As readers of this blog will know, the upgrade to 5 colour was done in a bit of hurry in order to get the printer ready for the TCT show. There were a few things that I wasn’t entirely happy about so I’ve been putting those things right, as well as making a couple of other changes to accommodate some other ideas that I’ve had.
The first thing was the mount for the extruders. At the time, I decided that fitting them in a circle would be the most economical use of space and give the most compact arrangement. Unfortunately, things are never that simple. The issues were that outlet from the Titan extruders isn’t central so the entire assembly had to be rotated in order for the Bowden tubes to line up with the heat sinks on the hot end. However, it was still impossible to find a position where all the Bowden tubes missed one or other of the horizontal X rails and still line up with heat sinks. In the end, I found a compromise position but it meant that the Bowden tubes were not as straight as I would have liked. Then I had to find a way to attach the belts but this caused issues with access to the extruder mounting screws. Here is a picture of the old assembly
Once the belts were fixed to the clamp in the far right, it was next to impossible to get at one of the extruder mounting screws.
Here is a picture of it all assembled and you can see how the Bowden tubes had to be twisted to line up with the heat sinks while clearing the rails.
The other issue was that the belt mounts were not “beefy” enough and became distorted as shown below.
Also, those belt mounts were off centre by about 3mm so the belts were not truly parallel with the X axis. It wasn’t the main hot end carriage so wasn’t a huge problem but I wanted to put it right. Here is an OpenScad image of the new mount.
The extruders are now mounted such that all the Bowden tubes line up better with the heat sinks, the belt attachment points are significantly stronger (and are properly centred) and it’s a lot easier to get at all the screws which hold the extruders. Of course, changing it over wasn’t a quick task. Here is what five E3D Titan look like when disassembled.
Here it is all re-assembled
Another problem I made for myself was the way I fitted the second CoreXY gantry, which had to be larger in both X and Y due to the extruder assembly being larger than the hot end. Basically the belts were fouling the uprights as shown here.
As time was very limited before the show, the most expedient solution was to file away the extrusion to clear the belt which is what you can see in the picture above. Now that I had more time, and as I had to remove the belts anyway, I redesigned the idlers to bring the rear belt forward. Here is old idler
I realised that the support pillars didn’t have to be the same diameter as the idler pulleys. They are only there to hold the idler in position while the belts are being fitted. Once the belts are fitted, the idlers find their own vertical position on the bolts. Because the belts are stacked, the idlers can overlap each other. So by making the pillars smaller, I could bring the rear idlers forward. Here is the new idler.
Which has had this affect on the belt path…
I also realised that I could reduce the size of the pillars on the lower CoreXY idlers but in this case, I moved the front idler back and reduced the size of the mount which gave me another 14mm of travel in the Y direction. However, I didn’t actually get the benefit of this additional range because I decided to add a purge “bucket” at the rear of the bed. It looks like this
Basically, it’s a shallow tray the width of the bed and fixed to two brackets. There is a slot at the front which takes a strip of silicone 10mm tall x 3mm wide and which protrudes about 3mm above the top of the tray. It is positioned such that the tip of the hot end nozzle will be about 1mm lower than the top of the silicone strip. The idea is that I’ll move the nozzle to the rear of the bed at the start of a print and while the hot end is heating, any “ooze” will be wiped off the nozzle when the print commences. I’ll coat the inside of the tray with silicone grease or some such, to prevent the hot filament from sticking to it. I also plan to use this “bucket” for purging after colour change when other methods aren’t practical. I’ll be doing a separate post on this topic when I’ve developed the technique further.
Finally, I’ve simplified the wiring somewhat for if and when I have to dismantle the printer. I have a combination of 12v and 24v fans as well as some LED lights and so forth. For that reason, I have a 24V to 12V DC converter and a separate 12V rail. So, I’ve moved the converter to the top section of the printer and changed the wiring so that all the 12v power is just in this one section. I extended the box that held my emergency stop button and put the 12V rail inside as well as adding a few switches.
Oh, and I finally succumbed and added a bit of bling
They are just 12v LED strips (black of course) which shed a bit of light.