Overall Integrated Design
After doing some research, we selected a Dremel 200-N/40 rotary tool for our router. Some advantages:
- Runs two speeds (15,000 RPM and 35,000 RPM).
- Comes with extensive available attachments.
- Designed to attach to a frame.
- Has a Ball-bearing universal motor to run cool and smooth.
- Was within our budget.
We will be using aluminum as the primary material in the frame. Aluminum fits well with our design objectives, being both light-weight and strong. Plus, aluminum just looks nice when used well.
The movement of the table and the router will be controlled by stepper motors directly driving ACME Screws. We had to give up on Ball Screws because of price constraints. While the accuracy and precision of ball screws would have been nice to have, ACME screws are an eighth of the price, and we have a limited budget.
These stepper motors will directly insert into our ACME screws, preventing any wobble or inaccuracies due to gear boxes.
Our screws come from MSC Direct, as do our pre-loaded nut and our screw-bearings. The screws are right-hand threaded with a three-eighths inch outer diameter. Riding on this screw is a preloaded nut, which consists of two nuts spring-loaded against each other. These opposing forces from the nut against the screw pretty much eliminate inaccuracies due to backlash.
The bearings on which the screws turn are self-aligning needle roller bearings. They come pre-lubricated, and in an aluminum housing, both of which are pluses for us.
After speaking with Rex Schieler of the milling company RouteOne, we decided to buy milling bits with an upward spiral and flat ends, in order to avoid gumming up the bits and then breaking off the tips. The standard flat end mill bits we ordered from the website www.bitsbits.net are "Great for drilling, slotting and all around milling," exactly what we want. We ordered three bit diameters:
- 1/8" for quick, non-detail work.
- 1/16" for mid-range work.
- 1/32" for tight corners and narrow traces.