Cold Saw/V1 Design Rationale

Conceptual Parameters

• Baseplate

• 2 Fixed Blocks (mounted to baseplate by XXX, 2 shaft holes, 1 threaded rod hole)

• 1 Moving Nut Block (rides on 2 shafts, driven by a threaded rod that moves a nut welded to the block)

• 2 Shafts (radially held on the Fixed Blocks, axially held by 2 shaft couplings on the outsides of the Fixed Blocks)

• 1 Threaded Rod (radially held on the Fixed Blocks, axially held by 2 shaft couplings on the outsides of the Fixed Blocks, drives a nut welded to the Moving Block)

• 1 Clamp Handle (welded to the Threaded Rod)

Block to Baseplate Mounting

• Permanent mounting methods include welding.

• Modular mounting methods include:

Bolt into countersinked baseplate hole into block hole into nut.

Screw into countersinked baseplate hole into tapped block hole.

Screw into block hole into tapped baseplate hole.

Threaded Rod and Shafts Radial and Axial Hold

• The shafts can be radially supported by inserting through a block at each end; axially supported by shaft collars at each end on the outside of the blocks.

• The threaded rod does not require much radial support as the shafts handles the brunt of it.

Clamp Threaded Rod and Shafts Positioning

• The initial design branch split is whether the mount holes for the Shafts and Threaded Rod are propagated along a common centerline or not.

• Common centerline positioning provides the highest possible power transfer that can be attained through the 2 shaft 1 threaded rod system- because disjointed positioning can cause friction and bend-related force vectors not along the clamping axis of motion.

However, because the workpiece must be clamped above the centerline clamp system, bending can still occur.

• So the real design issue is which mounting style minimizes the moving block bending forces. For the disjointed mounting style, because the shafts must not take up the clamping volume, they must always practically be below the workpiece like the Threaded Rod. The Threaded Rod has to be low anyway to allow space for the blade to bottom out on; the blade must descend at the Threaded Rod for maximum clamp rigidity during operation.

The optimal design equalizes the drive force of the Threaded Rod and the reaction force of the workpiece such that no bending forces occur and the shafts act like a carefully balanced seesaw. Hence the shafts should be somewhere between the Threaded Rod and the workpiece.

However, another major design objective is to minimize the radial forces on the Threaded Rod. Threaded Rod radial force minimization requires the shafts to be close as possible to the Threaded Rod.

The tradeoff between Moving Block bending and Threaded Rod bending can be minimized by having the workpiece clamped as close as possible to the Threaded Rod as possible.

But the blade needs to cut through the workpiece and through a bottoming-out space that is achieved by lowering the Threaded Rod mount holes. To avoid this issue entirely one must shift the blade descent plane away from the Threaded Rod, which lowers clamp rigidity during operation. But because the blade is spinning into one of the Fixed Blocks instead of the Moving Block, clamp rigidity is minimally affected! Hence the blade descent can be shifted away from the Threaded Rod! Given that...

The Threaded Rod and Shafts can be mounted as close to the designated clamping volume as possible. But the designated clamping volume is established by the Threaded Rod and Shaft location! Then to achieve high rigidity, the Threaded Rod and Shafts should be mounted as low as possible to the Baseplate such that the clamping volume starts close to the Baseplate as possible.

But in order for the Threaded Rod and Shafts to be as low as possible, their overall height must be as small as possible, which is most easily done by reducing the vertical distance between the Threaded Rod and Shafts!

So centerline mounting would minimize Threaded Rod bending and clamping rigidity but take a trade-off with Moving Block bending, but the Moving Block is significantly more stiff than the Threaded Rod, so the trade-off drawback is marginal.

Centerline mounting selected