By Greg W Johnson
What started as a small garage CNC turned into a full rebuild of the Genmitsu 3020 Pro Max, mainly because I kept running into the same issue—flex.
Coming from an old-school machining background, I didn’t want to just bolt parts on and hope for the best. I treated it more like setting up a manual machine: square it, measure it, fix what’s actually causing the problem. I used my trusted machinist toolkit—1-2-3 blocks, Starrett parallels, Mitutoyo calipers, an Interapid indicator, and a Noga mag base—taking my time with alignment rather than just rushing assembly.
Solving the Rigidity Issue: The 3040 Conversion
After converting it to a 3040, I realized the stock setup wasn’t rigid enough. I redesigned the Y-axis around HGR15 linear rails mounted to aluminum extrusion. Using a granite plate and dial indicator, I "sneaked up" on the alignment until it was perfect. The result? Less chatter, smoother motion, and predictable cuts.
I eventually stepped up to a 710W router, which required adapting a V2 Z-axis onto the V1 frame. I designed a custom bracket in Carveco, cut it out of 6061 aluminum on the machine itself, and machined the axis to fit. It was a classic "make the machine upgrade itself" project.
Machinist's Tip: Alignment and rigidity make a bigger difference than just adding power or speed. Don’t assume parts are square—measure them!
SainSmart 3020 Pro Max: HGR15 Linear Rail 3040 Extension Guide
1. Essential Parts List
- Genmitsu 3020 Y-Axis Extension Kit (3020 to 3040)
- Genmitsu 3040 Extension Aluminum Spoilboard (Optional for a larger workspace)
- 2 Pcs 20 series T-Slot 2060 Aluminum Extrusion (600mm, cut to final length)
- HGR15-600mm Linear Rails with 4 pcs HGH15 square carriage blocks
- Assortment of T-Slot Nuts: M3, M4, and M5 for 2020 Aluminum
Step-by-Step Instructions: Converting 3020 to 3040
This guide helps you extend the frame using HGR15 Linear Rails. The Aluminum Bed Extension is optional but recommended for more workspace.
- Disassembly: Follow the standard 3020-PRO-MAX extension instructions. Use a heat gun or torch: many fasteners and the leadscrew have Loctite. Don't strip the bolts!
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Drilling the Extrusion: Drill 6 total holes (3 per rail) in the front and rear aluminum plates.
- Pro Tip: Position the extrusion 1/8” (.125) below the frame. This maintains the lead screw carrier block position and prevents stress on the screw.
- Tap the holes for 6mm bolts.
- Frame Squaring: Loosely assemble the frame. Use a chop saw with a non-ferrous blade for the aluminum and a steel cutoff blade for the rails (keep them cool with a wet rag).
- Final Assembly: Use Blue or Red Loctite on all fasteners. Important: Slide your T-Slot nuts into the extrusion before mounting to the bed frame.
- Precision Alignment: Use a granite slab and 1-2-3 blocks to level the framework. My "OCD Machinist" approach got my bed flat within .003".
- Mounting HGR15 Rails: Bolt the rails down loosely at first. Use a Dial Indicator to sweep front-to-back, ensuring the rails are perfectly parallel to each other.
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Bed Extension Drilling: Mark the centerline of the HGH blocks to locate your mounting holes in the metal bed extension frame.
- Note: I actually used my 3020 Pro Max to mill the holes on the second steel frame for perfect accuracy.
- Tramming: Finish the assembly (skip Loctite for the bed-to-plate connection) and perform a final tram to square the spindle to the bed.
Final Build Notes
The HGR15 rails pictured are 800mm (a great value at only $6 more than the 600mm). If you use Carveco and want the bracket files I designed to adapt the Z-axis, I am happy to supply those!
Good Luck with your build!
