AltMill | AltMill | Sienci Labs

Meet the

Precise, reliable and built to last, giving you the confidence to take on bigger, more ambitious projects.

From $2,790 USD

Precision & Performance Driven

Our flagship brand has the production reliability and rapidity professionals need, and the value and rigidity advanced users want. Priced at an affordability you can trust.

Speed & Rigidity

The 2×4/4×4 models have a linear rail system allowing for precise, production-level cutting at 600IPM.

The 4×8 model packs an even bigger punch with 1,000IPM on a rack and pinion system.

Reliability & Performance

All models runs on NEMA 23 closed-loop stepper motors.

Runs on a grblHAL-CNC controller.

Close-up of a person’s hands tightening a screw on a black metal frame with silver rails and bolts

Setup Friendly

Ships straight to your door, and allows for easy integration and modification of accessories to suit your workflow.

Plus, we’ve got all the resources to help you get up and running.

Live-edge wooden table with a dark resin river and small white inlays along the seam in a workshop setting.

Project Ready

Offers 5.5″ of Z-Axis travel on the 2×4/4×4 and 8″ on the 4×8.

Handles woods, plastics, even aluminum and steel.

Industrial aluminum-framed machine with belt-driven linear rails and a vertical Z-axis carriage (CNC/automation gantry)

Dedicated Support, Today & Tomorrow

Built with advanced users and small businesses in mind, this production-level CNC system – that’s also easy on the wallet – is backed by an extensive library of assembly instructions, accessory support guides and a dedicated resource team.

AltMil Setup

Tech Support

FREE CNC Control Software

Every AltMill is fully supported by gSender, our FREE CNC control software. We built this open-source interface with features like surfacing, calibration start from line, tool mapping visualizers, and a whole lot more. gSender gives you everything you need to control your machine and over 60,000 people worldwide use it to get their job done.

Downloads available for Windows, Intel & Silicon Mac, Rasp Pi and Intel Linux.

Download gSender

CNC control software interface showing a blue wireframe 3D model on a grid workspace with tool controls on the right side and side panels visible on both sides. — gsender guitar

Two bearded men in black shirts discuss a project at a wooden worktable in a warehouse workshop with metal shelving and boxes in the background.

Incredible Community

No matter if you’re a beginner or an experienced CNCer, we’re here every step of the way to help, but so too are tens of thousands of worldwide Sienci Labs users.

Our community is packed with passionate CNCers, of all different types and skill levels, ready and willing to help you with tips, tricks and hacks. Join one of our communities today.

Sienci Forum

Facebook Group

Wide Selection of Accessories & End Mills

Whether you’re looking for dust shoes, end mills, design software or replacement parts, we’ve got you covered.

Browse Accessories

What Owners Are Saying

Must have Accesories

Specs

	AltMill 2×4	AltMill 4×4	AltMill 4×8
Price	$2,790USD	$3,160USD	$7,490USD
Working area	25″ x 49″	49″ x 49″	49.8″ x 104″
Max Z-height	5.5″		8.3″
Footprint	59″W x 38″D	59″W x 62″D	66″W x 114″D
Weight	Approx. 220lbs		Approx. 400 lbs
Max cutting speed (X/Y)	~590 IPM		~1,000 IPM (Y) / ~590 IPM (X)
Max cutting speed (Z)	~236 IPM on all sizes
X/Y motion	2.0NM NEMA 23 steppers, closed-loop, 16mm/10mm lead ball screws		3NM (Y) / 2NM (X) NEMA 23 steppers, closed-loop Y: rack & pinion X: 16mm ball screw
Z-axis motion	1.2NM NEMA 23 stepper, closed-loop, 12mm/4mm lead ball screw		2NM NEMA 23 stepper, closed-loop, 12mm ball screw
Linear guides	15mm HGR15 rails, sealed bearings		15mm profiled rails, sealed bearings
Controller	SLB-EXT _{(32-bit, grblHAL)}
Spindle mount	80mm — spindle sold separately
Homing	Inductive sensors
Power	48V, 500W_{(machine only)}		120VAC, ~500W _{(machine only)}
Legs / stand	Included _{4ft shelving-ready}	Included _{4ft shelving-ready}	Included _{4ft shelving-ready}
Warranty	1 year
Best for	Tight spaces, smaller projects	Most popular size balance of area and footprint	Full 4×8 sheet goods, production work
	AltMill 2×4Buy	AltMill 4×4Buy	AltMill 4×8Buy

As of August 2026. Prices in USD, machine only (spindles sold separately).

Requirements & Specs

Applies to all AltMill sizes.

Power	Two independent 120V circuits: 10A for the control box, 15A for your spindle or router
Operating temperature	5-30°C shop temperature recommended. Let the machine acclimate before running in colder or hotter conditions
Operating humidity	Keep it balanced. High humidity risks electronics and warps the MDF wasteboard; dry air builds static that can disrupt a poorly grounded machine
Storage	Components tolerate -20°C to 50°C when stationary. Keep storage humidity low to avoid corrosion and electrical degradation
Electronics	32-bit SLB-Ext controller running grblHAL firmware

Frequently Asked Questions

Does the AltMill come with an SLB-EXT controller?

Yes! The AltMill comes with a specialized variant of the SLB that allows for use with a higher 48V power supply and with external driver support.

What’s the difference between the AltMill and the LongMill

The AltMill was developed to be a higher-performing machine compared to the LongMill. Our main design goal was to create a machine that had the best possible value for dollar at a higher level and pricepoint. Learn more about the differences in our video.

What software does the AltMill come with?

The AltMill works with our free gSender software for controlling your machine. Any CAD/CAM will work supporting grbl and grblHAL. Download now. You can learn more about CAD/CAM check out these articles.

What else do I need to buy separately with the AltMill?

Besides the standard items we sell (machine, spindles), you’ll need to provide your own wasteboard (we recommend 3/4″ MDF), a computer (like a gControl panel computer) and end mills.

What accessories work with the AltMill?

Automatic Tool Changers, lasers, rotary axes like our Vortex, and a whole lot more.

What sizes does the AltMill come in?

We currently offer 4×8, 4×4 and 2×4 models. See the table for working area and other specs.

What are the power requirements for the AltMill?

All AltMills use a 110VAC, 48VDC 10A power supply, consuming up to 500 watts. The power supply comes with a North American Standard Type B NEMA 5-15P plug.

If you live in a country with 220V/240V power you must use a transformer to convert to 110V/120V.

See product listings for more details.

Can I add a toolchanger to my AltMill?

Yes! Our Automatic Tool Changer is the perfect fit. Learn more.

Can I modify, update, trade-in, my LongMill to a AltMill?

No, because of the significant differences between the LongMill and AltMill, there is no path for upgrade or modification. Additionally, we currently do not have the infrastructure to support trade ins.

Precision & Performance Driven

What Owners Are Saying

Must have Accesories

AltMill 1.5KW ER20 Spindle & Clear Cut Dust Shoe Kit

AltMill 2.2KW ER20 Spindle & Clear Cut Dust Shoe Kit

gControl Panel Computer

AltMill T-Shirt

AltMill Starter Set

AltMill Sign Maker Set

Specs

Requirements & Specs

Frequently Asked Questions