Removeable FR4 print surface
Flexible steel sheet covered by a PEI (Polyetherimide) layer is one of the most commonly used build surfaces of today.
They are a really great improvement in terms of print adhesion and very easy part removal.
Recently I have seen many successful attempts to use FR4 (Fire Resistant class 4) print surfaces, so I thought to give it a try on my Orbitron printer. FR4 is the base material used for PCB (Printed Circuit Board) manufacturing.
This design fits also on Voron v0 printers as well.
Motivation and the idea behind the project
I have to admit I have very good print results using the PEI covered flexible steel sheets. As usual nothing is perfect so I was wondering if FR4 based solution would improve something.
I have encountered two main issues while using the flexible PEI build surface:
· TPU is extremely hard to remove, I almost destroyed the PEI surface;
· The spring steel sheet attached to a magnetic sheet on the aluminum heated bed warps easily, especially when printing a large model and using lots of part cooling power for high sped printing.
Of course, in this case not the PEI surface is to blame, simply the magnetic force is not enough to keep the steel sheet flat. Could be improved using stronger high temperature magnets embedded in the aluminum heated bed.
This is what I mean by lots of part cooling power, which is a must if you want to print PLA extremely fast.
Part cooling power of Voron v0 is not enough to cause this warping effect.
Mostly I’ve seen attaching the FR4 via some kind of clamps. I prefer the idea of removeable print surface for a faster cooling, easier print removal and cleaning. Therefore, I have made a simple laminated design composed of an FR4 and flexible spring steel sheet (same as used to be covered with PEI layer).
I got some plain FR4 epoxy fiber glass panel boards with 1.5mm thickness, high temperature rated up to 155°C and 150x200mm dimension. Link to the FR4 board.
Designed using Fusion360 a build surface shape and milled the FR4 according to it.
You can also manually cut them to the required dimension.
Jason From LDO was very kind and sent me three plane sheets of flexible steel plates. The ones they are using to manufacture the build surface for Voron v0 just without PEI cover. You can use also use PEI surface damaged spring steel sheets, just remove the PEI coating before.
Laminated the two pieces together using a high temperature thermal conducting double sided super sticky tape 3M300LSE in bought from here.
I have attached the tape on the FR4 board first after which I have laminated it together with the spring steel sheet. The tape is very sticky so need to be careful and position it exactly from the first shoot. Press them firmly together, and squeeze out any remaining air pockets.
Evaluation and test results
First test I’ve done was to check the surface temperature compared to PEI covered steel sheet.
FR4 print surface
PEI print surface
Thermal evaluation shows no significant difference between the two build surfaces. The one degree difference is just due to picture timing, in reality they had pretty much the same surface temperature.
Some print results:
After the print was finished I detached the FR4 build plate. After letting it cool for a few seconds I removed the benchy. To my surprise it came of very easily, too easy I would say compared to PEI build plate.
TPU is much easier to remove and doesn't damage the print surface.
Warping effect is improved but not perfect.
In the left picture the model got off the print surface at the corner areas. Seems that print adherence is not the best for large parts which tends to warp heavily. Of course nothing what cannot be solved with a little hair spray as it can be seen in the right picture. Still the whole FR4 build plate warped a little, much less compared to PEI coated spring steel sheet, but still not up to my expectations.
The thin horizontal line at about 5mm height is the result of the FR4 build surface warping. You can download the 100x100mm test model here.
Overall the solution seems to work pretty well.
It does require a better way of fixing it to the aluminum bed for larger prints with high cooling.
From what I have read its lifetime could be shorter compared to PEI surface. The FR4 based print surface lifetime could be shortened by the many temperature cycles and warping forces it sees over the many prints we do. This can be seen as delamination of the FR4 layers. To mitigate this effect, I used high temperature rated FR4 not regular one.
This idea can be used to refurbish damaged PEI covered flexible spring steel build plates. The PEI layer must be removed first.
Overall its less flexible compared to PEI spring steel sheet solution, however this do not influence how easily the prints can be removed after the FR4 cooled down. The FR4 surface is less sensitive to surface scratches.
I'll report here how much it will lats.