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!


Feb-ulous SLB news

Greetings all, Chris here again to emerge from my SuperLongBoard development cave and provide you with my news!

For anyone who still has yet to hear about our new and most ambitious Sienci Labs electronics projects to-date, our arguably aptly named SUPERLongBoard, is the graduated version of our current LongBoard and has been designed to be even more SUPER at all things hobby CNC. 

This is a serious upgrade for a serious board, even if we had some fun with the name: culminating in what we hope to be an all-in-one solution and in many cases an upgrade to anything currently in its pricepoint on the market. The result is a 32-bit processing, on-board motor driving, Auxiliary output supporting, 4th axis controlling, laser, TLS, macro button -having board.

With that summary out of the way, you can catch up on past progress by looking at my update last month which also has links to past videos and past updates before it: 

Now let’s roll along to what new stuff I have to update you on this month 🙂

New Stuff

We’ve now pre-sold nearly 450 boards now…. and wow I’m so excited to see that everyone else is just as excited about this board as I am. To put into context: the current batch of boards we’ll be manufacturing was intended to be 500 but had to be reduced to 470 (I’ll mention the reason shortly) which means that we’ve nearly already sold out the whole batch before starting shipping! Needless to say, Andy and I already began discussions about a month ago on what our next steps are going to be if the reception to the SLB ends up being as good as we hope it will be to ensure we can have more on-hand in the coming months if possible.

Now the reason why we had to reduce to 470 is basically a math error, but in short:

  • Right on time to the schedule I posted in my last update – a couple weeks ago – we finally ordered the final production run of SLB boards! After the last run of prototype boards arrived we were able to very quickly redistribute them to Beta testers and vet any last changes we felt needed to be made so we could turn around and start prompting for production.
  • Already knowing that Lunar New Year would interrupt our delivery progress, we’d already ordered every other overseas part that we needed to produce the SLB (except the boards) at the start of January to ensure things would arrive on time by boat.
  • Knowing that we couldn’t do this for the boards since we needed more time to test them, we instead pre-ordered lots of the parts used for the board circuitry in advance as a way to help speed up production after Lunar New year finished. This included important stuff like the STM32F412 ‘brain’, TMC2660C motor drivers, and some other rarer items. We pre-ordered around 525 of these parts, but shortly after realized that we needed to do one final set of prototype boards and this used up 40 of the 525 parts.
  • After we add a small buffer for potential board failure, this left us with about 470 left for production SLBs that we can make available and would ship by air to catch up with everything else so they would all arrive around the same time.

Speaking of ordering parts, let’s take a look at what our full part table looks like right now as we start preparing to intake SLB parts and set up packing stations to check and ship them out:

SubsectionNameAmountShipping Status
Board PartsSLB important PCB components1Pre-ordered and now being used for SLB board production
SLB PCB assembly1Underway, scheduled to arrive by air on March 18th
USB-C Cable1To be ordered shortly after some more testing/validation
E-stopE-stop Button1Ordered, currently on boat and scheduled to arrive March 5th
E-stop PCB1Underway, scheduled to arrive by air mid-March
E-stop Cable1Completed, will be shipped alongside E-stop PCBs
Injection Moulded Case1Completed, currently on boat and scheduled to arrive March 15th
#4 screws3In stock
Enclosure PartsAluminum Extrusion exterior1Completed, currently on boat and scheduled to arrive March 15th
Front Panel1
Rear Panel1
Acrylic Cover1Arrived, to begin in-house production mid-March
Steel Mounting Bracket1Underway, should be made and plated in a couple weeks by our local steel manufacturer
M5-10mm SEMS3In stock
M5 T-nut3In stock
M4 Thumbscrew1Arrived
#4 screw6In stock
PackagingCardboard Box and inserts1Still being designed, should have a 1 week turnaround time by our local manufacturer

We’ve tried to time things out using a combination of boat and air freight for international parts and the shorter timelines of our local producers. Hopefully the information isn’t too much to look at, but the long and short of it is that everything looks like it’ll all show up around the same time!

Some of the great-looking production samples!

In the meantime, we’ve begun working on making space for packing and testing stations, working on designing our quality assurance procedures to test boards before they go out the door, all the while internal testing and Beta testing still continues forward as small tweaks to gSender support and to the Firmware are still being made to get everything working how we like it.

