and carefully document any changes.  In hind sight, it seems like a no-brainer to increase the number of Bottom Layers.  But I tend to be cautious, like the bomb squad defusing a bomb.  If I make this change, will I be buying a new printer?  (Do I cut the red wire, or the green one?  Wait, no, maybe it’s that purple one…)



Edited 4 time(s). Last edit at 04/16/21 23:16 by tmotor.

Great series and thanks for posting.

I did have a serious wedge as you describe that pierced the FEP and the result was disaster. I had let the print run overnight and woke up to a resin disaster! Now I only print during the day and check every now and then. On my Phrozen Sonic Mini the resin had managed to get under the tape which is the only barrier preventing resin from entering the inside of the printer. The resin dripped on the motherboard and ribbon connectors for the LCD and touch screen, destroying just about everything.

This is partly my fault, as settings could have been adjusted as described in the post, but I'm new at this and just trusted the defaults. But the printer was just about destroyed by this event, and spare parts exceed the cost of the original printer. I really feel there should be a molded gasket between the LCD and printer bed to ensure the resin can NEVER enter the printer. The tape gets soft over time and loses its ability to potect against leaks.

So I know I was just unlucky and hope it never happens to any of you, but do check now and then to be sure you are protected against leaks. My new printer arrived today.

Brian N.

Yikes!

Hey Brian!
So sorry to hear that happened, but I admire your tenacity!   I'm sure there is a similar FEP tear in my future, and I will do exactly what you did.  Get another printer and keep going.

The stock tape applied to the printer looks like electrical tape.  Its only function is to keep the resin from going around the frame of the LCD, and into the printer.  The fact that it did NOT protect your original printer is not reassuring.  Based on your experience, I'm glad I replaced the stock tape with one of these:
https://smile.amazon.com/gp/product/B081D4NLCH/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

The issue is it will need to be modified with a standard paper punch to clear the thru-bolts that secure the Vat to the printer. 
I used this one:
https://smile.amazon.com/gp/product/B0797HTYYW/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Using the Vat as a template, ran a thin screwdriver down the holes in the frame and made small dimples in the gasket.  I turned the punch over, and removed the shield that collects the punched circles.  I could see the dimple through the die and aligned the punch on the dimples with relatively good accuracy.  The 1/4" hole is large enough to allow for some wiggle-room.  
After pulling the black vinyl frame from the backing paper, the frame will be flimsy.  Trying to align it square to the LCD screen, AND the thru-bolts can be frustrating.  I ended-up trashing my first attempt.  (Good thing it has 3 gaskets in the package.)  For the 2nd attempt, I used a trick employed by pros to apply vinyl lettering.  "Vinyl Application Tape" was applied over the top of the entire gasket BEFORE removing any of the sticky-back paper. 
https://smile.amazon.com/Magicfly-Transfer-Adhesive-Application-Stickers/dp/B08NG3VWN3/ref=sr_1_15?dchild=1&keywords=Vinyl+Application+Tape&qid=1618584423&sr=8-15

This provided a means of keeping the gasket "flat" and square.  The Vinyl Application Tape was removed from the punched holes so the thru-bolts would clear.  The edge of the sticky-back paper was pulled-back on the left-end first.  It was relatively easy to align the left hole with the left thru-bolt, and let the gasket contact on the printer.  Then the trick is to pull the stick-back paper a little at a time as the gasket is smoothed onto the printer face.  Align to both bolts before pressing the left side of the gasket down.  Be aware that the right thru-bolt sticks-up quite a ways, and needs to clear the right hole.  After the entire left frame of the gasket was down, I was confident the gasket was aligned to the printer.  The rest of the sticky-back paper was removed, but the rest of the gasket was kept away from the printer.  The right hole was lined-up, and the gasket was slowly smoothed-down.  Eventually the entire gasket frame will be in contact with the printer.  

Smooth the frame to ensure it is attached.  There will be a rectangle of black vinyl waste inside the gasket  frame.  No need to press-down on it, since it will be removed.  Remove the sheet of Vinyl Application Tape, then remove the rectangle inside the frame.  Done.

The Mach5ive folks do not offer a gasket for the Phrozen Mini, because the thru-bolts make the install such a hassle.  Plus, the stock tape will make most feel the Mach5ive gasket is not needed.

