SV08 printable z-belt pressure plate

A replacement z-belt pressure plate for the SV08.  The OEM clip can weaken and break over time if the belt is over-tensioned or normal use. Issues with quad-gantry leveling, slack z-belts, or visible cracking around the clamp screws are signs of failure.  This is a replacement for Sovol part #JXHSV08-02006-D which can be obtained from Sovol (likely for free if the printer is in warranty), but printing a stronger version instead of waiting for support to mail you one is one of the many benefits to having an open-source printer.

This is based on the original open-sourced design from Sovol but thickened on one side to make it 3D printable since the original was designed for injection molding. The original design included a gap for excess belt material to protrude from, but in my testing this significantly weakened the part and is only necessary if there is a lot of excess belt material. If your belt has excess material from the factory (mine did not) and you already have maxed out the belt tensioner, you may need to trim your belt so that the two sides abut each other and fit completely inside the clip.

Orient as modeled (which maximizes strength along the axis of the internal teeth) with supports for the alignment tabs and print using a 0.4mm nozzle at 100% infill. Larger nozzles are not recommended since the internal protrusions need to have sharp edges order to bite into the belt during clamping.  I recommend using ABS,  but ASA or PETG will probably work also. Do not use PLA since the part needs to flex during clamping and could heat up if used in an enclosure. Trim any elephant foot or seem on the edge facing the frame since there is very little clearance on that side.

You will need to replace the original screws with M3*12mm to account for the added part thickness. The original used pan-head screws, but a socket cap works just fine in not over-tightened.

Tips:

• If your printer is still in warranty, take pictures before replacing to send to Sovol if you want to get an OEM replacement. Replacement parts ship form China and can take some time to arrive (hence this print). 

• If you do not have a second printer and do not want to wait for replacement parts from Sovol, you may be able to get by with filing an edge off of a washer (enough to clear the frame when installed) to hold the remains of the original cracked clip in place long enough to print the replacement. If you do this, reduce the belt tension as much as you can get away with to minimize strain on the broken part. 

• If this replacement is for one of the rear belts and you have an enclosure, I suggesting putting the printed part on the front and rotating the OEM clip to the rear for easier access in case it breaks.  Be sure to inspect/replace the other clips as well since they all experience similar stressors and tend to fail at the same time.

• Over-tensioning of the belt is a main cause of premature failure for this part. This print is stronger than the original, but still prone to failure if too much tension is applied over time. When reinstalling the belts, instead of tensioning using the inconsistent app method recommended by Sovol, I suggest measuring deflection with a printed gauge and shoot for the Voron recommended 7.05mm deflection (or the middle of the gauge if it is a unit-less version). The tension for the Z-axis doesn't need to be exact, just make sure they all match and are in the ballpark. This will prevent future failures and allow for more consistent gantry leveling. Sovol's official documentation can be found here.

• Since this is a high stress part and clamping flexes it along direction of the layer lines, I recommend vapor smoothing ABS/ASA with acetone for or heat annealing PETG for added strength.  This is optional, but only takes a few minutes and greatly increases layer adhesion. If vapor smoothing, be sure to tape over the internal teeth so that they remain dimensionally accurate. The edge facing the frame and internal teeth are the only areas that require a high-degree of dimensional accuracy so some warping during post-processing is not a concern as long as these areas are adequately protected.

• Changing anything to do with the belts will change the input shaping parameters.  Re-calibrate resonance compensation when finished to avoid ringing. Menu-> Advanced-> Auto-calibrate using the stock firmware or SHAPER_CALIBRATE if using mainline Klipper.

Bill of materials (for replacing all 4 parts):

• 4 x  ABS z-belt pressure plates (printable)

• 8 x  4*12mm M3 screws.  Pan-head preferred to avoid splitting the part, but hex-cap works as well if not over-tightend. Do not add a washer.

Tools:

• M2.5 hex key for removing the original screws

• Hex key for replacement screws (if different)

• Acetone or heat gun for annealing the flat face where part flexes along the layer lines during clamping (optional, but recommended)

• Belt tension gauge like this, this, or this for reinstalling belts (shoot for 7.05mm of deflection) or an app for measuring belt frequency (shoot for 110-140Hz). The app approach is not recommended. 

Modified geometry to make stronger and 3D printable. Open-sourced STEP files and blueprints in the github repository.