Posted by SainSmart on

Written by Graham Bland. You can find me on the Facebook group SainSmart Genmitsu CNC Users Group  All comments, suggestions and corrections are welcome.


I received this Genmitsu 4040-PRO CNC router to review ($50 OFF discount for SainSmart Member during BFCM) with very little information about it, I was half expecting it to be an expanded 3018, but it isn't!!!

Big box! 18.8kg (42lbs) which is quite full but very well packaged.

I could add more pictures but there is no real point.

It's a fixed bed (on the 3018's the bed moves in the Y axis under a gantry which is fixed in position, on the 4040 the bed is fixed in position and the gantry moves over it.) The bed is in 2 pieces both 15mm MDF with predrilled holes and 6mm inserts underneath for the clamps.

What you get

The frame and Z axis are entirely aluminum and steel construction.

There are 4 pre-assembled and pre-wired sections, the left- and right-hand carriage assemblies, the gantry assembly, and the Z-axis assembly including the spindle motor. The control board is already mounted and all the wiring is pre-installed, bar a few connectors to plug the modules together once assembled.

There is a single wiring loom cable that connects the control board to an also pre-mounted and pre-connected breakout box on the X-axis gantry. This works in a similar fashion to a drag-chain layout.

The Y axis is controlled by dual stepper motors running at each side on dual 16mm guide rods 75mm apart with a 10mm lead screw on each side.

The X-axis uses a single stepper motor on 16mm guide rods 75mm apart driven by a 10mm lead screw.

The Y assemblies and the X Gantry assembly are fully assembled and have aluminum side covers/dust baffles which should keep most of the debris away from the leadscrews. All the stepper motors have aluminum manual adjustment knobs fitted.

The Z axis is in an aluminum assembly using 10mm guide rods 50mm apart driven by a single stepper motor using an 8mm lead screw. This assembly weighs 1.8kg by itself, very sturdy.

The motor fitted is a 44mm 775, but this is mounted in an aluminum sleeve which when removed from the mount leaves a mounting for a 52mm motor. The motor mount can also be removed from the Z-axis assembly by removing 4 bolts opening more options for mounting a Laser, and other 52mm motors the manual implies mounts for 62mm and 69mm trimmer routers will be available in the future.

It is well-designed with rigid construction, and did I say it's big!!

Control Board


Worth a separate mention as this is a 32-bit Grbl board using a 32-bit ARM Microprocessor rather than the 'normal' 8bit ATMEL processor.  This is pre-mounted to the left Y-axis carriage with the wiring for Power, and Emergency Stop buttons and the Y-axis limit switches pre-installed.

There is a USB socket (type D, cable provided), Offline Controller (14 Pin), and an MPG port (whatever that is!) at the front, the 24V power input on the side, and at the back a 24 pin connector which takes the wrapped wiring loom to the rear of the machine. A cooling fan is also mounted in the metal case.

The wiring loom connects to a breakout box at the rear of the machine which has internally pre-wired connections to the X and Y stepper motors and Z axis stepper and limits switches plus connectors for the 24V Spindle Motor, 12V PWM Laser, (plus a control socket for an Air Assist, in the future) and Z Probe.

NOTE: The Probe connector is a 3-pin, not the normal 2-pin. But the Probe is also different as it looks to have flashy lights on it, more later.

It reports running Grbl 1.1f, Grbl for GD32 Version GD32 V2.1

It does expose the 'Air assist' pins which most 8-bit boards do not, but the Door switch is not enabled, this can be a useful safety feature if building an enclosure, but then nearly all 8-bit boards do not expose these pins either.


Pretty simple, follow the Manual. Did I say it is big, you will need a workbench space of 80cm wide and 67cm deep (32” x 27”) to assemble and use it at least.  

As it is largely pre-assembled and pre-wired. The pieces just basically need bolting together with a couple of other bits and then plugging in the wiring connectors to create a working router. Guide pins are used to keep the assembly square with minimal room for error.

I stopped to take photos and to document everything so it took me a while, but normal assembly should not take any more than an hour even if done carefully.  

Assembly Hints

  • I normally check all the bolts and screws on any pre-assembled parts for tightness and check everything is square, things can become loose in shipping! I do suggest that you check any router before you assemble it, screws can be tightened before and during assembly, and it's a lot more difficult to diagnose and fix any problems like this once you start to use it. But in this case, I didn't find a single problem.
  • It is also good practice to check all holes for any obstructions such as packing materials or in the spoil board clamping holes for any remaining swarf. It is much easier to remove any before assembly.
  • All of the bolts and guide pins had a spare, so don't be too worried about having bolts left over.
  • The two limit switches are unused.
  • Before attaching the Z Axis wiring guide thread a small tie wrap through the two front slots, it is much easier to do this before attaching the guide.

The finished item:

And one for a size perspective.

Power and Emergency stop

The on/off button and E-Stop buttons are located at the front of the left Y carriage, the Power button has a blue LED which lights when it is turned on and the 24V supply is on, it will not light when just the USB cable is connected.

