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[Bragging] Dust collection on BP... My solution.

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  • [Bragging] Dust collection on BP... My solution.

    Ok, the part is a polycarb/glass-fiber plastic impeller that has the gates INSIDE the bore. The bore is a hexagonal hole, whole thing slides over a small shaft.

    There are three gates, you need multiple gates when molding round parts otherwise Bad Things Happen such as packing out of round and shrinking out of round. Multiple gates allow you to control the flow better and make round-er parts.

    Now, this part forms in the mold... they designed it so the plastic injects through the pin that forms the bore. It's a "valve gate" design meaning a signal from the machine pops open a slide valve and the plastic flows in, is packed and the valve closes. Net result is no runner/sprue.

    Problem is... due to improper thinking/moronic thought processes/idiotic engineering the net result from this design is three rather obvious nubs in the hub () that need to be removed.

    Shop #1 tried removing them with a cutting tool mounted on an arbor press. Minimum-wage labor proved unable to operate the arbor press, results varied from chipped hubs, cracked hubs, boxes of parts with "finished" tags that aren't finished at all.

    Shop #2 tried a simple automated air-press with a rotary table and pick-up arm. Put part in nest, machine broaches part and pops it into a box. Problem arose with maintaining the machine, and getting people willing to sit there for 600 pieces an hour, 12 hours a day.

    Shop #3 is me.

    I built a set of fixtures for my BP CNC, laid them out on the table. Then I took a long skinny endmill... and set the program to start in the center then go out this way X amount then back home then in this direction this amount then back home then to this position... back home retract and on to the next fixture. Last fixture, return to the first fixture and repeat cycle until I stop the program.

    Five fixtures. At full speed I can keep up with the molding machine cycle-time.

    Problem is the polycarb dust that is generated by the milling, it adds up. Air blow makes it worse. Suction just relocates the problem.

    Called up the customer and asked the application. They are for a potable water application... while they do get washed in house they'd prefer that I don't use any chemicals on them if I can avoid it.

    The solution to keeping the dust down was dead simple. The controller has a signal for coolant on and off... and a valve. I swapped the valve out with a new one, and set the system up to draw clean water from a tank and squirt it down into the hub during milling. It turns off when the spindle retracts.

    All the "dusty water" flows down through the normal BP coolant slots, out the hole and into a bucket. I strain it with cheese-cloth... the water flows down the hose into the cheese-cloth into the bucket. Every so often I stop and dump that bucket back into the clean-water tank.

    So far, zero dust. Customer accepted the batch I sent in Wednesday and told me to proceed with my method as they don't see any unacceptable contamination.
    This product has been determined by the state of California to cause permanent irreversible death. This statement may or may not be recognized as valid by all states.
    Heirs of an old war/that's what we've become Inheriting troubles I'm mentally numb
    Plastic Operators Dot Com

  • #2
    Clever, nice work! Simple, to the point, and the customer is happy. What more could you ask?

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    • #3
      I fear rust may become an issue.
      This product has been determined by the state of California to cause permanent irreversible death. This statement may or may not be recognized as valid by all states.
      Heirs of an old war/that's what we've become Inheriting troubles I'm mentally numb
      Plastic Operators Dot Com

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