I am beginning the design of a unique bench top press with a capacity of up to ten tonnes as a target. It will be built from structural steel shorts and some small pieces of plate, require no welding, take up little space and may be operated by hand at reduced capacity like an arbour press or by inserting a hydraulic jack to provide maximum effort. The jack is not dedicated to the press, sits upright in the press at bench level and is merely placed in the right spot for operation.
This press will utilize a 6 bar linkage to provide approximate straight line motion and direction inversion to make this possible.
To this end I have designed a Sketchy Physics motion simulation of the 6 bar linkage. One of the bars is the background and is inferred as such. In the realization the linkage will not appear at all the same as this model. The purpose of the model is to optimize the straight line motion produced by the linkage. I have spent a number of hours and have the action good enough to proceed with the project but improvement is possible.
There are two aspects to the linkage that operate dependently on each other. One is the travel of the ram in rectilinear motion for as long a distance as possible. The second is that the ram remain square to the work table as closely as possible throughout the range of motion.
This is where any/all of you may help. Further optimization of the linkage is definitely possible. A 6 bar linkage may have a rigorous solution to the ratios of the lengths of the bars but I don't know how to derive it. Apparently neither do many others because there are current projects to discover other straight line linkages via brute force numerical methods.
I could spend many hours adjusting the positions of the pivot points in very small increments to find a better configuration but I have other projects that I must do to get ready for winter. I thought I would instead make use of the considerable talent on this forum and distribute the computing workload to all that would like to contribute.
Therefor I have made this simulator that can be easily modified moment by moment to try different configurations. You don't need to know how to design a Sketchy Physics model to use it. All that is necessary is to use the mover tool, the rotate tool and to know how to edit groups in order to apply these changes.
Hinges that reside in a particular colour of link may not be moved to another colour. They may be moved anywhere within that colour of link. Collision detection is turned on so that impossible configurations cannot be constructed. If you manage to disable the simulator, a distinct possibility, make sure you have a working backup of your last/best configuration. I will use whatever configuration that is submitted/discovered that produces the best motion and of course that person will receive credit for assisting in the design. When a better configuration is found, as I am sure it will be, then make sure to save the workspace as an SKP file.
The requirements are a computer capable of running SketchUp, the latest version of SketchUp, Ver 7.1, and the latest version of Sketchy Physics plugin Ver 3 RC1
Link to the simulator file for SketchUp (1.6Mb)
This is what it looks like as an animation. In actual usage you have full control over the movement by simply dragging on a linkage part.