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You’re probably wondering what’s taken us so long to get Hemera back on the shelves, so let us talk you through the changes that we’ve made from heat treating and lubricating gears to setting new visual standardsTeam E3D have been busy ensuring the Hemera we bring back is as superior as can be with quality and customer satisfaction the number one priority. A final thing we’d like to mention before getting into the detail is that if you order a Hemera, your box may well say ‘Hermes’, please don’t be alarmed, what you have received is a Hemera we just had a fair few boxes leftover and didn’t want to be wasteful!  

Gear Heat Treatment 

Status: Done - with further cosmetic improvements being investigated. 

 Issues Addressed 

  • Preventing gears cracking (total) 
  • 22T (Motor Pinion) 
  • 73T (Large Gear) 
  • 20T (Hobb & Idler Gears) 


Previously some gears were experiencing brittle cracking, as they were excessively hard (Great for wear resistance, a little less great for toughness during assembly) The heat treatment process for the gears habeen improved in consistency and the toughness of the gears has been improved by approximately 2-3x. Hardness has been very slightly reduced (by about 2 HRC for the metallurgy nerds out there); however, this does not appear to be affecting wear behaviour. The new heat treatment process may result in some colour variation; however, this colour variation is not an indication of a variance in hardness as it would be if one was just tempering in open air with a blowtorch. We are working on improving the consistency of the hardening process, by moving to only using the inert gas quenching process - which is the gold standard for heat treatment of metals. 

If you have gears that have not cracked then the likelihood of cracking happening is vanishingly low, however should it happen then we will gladly replace them. 

Motor Spacing  

Status: Done  

Issues Addressed  

  • Preventing gears cracking (partial) 
  • 22T (Motor Pinion) 
  • Reduced gear wear (significant) 
  • Will exhibit as reduced rusting in non-lubricated gearboxes 
  • Eliminate gearbox binding (total) 


The spacing between the shaft of the motor upon to which the pinion gear is pressed and the bearing pocket defines the spacing between the motor pinion and the large 73T gear. Issues with the tolerances of this distance caused some gears to be forced together too firmly, causing either total jamming or, more subtly, the appearance of ‘rusting’ due to the increased contact forces removing the passivated layer of the stainless steel and exposing ferrous material to oxidation. 

By working in collaboration with our motor manufacturers we have ensured that the spacing and tolerances of these features will no longer be problematic in all future motors.  

Some motors had features that were not in tolerance. However we were able to rework these out of spec motors into good, in-spec parts by machining out the bearing pocket to the correct position with a larger diameter, and then using a reducing ring that is press fit into that correctly placed pocket. You may find that your motor has one of these reworked or corrected bearing pockets, this is totally normal and means that your motor is definitely very much in spec. 

If you have an extruder that is turning well, and extruding fine you have nothing to worry about, however if you think this issue is affecting you please let us know, and as ever, we’ll sort it out for you. 


High - significant issue fully resolved. 

Side effects 

  • Nothing significant. 
  • Reworked motors will have a small metal “ring” inside the bearing pocket hole in the motor face plate. This is normal, and genuine E3D. 
  • At our very lowest tolerance band slightly more wear (rust) will initially occur than we should like.  

Gear Lubrication 

Status: Done - with further improvements being investigated 

Issues Addressed  

  • Corrosion on wearing surfaces of gears 


Gears wear, even very hard wear resistant gears will do so slightly. When they wear, particulate forms. The particulate and surface of the gear then appear slightly rusty looking as well as shedding some small particulate matter, this is innate to stainless steels and their passivated surfaceEven though these gears will last a lifetime the appearance of an orangey surface and dust is unsightly 

To significantly reduce this, whave started using a corrosion inhibitor which will be applied to the gear contact surfaces. This will prevent the unsightly appearance of an orange gear contact surface and dust emission. Adding a corrosion inhibitor makes a big difference and a tiny amount results in a much-reduced appearance of corrosion as well as capturing and preventing the shedding of wear particulates. 

Idler Pin 

Status: Done 

Issues Addressed 

  • Eliminate heatsink blowout 


Press fitting the original idler pivot pin into the heatsinks was causing the thin wall material at the end of the hole of the heatsink to create a somewhat unsightly burr. At first this was near invisible, but as tolerances changed the burr became worse. As we had okayed this initially, we continued shipping as it presented no mechanical issue, however we now have visual standards in place and have introduced a chamfer to alleviate the stress. 

A chamfer has been added to the pins to alleviate the high stress on the thin wall section of the sink and a slight change in length means we don’t have to press them as deeply. This has eliminated the cosmetic issue.  


Status: Done 

Issues Addressed 

  • Excess force applied to mounting points due to incorrect mounting 


When the incorrect length screw was used, or when mounted onto a surface of less than 3mm depth without changing screw length, the t-slots were liable to crack. The documentation was not clear enough about this. 

To ensure visibility of the mounting advice, all Hemera units now ship with clear guidelines for mounting, attached to all mounting point/t-slots. 

In Conclusion

We hope this has clarified things for you, but if you have any further questions then please leave them in the comments below. You can now purchase Hemera, spares and merchandise here - please note there is limited stock available so do take this opportunity to avoid disappointment.