Please still bear in mind though, due to there being things that could still be outside our control, I would still conservatively estimate that SLBs begin shipping out the door last week of March or the first or second week of April. This would cover instances where delivery by boat or air has a slowdown, or we find something with the final batch of boards that need our attention. For example:

  • We’ve now had problems with a couple RGB LEDs out of the 50 prototypes we’ve made where they light up random colours rather than turning the colour they’re told to be. This makes us think that our manufacturer is giving us slightly water-damaged components, so we spoke to them about baking the LEDs before installation and are also working on a way for them to validate the boards before shipping so they don’t show up broken. This is an example of nothing we’ve done wrong, but could pop up unexpectedly on a board as complex as the SLB.

Will there be more Videos?

Yes of course! To be honest, after the inrush of pre-orders after the SuperLongBoard launch I’ve had more of a sense of duty to test-test-test the board as much as I possibly can as a higher priority than filming the boards capabilities. This is because, though I know there’s lots that the board can do, clearly everyone who’s already pre-ordered is already on ‘board’ with the SLB so I don’t think it would be fair for me to spend my time building more excitement for the board when I can instead focus my time on making it more bulletproof 🙂

And I think the nose-to-the-grindstone work has been paying off! There’s been tons of bug squashing and pushing machines to their limits by us and our trusty team of Beta testers:

  • We’ve now had over 15 firmware iterations since the start of the project
  • We’re continuing to work closely with the grblHAL firmware creator to ensure great compatibility between the board and its functionality, we actually sent him a pre-production SLB of his own that he’ll be receiving shortly
  • Major work thus far has included implementing major features like reliable USB and Ethernet, standby current reduction and individual axis holding, 4th axis control, TLS support, action buttons and ensuring their behaviour is predictable in different situations when using the CNC, controlling the custom outputs, honing in on the new LongMill default settings
  • Lots of tweaks have been made to gSender to make it know all the things it needs to know to effectively communicate with a faster and more feature-diverse controller. There have been more delays than originally thought due to continuing to find unexpected edge-cases in how the SLB behaves differently from the LongBoard, but we’ll keep trucking along and expect to be done in time
  • Ikenna has now thoroughly vetted the SLB to work with our LaserBeam laser diode and is very happy with how it’s working, even now using SLB in his LaserBeam livestreams

When it comes to roadblocks we’ve hit, the last month has actually been very good. Beta tester feedback has been a split of 40% gSender compatibility problems, 30% improvements to board documentation, then about 15% tweaks to firmware and the last 15% changes we had to make to the board design before we began production. This is good news because software and firmware are things that we can -and have- continued to work on while things are being manufactured and shipped over.  This means that the gSender and Firmware teams still have most of March to finish polishing things up which seems very doable. The last remaining hurdles are to get things like 4th axis cutting and switching between spindle and laser working as smoothly as we can in gSender, and then completing the remaining documentation tweaks based on Beta testers continued feedback, then writing up a guide on how to do a full board swap for existing MK1 and MK2 owners. I’ll also be setting aside some time mid-March to establish final movement speeds and motor noise that can be expected.

With all that said, videos will definitely still be making more of an appearance as we begin to near the delivery date since I want you guys to see what you’re going to be getting before shipment begins 👍 Alongside this will of course be: continued updates to FAQs, starting to release parts of the SLB manual, starting to release a list of recommended hardware to use alongside your SLB for 4th axis, lights, and more. I might even do some Livestreams so you guys can see more of the board in action and have any of your other questions answered! Some of my current video/livestream ideas are:

  • Speed and noise comparison to the LongBoard
  • Trying and SLB retrofit onto a Mill One
  • I’ve been messing around with a RapidChange unit and am hoping to see if I can get it fully set up and working to answer any questions about the SLB supporting an ATC. If you haven’t seen this unit yet I’m very excited about what it might do to shake up the hobby CNC space for more affordable automatic tool changing, and Don who I’ve been speaking with over the last year is a really nice guy who’s direction I really love so far


If you’ve made it this far, here’s your award 🏅. This is to recognize that you once again lasted through another one of my treacherous, Engineering-writing posts, complete with its poor sentence structure and also a lack of pictures on this post especially.

In all seriousness, thanks for everyone’s continued support for this project and the other projects we’ve continuously strived to do with Sienci Labs over the years. It’s never been easy for us but the kind words and reassurance that the work we’re doing matters really helps to keep us going. Thanks for anyone who’s been helping give me and the gSender team the needed feedback to keep making more cool features and fix iterations that sometimes break things and thanks for posting all the cool stuff you do and helping each other out too.

If you have any other ideas for SLB content you’d like to see, please leave them in the comments of wherever you were when you saw the link to this post whether it was on Facebook, our User Forum, or elsewhere and I’ll try to find them and write them down.

Until next time!


