Looking for ideas to improve build platform

[danzen 0]

Hi guys, it's been a long time since my last post.

I was so hooked to 3D printing after receiving my UM that I simply did not have much time for anything else.

I've just finish my first reel of PLA and just got past the stage of just sitting there for hours watching the UM print (anyone else find it hypnotic?).

Anyways, I'm very happy with the UM, but I think its far from ideal.

Basically I'm looking to improve the build platform. Not the printing surface itself or the z-drive but the cantilevered stage.

What I like about the current design:

- The idea of a cantilevered stage in general.

- The acrylic bed is supported with springs. I occasionally crash my print head into the bed during my very 1st week or so. That doesn't happen anymore but I like the redundancy.

What I don't like:

- The structure of the platform in general is not as stiff as I would like it to be.

- The drive nut assembly is way too flimsy. Is this intentional?

- 4 adjustment screws. I think having the acrylic bed supported by 3 points, 2 of which adjustable, is better.

- How the acrylic bed is latched onto the platform. It's simple enough to attach and remove but the leveling is affected every time I do so.

It would be preferable to keep the build simple as well. Laser cut parts are fine, as well as basic sawing/cutting/drilling.

I'm thinking of using MDF and/or aluminium beams instead of plywood. The plywood used in the UM seems to work decent enough but I'm not fond of it for various reasons.

I'm also trying to think of a method to attach the build surface to the platform in a way that would make it easier to transition to a heated printing surface (or any other type of printing surface for that matter).

I won't be upgrading to a heated surface yet but will definitely do so in the future. Recently I printed a large part (wide and thick) and it got stuck to the bed because I printed the first layer at high temp and squashed it slightly to prevent warping. Took me hours to remove it and in the end the initial solid layers tore off from the sparse layers (was printing at 20% fill). Epic fail.

Any ideas would be greatly appreciated. Thanks guys.

[mastory 42]

I am thinking of adding some jack screws to the acrylic. By this I mean tapping an array of holes across the bed and installing a plastic set screw in each one. I am thinking maybe 9 holes spaced appropriately. The screws would be mounted from the back side and adjusted to be flush with the build surface. When the tape is applied, the flatness would not be affected.

The idea is that when a print is done, just pop off the plate, turn in a set screw or two to release your part. Replace the damaged tape and print on.

This would require that the holes are tapped perpendicular to the plate to a high degree of accuracy - best to be done in a milling machine and minimal if any chamfer on the top side. The set screws would also need a suitably qualified surface. A good way to do this might be tap all the holes, install the set screws sightly above the surface, jam nut them, and machine a new finish to the whole thing.

Also thinking of drilling and chamfering a small hole right at the 0,0 so a plastic blob can't accumulate there. Maybe changing my start code would also fix this.

Matt

[danzen 0]

Hi Matt,

Interesting idea. I'm not sure if it would work well though.

The problem I had with a large print was that the part was significantly thick that it could not flex. Normally with a part that has a large surface area but relatively thin, a small a mount of flex lets you "peel" the part of the bed from a corner or side.

I think your idea would work for prints with small surface area and/or thin profile but then again you would have to make sure to print on top of the set screws.

Plus, it would require that you reapply the tape after every print. My tape can survive quite a large number of prints as I use a spudger instead of blades/scrappers to pry the print off the bed. For those who don't know, a spudger is a nylon tool useful for prying open gadgets and whatnot. Yes, the spudger needs to be replace periodically but at least I don't damage the part or the tape/bed as much.

You have given me idea though. If the part can't flex, why not make the print surface flex? Maybe secure a transparency sheet or a mylar sheet on top of the acrylic, apply tape on it, and print. When done printing, the transparency/mylar sheet with the blue tape can be peeled off from the part. The only question is how to secure the transparency/mylar sheet on the acrylic bed so that it is flat and stationary. Right now the only thing that comes to mind is vacuum but it's too complex and expensive.

[fmotta 0]

Well rigidity is always a help. Using glass has solved the stickage issues for me on TOM and prusa. The actual surface of glass is probably an option. But Aluminum and glass are best.

But, as I learned there is no heated bed formally designed for this. The one on thingiverse is nice but not a kit even though it looks well designed I would prefer that it be an actual kit of qualified parts so I have a lesser probability of errors. Also, maybe a PCB that is designed for the area of the Ulti build surface.

Since PLA will not withstand the heat of many of my parts (LED mounts in many cases) then I need to use ABS so this is rather important for me.

[danzen 0]

So I did a quick experiment using transparency sheets as a printing surface. This is kind of off-topic but I'm not sure starting a new thread would be a good idea.

At first I applied blue tape to the transparency sheet and tape that to the acrylic bed. When I started my test print I realized I didn't apply enough tape and some of the PLA was printed on areas of the transparency sheet without any blue tape. I stopped the print after a while and was expecting that the PLA would not separate from the sheet but I was pleasantly surprised.

So on my second try I printed directly on the transparency sheet without any blue tape. The sheet was simply taped down at the edges to the acrylic bed. The test print was a disk 120 mm in diameter and 20 mm in height. As one might expect the sheet isn't completely flat on the bed but the first layer printed pretty nicely. One thing to note is that using the transparency sheet I can clearly see that the PLA was thinner at certain areas and thicker at others, in particular it exaggerated the unevenness of the blue tape that's on the acrylic bed. That's partly my fault as it's pretty difficult to apply the blue tape without any gap or overlap.

The adhesion of PLA to the transparency was very good. I say this because normally after a few layers, the part would curl and slightly lift off he printing surface. Printing on the sheet however, the part still curled but pulled and distorted the sheet with it to the point that it looks as if the tape used to secure the edges to the bed would come loose at any moment.

I didn't finish the print as the curling was pretty bad. Anyways, I removed the tape securing the sheet and proceeded to peel the sheet of the part. You wouldn't believe how effortless it was to remove the part. A very big plus was that the bottom surface of the part was as smooth as the sheet itself, something I think is only achievable if printing on glass.

I conclude that the transparency sheet is a pretty decent surface to print on from my initial experiments. The problem with actually using it is the need to secure it firmly and evenly on the bed, requiring something along the lines of a vacuum table. Taping it down at the edges just doesn't work at all.