Marlin Firmware and bed size settings

jpasqua

I'm a little confused about the bed size for the A5. I'm hoping someone can confirm my interpretaton.

The specs say it is 305x305mm. The Marlin code agrees:

        #define X_BED_SIZE 305

        #define Y_BED_SIZE 305
but also specifies that:

        #define X_MIN_POS -5 // thanks DaHai.

        #define Y_MIN_POS 0

The back of the heated bed says it is 314x314mm (see image). When I measure it, it is closer to 310x310.
Based on this, I am guessing that:

* The actual printable area is 310 in X and 305 in y
* The left 5 mm of the physical build plate won't be used unless the gcode specifies negative X coordinates
* The back 5 mm of the physical build plate won't be used
* The 314x314 numbers are just wrong - it's closer to 310x310

I'm making a magnetic build plate and removable spring steel sheet to replace the black diamond glass. I plan to make the spring steel sheet cover the entire build plate of 310x310, and try to find a source of a buildtak-like material that I can get in this size.

DaHai

Just a caveat: Magnets wear out when heated over and over.
And I'm a PrintBite Evangelist.  Prints stick like superglue when hot and slide off effortlessly when cold. No bending, chiseling or scraping. Used it for over 2 years and its not worn out yet. 
https://flex3drive.com/printbite/

sanjibukai

• jpasqua: I'm making a magnetic build plate and removable spring steel sheet to replace the black diamond glass. I plan to make the spring steel sheet cover the entire build plate of 310x310, and try to find a source of a buildtak-like material that I can get in this size.

Hi, I thought that this "black diamond platform" is actually a "wanted" feature..
Why do you want to change it?

• DaHai: And I'm a PrintBite Evangelist.  Prints stick like superglue when hot and slide off effortlessly when cold. No bending, chiseling or scraping. Used it for over 2 years and its not worn out yet. 

https://flex3drive.com/printbite/

Does the provided "black diamond platform" have exactly that same purpose, why wanting to use something else?

PS: I don't know how to cite comments... If anyone can tell me..

Samuel Pinches

 Sorry I haven’t put any quote feature into the forum yet, it takes a bit of work to get working well. 

 The black diamond coating works reasonably well, it’s just very sensitive to oils or fingerprints. If cleaned properly prints stick quite well (and are easy to remove) but perhaps not quite as firmly as with something like PEI. or printbite 

jpasqua

sanjibukai: I'm doing this primarily because I like the removable aspect of it. After the print completes I can pull off the spring-steel sheet (covered in something like PEI or Buildtak), flex it a bit to get the part off, then drop it back on.

sanjibukai

Thanks, I see..
I probably end up doing the same!
So your "flexible" steel sheet will rest directly on the heat bed without glass?

jpasqua

That's right - no glass. Folks like BuildTak sell kits that have all the parts (magnetic base, spring steel sheet, BuildTak surface). Theirs works well, but is quite expensive. You can assemble all of the components yourself for much lower cost. Please note that heat negatively impacts typical neodymium magnets at about 80C. There are high temperature magnets, but they are more of a specialty item.

sanjibukai

Ok..
Would you posts some pics at the end of your setup?

jpasqua

I'm out of town and away from my printer at the moment, so I can't send pictures. However, take a look at this design on Thingiverse which is a mount for a CR-10. This has a design for a mount for the magnets and provides links for the materials.

https://www.thingiverse.com/thing:2777120

sanjibukai

Oh...
I thought about pics later on when you will finish your setup..
I'm not in a hurry..
BTW, thanks for the link...