I was doing an “Intro to 3D printing” event at the Chicago HackerSpace, Pumping Station One. We were showing about 5 or 6 flavors of printers. Someone commented how complicated the delta printer looked. I tried to explain that they were actually simpler in my opinion. Rather than having 3 different designs for each axis, a delta uses three common linear actuators. The delta was a Rostock Max and it does look a little complicated. I decided to try to design the simplest delta I could.
- Make it smaller than a Tantalus or Up Mini
- Use as few parts as possible (part count).
- Use as few unique parts as possible (part type count).
- Use MakerSlide because….duh.
- Try to use parts I had laying around. I only had about 3 days to before the first build day.
- Try using the Spectra Filament instead of timing belts.
- Clean look and simple wiring.
- Limit fabrication to 3D printed parts, laser cut parts and simple tools.
- Try to build it in 1 night at the weekly PS:One meetup and involve as many people as possible.
Somewhere early in the design I got the idea to invert the end effector. The bed would move and the extruder would be stationary. This vastly simplified the design and I could use an extruder I already had. If I limited it to PLA, the bed would not have to be heated and no wires would have to go to the end effector. With the extruder on top, all electronic items except limit switches could be placed on a single laser cut plate.
The design was bounced off Jeremy BP of tinyworkshop.org a few times in an email thread titled “Latest Crazy Idea”. This is the rendering of the design going into the build. There is a pop can rendered on top for size reference.
I sent a note to the CNC Build Club forum asking if a few people wanted to help with the build. About 10 people showed up. I spent all my time handing out jobs. Jeremy BP was the primary fabricator and ran the laser cutter and other shop tools. There were a lot of newbies there so many of the jobs like setting the current levels on the stepper drivers turned into mini classes. There was a little SNAFU with the laser origin which wrecked the middle round piece. PS:One had plenty of replacements, but no black, so the middle piece is a creamy white
Here is a part of the team, One is tapping extrusions, one is pressing inserts into brackets, one is assembling V wheels and Jeremy is setting up the laser job.
Everything was going well until it came time to assemble the Spectra filament driven linear actuators. It was sort of a puzzle to work with the tiny pieces. AVRC and I could not agree on the best way to do it. Finally we each grabbed one and did it successfully different ways. The actuators worked but it was clear the design was not robust and might wear quickly. At about midnight we had the basic thing assembled less the rods and end effector.
I had posted the progress on the Delta Robot 3D Printers forum and several good suggestions came through. The best was the suggestion to use off the shelf rods. At this rod size there were a few that would work right out of the box. These are Traxxas 5538 parts. They are actually a turn buckle so they can be finely adjusted. I ordered them from eBay and got them just in time. They were only about $3 per linkage.
We laser cut a template that was used to set the rods all exactly the same length.
The template holes have been added to the lower circle piece so an extra piece is not require in the future.
The Spectra drive systems was replaced with pulleys and 1/8″ wide MXL Belt. Jeremy laser cut some toothy clamps out of delrin.
Motor mounts for the NEMA 14 motors and 18 tooth pulleys. The mounts have a captive nut on one side that can be used to pull the motor up to tension the belts.
Here is the electronics plate. It gets pretty tight even with small motors.
- RAMPS 1.4 Controller
- MakerGear Stepper Plastruder
- 35mm Fan.
- Limit switches were wired with a common ground under the base and (4) wires were run up to the controller inside one of the edge t-slots.
We assembled the end effector but the rods touched parts of the carriage as the outside edges. This was limiting the range. We installed some spacers to fix the problem. We also configured the firmware. We called it a night early this time at about 10:00pm.
All that really needed to be done was to setup the limit switch actuators to level the bed and enter the Z height information into the firmware and Repetier Host.
The first test was a simple calibration cube and printed perfectly. The part stuck tight to the tape and was a little tricky to get off the bed.
Everyone kept saying the printer looked inverted so we tried flipping the printer upside down while it printed. It finished the print without any problems. You could see a little line in the layering where we flipped it but both sides of the line looked perfect.