6/28/2013 – Extruder Assembly PART 2
Over the past week I’ve received my thermoster… actually two. I now have one for the hot end and one that came with the new 9”x9” hot bed mat. The hot bed mat is an “add on” that the Printing in Plastic book does not cover, but for the price of $20 and its purpose, this was a must have in my build.
A hot bed improves 3D printing quality by helping to prevent warping. As the plastic cools on the tray, it shrinks a little. Through the print process, the item printing will cool at different rates and it will cause slight warping in the final printed object. Using a hot bed on your printer tray allows the printed part to stay warm during the entire printing process. This minimizes the inconsistent temperatures which reduces the warping. The end result is a better overall quality printing.
So back to the hot end or extruder. Now that I have the final part for my extruder assembly, I was able to complete that phase of the project. The only problem I have, as mentioned in the earlier post, is the new and improved extruder kit looks nothing like the extruder provided in the plans for the Printing in Plastic book. With a little measuring and tinkering, I think I have a simple part that takes advantage of the existing mounting bolts and fits the new bracket. A number issues had to be overcome, but I believe I have them nailed down. Here is the modified mount attached to the Z axis rail. The Z axis needed to be removed from the 3D printer for some changes I described below.
1) Motor Power Wiring Path – Since the back-end of the motor sits facing the front of the 3D printer, the wires for the motor need a path to the back side extruder mount and up the Z axis rail, toward the control boards. I decided to cut out the hole for the motor a little higher to allow the motor wires a path through the mount to the Z axis rail.
2) Strong Mount for Extruder assembly – My current attachment method is 2 (two) #4 5/8” wood screws. The heads are wide enough to hold the bracket without a washer, sitting tight and flush with the bracket. I went with 5/8” length to make sure the screw did not travel in to the same space as the mounting bolts. I’m concerned that 5/8” length may not be a long enough screw to support the extruder assembly long term, though. When I begin printing we will see how well it holds up.
3) Filament Path to Extruder Head – The new mount I’ve designed, would have one fatal flaw if you did not drill a hole through the top. Without the hole the filament path is completely blocked. I noticed that mounting the extruder bracket directly in the middle of the extruder mount causes the filament entry holes to line up on the edge of the proposed ¼” drilled holes, but I don’t foresee a problem. If anything, the mount may become a better guide for the filament.
4) Air Flow for Fan Assembly – The last issue I ran into was probably the trickiest. When the extruder is mounted to the Z axis rail the extruder fan sits almost flush with the face of the rail, blocking the fans airflow. I fixed this by removing the Z axis rail and increasing the depth of the ½” holes used to hide the ¼” bolt heads. I sunk the holes down a full ½ inch to allow more of the bolt to protrude through the Z axis rail. This gave space for the fans air flow and provided the exact length needed to have the fastening nut sit flush on the bolt. When I had the Z axis rail apart, I went ahead and added the fourth bolt to the rail, which the book suggested you keep off.
That wraps up this post. Going forward, the Printing in Plastic book gets tossed aside as I get in to new electronics and motor controllers to create a much cleaner looking 3D printer. It’s all about the electronics now, as motherboards, controllers, switches, wiring and a power supplies are installed. Oh… did I mention that most of this stuff is sold out and out of stock? Hopefully the next update will be soon, but who knows at this point. Til next time…
Here is the final sketch I made myself for the new extruder mount.