Crossbeam Installation
Lay out the left and right Y rail assemblies. Then lay the five (5) crossbeams for the 4×4, or three (3) crossbeams for the 2×4, either on the floor or on a sufficiently large work table. Ensure the Y-axis assemblies are facing the correct orientation: the ball screw should be facing outwards, away from the crossbeams, and be above the linear guide rail.
Crossbeams and Y-rail assemblies for 4×4
Move the components so that the crossbeams rest on the ledge on both rails.
Crossbeam resting on Y-rail ledge
Re-position the front crossbeam and rear crossbeam so that the flanges face towards the center of the machine. For the middle crossbeams, whether you have one or three, the flange direction doesn’t matter.
Side view of crossbeams showing flange direction
Starting on either the left or right, install M5-14mm crossbeam screws through the Y rail into the crossbeams. Fasten all screws until just snug. Use a screwdriver instead of an impact driver or drill for this step, to avoid stripping the threads. There should be 13 screws fastened on each side.
Securing crossbeams to Y-rails
Table Orientation
For the remainder of this assembly, we will need to distinguish between the front and rear of your table/machine. We will use the Y-axis as reference. The end with the ball screw sticking out of the 4-screw bearing block, is considered the rear. The end with the smaller 2-screw bearing block, is considered the front.
Front and rear distinction on Y-axis
Additionally, from this point on we will refer to the left and right sides of the machine based on the perspective from the front. Standing from the front of the machine, your left side will correspond to the left side of the machine, and the right side will follow suit.
Table Legs Assembly
Take the leveling foot and remove the top hex nut. Rotate the middle adjusting hex nut all the way to the bottom. Pass the threaded stud of the foot through one of the legs from the bottom, then reinstall the top hex nut over the hole, loosely securing the foot. Repeat for the remaining three (3) feet.
Table leg with foot installation
On each table leg, loosely install two (2) M6-14mm button head screws and two (2) M6 twist-in T-nuts on the top row of holes. For two of the legs, make sure you install the fasteners on the outer face of the leg with the “ALTMILL” text. For the remaining two legs, install fasteners on the other outer face.
Pair of legs with M6 T-nuts and screws
We will now build two legs, either at the front or rear of the machine. First grab one leg and flip it upside down. Then position it at a corner of the table so that the T-nuts slide into the crossbeam slots. Loosely secure two (2) M6-14mm button head screws to connect the leg to the rail. Repeat these steps to assemble a mirrored leg on the other side. Finish tightening all the fasteners on the two assembled table legs, so that they are securely joined to the frame.
Aligning and fastening first pair of legs
If you are tight on space, rotate the AltMill table accordingly so that the legs are in front of the closest wall of your workspace, as shown in the illustration. This will make flipping the table easier. If your AltMill is still on a work table instead of the floor, it is best to move it to the floor for safer maneuvering.
Orienting the AltMill for table flipping
We will now flip the table. Use a chair or step ladder to support the table, so that it can stand upright.
Flipping and supporting the table
Repeat the previous steps to install the final two table legs. Align and loosely mount the legs using the T-nuts at the crossbeam slots. Loosely install two (2) M6-14mm button head cap screws through the lower row of holes in the table leg and into the Y rail.
Tighten the hardware on the two table legs until snug. At this point, check that all four legs are securely attached.
Aligning and fastening second pair of legs
Y-axis Cable Routing
Grab the Y1 and Y2 motor cables and identify the two ends; one end will go to the SLB, and the other will go to the motors (and sensors). Then re-familiarize yourself with the front, rear, left and right of the table, as described in the Table Orientation section.
Bring both of the cables through the upper compartment of the left Y-rail. From the rear of the machine, route the SLB end to the front. Thus the motor end will stay at the rear.
Y-axis cables, SLB and motor end labelled
Routing SLB end of Y-axis cables from the rear, to reach the front of machine
End Plate Preparation
Loosely install two (2) M6-14mm button head screws and M6 T-nuts into each of the four (4) Y end plates.
Y-end plates, noting orientation of T-nuts
Using four (4) M5-16mm socket head screws, securely fasten one rubber bump stop onto each Y end plate.
Bump stop installation
Take one inductive sensor, and thread a nut on roughly 3/4” (20mm) from the sensor end. Then install a lock washer on the sensor. Repeat these steps for the remaining three (3) sensors.
Inductive sensor preparation
We will only use two inductive sensors for the Y end plates, which will be used for Y-axis homing. You can put the other two sensors aside for now.
Insert one sensor through the end plate, ensuring that the sensor end is on the side with the bump stop. Thread a lock washer, then a nut to secure the sensor in place. Repeat these steps for a mirrored end plate, so you have one left and one right end plate.
Pair of end plates with inductive sensors installed
For each sensor, ensure that the sensor end is recessed 1mm from the front of the bump stop. You may need to adjust using the nut and lock washer.
Sensor offset from bump stop
We will mount the end plates with sensors on the back of the table, and the sensor-less end plates on the front of the table. Using the pre-installed T-nuts and screws, secure the plates to the appropriate corners of the table.
Make sure that the end plate holes align with the holes on the Y-rail. Then, use three (3) M6-14mm button head screws to complete the plate mounting. Repeat this step for all end plates, then check that the fasteners are all snug.
Y-end plate positions on AltMill
Now is a good time to put your machine into position and to level the legs front to back, and left to right, by adjusting where the hex nuts sit on each of the levelling feet. The side of the included wrench, along with a 17mm or adjustable wrench can be used to tighten these nuts.
Completed table foot installation
Pat yourself on the back and stop for a break, the most difficult (and exhausting) part of assembling the AltMill is all done!