User:Lmartin iii/Project 2: Printhead Changer

Week1 Narrative
Starting this next block, Project 2, I decided to stay with the Printhead Changer project. My goals this week was to print the 2nd prototype of the base and adapter, and test it to see if it would fit with the printer, then note and make adjustments as needed.

Prototype 2 Print
On Monday I was able to successfully print the model.

They fit together nicely, as designed, but when the model was compared with the printer there were several noticeable issues that didn't allow the prototype to fit on the printer. First, there wasn't enough space between the rear supports to fit around the back plate, so that space needed to increase. The rear screw insert cutouts were not spaced far enough apart and they needed to be notched out to fit in/around the back plate. The rectangles in the surface of the base for the side support arms were too small and needed to be widened. Also, I needed to create a way to attach the side support screws.

There was too much vertical space between the adapter plate and the guide arms. I had to reduce that to create a more snug fit. I also needed to increase the diameter of the screw head inset in the adapter plate so the screw could sit properly in the plate. Finally, I needed to create ramps on the guide arms so the insertion of the adapter plate into the base is smoother.

At the beginning of this week I was alone on this project. When Brandon joined the project on Wednesday I had to get him up to speed on the design and the electrical (since my previous teammate was no longer in the class). Since I was tasked with reworking the base and adapter design, we discussed how he could work on the electrical portion of the design.

Week2 Narrative
This week my goal was to complete the design modifications for the base and adapter, and print an updated prototype.

Prototype 3 Design
I reworked the design of the Quick Change base and adapter incorporating all of the modifications noted in week one. I also added a small tab-stop in the design, on the guide arm, to help hold the adapter plate in position once it is slid into the base. While creating the tab-stop in the adapter plate several surfaces were removed, and I didn't know why. I was able to recreate the surfaces to complete the model.

Prototype 3 Print
I printed the updated prototype. When I prepped the base for printing I had to use support material this time to hold up areas of the model that may have otherwise collapsed without it. This is an option that can be selected in MakerWare. Afterward I cut away all support material from the base. The fit, of the adapter to the base, was very tight so I lightly sanded the adapter. That allowed it to fit into the base with more ease.

Also this week, Brandon was able to secure 15-pin D-sub connectors for the electrical connections, which should work great for our purposes. He was able to solder the connections to the paste extruder and test it with an arduino...it worked.

I recorded detailed measurements of the D-sub connectors, with the plan for incorporating them into the base/adapter design. The class gave great feedback during the presentation regarding incorporating the D-sub connectors, which I plan to use when I begin redesigning.

Week3 Narrative
This week my goals are to see if prototype 3 will fit the MakerFarm printer, determine locations for the D-sub supports and add them to the base and adapter, and print another model.

I was able to attach prototype 3 to the printer. It fit snugly into the back plate and side supports.

The problem came when trying to attach the screws for the side supports. The v-shaped recesses for the screws to pass through were not deep enough. The side of the screw head pressed against the base which made the screw go in at an angle instead of straight. Will correct that in the next design iteration. All the other modifications worked great.

Prototype 4 Design
My first solution for incorporating the D-sub's was to put it in the side of the base. This was the simplest option, and would require minimal changes to the model in SketchUp. I cut a hole in the side of prototype 2 to attach a D-sub there. With this option you would slide the adapter into place, then plug the printhead into the connector in the side. I didn't have any properly sized screws to attach the D-subs, so I went to Lowes and purchased some (#4 - 40 x 1/2" machine screws).

Upon further conversations with my teammate, Brandon, and the instructor, we determined that it would be better to attach the printhead in one motion...setting the printhead in place and making the electrical connection at the same time. I then sketched a design where the D-subs were incorporated on the underside of the base (left and right), and on the new, modified adapter sled. I added the modifications for the D-subs to the design in SketchUp, as well as a place to mount the fan, and to route the electrical wires. I also increased the depth of the v-shaped recesses for the side screws.

Prototype 4 Print
When I sent the updated prototype 4 to print I ran into issues with the MakerBot nozzle getting clogged. The model had started printing, but maybe 15-20% of the way through the print the nozzle clogged and PLA stopped coming out. This is where I spent time learning more about how to disassemble the printhead on the MakerBot, and clean the feed tube and nozzle. Eventually, Okshay (sp?) was able to get a nozzle cleaned and working again. That allowed me to successfully print prototype 4. In this iteration, the base and adapter had to be printed with supports that I was able to cut away without damaging the model.

With the models cleaned up, I was able to attach the two 15-pin D-subs (male & female) to the base and adapter, then connect them. Everything lined up as intended.

Also this week, Brandon was researching different types of switches/levers to control the fan (We had originally thought to use one fan, attach it to the base, and only turn it on when a heated extruder nozzle is used. I've since opted for a different design...attaching the fan to the adapter plate.), and to communicate to the printer when the printhead is fully engaged. I eventually learned that my teammate was dropping the class, and that left me alone on this project.

Week4 Narrative
This week my goals are to make sure the modifications made for prototype 4 actually fit the printer, then solder the electrical connections into the D-subs.

I first checked to see if the fan fit into the new opening in the adapter plate. It did not. It was too tight, so I used a metal file to file down the inside of the opening. Afterwards the fan was able to slide in easily. I then created two holes so I could secure the fan in place with screws.

The way the D-subs are made they require a lot of force to connect and disconnect. Mr. Dolge had suggested we modify them to reduce the pressure it took to engage and disengage them. Brandon had previously modified one. I used the Dremel with a cutting wheel to modify another, by cutting off the shell around the pins. This allowed for smoother connection and disconnection, with very little force.

I cut the wires connecting the stepper motor, fan, and extruder nozzle to the printer, then began using the soldering iron to connect them to the D-subs. I was able to complete the connections for the adapter sled.

I need to finish making the connections to the base, attach the base to the printer, then test it to verify things are working as intended.

I also printed a second adapter plate for the paste extruder, and cut away all support material from it. It fit seamlessly with the prototype 3 base.