I just finished building my 1st 3D printer a RepRapPro Mono Mendel.
While it still needs some calibration and the fillrate isn’t optimal it is already very precise as far as I can tell.
I’m loving it.
When I had kit for reprap prusa mendel it took me around 10h to get first 20mm cube test print. then some tweaking and calibrating to get really straight cube 
@Robert_Ristine @Steve_Wall I don’t know about prebuilt systems. I choose a kit because I was interested in the process of building a 3d printer. It cost me 648€.
I built this printer without any previous knowledge about 3d printers, but with previous knowledge about electronics and some about mechanical stuff.
When I built it I just followed the instructions which for the most part are very good.
In total up to this point I think I spent about 20h assembling the printer and calibrating it, which is the more tedious part of it. I hope I could help you with this.
i want to make my own 3d printer can you guide me
I think you heated bed (pcb) is not sufficient for that big aluminium plate + glass. Your part is warping at the corners.
For aluminium heatbed you can better use the heater resistors that are used for the nozzle too. A couple of 6 should be good i guess. 9 if you want to be perfect.
Make sure your powersupply can handle the current draw.
@Mano_Biletsky_Open_M I tkink that my heated bed is sufficient but that I maybe have to increase the temperature. The testprint was done at 60°C
Do you have your thermistor on the pcb bed or on the glass?
The glass is colder that the heating pcb.
@Mano_Biletsky_Open_M the thermistor is on the aluminum sheet between the PCB and the glass. Do you think I should try using only the aluminum with some krapton tape instead of the aluminum, the glass and the tape? As for the power of the PCB heater: I measured the power draw of it and my meter says it draws about 160W so that should be sufficient in my opinion.
You don’t have to remove your glass if it gets to the right temperature.
You should only place the thermistor on the same surface as where you will print. In your case the glass plate. This way your temperature reading is the most accurate.
The closer you measure to the heated pcb, the higher your reading is. You loose a lot of heat between the aluminium and the pcb. Thus the surface (glass) temperature is lower than the pcb temp.
Excellent job!
Printing on bare glass is the way to go, at least for PLA. I usually have my heatbed at 80C (others use 70C fine). If you’re doing ABS you can put kapton tape on, sand it, and apply some “ABS glue” (scraps of ABS put into a 2-liter soda bottle with some acetone that you swoosh around until dissolved). But I prefer PLA.
BTW it’s totally fine just taping the thermistor to the bottom of the PCB with kapton tape. Even if it’s off by some small amount, you’ll learn that and use that new value. Bed temperatures don’t need to be super accurate. Extruder temperatures matter much more.
@Jeff_Keegan Accually the difference between the pcb and the glass can be quite large. Especially with a aluminium plate in between…
Yeah I don’t have any experience with having an aluminum plate in there, so I’ll defer to your experience. I have the PCB with glass binder clipped to it (and as the PCB heats up it bows up into the glass). I suppose the purpose of the aluminum plate is to even out the heat distribution?
@Jeff_Keegan I don’t know how printing without a aluminum plate in between is like but I compensated for the extra thermal mass by increasing the hotbed temperature for PLA to 65°C which is about 58°C on the glass.
58 degrees is pushing it. Recommended is 60, but i hear more and more people printing at higher temperatures.