To produce the necessary G-code I use Seeedstudio Fusion PCB service CAM script to create Protel compatible Gerber files for bottom layer and drill data, then load the Gerber in CopperCam. (Tip: In CopperCAM, turn off Parameters->Automatic Alignment to have drilling holes proper aligned manually).

The tools I choose is 0.1mm, 30° engraving bit for isolating, 0.9mm drill bit for the holes and 1.5mm endmill for outline cutting. The cutting depth for isolating path is set to 0.1mm. I choose not to hatch out the excessive cooper as I plan to peel them off manually.

The flatness of board is critical in PCB milling. I use a 5mm acrylic board as the “sacrifice” base and double side tape a blank PCB on top of it. Double side tape appears to be pretty handy here because otherwise when the board is clamped down at both sides, the centre part tends to bend upwards.

Since the cutting depth is only 0.1mm, an absolutely accurate zero in Z axis is crucial. USB CNC Controller software provides a very useful function, using a tool sensor as Z- limit switch to measure Z offset. During the measurement, the spindle is moved down until the tool touches the sensor block. The software will record this point, then subtract the block height  to receive Z axis zero.

As recommended by many people, drilling should be done first. This is because otherwise for small pads the high shearing force during drilling could remove the whole pad. Step 2 is mill the isolation tracks, followed by cutting out the board.

Here is the result. Looks pretty decent for first time milling. Notice the residue copper in between the tracks. I believe this is less than 10mil.

After peeling off the excessive copper, the final PCB looks great!

Final words

From young I’ve been using ferric chloride etching method to make my own PCBs. However several years ago this chemical was banned by the government here in Singapore because some irresponsible people had been pouring wastage into the drainage. The ban is reasonable. No shop sells ferric chloride any more. But under the spirit of Kiasu shop owners dare not carry other environmental friendly solutions such as Sodium Persulfate either. Ironically they do carry other etching necessities like photo sensitive PCBs and developer solutions. But who will buy these without the etchant?

Many innovations have since been killed in the infancy. While the government keeps advocating innovation and improving productivity, without a proper environment of promoting science studies, without an open community, without the courage to step forward, people will forever crawl in the cradle.

Anyway, new year, new start…

The post MF70 CNC PCB milling appeared first on Digital Me.

Back in time, these were the memorable photos when the MF70 was first purchased and unboxed.

My BOM also includes:

• A set of step motor frames and connectivity kit from eBay seller mbbilici. I compared quite a number of designs and settled with this one. The major advantage is that this set does not require permanent modifications to the MF70 body, especially the X-Y lead screw. I can easily revert MF70 back to its original state in case of warranty claims.
• A USB control board, from a Chinese seller. It is a derived version of planet-cnc’s open source Mk1 DIY controller. The seller added a DC-DC buck-boost regulator in USB 5V power rail to cater for voltage drop. I actually doubt it’s necessity but it is definitely better-than-nothing.
• A 3-way stepper motor driver from the same Chinese seller. The driver board contains 3 Toshiba TB6560 controllers, each provides 3A maximum driving current, more than adequate for my application.
• A Meanwell 24V/100W switch mode power supply.
• 3 step motors (Moons 23HS0410-01). Unfortunately I burned one of the them during testing. And I fixed it by buying another three (Sumtor 57HS5106A4, 0.62A/1.1Nm)

Here are the controller and CNC body after assembling. Every single effort goes into the design of proper chassis.

It also took me nearly a month to wire up the motors, mainly to source for proper connectors and strain relief methods for the flimsy cables. I finally settled with 4mm stainless steel flex-tube, which is amazingly strong yet flexible. And most importantly, it looks really cool!

First cut was on a piece of 2mm thick clear acrylic. I took the sample DXF file from PlanetCNC software and loaded it into CamBam to create G-code. Murphy didn’t catch me this time, everything (just) worked at the first attempt.

The heart belongs to my dear wife. Thanks as always for her support 

P.S. During the early testing stage I encountered some USB communication issues. I kinda found the culprit but did not fully figured out the underlying reason. It may deserve another blog post once I fully discovered it.

P.S.2 The machine is not fully finished yet. I plan to make a nice front panel and possibly add a manual jogging controller. But now with CNC it could be much fun…

The post MF70 CNC appeared first on Digital Me.

After some study I decided to use DIY USB controller plan from www.planet-cnc.com. In fact I simply bought a ready made USB controller from a Taobao seller together with a 3-axis Toshiba TB6560 based step motor driving board. I think it is much cheaper than building my own and since the schematic is open source, I won’t have much support issues. I also ordered 3 NEMA23 step motors (Moons brand 23HS0410-01, no specification whatsoever!) , a Mean Well 100W 24V switch mode power supplier from another Taobao seller. For the mechanical part I ordered a set of MF70 conversion kit from eBay seller mbbilici, a well know guy in the community. It took 2 weeks for the kit to be shipped from Turkey to Singapore but it well worth the waiting. After some more shopping from local Sim Lim market my CNC machine is just waiting to be assembled …

Oh? … Oh no I still need some more boards. I need a relay board to control MF70 main spindle. I need a keypad board for manual control, and I need a 24V ->; 5V regulator board for main controller power… Maybe other boards, who knows? But the relay board is definitely high priority because I need it now to plan the rest part of the casing.

Now it sounds like chicken-n-egg story. I need the MF70 CNC to make PCBs but now I need a PCB to build MF70 CNC. Any yet I do not want to waste money and time with a PCB house. So what to do? Let’s do a manual CNC

( Here starts the keyboard saving part)

( No more lazy fingers)

So happen TODAY is my birthday. I spend half a day to work on the board and the balance write this blog. Did not go out enjoy much, but the level of happiness is unmatchable

P.S.

1. Casualty of milling: 2×0.4mm and 1×0.8mm end mill bits when I overturn the table, still trying to locate the broken pieces before it pierces my foot. (Hope this will never happen after my CNC is ready)

2. Lesson learned: need to add light sources to the CNC machine plan.

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