Congratulations on your 3d printer! You’ll have fun building and using the MPCNC, but there’s lots of other fun things to do with the printer as well.
You certainly can print multiple parts. Under normal circumstances, printing multiple parts will not result in weaker parts. However, I advise against printing multiple parts. There are a lot of things that can go wrong during a 3d print. Sometimes those things go wrong when the print is 90% complete. If that happens near the end of a 5 hour print of a single part, you’ve lost that part and the time it took, but if it happens near the end of a 20 hour print of four identical parts, all four parts are ruined. It’s a much bigger waste of time and much more frustrating.
Trust me, print each part separately, and when each part is done – especially the first one of that type – inspect it carefully to make sure it came out right. The parts are brilliantly designed to print without support (except for one), but it’s worth checking each piece over. Take the time to calibrate your machine. Parts can be drilled/filed/sanded to make fit if needed, but the closer you can get the specified dimensions, the easier everything will be. Print the parts in PLA.
Lots of folks here, including Ryan, who designed the MPCNC, are ready to help out – just post your questions when you have them.