In the recent months we have done some work concerning using the Ultimaker with materials that require high temperature, as well as trying to do create heating bed in which the heat is distributed more evenly over the surface of the bed.
I was thinking to use it for business purposes, but due to me leaving China I decided to share the information with the community. It might be helpful to some of you.
Generally speaking, we tried to replace the standard heating bed material and the PEEK insulator, which are limited in their temperature ranges with Ceramic materials and Silica glass. The reason for it is, that we think that with the correct modifications to the machine, it might be possible to 3D print with alloys. I didn't try the thing itself, but I think it is worth a try, it might open new fields of applications for these modest printers.
Concerning the heating bed, after experimenting with Silica glass (Mohs 7 hardness, transparent), and seeing that the tolerance of the heat around the surface is too big (Silica glass is not a good heat conductor), we started to use 99% Alumina ceramic board. 99% Alumina has reasonable heat conductivity (not as good as Aluminum, but much better than glass). With our equipment we came to heat distribution of around +/- 4 degrees on most parts of the surfaces, besides the edges.
Alumina 99% is an expensive material, but for high Temperature application like this one it is a good candidate. It is hard, can stand temperatures of up to 1,300 degrees, is quite capable of standing thermal shocks.
Together with the boards, we also made new springs, which are longer and stronger. They can carry the weight of the board and their length makes it easier to adjust the height so the surface is straight, and doesn't have slopes.
We have also changed the PEEK insulator to use ceramic material. The problem here is the connection with Bowden tube, we were worried that the high temperature will melt it. I believe that machines operate in high temperature will not use the tube anyhow.
As a replacement for the PEEK part we chose at first Alumina 99%, but we feel its heat transfer is too high, and you cannot really use it as insulator. We then machined parts from Macor, which is much better insulator. Macor is limited to environments of 800 degrees, but for alloys it should be enough (melting point for many alloys is around 650 degrees or less). One advantage of Macor is that it can be machined to keep very demanding mechanical tolerances. It can fit will with a machine, and the fact you can machine it, can save initial investments on molds etc.
Of course, when users will start operate in these temperature, the small aluminum block connecting the nozzle and the PEEK part will have to be replaced with a material that can stand the higher temperature, probably bronze.
As I wrote earlier, we also created silicon heating pad with a new pattern of the heating lines. It is not rocket science, but still, it required some experimenting, and we found it to keep very nice balance over the heated surface. For those of you who are interested, please email me and I will send a photo of the layout. We saw that feeding it with 300W, heating was fast and consistent.
I hope some of you will find this entry helpful, and naturally, if you need further information, please let me know.