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A CNC Machine to die for…
When we set out to design the KillerBee, our goal was to address some of the most common criticisms of two very popular open-source OpenBuilds based CNC Machines: the WorkBee and the Lead CNC.
These machines are great to mill softer materials, but as you move up in machine size and on the material hardness spectrum, you will quickly find their limiting factors. The KillerBee uses the WorkBee/Lead design as a foundation, but builds on top of it to considerably push these limiting factors further out, allowing for a huge performance boost at a very reasonable price point.
One of the most documented factors that limits the performance of the WorkBee and Lead CNC is flexing of the machine’s X axis in response to torsion forces on the spindle. These artifacts can result in loss of precision and can be especially noticeable when you’re cutting harder materials on machines with a longer X axis.
We stacked the Workbee design against the KillerBee design on a computer simulation, to determine machine flexing/deformation in response to different force inputs. We chose inputs that match the typical forces that a CNC Machine is subjected to when the tool is working. All simulations showed around 3x less flex/deformation on the KillerBee.
These sturdiness improvements are the result of a few important upgrades, listed below.
8mm Steel Plates
Forget about aluminium plates if you’re serious about performance. A strong machine needs a strong foundation. The KillerBee uses 8mm thick Q235 steel plates, up to 8x stronger than the Workbee plates, so the machine won’t break a sweat, whatever you choose to throw at it.
MGN15 Linear Rails
Perfectly milled edges require perfect linear motion. Smooth, precise, reliable and repeatable motion. To achieve this, slack needs to be down to an absolute minimum, and strict manufacturing tolerances are required.
The Workbee/Lead use wheel-based motion. But wheels are hard to tune right, need a lot of maintenance, and have many moving parts that wear out with time.
The KillerBee moves away from a wheel based system in favour of a MGN15 Linear Rail system:
– Manufactured with very strict tolerances for almost zero slack
– Load is carried by dozens of rigid, incompressible, low friction, stainless steel ball bearings which circulate inside an ultra compact carriage – saving a lot of space while ensuring smoothness, sturdiness and complete rigidity.
– Ball bearings are protected from dust and other contaminants by seals all around the carriage
– Rails are made of steel, providing additional structural reinforcement of the machine’s frame
– 2 rails are used on each C-Beam with 2 MGN15C carriages per rail (for a total of 8 MGN15 rails and 16 MGN15C blocks)
The Linear Rails are one of the most expensive components on the entire machine, since they require industrial-grade manufacturing. Linear Rails should be protected from humid environments and require proper lubrication for consistent performance. All you need to know about linear rail maintenance can be found here.
If you take good care of your linear rails, your machine will provide consistent, high-level performance for many years to come!
Long machine axis are driven by long lead screws. At these lengths, the mass of the rotating lead screw is subjected to centrifugal forces that can create lead screw whip, an artifact where the lead screw starts behaving like a jumping rope, instead of staying straight. Artifacts like this create vibrations that can be propagated to the material you’re cutting, creating inconsistent cutting.
The KillerBee is equipped with the Tingle tensioning system on both the X and Y axis of the machine. The tingle system allows you to adjust the tension your lead screw is under, to prevent lead screw whip. Tingle tension uses thrust bearings, to ensure that the tension load doesn’t create friction and is not passed on to your motors.
No Stand-off Nut Blocks
Workbee/Lead use stand-off Nut Blocks, which create torsion forces as the machine moves, since they act like levers.
On the KillerBee, all nut blocks sit directly against the plates, so no torsion exists.
Cap Head Screws all Around
Workbee/Lead use soft Low Profile Screws. While they look great, these heads are fragile, and not suited for a Heavy Duty machine. The KillerBee uses Cap Head Screws wherever possible.
Low Z Configuration (coming soon)
Users who want to push their machine to the limit may benefit from this small upgrade that lifts the height of your spoilerboard and reduces Z travel. This reduces the lever-effect of the Z axis on the X axis, allowing for even more precision and performance while cutting harder materials.
You should check the critical dimensions of your desired machine size before buying (Footprint, Spoiler board size, Working Area, etc).
If you acquire a MESH Workbench matching your machine size/name, the benchtop will be about 10cm wider than your machine on every direction, to allow enough clearance for an enclosure (coming soon!).
Not included in the kit
– Power cord – you will need to source a power cord with a plug, to connect your machine to the wall. We don’t supply them since we ship worldwide and different countries use different plug types.
– Spoiler board – you will need to source this locally. An MDF board with 12mm thickness is suggested. Check the correct spoiler board size for your machine here.
– You may need a few zip ties for cable management.
Check out the 3D Model of the KillerBee on Fusion360 On-line.
Explore the model directly from your browser or download it for free and open it in your favourite CAD software.
Step-by-step Build Guide can be found here.
Bill of Materials
Rat Rig KillerBee BOM
STL Files for KillerBee Printed Parts
Join the KillerBee community on Facebook to stay posted on all product updates, ask for support, and share your creations with other KillerBee users: Rat Rig CNC Machine Community.