sorry, that was just a typo in my question. But even if I type

plot3d(sin(x*y),x=0..2,y=0..0.2);

the problem persists. Alos, not even the help page for plot3d can be fully displayed.

By I different channel, Mickael Conessa gave me the following explicit suggestion (merci !)

mafi := proc (Bild, Datei)
     local fd; fd := fopen(Datei, WRITE, TEXT);
     writedata(fd, convert(op([1, 1], Bild), matrix));
     fclose(fd);  
  end;
 

with the toy example:    p1 := plot( 2*x+1,x=0..4,numpoints=9);

use it as follows:            mafi(p1, `donnees.dat`);

and the file donnees.dat will contain two columns of values (x,f(x)) - I used the option numpoints merely to make this list short.

I tried it out on my implementation Maple2015 and it works.

Thank you & best regards, Malte.