When I got my proMega it felt like a bit of a step backwards going to a glass bed after using the removable spring steel beds that my 2 prusa MK2.5's have. So after a while with using the glass bed I decided to see what options I could find that would give me the same convenience that I am used to with my prusa's.
I looked at multiple sources for a sheet of spring steel that would be large enough for the proMega, I was planning on put a PEI sheet on it and just using binder clips to hold it down if needed. Over all it would have worked just fine but I couldn't find any supplier that had one big enough, or would provide me with just 1, or the price was restrictive.
So I had a look to see if some of the 3d printer bed systems out there could accommodate the size of the proMega's bed. I'd heard of the buildTak system so I checked with their site. They have their flex plate system, and one size they provide is 406x406. This would work just fine for the proMega, however it's a steep $200USD, or $260CAD for me. A bit pricey but would work.
I also found another called WhamBam (whambam3d.com) that has a size of 410x410. This would also work great for the proMega. It's price was $140USD, or $180CAD for me.
I ended deciding on purchasing and trying the WhamBam system, shipping was reasonable and it came from china which was a little odd to me.
It comes with a Magnetic sheet, steel sheet, their PEI alternative called PEX, some shims(thicker aluminum foil with a sticky backing) and a small thing of steel wool. The magnetic sheet and the PEX have 3M adhesive backing which leaves you little room for error. They want you to use a flat edge and check your bed that your mounting this to for low spots, and if there is a low spot you use a shim or portion of one at the low spot so when you install the magnetic base it's as flat as possible. I didn't need to use any shims.
I had decided to install it directly onto the heat bed. I cleaned the bed off really well and using all the concentration I could muster, installed the magnetic base onto the bed. Need to use patience, the 3M backing is unforgiving and you have to get it all lined up perfectly before you start sticking it down. But I got it in place.
Next thing is that the PEX doesn't come installed on the spring steel sheet, so I had to install it on. This does let you use something other than their PEX sheet but I installed the PEX sheet. This one I had off by a little bit, but one area had 2-3mm missing from it which was no big deal.
With this all installed I notice that, unlike the prusa bed, there's nothing to make it easier to line the bed up with the magnet perfectly. I may look at making some sort of stop/alignment things that make it easier but how it is now is fine.
Next thing I did was spent a bunch of time with bed leveling. I found the bed level was closer to level than when I had the glass bed and made a few adjustments until I was happy.
For printing on the PEX they recommend that the bed temp be raised 5-10c higher than you normally would. I was unsure about this and ignored it at first. They provide the steel wool so you can scuff up the PEX. So I will use 99% IPA like they recommend to clean the PEX between prints and use the steel wool every now and then. Even so I've had some issues with bed adhesion, after raising my bed temp 10 degrees for PLA I had a much better time with adhesion. I was reading that it's needs a little more heat than PEI. We'll see how the PEX works out, if it gives me too much grief it can be removed and I could put on a PEI sheet or something else as I see fit.
I did realize after the fact that if I ever need to get at the bolts holding the heat bed down then I may have to cut out small sections of the magnet to get at them.
Conclusion - Overall I like it. having a removable spring steel bed on my proMega is great. Hopefully I have all the adhesion issues I was facing worked out but I have other options if I have to for that. The price is high, less than the buildTak system tho.
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