After spending a few years and countless projects with my first CNC router build I have decided its time to fix the major issues I encountered.
The main issues with the original build
- Machine base was not big/strong enough in relation to the gantry size/weight
- Under high acceleration/deceleration I can visually see flex in the base when the gantry stops
- X axis motor mounts and ballscrew mounts where not properly braced for the loads
- Epoxy leveling
- The epoxy leveling worked to within a 5-10 thou for flatness but with no rail reference relying on clamp torque on rails not ideal for such a large gantry
- No bearing block reference edge on the gantry feet
- X axis rails not full length
- Original rails purchased used to save money, without proper rail reference it is difficult to keep rails properly aligned. Blew out a bearing block when it caught on the misalignment.
These items above can be mostly worked around by slowing the machine down considerably. Original design should have had the machine at ~2000ipm rapids with very snappy accel. I have reduced to 1000ipm for rapids and rounded off the accel considerably.
The NEW machine
- Base material size considerably larger than original
- New Gantry larger legs with better feet bracing
- Integrated vacuum hold down plenum
- Still 5x10 machining area
- Still 18 inches under spindle nose (no tool) when fully up
- Small wood storage under machine (I keep my rough board stock under current machine)
- Steel structure stress relieved
- All linear rail and block locations machined with reference and rail lock provisions
- All drive and motion components to be moved from current machine
- except X axis rails, new full length 30mm rails to be purchased for new machine
Current machine motion parts to be moved
- X axis
- Full length 25mm x25mm lead ballscrews
- Dual 1 kW Servo motors
- **New 30mm Hiwin Rails
- Y Axis
- 20mm x20mm lead ballscrew
- 0.75kW servo
- Schaeffler Linear Rails 25mm
- Z Axis
- Entire Z axis will be moved over to new machine
- Current Z consists of 20mm x20mm lead ballscrew, Schaeffler 25mm rails, 0.75 kW servo, 10hp Coulombo ISO 30 Spindle
- New Z to Y plate to be machined to account for larger Gantry
Design
I started designing the base and gantry over Christmas break trying to optimize strength and cost. I then came upon a deal on some large section box tubing at scrap cost so I redesigned around it. The box tubing is 10x10x3/8 inch and 8x8x5/16 inch the design below was optimized for this material.
Photos Attached of Design - Having trouble putting them inline