Monday, 7 November 2016

Project: Proteus Delta Part 3:

Proteus Delta half assembled
     It's been awhile since I last posted on this project, so here's how to assemble the slider/carriages and drive belts. Parts for this stage included 7 meters of GT2 belt, 9 Openbuilds solid V-wheels, and the 3 Nema 17 stepper drive motors.

Slider/carriage half assembled
     Once the printed parts are made, putting the sliders and carriages together is fairly straightforward, the only real tricks are that you'll need to print the front plates individually to avoid fractures and print the short version of the spacers, not the long ones which are on the left in the picture above, otherwise the belts won't line up properly. Otherwise, assembly is fairly simple, just insert some M3 nuts into the traps and screw the carriage to the slider, then insert and loosely thread a M3x20mm screw into the tensioning hole. Finally, use a pair of plyers and a 4mm hex key to put the spacers onto the M5x45mm socket bolts, followed by the solid v-wheels. The very last step is adding a nylock nut to the end of the bolt to hold everything, be careful not to overtighten it, the wheel should still be able to turn freely when everything is assembled.

Slider/carriage with short spacers installed
    As for installing the sliders onto the towers, it's simply a matter of pressing one side into the groove between the tubes, then twisting the carriage around the tower until all three wheels are aligned, followed by tightening the tension screw until the carriage has a firm grip.

How to properly assemble the idler mounts for installation
     Now that the carriages are installed, it's time to add the idlers and drive motors so the belts can be added. The Emmett delta design is a bit strange in this regard, since both the motors and idlers are adjustable to handle belt tensioning. For the idlers, there's a couple printed parts, along with a few M5 nuts and bolts to assemble everything. I'd recommend leaving things slightly loose until the belts are on, or you can tighten them down now and just use the motor mounts to adjust the belts.

Idler assembly fully installed
     Now that the idlers are installed, the next step is assembling and installing the motor brackets. I've used a slightly odd method for mounting the motors, a pair of M3x16mm screws with a couple of M3 nuts on the end as spacers, this is not something I'd recommend copying, it's just the result of my local hardware store not having M3x10mm screws in stock.

Motor assembly ready for installation
     For installing the motors, the sequence is bolt the mounting plate to the front of the motor, then install the drive pulley as shown. Make sure that one of the grub screws for the pulleys is aligned with the flatted side of the steppers shaft if you're using D-shaft steppers, this generally helps prevent the pulley from slipping during use.

Motor assembly installed and ready for addition of the drive belts
     Now, installing the mounting bolts for the motor brackets is a bit tricky, it's too tight in there for a crescent wrench or ratchet, so you'll need a 7mm metric wrench to tighten the bolts down there. I'd recommend leaving the upper bolts loose and tightening the lower ones to hold the motor at the top of it's range of motion, otherwise you will have difficulty tightening the drive belts to full tension. 

Using a rubber band to keep the sliders out of the way during motor installation.

I also found it helpful to get the sliders out of the way since they tend to rest directly above the motor mount and make access to the mounting bolts a bit difficult until the belts are installed. A simple rubber band provided a quick fix to this nuisance, although it's probably avoidable if you install the motors before the sliders.

Sliders with alternate carriages installed.
     I'd originally installed the Folger tech style carriages that are part of the printed parts listing, but they have a very strange way of locking the belts into place that just wasn't working for me, so I installed a set of these self locking carriages instead. After they where installed, it was fairly simple to loop the belts into place and then lower the motors to bring things up to tension. I've included a video below to show what the belts look and sound like once everything is tight.
Proteus Delta with motors and carriages/sliders installed

Drive belt installed on one of the carriages
     And that's it for installing the drive belts. Next time I'll cover how to build and install the rod arms and effector platform. I've also had the MPCNC involved in making a support for the build plate, I'll have more on that in a later post, but here's a teaser of the initial prototype.
Test fitting the prototype print bed support, still needs some work
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