Feeling the heat, and soft plastic?
After the last post, days after, I had an unfortunate failure develop in the printer. After precisely calibrating the machine so that the extruders were perfectly aligned again and had zero Z offset, I went about printing and designing things. Mainly for the next change I am making – installing an E3D Hemera extruder.
I printed a new fan ducts for the new Hemera mount, and went to print the mount itself. When I did the head crashed on the same extruder into the glass. 1 hour before this the head was perfectly aligned… what happened?
I noticed that the screws for the E3D Titan Aero which holds the stepper and such in place on the mount were finger loose all of a sudden. I didn’t use any thread lock on the screws since I do remove and adjust the Extruders now and then, but I’ve never had them get loose like that. So I readjusted the height and printed the mount. Half way through that the screws were loose again!
After the print I took the extruders off (both were getting loose, even the one not being used!)
I am printing at no higher temps, and the current to the steppers are no higher. So my best guess is my print job was just bad on these mounts! I looked at the mounts I printed years ago that were in similar use and they had zero indication of this kind of deformation. I did print these at 4 walls and heavy infill, vs I think the originals (using same brand of filament, but different batch) were 5 or 6 walls.
This changed the geometry of the hot ends, and made it imposible to keep the machine calibrated. I am guessing part of it was the new heating routine for the chamber that has the hot ends sit essentially over a 100C heated bed for 20 minutes, but the HdT (High Temperature Deflection) rating for this material is close to 150C.
Since I was going to take everything apart to install the Hemera anyway I figure I would just get one hot end aligned well and finish the Hemera mount print and then swap these out after.
E3D Hemera Install / Custom mount
The E3D Hemera is a newer dual drive/gear extruder setup released last year. It is innovative for how small it is, the mounting mechanism, and that it fits a dual gear (presses and drives the filament from 2 sides) extruder in such a small package. It uses T slots on the Stepper itself as a mounting surface. No clamping material like above. The downside is that Hemera comes in a configuration not entirely compatible with the printer.
- The Idler lever out the top is so wide it wont let anything mount from above easily
- The wires exit out the stepper going vertical, directly blocking install on my printer due to the belt locations.
- The mounting surfaces are on the stepper so rotating parts of the stepper change the mounting options.
- The front face of the stepper cant be flipped as it is part of the extruder.
So I had to get creative and break the warranty. I worked in FreeCAD for days on a design that would keep the Hemera aligned with the Titan Aero that will be on the other tool going forward, but also securely mount it and keep clearance of the parts that need clearance. To make this easier I cut the inside tab off the Idler handle (its not needed anyway), and opened the stepper and rotated the mid section and the base 90Deg to let the wires exit out the side. This has no effect on the stepper movement but did change that the T Slots on the back were now top and bottom.
The new mount came together better than I expected. It features:
- 6 Mounting points to the extruder, 4 on the front sides with big 10mm beveled washers. And 2 more in the back top. The ones in the back aren’t exactly needed as the front makes it very stable already.
- The Hemera is slung lower under the X Axis than the Titan due to its compact size and to keep the nozzles closely at the same height between the Titan Aero and the Hemera.
- 1 Piece fan duct. I took an existing duct design from the Titan and made it fit the new mount and made it a 1 Pc print. It mounts in 3 places, 2 on the back and uses the bottom T-Slot on the stepper as a forward mount
- Mounting lugs/provisions for other attachments on the bottom of the mount structure, to use different fan/part cooling ducts similar to ring coolers and stuff down the road.
- Slightly changed top design (which was carried over from the new Titan mount I made) to give more clearance at the front.
Overall the mount is a bit bigger and bulkier than the Titan Aero one since all the structure needs to be on the sides now instead of sandwiched in the middle. But in the end its a lighter setup and more solid than the titan mount!
(Note, some parts of the pictures are pixelated due to NDA on some parts being tested)
In the end the mount came together as expected, with the first print of both the fan duct and the main mount working on the first try. I printed the new mount for the Titan and the Hemera in a heavier print setting of the same material. I am going to test to see if these resist the heat distortion that the past ones struggled with, if so I am going to switch and print these in Matterhackers NylonX instead which I know I don’t have issues with. (remember I had BIG heat distortion issues with a batch of 3DXtech CarbonX a couple years ago, where I am pretty sure it was PETG CF and not Nylon CF like they labeled it. ) I took the replacement of the Titan mount to adjust some minor clearance issues I noticed from the last install.
There are some additional clearance issues between the E0 and E1, I had to move the parking location for the E0 over by 3mm to keep the BLTouch from contacting the side of E1 when the E1 is at the edge of the print area near it.
Also – Fun fact – The stock Hemera is in roughly the same nozzle alignment/placement as the Mirrored Titan Aero. Which is why it went in place of the E1 on my printer replacing the Mirrored Titan Aero I had there. If/When E3D releases a mirrored Hemera I will replace the Titan on E0 with one.
Fixings!! Nuts, Bolts, Washers!
One of the things that the slipping extruder showed me was the value of using proper lock nuts/washers or thread lock. Some things I am resistant to use thread lock on as it shouldn’t be reapplied often or used on screws often removed and reinstalled. One solution I realized would have saved me some headache from the moving extruder, would be split washers or washers in general.
I am a screw geek, I have boxes of screws and fixings (mostly bought during the initial build out of the printer. I am pretty sure I have a standing line of credit at McMaster-Carr at this point. I wouldn’t say I have a screwing addiction, but it is a serious vice 🙂
This got me to look at what to use when I rebuilt the X Axis again.
- For the Hemera I knew the sides would need a well spread out washer interface so that I could put a lot of pressure on the stepper from the sides and not distort the plastic excessively. So I found some nice machined aluminum 10mm washers that are light and let me use a small 3mm flat head screw. They worked great!
- On other parts I used a standard 9mm washer to distribute some screw head loads on the soft plastic more evenly.
- I’ve also used square 3mm screws in inserts in 3D printed parts for years, they work FAR better than hexagonal screws.
- Then the key part – 3mm split washers. These are small springy lock washers, that help hold a bolt from turning, but even if it does, it keeps consistent pressure on it to keep it from turning more. I installed these on every metal/screw interface on the new build. They are cheap and great insurance from a screw backing out and potentially leading to damage of your printer or any other high vibration machine.
- Not shown are Nylock lock nuts. I dont use them often in plastic inserts because of the size and the fact they tend to spin in plastic, but they are very effective to keep screws from loosening if you can use them.
- Red and Blue thread lock when applicable. I use Red thread lock on stuff that I should not need to remove… ever. And blue on stuff that I may need to. Note – in general Blue thread lock is not good with heat and breaks down fast. Thread lock also generally doesn’t work on plastics.
In the end the goal is to avoid damaging parts but at the same time torqueing them down enough to keep them stable and immobile when they need to be. Use the right fixings for the right job!
Now I will be monitoring the hot ends to check if anything loosens over the next few prints, but otherwise I hope to be done wrenching on the X Axis of this printer for a bit and get down to seeing what I can do with the Hemera for flexible filaments and such.
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