Tronxy X5S Gantry carriages and belt geometry alignment

cults3d

Currently building a Tronxy X5S and I'm feeling somewhat let down by some of the "Out of the Box" design issues with this printer. Saying that, it seems like the company is listening to feedback as there have been several design changes made to the original machine spec. My first issue was with the gantry carriages. The way flimsy acrylic is used to pre-tension V-wheels is diabolical and bound to fail in the future. The design makes the gantry stiff to operate and seems out of square, despite much tinkering with belt tensions and frame squareness checks. I downloaded and printed a set of "Mega Gantry blocks" by "Graham01," which looked great. However, it appears that the design of the extruder carriage has been changed and now has a rear-mounted belt attachment point, which collides with the Mega Gantry blocks. The new design also means the belt path geometry is out of alignment. Speaking of belt path, I worked out that the reason for the stiffness in the motion of the gantry was significantly due to the utterly crap design of the belt idler system. A ball-race sandwiched between fixed penny-washers using spring washers as spacers meant the bearings didn't sit perfectly horizontal and caused the belt to ride up and rub hard against the non-rotating penny-washer, creating friction. So, they had to go. I downloaded and printed off the corner pulley guides and gantry pulley guides by "HanCheol" and had a go at fitting them. These are super strong but I had a problem fitting one of the T-slot nuts as it clashed with the frame fixing screw head inside the aluminum extrusion, preventing the nut from rotating and locking. I've had a remix. As I couldn't use the mega gantry blocks STLs in Fusion 360, I scratch-drew them up but they're based on the original design by Graham01. Consequently, the gantry pulley guide is also scratch-drawn but of similar design to that of HanCheol. The corner pulley guides have had a simple change: the fixing hole nearest the corner of the frame has been moved a couple of millimeters to clear the screw head. This allows the T-nut to turn and lock into place, so an otherwise excellent original design. The gantry blocks have had a clearance slot made into the X-axis support to allow the rear of the extruder carriage to pass above. The hole for one of the idler pulley screws has been realigned to provide a straight belt geometry between the corner idler and the extruder carriage. The mounting hole is now threaded M5 to remove the requirement of fitting a nut underneath the carriage block. The 2nd idler pulley now shares its axle with the rear inside V-wheel. To avoid preloading the pulley bearings while securing the V-wheel, an hexagonal hole has been located in the spindle hole for an M5 nut to be fitted. This allows the screw to be moderately tightened from the top to avoid crushing the pulley bearings but allows the V-wheel nut to be tightened firmly to prevent any play. The gantry pulley guides then had to be redesigned to fit the new configuration of the carriage blocks. Update: 24 Mar 19. I've added a Version 2.1 for the gantry Pulley supports. The only difference is the addition of a hole directly above the screw which secures one of the T nuts in the top of the gantry (X-axis) beam. I realized after printing that this would be helpful. Update: 26 Mar 19. This is pretty much complete now, so I'm taking the "Work in Progress" status off. I still intend to make some motor mounts to replace the crap OEM ones and that will ensure geometry is maintained but I'll update when I get round to it. I'm still in two minds about the limit switch bracket too as I quite liked the adjustment with the screw. Update: 24 April 19. Motor mounts are now designed and available. These are screw-adjustable and maintain the correct belt path geometry while providing a strong and rigid mounting for the steppers. The detailed instructions are on the link here: https://www.thingiverse.com/thing:3584805 Update: 20.09.19. I've added a version 2.2 of the gantry carriages with a modification to the front outside edge. I noticed the limit switches were being contacted virtually flat onto the front of the carriage, which could give the switch body some punishment. So, I've added a 3mm protrusion which contacts the switch lever and allows the springiness in it to absorb the collision forces rather than the switch body.