Posted on

Introducing the LongMill MK2.5

For those of you that have followed us as we develop and improve our products, or read Andy’s Production Updates, you probably know the drill by now – it’s time for our LongMill CNC to see some new improvements!


The LongMill used to be called just that when we launched it back in October of 2019, but the naming quickly got expanded:

  • LongMill V2 which began shipping March 2020
  • LongMill V3 (Aug 2020), then V4 (Jan 2021), then V4b (Aug 2021)
  • LongMill MK2, which marked a complete redesign of the LongMill CNC to continue our focus on ease of assembly, rigidity for price, and designed with add-ons in mind. This began shipping in March 2022 and retroactively grouped all prior LongMills into the “MK1” naming.
  • LongMill MK2.5 which we will now be ramping up to begin shipping for June 2024

Why do we make these updates? Since we launched the LongMill, we’ve continued to maintain a solid idea of where we felt it should sit as a CNC and more generally as a tool. If you’re looking for a CNC that can create any reasonably-sized project an individual would be looking to make at home with great support and reliability, it’s the machine for you. It’s akin to a home printer, you could save money and spend less on stamps or small label-makers, and you could also spend a lot more on a large laminate printer or printing press, but the home printer can really hit the sweet spot for most individuals. We’ve never wanted it to trend upwards in price and features until it starts to resemble an industrial piece of machinery (that’s what our new AltMill is meant to do), but we also recognize that we can take action when opportunities arise from:

  • User feedback
  • Production at scale as our company grows
  • New understandings of our users priorities as we see how everyone uses our CNCs

Making steps while ensuring that the changes are worth our time and everyone’s money makes us feel that we’re continuing to update our products with the best that we have to offer to the CNC community. This is exemplified by the transition from quite a few 3D printed parts in the original LongMill to now being all metal and one injection mold in the MK2.5. Another example is the MK2 redesign which made the LongMill 2-3 times stronger than the MK1 design for the exact same cost and nearly halved the assembly time. All of this with very few price adjustments along the way to keep up with changes during COVID, inflation, and continuous improvements we continue to pour time and energy into to build and support such a user-friendly machine and ecosystem. Would you believe our 30×30 model started at $950 and by the MK2 it was still only $1350 USD?

What’s changing?

We’ve got two new heavy-hitters that we’re very excited to announce as a part of the MK2.5 update, alongside some other smaller improvements.


Many of you might already be familiar with this new development that’s been over 1.5 years in the making, but if not we have many prior blog posts that can bring you up to speed. The bottom line is that with the successful launch of the first 500 pre-ordered units and the positive reception, we’ve decided to fast-track the SLB to be standard with the LongMill moving forward (it’s also what we’ll be building off of to power our new AltMill CNC).

Since my last SLB update, we released a great summary video on what you can look forward to that also explains why we think it makes sense to move forward on this new electronics architecture. The main benefits to all users will be:

  • Faster movement, homing, and probing from new motor drivers that are more robust and anti-resonant
  • Smarter drivers also reduce motor noise, allow changes on-the-go over firmware, and are expected to be more reliable
  • Improved cutting reliability against ruined jobs and material due to high-grade EMI measures implemented in the board redesign which also includes Ethernet connectivity
  • Smarter and more responsive system resulting in faster probing, safer E-stop, and room for even more future expansion
  • Even more extras for the true enthusiasts like RS485 VFD support, 4th axis cutting, TLS, and more

It’s been very exciting seeing the SLB get into peoples hands over the last two months, especially so after some have already contributed their own guides and videos showing installation, reduced motor noise, and increased speeds. I was getting concerned that the shipping status table posted in the last SLB update would encounter more delays but I’m happy to say that we were able to keep things relatively on track in that first batch. I really appreciate everyone’s understanding and patience as we’ve been preparing to get more SLBs in for MK2.5 and also the lineup of already another hundred or so orders from people looking to upgrade their existing CNC systems. The strong reception we received in the initial pre-orders, combined with the feedback we’ve gotten so far from them in action, is what makes us confident in rolling out the SLB to everyone else for MK2.5. We’ve already had many more updates to our docs from the wider feedback such as:

  • Troubleshooting when the SLB is too fast for your machine
  • Post processor selection
  • Options for new options for motor holding
  • Clarified RGB LED strip hookup
  • Clarified 4th axis driver hookup diagram plus extra firmware setup steps

To all those who back-ordered their SLBs, don’t worry you still have your place in line since MK2.5 was always meant to be a part of this same batch of boards. Currently we’re still doing our best to have the boards ready to ship out by end-of-May but it seems that there’s been another delay from one of our manufacturers which might mean that we won’t have boards show up until the start of June.

Spring Loaded Anti-Backlash Nuts

There’s also been a lot of coverage documenting our long process in trying to figure things out with these, but now we’ve gained confidence we can produce them in bulk and are excited to introduce them as a part of MK2.5!

Since we premiered this new part, demand has remained super high and every time we’ve restocked it’s sold out in just a couple days. The reason people have jumped to buy the over 4000 we’ve made so far is that it offers self-adjustment to maintain no backlash on all the LongMills axes. This is normally a very expensive technology to access, and is normally solved on other CNCs by using ball screws (more expensive and require more cleaning maintenance) or belts. To-date we’ve used an OpenBuilds-based design that allows for no backlash on lead screws but requires manual adjustment, but with this new upgrade it means one less step for y’all to have to worry about when it comes to CNC assembly and maintenance; giving you a reliably precise CNC system while still having the benefits of the low maintenance of lead screws.

Other Updates

Some other updates that were already introduced during MK2 shipping were new coupler and clamping nut designs that now use M5 hardware instead of M3. This change has meant that we have mostly eliminated people having issues with stripping hardware (some of our users have gorilla grip) or not being able to tighten them down hard enough on the lead screws.

We’ll also be rolling out injection molded feet which will be replacing our currently 3D printed middle feet. These support the Y-axis rails to create a more rigid system, but these parts have never really caused any issues or showed signs of needing an upgrade, we just haven’t changed the design for a while now so we decided to save the time for our 3D printer farm and opt for higher-quantity manufacturing.


We’re excited to announce everything that’s on the MK2.5 docket! Due to the changes, MK2.5 will also be coming with an approximately $150CAD/$110USD price increase compared with MK2 to reflect the addition of primarily the SuperLongBoard and the other additions.

We are continuing to work our way through the materials from Batch 8 (MK2) and are waiting on Batch 9 (MK2.5) parts to arrive which we expect to start shipping out later in June. We’re also already underway on putting together new revisions of our assembly manual and other LongMill resources and are looking forward to continue further expanding those resources in the coming year in other areas as well.

Of course, as MK2.5 starts to arrive in users hands we’ll continue to bring any other improvements we can like we’ve done for all prior LongMills, and anyone who’s looking to manually upgrade we already list all the new parts on our store for individual purchase. Also if you ordered a MK2 that hasn’t shipped yet and you’d be interested in upgrading to a MK2.5 instead, please just call or email us to arrange paying the difference and we can happily update your order.

Until next time!