The Emergency stop button is a momentary press button so it does not need to be released, press it once to stop everything. I would prefer something bigger and redder though, this is a bit small and inconspicuous for my liking, but as it is mounted at the front of the machine bigger may not be better. I will have to think about that one a bit.



This one has 2 LEDs, the blue one lights when it is connected and ready. When contact is detected the red lights and the blue one is extinguished. It uses a 3-pin connection which means it is not compatible with 8-bit GRBL control boards. The cables are very flexible allowing it to stay where it is put when probing which is very useful.

Mine measured a thickness of 11.8mm using calipers, yours may be slightly different due to manufacturing tolerances.



The Bed is 15mm MDF with drilled holes and metal threaded inserts to take the standard 6mm screw on the clamps. The grid of holes is approximately an 8cm x 8cm (3.15 x 3.15”) grid, the center holes being spaced on the X axis at 6cm (2.36”).

The clamps are basic, they allow effective clamping of materials up to ~2cm (0.75”) thick. If you are going to use thicker materials then you are going to need better clamps! SainSmart has these as do others and there is always double-sided woodworking tape or painter's tape and super glue.

Using it

Cutting area

I am so used to seeing a router with a usable cutting area not quite living up to its size. Well, my measured travel is an X-axis of 43.45cm (17.1”)  Y-axis of 40.35cm (15.8”), and a Z-axis of 7.9cm (3.1”) which exceeds the 40x40cm (15.75”).

As the motor is obviously mounted on the side of the gantry so the center of the spindle is offset this leaves the back (~20cm) of the bed unused on the Y axis, using the standard motor mount the spindle nearly reaches the front of the bed.  

Control Board and Grbl

This version of Grbl is not behaving quite like the previous versions I have used. I am used to a machine with limit switches and homing enabled to power on in an alarm state which can be cleared by running a homing cycle to set the machine coordinates (or an unlock command). This behaves slightly differently, it does not enter the alarm state, and the machine coordinates are set at zero wherever the spindle happens to be.

My 8-bit Grbl routers set the machine coordinates on homing to the position that the limit switch was triggered, as it then backs off to deactivate the switch the machine coordinates at the usable home position are normally -1. This does not, after homing including the back off the machine coordinates are shown as Zero. I always thought this would make more sense, but it is different.

At power on or reset all the $ settings are displayed with text descriptions, much earlier versions of Grbl used to display descriptions of the settings but these were removed to free some more memory space on the limited boards used. Unfortunately, there are some obvious spelling mistakes in the text descriptions.

The $ settings include the ones for the A axis, this is definitely a possible future expansion so I am not commenting on these now, there is a separate A (or fourth) axis connector on the control board so this is not a surprise.

Triggering a limit switch when operating does put the machine into an ALARM state, it also continuously sends a [MSG: Check Limits] response until the limit switch is de-activated by jogging away from it. This just fills the console pane up quickly.

I had an older version of UGS (2.07) installed. This would not recognize the router, after upgrading this to the latest version (2.0.12) I have no problems! This was the version provided on the SD card with the router.

All the default Grbl settings are sensible without anything out of place so it is usable out of the box.

I have not been able to find any source code or repository for this version of Grbl.

I have found no really significant differences in usability, just that it works slightly differently.


A very good router with a large cutting area and the potential for lots of motor expansions. I don't think any size expansions will be available for this router, there would be too many parts that would have to be replaced, in fact nearly all of them! which would be too expensive, but I don't see that as a problem.

It is a budget version, nothing wrong with that! Compared to the 4030 and 6050 it has a 775 65W motor, not a 300W one, the stepper motors are the less powerful NEMA17's, not NEMA23's, uses large guide rods rather than linear rails….

But It's much cheaper, A 3018 PROVer with a 3040 expansion kit is $449, a PROVer XL4030 is $999, a PROVer6050 Plus is $1,799, this is $649 and delivers a full 44 x 40cm cutting area!

 [NOTE: Prices are a guide only, they exclude any shipping, offer, or sale prices and will not be updated!]

It fills the gap for those woodworkers (I would use this for soft metal engraving, but not metal cutting) who want a large area at a very reasonable price.

What I like the most

  • It's big! A Large cutting area of 44 x 40cm (17.25 x 15.75”). It will take a maximum material width of 51cm (20”) and a maximum material depth of ~9.5cm (3.75”) The ends on the Y axis are totally clear so using tiling there is no practical limit for the material length
  • Very well designed.
  • Largely pre-assembled meaning a simple and fast assembly.
  • Robust and sturdy frame and motor mount.
  • Large guide rods for rigidity.
  • Dual Y-axis steppers.
  • 32-bit control board with Air assist and A axis for future expansions.
  • The Motor mount has a lot of flexibility, Motor and laser options.
  • Improved Z Probe with indicator lights.

What I don't like

Low-cost tools and clamps, but they work and I like the price so that's not really fair!

My Overall Rating


5 stars! Very good price point, a large cutting area, is well designed and works well.

This fills a gap in the range for a large but affordable hobby router.

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