Using the default frame (https://github.com/MaslowCNC/Mechanics/wiki/Choose-A-Frame-Design#the-default-frame) with non standard weights, on the ring sled, with the the recommended Ridgid R22002 router, with Z-axis kit. Latest fimware and GroundControl (1.2.4).
My sled uses 5 Lbs diving weights which have been angularly aligned and positioned to where the Brick’s CG was. Wish to understand how position of weights and their weight influences movement.
The ‘Ring’ on my sled is set at ~3" above the top of sled on Z axis. Had figuring out this height as I could not figure out clear directions. So maybe got it wrong. The clearest instructions were found under Step 4 in “Maslow Ring System Sled” (http://maslowcommunitygarden.org/Maslow-Ring-System.html?instructions=true) it says:
“Step 4: Attach the ring and bricks” - “Note that the ‘L’ brackets are designed to let you move the ring up and down to adjust for your router’s center of gravity. When supported by the ring the router should hang vertically. You can move the ring in and out to account for your router’s weight distribution.”
I assumed I should balance the sled using the top most (z-axis) point of the ring but this caused problems with the sled tipping when aproaching the edges of the work area. The closest cuts to the edge were 2".
The angle of sled changes depending on the position it is in on the cutting area. Here is a quick crude diagram.
This is a side view (z-axis) from cutting surface.
⦁ RED is cutting surface.
⦁ BLUE is sled position (at top and bottom) of cutting surface with tilting effect.
⦁ GREEN is dimensional center of sled (Not CG of sled).
⦁ ORANGE is contact position of chain to sled ring.
⦁ YELLOW is mount point of motors and the chains.
⦁ BLACK is current sled angle when supported by rope from top of ring.
⦁ Diagram is not to scale and exageratted to emphasize points.
- When sled (BLUE) moves to the top of the work area then the chain contact point to the sled (ORANGE) moves below the the physical center of the sled (GREEN). The top of the chain at the motors is at least 4" further out, away from work area, than the sled ring and causes the sled to start tipping over the top of the work area (RED). Conversely when the sled is at the bottom of work area the chain is almost vertical, and the contact point to the sled is high on the ring, which maybe pulling the top of the sled away from the work area.
- Another factor is the CG of the sled which is below the physical center. So when the sled approaches the bottom edge of work surface the CG moves of the board and cause top of sled to tip away from work area.
- I lose accuracy (badly) when cutting within 1’ of left and right edge of 8x4 board. The pieces shown below should look the same left to right (mirror image) but the left side is horibbly disfigured.
To fix these I adjusted the sled to NOT hand straight vertically when supported by rope at the top of the ring. It is more like 5-10 degrees (BLACK). This seems to be the optimal angle to keep the sled from tipping. I can now move the sled so that the router bit is directly on the edges of work area, top and bottom, without the sled tipping. It also helped to stop a slight tip on left and right edges of work area.
- Have I balance the sled properly?
- What is the minimum/maximum for sled weights?
- Should I change the sled balance setting in Ground control? This uses a measurement from center of router bit to CG? How does this setting affect the calculations?
- Should I move the motor mount beam closer to the edge of work are to reduce the angle of chain to the sled?
- Could moving the sled weight closer/further to center, OR up/down influnce accuracy when working on left/right extremes of 8x4 board?