Desktop CNC Milling Machine (Genmitsu Pro Max V2)

[Durley]

Hi All

 

I’ve recently acquired the new CNC milling machine and thought I’d share some thoughts. I’ll start with a disclaimer, the machine was bought paid for by me. I have no relationship with the manufacturer other than being a satisfied customer!

 

I had been looking for a CNC machine to allow me to accurately make parts in brass or nickel silver for various railway modelling projects. Mainly I was looking at 2D profile milling in sheet material for things like locomotive frames, valvegear parts, W-irons, etc in various sheet thicknesses from 0.3mm to 2 or 3mm or so. Until recently, the choice of CNC machines capable of cutting metal has been limited to professional steel framed machines priced in £thousands. Cheaper aluminium extrusion based machines, typically diy home builds or from Chinese manufacturers, have been available but weren’t really rigid enough to cope with machining metal. These machines have been improving however and the recently upgraded Genmitsu 3020 Pro Max V2 CNC promised to fit the bill, being marketed specifically for machining in metal and priced at less than £500, it looks good value. With a bed size of 30cm x 20cm, it’s large enough to cover the sort of jobs I wanted to use it for, but still small enough to be used on a desktop.

 

Machine Setup

 

The machine comes mostly built, but requires some final assembly to attach the z-axis to the bed and install the spindle motor. This was achieved in around 30mins following the excellent instruction manual.

 

The machine comes with an offline controller, so machining projects can be undertaken without the need to connect a computer (although this is an option and a usb cable is also included). Projects are loaded to the offline controller via a (included) SD card. The card comes preloaded with a few example engraving projects for use with the supplied vee bits, so I was able to try it out the machine on a wood off cut, to get used to its operation.

 

For precision cutting in metal, a level bed is important so I acquired an MDF spoil board and surfacing bit, to ensure the x-y bed is perfectly perpendicular to the z axis.

 

G code files

 

These machines use GRBL firmware, requiring the project to be machined to be produced in G code (.nc) format. There are many software products available to produce the required G code files. I used Fusion360 as this allows both CAD (design) and CNC (manufacture) to be undertaken in the same software. I was already familiar with Fusion360 as that is what I use to design models to 3D print. There a loads of video tutorials for Fusion360, making it accessible, and it is free for hobby use.

 

Metal cutting end mills 

 

There is a bewildering range of milling bits available so finding an appropriate milling bit compatible with both the milling machine and material to be cut can be a daunting challenge. Having done some research online, single flute end mills looked like the way to go with this kind of machine for cutting brass. The single flute allows cutting at a sensible feed rate with the relatively low spindle speed of 10,000rpm that the machine provides. I bought 1, 2 and 3mm end mills to give me a few options. The machine comes with a 1/8 inch collet so the bits need a 1/8 shaft. Buying other diameter ER11 collets allows for a wider range of bits to be used.

 

Feeds and Speeds

 

Milling requires parameters to be specified covering most importantly the spindle speed, feed rate and depth of cut. There are calculations that can be done to determine the range of these variables for a given end mill and material combination. To be honest, I just copied the parameters from this video on YouTube and have adjusted from there. These settings are very conservative so make a good starting point.

Work holding

 

There are various ways the material to be machined can be held on the bed. The machine is supplied with 4 screw clamps which are fine. I however found by far the easiest option for sheet materials was to use the tape and glue method. This involves applying masking tape on both the back face of the material and the surface of the bed. The two can the be glued together using CA glue, ensuring the material is firmly held on the bed but allowing the finished parts to be removed cleanly by just peeling them away from the masking tape.
 

Machining in Brass

 

So how well does it machine brass? With the correct settings, amazingly well I think! Finished parts are cleanly machined and I am getting within around 0.01 to 0.02 mm tolerance when measured with digital callipers, which is plenty accurate for my applications. The specs for the machine state 0.1mm tolerance which I suspect maybe closer to what is achieved on larger parts using the whole bed.

 

Here are a couple of videos showing my machine in action. The first is 1mm brass sheet machined with a 2mm bit and the second is the same brass sheet machined with a 1mm bit. Feeds and speeds I used are included in the video descriptions. Pictures of the finished components are also attached. I’ve successfully cut thinner sheet (0.3mm, 0.6mm) and up to 1.5mm which is the thickest I currently have in stock.

 

 

In summary, I’ve been really impressed with the machine, its capabilities and ease of use. I now have a stack of project ideas I want to use it for!

Edited October 30, 2023 by Durley
Typo

[Bedders]

Thanks for the clear summary of this machine.  Hopefully you can keep us updated with your progress as you get to know it better

[stevel]

Thank you for the review, I have been on the fence with these machines because of the flex that most of the less expensive machines, and want to use it for the same use as you, to make chassis etc, for my 3d printed rolling stock. Will be following with interest.

[Durley]

A quick update with some parts I have made on the CNC machine. These are for an O gauge diesel shunter that I am scratch building, incorporating continuous springy beam (CSB) suspension.

 

I’ve designed some CSB tags that I can use with Slaters hornblocks. I’ve then made an inner frame to retain the hornblocks and position the CSB mounts (repurposed handrail knobs). This will all be mounted on the inside of the outer mainframe (yet to be made). I intend to use slots in the outer mainframe as the guides for the hornblocks. I’ve also made the coupling rods.

 

Brass parts are 28 thou (0.7mm) and the nickel silver rods are 64 thou (1.6mm). I’ve measured the finished parts to be spot on intended dimensions with my digital vernier callipers which measure to 0.01mm. 

[Durley]

I’ve completed the basic chassis on my Drewry shunter project and given it a first test run. All parts cut on the CNC. Testament to the accuracy of the machine, it ran perfectly with no fettling needed.

 

 

The loco is DCC Bluetooth controlled and powered by an onboard battery, but that’s a story for another thread!

Edited November 19, 2023 by Durley
Typo

[Nick52]

Many thanks for posting this. I bought athe same CNC cutter ( bit of an impulse buy on Amazon as it was significantly reduced in price) I've only used it to router thin MDF so far but want to use it on brass .so this has been really useful. I also use Fusion 360 for 3D printing , but not yet tried it for design of brass parts to be milled. 

Edited April 22 by Nick52