Last time on the PEI bed channel I showed you an energetic branded bed that I purchased
and tried out and found worked really well on both sides.
On both sides.
Some of you who have PEI beds raised an issue though - one side, is plain steel.
Except, it's not.
Or is it?
Well let's dig a bit deeper.
See, the issue is that when you buy a PEI bed normally, well, this is the first issue
really I think.
Everyone buys their own PEI bed, and talks about it, but there's not much out there in
terms of concensus as to what a PEI bed is, PEI as I previously mentioned is a coating
of a thermoplastic.
You can buy this as a sticker you apply yourself, you can buy this as a pre-applied sticker
or what looks like a sticker that someone else has done for you, and this option seems
to be very common, and finally you can buy beds that are thinner and seem to have been
coated in another manner.
To settle this, or at least to get more answers, I bought a new PEI bed.
Yes - spending more money on a thing I don't need is how I solve problems.
Anyway - I bought this bed because it looked like it was the pre applied single sided sticker
type, and luckily I was right, that's what arrived.
As you can see here it has the sticker on it, which is thicker than the bed in the last
video, a lot thicker, I guess it has to be to apply it, but either way it has a notable
thickness, and it's totally smooth, but clearly a plastic sheet.
And importantly it's clearly applied to a plain stainless steel bed.
Which is totally different to the bed in the last video, as I show you them side by side.
The energetic branded bed is thinner and has no such sticker.
I have spoken to people in the know and they think that the energetic bed was manufactured
through an electrostatic coating process where the plastic is coated as a dry powder then
baked on, I should say I did email energetic for comment but they did not reply.
If they do I will obviously feed it back but in absence of any answer this is my best guess.
This coating though is thinner and really pretty much invisible in any way other than
the colour.
I should say that the rough surface is actually a powder coat layer and entirely separate
to the PEI plastic, it's presumably silica or something and essentially not part of the
discussion as I wouldn't have a clue how they put this on, although there are hints that
it's sprayed.
The contentious point is the reverse side of the sheet as I mentioned.
If I put both sheets upside down next to each other you can clearly see the one is silver
and the other looks the same colour as the front side.
Of course it's possible to treat steel to make it turn this colour, I am aware of that,
but to pre-empt that argument I also scratched an inconspicuous area of the plate and without
much effort found a steel colour.
So I would say this is pretty compelling evidence here that this bed is coated both sides.
I think, if I were to guess, it is coated both sides as a result of the manufacturing
method rather than on purpose, and I would definitely concede that it's probably not
*intended* that we use the reverse side, but my retort to that is, so what?
If it works?
There are a couple of outstanding things I want to cover before I wind up this episode
for good hopefully unless I have to do a part 3.
Firstly, which of these beds is better?
I'm going to be brutal here.
The energetic bed works way better for me.
Both sides of it stick better for me than this new one does.
Sure, it works, and if you didn't have them both to compare, you would not be able to
see how much better the energetic one is, but I have been testing both of these beds
with the print in place engine models from Sunshine, link below, and these models often
fails for me, I figure there's no use having a bed adhesion torture test that doesn't fail,
but it allows me to push bed adhesion to its absolute limit and I had a lot more bits of
the print breaking off with the applied film bed than with the energetic one.
It's also worth mentioning that based on my very limited interaction with these beds,
but also with other bed types, you can easily get snobby about the surface of a bed but
a textured surface on average will perform more reliably than a totally smooth one.
I said on average because literally that's what I think is going on.
If you look at this diagram, a smooth bed not only has a much lower area of contact
with the part, but if you also imagine at a closer view, the average level of a textured
bed could be seen as halfway between the top and bottom of the textured layer, so you have
the luxury of being able to be inaccurate with your first layer and still get contact
with the surface.
This is just a theory and I should probably look at this under a microscope at some point
but let me know what you think.
I can say that I had much much more reliable first layer results - and less mistakes with
levelling - on the textured side during the tests so I would recommend a textured PEI
if you have a choice.
The last point, is, well, what if the back side of that bed IS an oddly coloured plain
steel?
Well, I thoroughly cleaned the new bed's steel side and tried a few attempts at printing
on it.
So this answers the question about whether you can print PLA onto steel.
It seems like the answer is, kind of.
It sticks, but I would say not consistently.
If this was the only surface you had, you could print on it, but not models with a lot
of small areas, it just doesn't stick that well.
So anyway congrats if you made it this far.
I will see you in the next one.
Remember to comment and stuff, and I will see you next time!