Carriage Assembly

Bolting plates, extrusion, and sensors together, mounting and aligning rails and ball screws, to build CNCR-CAR ()

Components

Custom Parts

Purchased Parts

  • 4 x Inductive Proximity Sensor (OMRON #TL-W5M or similar) [DWG#39]
  • 1 x Z Axis Homing Switch (Panasonic #PM-Y65 with matching cable #CN-14A-R-C5) [DWG#42]
  • 2 x Z Axis Ball Screw Kit (1204 x 350mm) with ball nut, ball nut mount, BK10/BF10 mounts, and motor coupling (14mm) [DWG#5,6,7,18,19,20]
  • 2 x Z Axis Linear Rail Kit (HGR20 x 400mm) with 2 x HGH20-CA bearings each [DWG#4]
  • 1 x Z Axis Motor (NEMA 24) [DWG#14]
  • 2 x 1.5″ x 3″ (or 40mm x 80mm) box tube end cover (McMaster #9474K59 or similar) [DWG#21]
  • 1 x 4080 T Slot End Cover (McMaster #5537T29 or similar) [DWG#22]
  • 2 x Anchored Zip-Tie (‘fir tree’) for 1/4″ (6mm) hole (McMaster #7565K85 or similar) [DWG#43]
  • 1 x Z Axis E-Chain (IGUS #1500-050-100-14050-34PZA4-0533m) [DWG#12]

Hardware

See the Bill of Materials in the drawing for a full list of hardware. Hardware is referenced in this guide using the Item number from the bill of materials [DWG#XX] of the associated assembly drawing. Note that in some places low profile cap screws are required to maintain the necessary clearance from other components.

Carriage Plate Assembly

The main structure of the carriage is a single machined plate: CNCR-CAR-PLATE (). A multitude of sensors and structures connect to this one plate to build out the entire assembly.

Rail Alignment

Start by mounting the right side rail to the front of the plate using M5x20mm cap screws [DWG#25]. The outside edge of the base of the rail should sit flush with the machined outside edge of the plate (use a 1-2-3 block or similar flat reference to enforce this alignment). The remainder of the rail that does not lay coplanar with a machined edge can be tightened in place and assumed straight (due to its short length), but by using a straightness reference or dial gauge the remainder can be measured and adjusted if desired.

Once the right rail is in place mount the second rail on the left. Using a similar method as with the gantry rails, mount a dial indicator to the original rail and use it to measure the opposing rail position. Tighten down the screws one at a time, in order.

If the spindle plate is already partially assembled, now is a good time to do a test fit and ensure that the bearings slide on and off of the carriage plate smoothly. If they do not, adjust the left side rail or bearings until the spindle plate moves smoothly along its entire travel.

Be sure to remove the spindle plate after checking for rail alignment.

Ball Screw Mounting

Bolt the Z axis ball nut to its mounting block (both items from CNCR-SPIN ()), ensuring that the lubrication port is facing the correct direction (see drawing).

Connect the Z axis ball screw [DWG#7] to the fixed mount, BK10 [DWG#5] using the included hardware. Bolt the fixed mount to the carriage plate using 4 x M6x40mm cap screws [DWG#24]. Connect the Z axis ball screw to the free mount, BF10 [DWG#6] using the included retaining ring then bolt the free mount to the plate using 2 x M6x40mm cap screws [DWG#24]. The M6 bolts will be tightened to their final torque once the ball screw is aligned.

Again, if the spindle plate is already partially assembled, now is a good time to do another test fit. The clearance between the ball screw mounts and the spindle plate bearings is microscopic, so some adjustments may need to be made to the ball screw mounts to prevent collisions.

Be sure to remove the spindle plate after checking for interferences.

Rear Structure

Flip the carriage plate over to access the other side.

Bolt the 40×80 T slot extrusion CNCR-CAR-TSE-LPS () and 40×40 T slot extrusion CNCR-CAR-TSE-SPS () to the carriage plate using M8x25mm low profile cap screws [DWG#35] and M8 T-nuts [DWG#34]. The extrusions should mount flush to the top and but up against the right side lip of the carriage plate. Use threadlocker to ensure a permanent connection.

The Z-Axis E-Chain Mount Box Tube, CNCR-CAR-ECM (), bolts onto the t-slot extrusion using M8x12mm cap screws [DWG#29] and M8 T-nuts [DWG#34]. Next, the Y Axis E-Chain Mount Extrusion, CNCR-CAR-TSE-ECM (), bolts on to the box tube using more M8x12mm cap screws [DWG#29] and M8 T-nuts [DWG#34]. Ensure that the inside edge of this extrusion is flush with the other 40×80 extrusion. Use threadlocker on this hardware to ensure a permanent connection.