SLB January Updates

Hey all! Chris here again with some more juicy SLB updates

There’s been a lot of great news to come since you last saw me with my major SLB update post at the start of November, and then our very successful SLB launch on December 4th. If you missed them feel free to look back and get caught up:

What an Exciting Start

Firstly, thank you to all of you who have pre-ordered! We sold almost half of our first batch of 500 in the first 3 days, and are now at 357 total pre-sales, we might be sold out before we’ve even shipped the first board! Me and the whole team behind this effort really appreciate the trust and excitement we’ve seen for the SuperLongBoard and will keep working diligently to come out with something that we’re proud with and in a timely manner.

Thumbs up from one of our test setups at the new Sienci HQ!

Just a reminder that we’ll still be sticking to our word and offering anyone who orders an SLB before Jan 31, 2024 a reduced price, this means that if you’d like to show us some early support in this project and save some bucks while you’re at it, you’ve only got less than a week left to join the pre-orders 🙂

Some Meat and Potatoes

SLB Beta testing and board development rolls on 🚂. Since you last heard from me late December, nothing notable was hinted to since there’s A LOT of complexity to timing a product like this that has been going on behind the scenes. The one fun you might’ve seen was an SLB-powered Christmas Tree display which was a great break for me to enjoy a hands-on project, especially after the many countless hours I’ve spent recently behind a computer on documentation, emails, bug testing:

Happy SLB-mas!

Getting along to the juicy stuff, the SLB production progress has been continuing to pass more milestones:

  • SLB Enclosure 3D design finalized
  • E-stop PCB finally designed after the hurdle of the E-stop connector not being able to be tracked down so we got around it by attaching a connector to the other side
  • Enclosure samples arrived, tweaks made, production started
  • Major slowdown in receiving new SLB prototypes because of shipping confusion from UPS since we moved offices
  • Now at 5 Beta testers who are all talking on an the expanding private SLB Forum (will become public at launch)
  • E-stop samples and sample 2.5m E-stop cable arrived (longer length allows for more options on where to place the E-stop)
  • Found we won’t be hitting any major roadblocks when it comes to certification
  • Manufacturing of E-stop wires and injection molded E-stop enclosure complete
  • Manual & documentation now reaching reasonable progression in outlining all board features and testers now having hands on with the majority of options the new board makes available
Most-finalized SLB design, basically ready to go!

I hope you’re all as excited as I am about all those major steps that have been taken. We’ve also been iterating very quickly on improvements to the SLB’s firmware and bringing gSender up-to-speed to properly support the new board. These we know we have more time to complete since physical production is the MOST important to move along ASAP, but software and Firmware is still great to put our minds at ease to ensure everything works as expected as soon as possible:

  • 6 new SLB firmware versions since my last big update, now at 5.0.1 which fixes and improves some great stuff
  • Status light overrides
  • Improved PWM switching with separate inversion control
  • TLS inversion should now be fixed
  • SwitchBank control now happens over software
  • Laser will be changed back to not be default behaviour for safety reasons, but gSender is being worked on to support easier changing between Spindle and Laser
  • 3 more gSender Edge builds and now the new 1.4.0 Main version to better support SLB (see more about it here:
  • Controller jogging finally smoothed out, improved time estimation, more progress to resolve HAL Rotary behaviour, among other things
  • Whole ordeal now almost straightening out where we had massive delays due to software certification regulatory changes, requiring us to reapply and have our costs doubled to $800/yr just to be a trusted distributor

Here’s some more detail you can see on some of those points. Please read to the end if you want to see information about the remaining steps we have ahead of us and where my thoughts currently lay for the delivery timeline ↓

Finalized SLB Enclosure and E-stop

Sooo much iteration we went through to try to make a from-factor we were happy with

To give some context, we started ideating the enclosure the SLB would fit inside before the board even existed! We wanted to make sure it would accomplish a range of things to accomodate all the new plugs, keep wiring clean, look nice but also robust, not break the bank since the value should be coming from the board itself, and much more. A while ago I even started a thread on our forum when I thought I’d finally reached the end of our design vision (….. aaand it was met with mixed reviews. In light of this we went back to the drawing board and I hope what we came up with will be able to meet everyones needs.

