Slot constraint in Pro Engineer Wildfire 4.0

[sp8472]

I'm working on a vertical chain-driven conveyor system. It is to have several trays attached to the chain, which will move components past a paint sprayer system. The machine is meant to permit an operator to place the components onto the trays, push a button, and come back in 45-60 minutes to unload everything after each tray has been sprayed and permitted time to dry between coats.

I'd like to create an animation to not only demonstrate the intended final operation, but also to produce something of a motion envelope to be sure that nothing's going to get in the way of anything else.

I did (finally) find the Slot constraint in WF4's Mechanism section, and set that up for one of the trays. For the slot constraint's Point on Line constraint, I selected a datum point on the tray, and then Ctrl+selected all six segments of a sketched path on the chain mockup.
There's also a "Slot Axis" constraint selection within the Slot constraint setup. I'm not sure what to pick for this. The automatic selection filter will only permit me to pick a vertex or datum point.

For orientation, in order to keep the tray centered and upright, I used a center datum plane that is Coincident to the assembly's center datum plane, and a horizontal datum plane that is set to be Oriented to a horizontal assembly datum plane.

With all that set up, if I grab the tray with the Drag Packaged Components tool and move it manually along the path, it moves precisely as it should, following the entire path perfectly.


In Mechanism though, I have some issues getting it to do a full loop, or even half of a loop.

I have a Servo motor configured in Mechanism:
Driven entity: Geometry. I've picked a datum point on the tray.
Reference entity: I'm honestly not sure what I need to select for this. Pro-E tells me to "select a point, vertex, datum plane, or planar surface." I went with a datum point on the chain.
Motion Direction: "Select a translation vector or an axis of rotation." Well I'm not rotating, so I assume I need a translation vector. I chose an edge of the chain.
Profile tab: Use a constant velocity.

When I do a Mechanism Analysis and click Run, the tray begins to move along the selected path. But once it gets to a point where it would have to move perpendicular to the selected Motion Direction, Pro-E (not too surprisingly) tells me "Error - Assembly Failed! The mechanism constraints could not be satisfied. The mechanism could not be assembled," and the tray will move no farther. I'm not sure what I can select in order to make it continue moving regardless of direction along the curve.


I have seen some nice animations on Youtube of objects doing precisely what I want to do: Follow an arbitrary curve. However, I've not had much luck in finding instructions on how they were created, or else the instructions consist of "Add model to assembly. Then add proper constraints. Run animation."



Thank you in advance.

 

[sp8472]

I'm trying to get rid of the hotlink protection on my website so that the image attachment can be displayed. I also can't help but notice that there isn't an Edit function here. Huh.

I've got eng-tips.com added as a permitted domain, but it still isn't doing the job.

Maybe an embedded image will work?

 

[3DDave]

I've done this without mechanism by following a datum point on the curve and setting the point as a ratio along the curve.

If you create a relation like:

steps = 34
point_location_ratio = point_location_ratio + 1.0/steps
if point_location_ratio >= 1.0
point_location_ratio = 0
endif

The above assumes the name of the ratio has been changed to point_location_ratio.

Each time you regen, the point will move by the amount of the next step until it gets to wrap around and start over.

You can capture each frame and stitch them together with any number of image -> movie programs.