PCB Prototyping Machine
About[edit]
- Make: AccurateCNC
- Model: A350
- Forum thread
| Working area (XxYxZ) | 305x254x22 mm, 12x10x7/8 inch |
| Machine design | Heavy duty aluminum and stainless steel platform |
| Machine table | 16 mm, 0.625 inch stress relieved high stability aluminum alloy |
| Resolution (X,Y,Z) | 2.54 μm, 0.0001 inch |
| Repeatability (X,Y,Z) | 2.54 μm, 0.0001 inch |
| Spindle speed | 8000 to 60000 rpm programmable |
| Spindle design | Stainless steel body, ABEC7 hybrid ceramic bearings |
| Spindle motor | High quality brushless DC |
| Tool collet | 3.175 mm, 0.125 inch |
| Collet design | Precision polished hardened tool steel |
| Total TIR | 5 μm, 0.002 inch |
| Collet control | Hex key on top end of the spindle |
| Minimum drill diameter | 0.2 mm, 0.008 inch |
| Drilling speed | Up to 120 drill cycles per minute |
| Homing System | Gold Plated precision needle contacts |
| Max Travel speed (X,Y,Z) | 127 mm/s, 5 inch/s |
| X/Y positioning system | 2 phase bipolar stepper motors, precision lead screws with ActiveCAM™ anti-backlash SuperNuts™ |
| Z positioning system | 2 phase bipolar stepper motor, precision lead screw with springloaded nut and micrometric dept limiter. Limiter is removable for populated board rework. |
| Interface to PC | USB or RS232 (COM port) |
| Spindle and vacuum start-stop | Manual and/or program controlled |
| Feed rate and Spindle speed | Manual and/or program controlled |
| Dimensions (WxDxH) | 508x432x305 mm, 20x17x12 inch |
| Weight | 25 Kg, 55 Lbs |
| Power Supply | 100÷240VAC, 50/60 Hz 225W |
| Machine control system | DSP micro controller, true 3 axes interpolation |
| Machine control programs | Industry standard G & M codes ASCII files |
| Control and Edit software | Windows based – PhCNC or [DeskCNC |
| Imports | AutoCAD DXF files, 3D STL files, computer image files, Extended and Standard Gerber PC Board files, Excellon Drill and Definition files. |
| Programmable post processor. | |
| Made and serviced in USA | Accurate CNC, Inc. |
| Testing time before shipping | 5 days, 40 hrs complete test |
| Source | |
Notes about using the AccurateCNC A350[edit]
IMPORTANT - Penetration depth for tools is set manually, using the micrometer on the depth limiter.
In PhCNC, The "Tool Table" contains a list of all available tools (engraving, milling, drilling, cutting) available to be used in the system.
When importing a Gerber project into PhCNC, specific insulation, rubout, drill, and cutting tools are selected from the tool table to be used for the project. PhCNC will use this tool information when calculating the tool paths in CAD mode.
When moving from CAD mode to CAM mode, by pressing the 'CNC' button, PhCNC will generate the G-code. Values from the Setup "PCB Router, Drill, Rubout, Cut & Stencil" screen are used to set the penetration depth specified in the G-code created by PhCNC. It is normal for the depth to be set to 0.1 inches - this will tell the machine to plunge the tool much deeper than the actual desired depth, allowing the depth limiter micrometer to be used to stop the penetration at the desired depth.
Note: If there is more than 0.1" difference in height between different tools used in a CNC process (example: rubout), the tool change and depth limiter adjustments will not work properly with the normal PhCNC workflow. In this case the tools must be changed and the Z axis zeroed in the software, probably requiring cancelling the rubout process, manually editing G-code to remove the paths for the first tool, and restarting the process to begin with the second tool. It is much easier to use tools with depth rings installed, to keep the tool depth within allowable limits.
The contact pad has an isolated ring so it can be pressed flat against the depth limiter, then the tool depth is adjusted with micrometer until it just touches the contact pad and the yellow Z limit LED on the right side of the machine lights up.
Note: The jumper wire connecting the bit to the machine body (ground) must be connected for the contact pad and Z limit to work!
- Documentation: Step by step AccurateCNC PCB Milling Process
Tools (bits)[edit]
The AccurateCNC A350 uses 1/8" shank tools. A small selection of inexpensive bits (cost approx $1 ea) are available for use with the machine. These tools work, but are not all the highest quality required to get the best and cleanest results with the A350. Note that these inexpensive V-tip bits are shorter than most end mills and drills, so this complicates the tool change process.
For milling circuit boards, higher quality tools are recommended
Using bits from PreciseBits gives noticeably better results and finer detail is possible. The tools from PreciseBits cost about $10-$20 ea. The 60 degree V-tip 0.005 in diameter has produced good results, along with a 1 mm end mill. The people at Think & Tinker (PreciseBits) are familiar with the AccurateCNC machines, and they are the manufacturer-recommended source for bits.
If you want to try the PreciseBits tools, User:Chrisgerlinsky has a small selection available. Because of the cost and fragility of the bits, they haven't been left out in the open.
The PreciseBits tools have depth rings on them, which is very helpful when changing tools to keep the tool depth within acceptable range. With these bits, the A350 tool change procedure can be followed, making the process more straightforward.
Milled PCB sample[edit]
Above: This PCB was milled with AccurateCNC A350 2018-04-11. Scanned at 1200 dpi. Board dimensions approximately 0.62" x 0.52"
Line size and spacing: 20 mil, 10 mil, and 8 mil.
Tools used: isolation - PreciseBits V60, rubout - PreciseBits 1mm end mill.
(holes in this sample are slightly misaligned due to copper board not having being properly fixed flat on the workholder)
Resources and links[edit]
Sign-off review checklist for PCB designs, written by Andrew Zonenberg