Bed Sag

At first I was thinking about doing a metal bed, however I was concerned about the heat sinking effect it would have. I imagine you'd have to take extra precautions to ensure adhesion and no warping.

Acceleration will definitely have to come down. I actually havent played around the setting too much, as I usually drop it to around 500-1000 and leave it there, but I will once I get my glass bed. As mentioned in my previous post, I should hopefully have it installed this weekend. When I do have it installed, I'll make sure to post my findings for you.

mvanderploeg said:
Hi everyone.

So I got my hands on an 18x18 piece of 1/4" aluminum. It weights the same as tempered glass, but it's easier to mill holes into. I'm planning on putting a 1/16" piece of acrylic on top with binder clips, but I'm concerned about the inertia (from weight) of the assembly weight causing the Y axis to skip or slip.

Has anyone who replaced the bed with 1/4" tempered glass had problems with skipping?

I'm planning on turning down acceleration to 300, having said that, what speeds has everyone been printing at?

I'm going back and fourth if I should return the aluminum for a thinner piece and pay a restocking fee, or if I should go with the stout 1/4" plate.

The heat sink effect is the main reason I'm using the bed :)
(I'd like to attach heating leads to a routed out section in the future for a heated bed for printing ABS)

For now, while using PLA, I'm attaching a 1/16" sanded acrylic sheet with binder clips for a print surface.

I ended up returning the 1/4" sheet and opted for a 3/16" sheet with aluminum C channels instead of the angles.

I think it will be a bit lighter, while giving enough rigidity and "flatness" to do some larger 12"x12"+ prints.

Will post pictures when finished.
Here is my setup with the 3/16" plate aluminum bed and 3mm acrylic print surface attached with binder clips. It works amazing and the tolerances are really tight.

I used 3/4" aluminum C channels as well instead of the angles. I also recut the bed attachment plate out of 9mm acrylic and removed the cut outs to make it much more stout.

I also added some lock-tight to the wing nuts to keep them from vibrating out of true.

The whole thing cost me about $75, but it was well worth it. Using the aluminum plate also allows for a future heated bed if I decide to print more with ABS.


I ran into this as well. Apparently it is not uncommon and the acrylic plate of the Replicator 2 also suffered from this. In my case it is just the back 3" that curls up. I went to my local hardware store and had them cut me a 18"x16" piece of 3/32" thick glass for $5-10 and clipped it in place with binder clips. I use blue painters tape under white masking tape and it works like a charm. Haven't had to do any large prints yet but I am not worried about my bed melting if it isn't level at the corners of the build plate.

I might go on the hunt for a flat acrylic plate at some point but am not in a big hurry at the moment.

I have not run into any inertia issues with acceleration set at 350 mm/s².
Andrew, I might do that in the future when it comes time to replace the acrylic. This glass is definitely cheaper and it'll be nice not to have melted holes in it from all the issues when I was getting started.

As for now, what I have done is purchase 1/2" MDF at Home Depot and had them cut me 2 * 18.25" squares from a 2' x 4' sheet.
One of these went under the acrylic, I lined both up and used the acrylic as a guide to drill holes. Now the bed is perfectly flat. The 2nd piece of MDF is going to be clamped on top of the first to be used as a spoiler board, I created a carriage that holds my Dremel 3000 and I'm working on getting this thing to be a CNC mill.
Eric_the_Builder said:
I replaced the bed with 1/4" sand blasted glass. Works like a charm. Just make sure to set the acceleration to 300mm/s^2

I also strengthend the y gantry with an aluminum plate. this gave it the stability it needed to reach higher speeds.

I can now do multiple prints with minimal or no bed leveling!

Thanks for the upclose pics. I just got my gmax assembled and ran into this sag first thing while trying to level the dual extruder. I'm going to implement your fixes here. Much appreciated!