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Abstract:
This video documents Part 5 of a homemade CNC router build, transitioning from assembly to initial operation and refinement. The creator focuses on achieving proper machine alignment, installing safety features like an emergency stop, and enhancing usability with enclosure panels and a CNC pendant for precise control via the Duet board. The core project involves machining the aluminum cutting bed into a 178-hole fixture plate using drilling, counterboring, and efficient thread milling techniques, overcoming challenges like tool flex and limited Z-axis travel. The video then details the process of machining the first aluminum part – a rigidity block – highlighting the learning curve involved with speeds, feeds, workholding (initially using an inadequate drill vise), and machining strategies to achieve a good surface finish. The creator reflects on the initial successes and failures, discusses upgrades like a proper milling vise and touch probe, and outlines future plans for chip management and continued learning.
Building and Refining the Homemade CNC: First Cuts and Fixture Plate Machining
0:00:09 Machine Alignment: The cutting bed required alignment adjustments as it wasn't flat or square to the frame, likely due to countersunk bolts preventing adjustment.
0:00:26 Bed Modification: Holes were counterbored to accept socket head bolts, allowing for fine adjustment and better squaring (.037" X-axis, .032" Y-axis deviation achieved).
0:00:48 Enclosure & Protection: 3D printed brackets were added for a removable side panel, a polycarbonate front door, plastic infill strips for extrusion slots, and TPU covers for limit switches to protect against chips.
0:01:31 Safety First: A crucial emergency stop button was added to the front of the machine.
0:01:38 Initial Control Setup: A cheap touchscreen monitor connected to a basic PC was set up for web control of the Duet controller.
0:02:04 Enhanced Control: An AliExpress CNC pendant with a jog wheel was integrated using an Arduino, allowing precise manual control of the X, Y, and Z axes.
0:02:35 Spindle Warning: A practical tip: ensure the collet nut is tightened before spinning up the spindle for the first time.
0:02:44 First Test Cut (MDF): A simple part was cut in MDF using tape and superglue for workholding to verify basic functionality. Finish quality was suboptimal.
0:03:24 Fixture Plate Project: The main task was converting the cutting bed into a fixture plate by drilling, counterboring, and threading 178 M8 holes.
0:03:37 Drilling Challenges: Initial attempts to drill aluminum revealed issues with the spindle's low RPM torque and significant drill bit flex due to the required length.
0:04:13 Thread Milling: A thread end mill proved highly effective and efficient for creating the M8 threads directly in the drilled holes.
0:04:41 Z-Axis Limitation & Workaround: Limited Z-axis travel required the endmill to stick out far; the spindle mount was temporarily lowered to compensate, increasing crash risk.
0:05:07 Fixture Plate Machining: The 178 holes were successfully drilled (in stages for checks), counterbored (with some finish impact from tool flex), and thread milled.
0:06:28 Aesthetic Finishing: Holes were chamfered for a more professional appearance.
0:06:41 First Aluminum Part (Attempt 1): Machining a block to replace Y-axis standoffs, using a drill vise for workholding.
0:07:31 Tool Breakage: A 4mm endmill broke while boring deep holes (25mm stock), leading to a change in strategy (partial boring, manual finishing).
0:08:18 Surface Finish Issues: Significant tool flex (long 4mm endmill) and poor chip evacuation in slots resulted in a poor surface finish.
0:09:23 Second Aluminum Part Attempt (Machinist Mindset): Focused on rigidity, switching to a 6mm endmill and altering the machining strategy (facing sides first, leaving slots/tabs).
0:09:45 Improved Results: The change in tooling and strategy yielded a significantly better surface finish.
10:25 Workholding Failure: The part slipped in the drill vise while machining tabs because the vise jaws twisted when clamping off-center, demonstrating why drill vises are unsuitable for milling.
10:53 Workaround: Using the previously machined block as a parallel spacer in the vise helped stabilize the clamping.
11:09 Rigidity Limits Tested: Pushing the machine too hard during material removal revealed its rigidity limits, causing vibration/chatter.
12:15 Upgrade - Milling Vise: A proper, heavy milling vise was acquired to improve workholding. Clamps are being prototyped.
12:42 Future Improvement - Chip Management: Plans to add brush guards or other solutions to prevent chips from contaminating rails, ball screws, and falling through the frame.
13:17 Future Improvement - Touch Probe: A small touch probe was purchased to enable faster and more precise workpiece zeroing.
13:44 Pendant Utility: The CNC pendant is highly valued for its precise incremental control (1mm, 0.1mm, 0.01mm steps).