Big CNC
The Big CNC is a custom CNC router designed and built by Danny Miller. It has a maximum cutting area of 5' by 8'
Max Z height is approx 7.5" from nut to spoilboard, but this does vary as spoilboard is added or removed. Note that the max usable stock height will typically need room for your bit to go on top of it
Spindle 3KW digitally-controlled VFD using an ER20 collet system. Manual bit changes, no ATC.
LinuxCNC control system
Z-height may be set by wireless toolsetter provided, or eyeballing it
CAM postprocessor should be "LinuxCNC", and not an ATC version. If nonarcs is an option, this is recommended over the arc option, but arcs will work. LinuxCNC used to be called "EMC2" long ago, "EMC2" postprocessors should work.
Members must complete the Big CNC Class before using this tool
Checklist
Before I Start
- Make sure rail travel is free of obstructions such as vacuum carts
- Switch on the two power outlets
- Wear Glasses and Closed Shoes
- Fix your work to the table (nylon nails, screws, double sided tape)
- Mount the bit
- Unrack & Home
- Switch on Dust Collection
When I'm done
- Shutdown the two power outlets.
- put wrenches, bolt, thingy back in the box in the CNC cabinet.
- Clean up the remaining dust.
Tooling
Users must bring their own bits
Places to get bits in town
Sparktech in Round Rock has a very comprehensive range of carbide tooling appropriate for CNC routing http://www.sparktechinc.com/
Easiest shopping is through eBay, most inventory is listed. Select "local pickup", check out, drive to Sparktech
Sparktech's ebay store is CarbidePlus aka OliverToolCompany, username is DrillMan1
https://www.ebay.com/str/carbideplus?_trksid=p2047675.m3561.l2563
Woodcraft (limited range). Note that most hand routing bits are not appropriate for CNC
Dixie Tool Crib https://www.dixie-tool.com/
Online
Amazon and eBay, the obvious choices
Full ER20 collet system provided in Inch and Metric. However, they are communal and prone to wear which adds runout and reduces the hold, and you may wish to get your own collets so you know the condition. Collets are generally cheap, the Techniks brand is consistently higher quality for about $15-$20 collet. In practice the majority of carbide tooling is 1/8", 1/4", and 3/8", so that may be the only Techniks collets you need to get.
https://www.amazon.com/s?k=techniks+collet+ER20&ref=nb_sb_noss
Videos explaining differences of upcut, downcut, and compression bits on wood
https://www.youtube.com/watch?v=seAmL6mtqgM
Video explaining superglue-and-tape holddown method
https://www.youtube.com/watch?v=gTUAAm0DFOQ
Resources
Maintenance
This tool is owned by Danny Miller and hosted at Asmbly for members to use. Please contact the workshop committee if maintenance is required.
