When it comes to printing surfaces there are a lot of options and I've tried many of them. I've tried glass beds with a textured surface, magnetic PEI spring metal that you can bend to easily 'pop' off your prints, and others. But in the end, I print exclusively on plain flat untextured glass.
What's wrong with magnetic beds?
Magnetic beds require you to put a giant magnet sticker on your bare bed hot plate. One day you might want to remove it, and after a lot of use it practically melds to the aluminum making removal really annoying. It usually requires a razor blade and some kind of adhesive remover like Goo-Gone.
The magnets are also usually polarized in my experience. This means the metal bed wants to shift slightly forward or backward or left or right. Sometimes it shifts off-center and you have to lift it off and put it back on just right. It's not a huge deal breaker, but it can also be annoying.
A magnetic bed has a limited life span. After a while the coating will start to come off, sometimes welded into the plastic of your prints. It's easy to scratch the coated surface if you crash your print nozzle into the bed with a bad z-offset, or if you manually moved the z-axis and auto-homing drags the nozzle acrossed it. You may also scrape it during bed leveling. PETG will also bond to those coatings and rip a chunk of them off, ruining the flexible sheet and forcing you to buy a new one.
Textured surfaces also show up in your print. Maybe it's on the bottom of an object and it doesn't matter. But often you need to print something top side down or on it's side to avoid supports. I hate supports, and brims for that matter. I like to print and be done, not spend 20 minutes scraping and sanding away excess plastic bits. Sometimes I even redesign models I find online so they can be printed without supports. The end result is a cleaner, nicer looking object.
But the biggest drawback of a magnetic removable bed is it's main selling point: flexibility. You bought it so you could take it off when a print is finished and flex it slightly so your print just 'pops' right off. Well that sounds great, but lets go to the dark side Luke. Your bare hot bed is an aluminum plate. For most printers (Ender and such), you level that bed with those big knobs underneath. Rotating them one direction pulls down on the metal, and rotating them other way releases the tension and moves the surface upward. Most likely you upgraded the weak factory springs to some strong thick springs or silicone spacers. Since you should be leveling your bed when it is heated, the aluminum is softer and can be bent...permanently. Just a little overly zealous knob tightening and you have a hot plate with a bow or dip in the middle, especially on the side closest to the wiring underneath that goes to the heating element. Since your magnetic build plate is flexible, it conforms to the new bent shape of your bed. Congratulations, you now made it nearly impossible to level your bed with decent precision. This is most noticable in the middle. All the edges will be nice and level, but the center will be just a millimeter or so high or low. Sure, and automatic bed leveling probe will compensate for that, but your prints will technically not be flat. If your bed has a slight dip in the middle, your print will have a curved bottom. Don’t get me wrong, I love a curved bottom when I see one, just not on my prints.
Why Smooth Glass Is The Best Printing Surface
You know what always stays perfectly flat and smooth across the surface? Something not flexible like... oh I don't know.. glass. Even if the aluminum hot plate is bent, the glass won't be.
But Mr. Wyqid, my prints sometimes don't stick to glass well and sometimes they are really hard to remove when they do. Sometimes, Mr. Wyqid, I have to practically chisel them off with the scraper that came with my printer.
Yeah, you are absolutely doing it wrong.
First of all, if you are printing PLA, you don't even need to use a glue stick (although I still recommend it) if your bed is properly leveled, clean, heated to the right temperature, and your Z-offset is set properly. If your prints don't come off really easy are you being impatient? When the bed cools down to room temperature my prints lift off as easy as a five year old's lost $25 balloon at Disney World. For PETG, using a thin coat of glue stick or Wyqid's Bed Tack is not to help the print stick to the bed, its to make it easy to remove when the bed is cool. PETG sticks just fine on it's own. PETG can occasionally bond hard to glass similar to those textured beds, but glue-sticking or using tack before a PETG print makes this a non-issue.
That, in a nutshell, is why a smooth glass surface is the best. Borosilicate glass is common because it can handle quick changes in temperature and uneven heating without shattering. But it's not really needed for 3D printer beds because the bed should be heating and cooling slowly and evenly. Your printer probably came with a glass bed. Simply turn it over and print on the untextured side. If not, most glass printer beds around only around $15 more or less.
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