They do offer a shield (probably an iPad protector) that goes over the entire LCD screen of a Saturn.  The idea is to protect the face of the LCD from resin being cured onto it after a leak.  I did purchase one of these shield kits, modified it, and installed it on my Mini.  However, the clear shield did not evenly adhere to the face of the LCD, creating "clouds" underneath.  I ran with it for a while, but eventually removed it.  I wasn't comfortable with the idea that the "clouds" would diffract the light and slightly compromise the mask image.  Since every layer of resin passes thru the cloudy shield, I had to weigh the Safety Factor vs. the potential loss of detail.  Since the whole point of this exercise is to see how far I can push the Mini, I decided to remove it, and install just the gasket instead.  In the future I may revisit the use of the shield.  After I have some parts to use as a baseline, I would install the shield, and then carefully compare part details.  If there is any difference, the shield will be removed, and I will live with the idea that the next print run could be the last for this printer.

The video at the bottom shows how to apply the shield with the Vinyl Application Tape.  It is useful to watch to get an idea of how to apply just a gasket (without a shield).
https://mach5ive.com/collections/screen-protectors/products/mach5ive-lcd-screen-protection-kit-for-anycubic-photon-mono-x

Very Best of luck with your new printer!
I'm sure you will be cranking-out great parts with it for a very long time.
Dave


briancdn Wrote:
-------------------------------------------------------
> Great series and thanks for posting.
>
> I did have a serious wedge as you describe that
> pierced the FEP and the result was disaster. I had
> let the print run overnight and woke up to a resin
> disaster! Now I only print during the day and
> check every now and then. On my Phrozen Sonic Mini
> the resin had managed to get under the tape which
> is the only barrier preventing resin from entering
> the inside of the printer. The resin dripped on
> the motherboard and ribbon connectors for the LCD
> and touch screen, destroying just about
> everything.
>
> This is partly my fault, as settings could have
> been adjusted as described in the post, but I'm
> new at this and just trusted the defaults. But the
> printer was just about destroyed by this event,
> and spare parts exceed the cost of the original
> printer. I really feel there should be a molded
> gasket between the LCD and printer bed to ensure
> the resin can NEVER enter the printer. The tape
> gets soft over time and loses its ability to
> potect against leaks.
>
> So I know I was just unlucky and hope it never
> happens to any of you, but do check now and then
> to be sure you are protected against leaks. My new
> printer arrived today.
>
> Brian N.



Edited 3 time(s). Last edit at 04/16/21 09:12 by tmotor.

Your article title reminds me of a soap Oprah.

tmotor Wrote:
-------------------------------------------------------
> Hey Brian!
> So sorry to hear that happened, but I admire your
> tenacity!   I'm sure there is a similar FEP tear
> in my future, and I will do exactly what you
> did.  Get another printer and keep going.
>
> The stock tape applied to the printer looks like
> electrical tape.  Its only function is to keep
> the resin from going around the frame of the LCD,
> and into the printer.  The fact that it did NOT
> protect your original printer is not reassuring. 
> Based on your experience, I'm glad I replaced the
> stock tape with one of these:
> https://smile.amazon.com/gp/product/B081D4NLCH/ref
> =ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

Great idea! I will try that on the mini. I finally did get the Mini to work again, with a new motherboard.  So now I have two printers! And the learning curve continues!
Brian N.
 

briancdn Wrote:
-------------------------------------------------------

>  I finally
> did get the Mini to work again, with a new
> motherboard.  So now I have two printers!

OUTSTANDING!!
Resurrected from the dead.  How appropriate, being so close to Easter.  :-D
You now have the beginnings of a 3D Printer Farm.  

> And the
> learning curve continues!
  
Indeed!
3D printers are continually evolving. 
Because of the drive to keep prices low, they will be making compromises in materials, as well as fit and finish.  This means they will require some fine-tuning.  But considering their price-point, what they can do is pretty amazing.  
The Mini is basically the economy version of the Phrozen Dental 3D printer (used in the dental industry for printing dental models).
https://phrozen3d.com/products/sonic-4k-3d-printer-phrozen
The dimensions of the Build Volume is the same except they reduced the Z-axis by nearly 3".
Is it worth the extra $1k for that extra 3" of height?  For most folks, no.  However, the 7.8" Z height would allow printing a full 53' HO container; no need to break it into parts and deal with joint seams.  
My problem is I won't be happy with the Z height until I can print a 90' flatcar in one piece, which would be a 13" Z height, with an XY resolution of 35 microns (or better).  :-0 
So I will be gluing seams together for a very long time.  But there is NO WAY I could ever touch this level of detail with the old school Evergreen Strips and brass rod method, so I will gladly accept gluing a few seams together.

Appreciate the update. 
Dave
 



Edited 1 time(s). Last edit at 04/18/21 18:56 by tmotor.