The CNCR-CAR-BNM () plate is used to further secure the E-Chain Mount Extrusion to the assembly by means of M8x20mm cap screws [DWG#36] and M8 T-nuts [DWG#34], but it is not connected until after the carriage is mounted to the gantry.

Motor Mounting

Bolt the CNCR-CAR-MM () to the top of the assembly using M8x25mm cap screws [DWG#31] threaded directly into the end of the T-slot extrusion. Use threadlocker to ensure a permanent connection.

Mount the stepper motor [DWG#14] to the motor plate using M4x12mm cap screws [DWG#33]. Connect the stepper motor shaft to the ball screw using the flexible shaft coupler [DWG#18,19,20]. Adjust the motor position on the plate to minimize misalignment before fully tightening the mounting bolts.

Sensor Mounting

Two inductive proximity sensors [DWG#39] are mounted to the back of the carriage plate using M3x12mm cap screws [DWG#23]. They are difficult, but not impossible, to replace after mounting the carriage. To ensure that the cables for these sensors do not get caught on anything during operation, use an anchored zip tie [DWG#43] to tie back the cables between where the two upper bearings would mount.

Two more proximity sensors [DWG#39] are mounted to the front of the carriage using M3x12mm cap screws [DWG#23]. Be sure to feed the cables through the clearance openings.

Other Components

CNCR-TSE-ZTM ()

This 3D printed zip tie mount is bolted in the center of the rear of the assembly between the motor mounting plate and the box tube. It will secure many sensor and motor cables in the future. Bolt the components on with an M6x16mm flat head screw [DWG#28] and M6 T-nut [DWG#30].

CNCR-HSF ()

The X Axis homing switch flag is mounted to the back of the assembly, with the wall face butted up against the machined edge of the plate. Secure the flag with M3x12 cap screws [DWG#23], although they may be adjusted later.

CNCR-CAR-TSE-SS ()

These two miniature pieces of extrusion are used to seal off the side of the assembly from dust and debris. Mount them to the front of the carriage plate using M5x25mm cap screws [DWG#41] and M5 T-nuts [DWG#40]. Adjust the extrusions so they are in their most outward position possible to provide maximum clearance for the spindle plate mounting, then adjust them back inward once the spindle is permanently mounted.

M6 Rivet Nuts [DWG#27]

Install two M6 rivet nuts onto the E-Chain mounting box tube. These nuts will allow the Z axis E-Chain to be mounted once the spindle assembly is installed.

CNCR-BUMP ()

Install the adhesive hard stop bumpers onto the Z axis motor mount plate if it has not already been done.

Mounting The Carriage Plate

Bearing Attachment

Arrange the X axis bearings on the gantry rails in their approximate relative location. Ensure that the lubrication ports are attached and facing outward. Lift the entire carriage assembly up and rest it on the X axis bearings. The top of the lower two bearings should be contacting the machined lip of the carriage plate. Starting with the lower two bearings, attach all four X axis bearings to the carriage plate using low profile M5x20mm cap screws [DWG#26].

Ensure that the entire carriage can slide smoothly throughout the entire range of motion of the X axis. If the motion is tight everywhere, consider adjusting the top two bearings. If the motion is tight only in some areas, consider adjusting the lower rail position in those areas.

Ball Nut Attachment

Ensure that the X axis ball nut is threaded onto the screw with the flange on the right side, close to the fixed end of the screw. Move the carriage to the left of the ball nut.

Connect the X axis ball nut [DWG#15] to the X axis ball nut plate, CNCR-CAR-BNM () using M6x20mm cap screws [DWG#32]. Use threadlocker to ensure a permanent connection.

Slide the carriage to the right until the ball nut plate contacts the T-slot extrusion on the back side of the carriage. Secure the plate to the extrusion using M8x20mm cap screws [DWG#36] and M8 T-nuts [DWG#34].

With the free-side ball screw mount plate of the X axis loosened from the T-slot gantry beam, manually rotate the X axis ball screw until the carriage is at the other end of the gantry. Secure the free-side ball screw mounting plate to the gantry with the carriage in this position.

Other Components

Mount the box tube cover plates [DWG#21] to the ends of the E-chain box tube, and mount the T-slot extrusion cover plate [DWG#22] to the end of the E-chain extrusion.

Install a fir tree zip-tie anchor onto the X axis ball nut mounting plate. Use it to secure all of the cabling from the 5 sensors installed on this assembly.

The free end of the X axis E-Chain can be connected to the T-Slot Extrusion E-Chain mount using M6x16mm flat head screws [DWG#28] and M6 T-nuts [DWG#30].

The fixed end of the Z axis E-Chain can be connected to the box tube E-Chain mount using M6x16mm flat head screws [DWG#28].