Automating a CNC drilling machine
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  1. #1
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    Default Automating a CNC drilling machine

    I have posted about my grandson working with me at my job and we are getting ready to start on a new project. The company purchased a 2 axis drilling machine with 5 spindles to drill 104 holes in polypropylene header pipe. It was here when I arrived and they asked me to get it up and running after another engineer had installed guards and such. It is a Chinese machine and basically junk made from scrap metal. However I did manage to get it to do a beautiful job and I cut the cycle time from almost 3 minutes to 1 minute flat. Because it was running at 3 minutes they had already ordered a second machine, double sided with 16 spindles! That is the one we are taking a whack at now.

    I thought I'd write about it because I think I have figured out a way to automate it, eliminating 2 operators per shift over 2 or 3 shifts. We extrude our own pipe and the pipe must sit for 24 hours between being extruded and cut to length before drilling because the material spirals a bit as it crystallizes. So the pipes must be stored in large racks. So I felt the key to automating this process was finding a way to automate unloading the racks, and possibly loading them automatically.

    What I came up with is two flat straps across the rack and under the pipes attached to an unloader that sits on top of the rack. A shaft on one side with slots for the straps like tie down straps is turned by a gear motor that rolls the straps up. So the whole 1000 lbs of pipes rise in the rack and flow over the fixed side and down a ramp into the machine. An eye senses the ramp is going empty and turns on the lift motor and it goes off when the ramp refills. There are two sets of clamps that are parallel for drilling. So the ramp leads to a shaft with slotted disks. Pipes fall in the slot and the disk rotates left or right and rolls the pipe into the loading station.

    The pipes are sitting in the loading station on the left. I've added a gripper to both ends of the Z axis each with an air slide to drop them below the spindles. Th Z axis picks up the pipe in the load station with the left gripper and the finished pipe in the right gripper and travels to the right end of the machine. It puts the new pipe in the clamps and drops the finished pipe into one of the 6 carts my grandson just finished building. Then the machine drills its way back to the starting position using the 16 spindles.

    We are fabricating the rack unloader right now. We have lots of racks already. The key is getting the rack unloaded, if that works everything else is fairly simple. No CNC controller, using a PLC that can handle the 3 axis motions, and 8 sets of air operated drilling clamps and the HMI. A second identical PLC on the Y axis carriage handles about a dozen sensors and limit switches along with 12 air valves. Only a 24vdc power cable and an Ethernet cable connect the two PLCs.

    If this works out we will be building a second machine. This machine will be a lathe that picks the pipe off the extruder line again with a linear axis and double grippers. The new pipe gets placed on the expanding arbor by the first gripper and the finished pipe is picked and dropped into a vertical conveyor that drops it in the racks that feed the drill machine! You can't just drop pipe 5 feet into an empty rack. So the straps in the rack will be wound up tight and as the pile builds the straps will slack off lowering the whole bundle to the bottom. When the pile starts rising above the rack, it's full and the operation stops. A gate on the extruder lets it keep making pipe and dropping them into a manual bin for a short time.

    The lathe does 3 operations on 4 lengths of pipe. So it has two servo operated 2 axis carriages. One by the chuck grooves the pipe and chamfers the end. The other end of the lathe has an expanding chuck on the tailstock. A second carriage grooves that end, trims the length, and chamfers it. The tailstock and both carriages run on the same linear rails. So the program moves the tailstock and second carriage as needed for the different pipe lengths. This lathe eliminates two more operators.

    If you think we are getting rid of lots of employees, it is actually a small number, because our process is REALLY labor intensive and lots of jobs require thinking and sensing and handling that simply can't be done by robots or machines as the solar collectors we build are floppy and vary in size from 2' x 4' to 4' x 20'

    I'll post some photos if people are interested.

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    134505a6-20a8-4768-be4f-43e227be7971.jpg1ca1be0a-fb0c-4894-b7d1-deb6428662b9.jpg
    Here is my grandson with the machine. One side is still assembled, the other sid he has taken apart.

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    I tried to think of a way to have a tooth pick dispenser for bundles of pipe. Having an indexing chain feed bunk with three spaces would drop the pipe the last bit into a set position.