Finalized aluminum SLB enclosure and cable, E-stop to be injection moulded

This new design should give the best of both worlds! Universal flat mounting via flanges to accommodate a range of setups or machines inside enclosures, with a subtle bracket that will allow for Y-axis rail mounting for any LongMill MK2 owner if they want to keep all their wiring tidy and together. The front is easy to open and allows some wire management inside the enclosure itself, with most wires going out the rear, and I’m sure you’ll be happy to see how the status lights turned when we do a final reveal. You can also see the detached E-stop with it’s longer cable and 3 customizable Action buttons! These will all come standard with each SLB kit

Beta Testing

We’re in our final push on Beta testing to see if we can find any last issues with the board. This process has been ongoing for several months now with us finding little quirks here and there – but luckily most of these have been easy fixes that weren’t due to the boards themselves and instead the software or firmware. Below you can see a new setup for one of the testers, and if you pay close attention you’ll see some of them posting updates on their testing experiences on our Facebook group or Forum (like

I rotated this picture to fit better onto the page, sorry Ian 😐


A labour of love to keep our level of product support to the standard you’ve come to expect from us, we’ve now passed 50 pages of documentation covering all aspects of mounting, features, configuration and more for the SLBs. Another thing I wanted to let everyone know of is that one of my goals for this year is to transition all of Sienci’s documentation to be publicly contributable so that anyone can submit improvements or entirely new write-ups on how to use our products and just to share CNC resources in general. I’m very excited about this prospect and hope that I can do it in a way that best honours our ever-growing community.

Ongoing work on over 50 pages of documentation on all aspects of the SuperLongBoard

What this all Means

It means we’ve been working hard and seeing results! There’s still many more steps to go though, and with now everything in production except the boards themselves, I have to admit that the March delivery date might push into the end of March or start of April depending on our luck with slowdowns overseas from Lunar New Year. The board design as of tonight is fully complete with any other small tweaks we felt it needed to be ready for production, so the last thing holding us back is any remaining feedback from Beta testers that might tell us that there’s anything else we might’ve missed on the boards – otherwise if we have the confidence then that would be the last big piece of the puzzle completed. We want to try the best we can to not miss anything and have been trying to run Beta testing and in-house tests for over 5 months now to gain the confidence that we hope to see play out once everyone else gets their hands on the SLB.

Most recent round of prototypes being sent out to Testers to collect as much feedback as we can

Any other remaining steps and timeline as we start to see the light at the end of the tunnel:

  • Ongoing Internal validation on the new batch of boards, between Johann on General checks and Ikenna on LaserBeam compatibility alongside Expatria on their own setups we’re doing one last big effort to ensure boards can begin production and Firmware is as progressed as possible 
  • As of the start of this week and until the end of next week, the -hopefully- last version of the board prototypes arrived in the hands of Beta testers alongside the mostly finalized E-stop, enclosure, and new firmware. We’ll be looking for any remaining feedback to hopefully conclude any remaining findings they can provide before we begin production: using the E-stop and Action buttons, the form-factor and fitment of the enclosure, anything else they’d still like to see improved or fixed with their SLB experience
  • Continuing to order full 500 quantities of anything we’re sure about like the thumbscrews that just arrived today and will soon be starting to vet USB-C cables
  • Board PCB production should begin the last week of January or first week of February, and in the meantime we’ll be pre-ordering all the board components to hopefully reduce production time
  • Design box packaging
  • Start to prepare jigs and processes for QA
  • Throughout February and until we begin shipping, continue to make updates to FAQs, short videos to show board capabilities, SLB Manual, gSender HAL support, and SLB Firmware

Me and the SLB and gSender teams have been, and will continue to be, working diligently as the March delivery window continues to approach. This has been an especially big project for us to undertake so we want to do whatever we can to set up the SLB to succeed. As 2024 starts to pick up steam, I’m really excited for the impact that the SuperLongBoard might have on the future of hobby CNCs and hope to be proud of the 1.5 years spent to bring it to life.

Watch out for more videos I’ll put out to show what the board can do and feel free to keep asking questions 👍

gS release schedule

Please let us know what you think of the new 1.4.0 (! It’s an accumulation of over a years worth of work in a package that we called “Fundamentals”. We wanted to bring new things to the table but also really take the time to go back into what fundamental things we could improve about gSender to make the day-to-day CNC experience more pleasant and reliable. This included new joystick controls, touch plate probing on all corners, much more accurate time estimation, faster file loading, endeavouring into maintenance reminders, and more. We know it may have a couple bugs in it here and there but we’re committed to fix those in the coming weeks and make 1.4.0 the new, best version of gSender for everyone to use!

Our next big push we’ve decided to call “New U”, where we’ll be aiming to take everything we’ve learned about the CNC control experience and put it to work in doing a complete overhaul on gSender’s UI. I know this may be a polarizing topic but we do feel like we can take something that we already felt we’ve done so well on and push it even further. We hope to take plenty opportunities to get everyone’s feedback as we begin this process but we feel hopeful that once we come through on the other side this will certainly be for the better and a better gSender overall.

Thanks yall for your time and hope to see you more soon!

-Chris signing off