hi @Eguipegui and welcome! in my experience, there are three critical changes required to a stock CR-30.
- replace bowden tube with capricorn and bowden couplers
- loosen 1/4 turn 5 of the 6 heated bed bolts or add shims
- upgrade X axis with a linear rail
once calibrated, your printer will then be reliable. these changes cover 95% of the common failure modes. other recommended upgrades (firmware or hardware) are for performance and should be done after these.
an explanation for each:
bowden tube and couplers
the CR-30 uses a very long bowden tube which means longer retractions are required for clean prints. this puts stress on the couplers and increases the likelihood of a hot end clog. the stock couplers are weak and fail often. the capricorn tubing has a smaller inner diameter. this means less retraction is required.
heated bed
the CR-30 heated bed installation suffers from a design flaw. it is constrained at 6 points along the edge. when the bed is heated above 60C, it starts to warp (expanding metal needs to go somewhere). if it is held at higher temps for any period of time the warp becomes permanent. because of gravity, the warp goes down creating a dip in the middle of the bed. this turns the belt into a drum floating over the bed. any amount of space, even 0.01mm, between the belt and bed means prints will not stick reliably.
loosening 5 bolts (leaving the center bolt closest to the end of the leading edge of the belt tight) provides some ability for the bed to expand without warping. the belt tension will hold the bed down.
a more permanent and reliable fix is to add 12mm aluminum shims under the center of the bed to physically prevent it from warping down. I have used old E3D heater blocks (which have one side at 12mm) held in place with kapton tape. if your bed is already warped (or suspected), then use a straight edge across the bare bed with a light behind it to confirm
linear X rail
the X axis suffers from torsional loading due to the angle of the head. this is a really bad place to use roller wheels to hold something in place. that loading pattern will, over time, destroy the wheels. the Y axis can get away with this because it’s a beam held in two locations which prevents uneven loading. the stock X wheels are also known to be installed poorly. if this happens or if they are degrading, prints will start to fail.
the linear rail is a more rigid motion system with all metal parts that have very tight tolerances. it will not fail over time and provides a much more reliable base to mount the head. this upgrade is mandatory if you plan to add direct drive at any point since that will increase the weight of the head and thus torsional loading on the X axis.