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    Mr. Lucas
    I was cleaning out my desk today, and found an email from you from 2004, helping me with a water flow test procedure.
    You didn’t know me, but you took the time to type out a full page of your advise.
    I want to thank you for being the type of person who makes the world a better place.

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    Damn,
    That’s nice of you!

    You know at my new job we make solar heaters for swimming pools. Not really making the world a better place in my mind. My last job I was inventing waste treatment plants that turn sewage into water so clean you could safely drink it. I felt I was making a contribution to the world and I miss that.

    Last night I was speaking with a guy about building sensors that I came up with which make those plants turn out even cleaner water, using less power, far less expensive chemicals and are cheap and easy to maintain. I think I am going to persue this on my own time with my grandson.

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    I just ran across your post, and it's very interesting.....please post more as you progress! A couple years ago I read some of your posts and if I'm not mistaken you were between jobs?

    Anyway, this thread is very informative! Jeff

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    Yes I lost my job with a wastewater treatment plant manufacturer because I made the mistake of unloading on the owner, when a slacker took a text out of context and sent it to my boss, who's response was that I had done something wrong, instead of asking me about the situation first.

    The company has been posting on LinkedIn about the projects that are now reaching completion and of course the owner, the engineers, the contractor and the customers are all standing around with big smiles on there faces like they did something special. Actually the entire plant, the electrical, the PLC programming and every one of the unique features of that plant were done by me personally. I guess I should just be happy with the royalty checks for thousands of dollars that I get from each one they complete. It will be interesting to see how they fare over the next couple of years with the actual innovator gone.

    I will keep posting about this project. It is actually kind of neat. Currently we have torn the whole machine down to its basic frame and will shortly start putting it all back together.

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    I don't want to argue against building custom automation, but it seems like you could rig an LNS bar feeder or similar for a lathe to grab a pipe from the hopper and feed it into position.

    Then all you'd need would be a couple kicker cylinders to push the finished pieces from the machine to a "done" pile on the front.

    LNS already has indexing individual rounds from a hopper and pushing them to a servo-controlled position handled. Why re-invent? Worst case you'd need to extend the length of the hopper and make a custom tip for the pusher, but the pipes are light.

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    I’ll have to post some pictures of what I am doing. I think when you see it you’ll be amazed at simple this automation is. I’ve done lots of automation projects and have a good track record so I think it will work. I always have a Plan B if it doesn’t.

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    drill.jpg
    A SolidWorks model view of the machine. The rack on the left will hold about 300 pipes 4' long and the straps will pull them to the top to overflow into the machine. The gripper on the left end of the carriage grabs the pipe to load and the gripper on the right end grabs the pipe to unload. Carriage moves to the right and dumps the finished header into the cart, while placing the next one in the clamps. It then drills its way back to the start. The whole mechanism is duplicated on the back of the machine.

    Lots of I/O, 12 air valves on the carriage and 13 valves on the base. 16 sensors on the carriage and 16 more on the base. So it will have 3 Do-More BRX PLCs, one in the main cabinet for motion and spindle drives, one in the base, and one on the carriage connected via ethernet. Just two control cables and no junction boxes. The air valves are in the PLC enclosures and premolded sensor cables easily reach the local PLCs.

    I should have all the parts for the whole upgrade in about 2 weeks. Worse part is I have lost my chaffeur/assistant to High School!

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    So today I finally got to test my prototype Auto Rack feeder. It works! Needs some revisions but this was built from scrap I scrounged from around the plant and a gearbox from a machine I built 25 years ago.7b10b731-d63c-4e29-b858-e789866791c5.jpg6cf4dfd4-4576-43a8-9193-3bc63dfe6ed4.jpg
    Attached Thumbnails Attached Thumbnails 4df22575-d7bb-4280-98c9-b7c31601a507.jpg  

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  17. #12
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    Well, the sideways pix are not that clear but I can't figure out where the Z axis moves the pipes. How does that happen?

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    That hydraulic schematic is an oops, not part of this project.

    The pipes get moved by grippers on each end of the Z axis that drop down to grab the pipes. Then X axis moves to the right to bring one in and send one out.


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