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Using flex plates: my lessons learned
#1
Lightbulb 
We are all familiar with this situation: Either our print does not adhere to the printing platform and remains stuck to the FEP, or the print adheres so firmly to the platform that it is difficult to ever get it off the platform again undamaged.

I tend to have the latter problem with my Mars 2 Pro. Of course you can now play with exposure times etc. - but mostly you always have to adjust this depending on the model you want to print to compensate for factors such as contact surface, height and weight. 

As a workaround, it helped me to heat the print object with hot water including the print platform (after curing, of course) and then quickly cool it down with ice spray. Most of the time, I could then remove it relatively easily. But I have also broken models with needed 19 hours of printing time Sad

As an alternative, there are recently the flex plates. These thin metal sheets  are held to the platform with the help of a magnetic intermediate layer. After printing you can detach the flex plate from the printing platform, bent it and your model will detach from the flex plate easy. -easy peasy 

But this method also has disadvantages: The flex plate and the magnetic sticker build up relatively high (about 2.2mm in total). This makes a new leveling necessary.
If you try this "just like that" like I did, you will experience a surprise:

The home function of the printer does not ensure that the last set zero point is directly approached. Instead it works like this:

The printer lowers the platform until a flag at the back of the threaded spindle interrupts a light barrier. This sends a signal to the printer that it has now reached the "absolute zero point". AFTERWARDS the platform moves to the last set position according to the calibration value.

If you do not know this and just hit "home" -the printer tries to approach the absolute zero point with its platform. 

However, since the platform is now thicker, it may not be able to do so (the clearance of the platform axis may also be insufficient). Then printer is going to make a horrible crack sound when the slip clutch of the motor is released, to prevent damage to its components.
<Time for panic mode!>  Smile

If one had dealt attentively with the topic, one would have realized that one must print out a spacer with the old platform BEFORE modification, which must be inserted between the flag and threaded spindle. Additionally you need to replace the 2 screws with matching ones, because the original ones are  too short, of course. Sad

If you get that right and the print holds on the flex plate (more on that in a moment), it's a great thing.

But besides the points mentioned above, this has not only advantages:

- the maximum height is reduced by about 3mm

- the magnet pad can detach from the platform if the glue is dissolved by IPA or similar agents (has happened to me).

- You can't just "go back" without having to clean the plate from glue residues etc.



After all the preliminaries, here are my lessons learned:



I wanted to use both advantages of the systems without having the disadvantages. So the magnetic sticker has to go! 

For this purpose I used 2 super strong neodymium magnets in the size 20x40x5mm, which I had lying around here and glued them with super glue on the TOP of the platform. 

   


For ensuring that the print sticks to the flex plate platform, I also roughened it with 80 sandpaper and a random orbital sander - now the prints adhere super to the flex plate, the flex plate adheres super to the platform. If I want to print without flex plate, I just have to pull it off and recalibrate the printer (an update of the firmware would be desirable to be able to save 2 different calibration values) -the sheet is about 0.4 mm thick.
   



All in all, printing with flex plate is much more relaxed, since the objects are easier to detach and since I had ordered 2 at once, I can directly stick the next plate on the platform and continue printing while I continue working on the printed object.



Hope it is helpful to some of you! :-)



Happy printing,

Chri5
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#2
tHE onlt "too much" platen adhesion prolem I have expedrienced was with that damned useless 'water washable' resin. I wrote a nasty reveiw on Amazon and Elegoo contacted me offedring a 1 liter bottle of any resin I wanted--i.e. they know it's garbage--read more about my experiences with it here.

80 grit is pretty harsh--I had purchased a "Pro" platen to experiment with and roughed it up "just a bit" with 180 grit using a random orbit sander. I had to use an 8" coarse wire wheel in a 3600 rpm bench grinder to get that damned water washable crap off the plate...
-cliff knight-
[Image: 816-20120803-wide800.jpg]
paladinmicro.com
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#3
(01-28-2021, 06:58 PM)cliffyk Wrote: tHE onlt "too much" platen adhesion prolem I have expedrienced was with that damned useless 'water washable' resin. I wrote a nasty reveiw on Amazon and Elegoo contacted me offedring a 1 liter bottle of any resin I wanted--i.e. they know it's garbage--read more about my experiences with it here.

80 grit is pretty harsh--I had purchased a "Pro" platen to experiment with and roughed it up "just a bit" with 180 grit using a random orbit sander. I had to use an 8" coarse wire wheel in a 3600 rpm bench grinder to get that damned water washable crap off the plate...

You are right, 80 grit for roughing up the plate of the printer itself would be too harsh -BUT remind that the flex plate is, as the name suggests, flexible. So too rough (which equals to "too sticky") is no longer a problem when using flex plates and you never have to worry about prints stucked to your platform. Just a little bending here and there and your print will come of easy.

The trick (from my experience / from this modification) is flexibility AND roughness combined. 

At least it worked for me with models larger than 130 mm and really heavy (last model about 250 grams!).

[edit]
Just ordered some black water washable resin for testing. Curious how it will work out with this.


Happy printing,Chri5
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#4
I have a plain ol' Mars (a silver one) on which the platen had been powder-coated and had a typical glaze-like powder-coated semi-gloss finish. I did initially have non-adhesion issues but soon realized it was that semi-gloss finish that was the problem and sanded it lightly (just enough to break the glaze) with a random orbit sander and a 320 disc. Have not had any adhesion issues (over- or under-) since them (nearly a year now)--other than when using that god-awful water based crap.

Thank you for your thorough report!
-cliff knight-
[Image: 816-20120803-wide800.jpg]
paladinmicro.com
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