Print is too small!

[mirage1207]

Hey guys!
after hundrets of prints.... kilometers of filament, it was time for a little revision of my Rostock Max. At my last print the machine got a little issue and crashed "INTO" the glass Plate... AAAAAAAAHHH!!!! Plate brocken... but nothing more... ithougt..... Bought new parts (Glass Plate, Nozzle and some more things) set new Z-Hight and start up my !first" print... now i have i little Problem... THE PRINT IS TOO SMALL.
i Print a calibration cube 25x25x25mm- this one is 24,92x24,93x25mm.. ok not bad..
so i make it bigger 37,5x37,5x37,5mm- print 37,3x37,3x37,5mm... and the next one 50x50x50mm get:49,5x49x5x50mm..
the print in X and Y is too small... but in Z its still perfect!
my Glass plate is ok... not wavy or something... Z high is also good-have 0.05mm.
but why prints the prointer too small? who could i calibrate this?? sorry for this really newbee question- i have this printer sitll one year - but i really dont know who could i fix this problem.... shame on me
hope you could give me some tips.....

THANK YOU!!!!

[Tincho85]

A quote from this thread: http://forum.seemecnc.com/viewtopic.php?f=77&t=5933

As for overall dimensions, try adjusting your arm length and radius in the firmware to make your prints slightly bigger. Outside dimensions of large parts should be a good indicator of your size calibration. If they're too small, try decreasing your arm length in the firmware to make your printer think it has to move further than it actually does.

I've never tried myself, but it might help you.

[Nylocke]

Which arms do you have? If you have magnetic arms that are custom made there is a fair chance they aren't quite the stock length. Otherwise I wouldn't screw too much around with your arm length. Your XY sizing is only off by around 1%, mine is probably around the same, and yet I create tons of parts that fit together all the time. I've printed numerous 3D printer parts for numerous models and they all fit perfectly (Mini Kossel parts that fully encompass the extrusions, parts with critical hole positioning, etc). Really your "small parts problem" is probably due to things like very slightly incorrect extrusion rates, plastic shrinkage, Slicing engine errors, etc. I wouldn't fret too much about 1%

[mirage1207]

hey guys, thanks for your answers! but the problem is still the same.... print a cube 50x50x50mm, the print is 49,5x49,5x50mm! bevor the crash, my parts are 100%...
never had this problem before (i think). its sirious.... i really dont know whos the problem....