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Thread: Master caster electronic automation - some questions

  1. #1
    Boolit Mold
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    Master caster electronic automation - some questions

    Hello Everyone

    I’m at the very start of automating my Master caster. I decided I would program a Single Board Computer (Arduino or Raspberry - cost effective) to operate a step motor for replacing the handle and an electric actuator for regulating the pour. The SBC could read out potentiometers or a dip switch to set the required delays at the mold position and how I want it to shake out the boolits at the end.

    Big part of the costs is selecting the torque of the step motor and max current associated with it for feeding it.

    I removed the handle, made a kind of 1/2” connection so I could plug a borrowed torque wrench on the axle. Only to find out it is a counter clockwise torque measurement, and most torque wrenches only gives a clockwise torque for fastening stuff.

    Here is my question: Can anyone give me an educated guess of a worst case torque that normally is applied on the handle? I assume that mechanics who are familiar with torque measurements can give a rough estimation just by feeling it. Biggest mold I cast is 45acp, dual cavity.

    I need an answer on this question to avoid any of the following situations:
    - buying a left handed torque wrench (200-300usd, only need it once)
    - buying a step motor too small
    - buying a step motor too big (can cost over 500-1000usd)
    - buying a H-bridge driver too small or too big along with the motor and the power supply (same problem)

    Thanks for the input
    Kind regards

  2. #2
    Iíve thought about doing the same thing with a Master Caster. If you look at the AmmoBot, they use multiple chain driven sprockets to increase the torque of their stepper motors. I think this would be key as once you go over 2200 in-lbs in a stepper motor the prices increase dramatically.

    Iím curious what you plans are for actuating the lead pour? Like you, I want to stay away from air cylinders but in this case the speed of an air cylinder is exactly what you need. Most linear actuations are far too slow so I would assume a high speed Servo motor or powerful solenoid would be required.

    Anyway, Keep us updated as you venture into this project.

  3. #3
    Boolit Mold
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    Ammobot? Do you mean this?
    https://www.fishpond.com.au/Toys/Wor.../0018859813009
    Sorry just joking

    Depending on the needed torque and available budget, I may need to adjust the ratio of the transmission if I use a V-belt. Anyway, I thought using a V-belt may be safe if the step motor operates the mold further than it’s supposed to be, then at least the belt can slip before some part gets broken.

    Razorfish, to answer your question: I wrote down ‘linear actuator’ but probably a solenoid would be a better idea. Other stuff comes to my mind, but before I want to try this out and share my experiences, I need to solve the biggest issue:

    —> What torque do we approximately exert ont the handle of a master caster? Say, worst case, a .45 double cavity bullet mold with a normal alloy?

    As written above, I made a whole test setup only to find out my torque wrench doesn’t measure counter clockwise momentum. Feel a bit silly.

    If anyone can give a rough estimation of the torque we need to apply to operate the Master caster, that would be really helpful!

  4. #4
    Boolit Master
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    Looking forward to seeing how this project goes. I rescued some stepper motors on the weekend to use on a bullet collator, still need to work out how to wire them up....

    Keep in mind that an Arduino is not industrial and potentially will glitch on you. My master caster is automated with one and it does glitch on me, it uses air cylinders for pour and dump. The dump really does need a lot of torque, if the sprue has hardened too much, it can be a job to cut it with a motor running at a linear speed. With the handle, you can at least get a run up to shear it off. I liked the idea of using a gear box of some sort to give more torque.

    Be careful of what type of electric solenoids you use, i used a 240v solenoid for my pour, the EMF given off when it released messed with my arduino, it took me MONTHS to work out what was causing the glitch, but when i swapped it out to an air cylinder, it glitches one in a thousand or so.

    A good source of stepper motors are photocopiers. I got about 10 out of one on the weekend, a fairly large one, 3 medium and a bunch of small ones.Click image for larger version. 

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    Hopefully that attachment worked, those tiles are 400mm square for perspective.
    Last edited by Tazza; 09-25-2018 at 05:20 PM.

  5. #5
    Boolit Mold
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    Hi Tazza,
    Thanks for the hints. If I use large coils like a solenoid then I will think of a diode snubber to contain the back EMF when the current through the circuit is cut. Also separating galvanically the power supply of the Arduino and the power electronics for the solenoid + step motor would help. Maybe a little more filtering like soldering rod core chokes in series with the 5V or 3V power supply of the Arduino will help cleaning up the supply voltage, and maybe an input capacitor. This should reduce the glitching regardless of which single board computer is used, being it a Beaglebone, Raspberry or Arduino.

  6. #6
    Boolit Master
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    Diodes would help for sure, mine was a 240v ac coil, so diodes weren't an option Possibly a capacitor across the wires might have helped.

    Any extra filtering will help, i may look at adding that to mine. Mostly it does run right, but every so often......

  7. #7
    Boolit Mold
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    Is there really no one able to help me with a rough torque estimation of the Master Caster?

  8. #8
    Boolit Master


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    You can have someone measure the air pressure they use on a cylinder and the piston diameter. That will give you the force

    Then measure the distance between the pivot point and cylinder.

    That will give you the torque needed.
    Don Verna

    NRA Endowment Member

  9. #9

    Master caster electronic automation - some questions

    Quote Originally Posted by Pebbles View Post
    Is there really no one able to help me with a rough torque estimation of the Master Caster?
    I would like to know the answer too but I think the answer is going to be more complicated. Notice that there are a couple of popular auto drives that use stepper motors but they use gearing to increase the torque. So, from a power standpoint a large stepper motor should have enough power if geared properly.

    The question might be if the stepper motor can gain enough speed (accelerate) to knock the bullets/sprue out of the mold. If not, you ďmayĒ need tappers. (And if they have enough holding power to stop immediately without skipping steps)

    You can probably calculate the force that the more popular air cylinders create but they have an advantage of accelerating very quickly so it may not be a fair comparison. There is also designs that use electronic motors and a horsepower rating could be helpful.

    Again, Iím not much help but if you look closely at some of the auto drives for progressive presses, youíll probably be closer to an answer.

  10. #10
    Boolit Man
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    RazorFish,
    I agree with you the pressure of the cylinder on a Wyman/Hatch setup is not all you need. I would recommend not accelerating to knock bullets out like the air system.

    Pebbles,
    Why don't you take your master caster out and pull on the handle a few thousand times. (You will get bullets out of it and they can be used so no time wasted)
    Then take your Torque wrench put the end in a vice and pull on the handle and try to duplicate the pressure you used to shear a cold bullet that sat in the mold too long (worst case scenario)
    Then convert the Nm or ft-lb back to the shorter handle.
    -Wildcat

  11. #11
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    Sorry i missed this thread.

    There are too many variables.
    The amount of clearance between the rails and the mold carrier.
    The amount of lube on the bearing surfaces on the shaft and rails.
    The temperature and alloy of the lead.
    The timing of the machine itself.

    Now your gonna ask why does the temp and alloy of the lead matter? Why does the timing of the machine matter??
    Simple, softer lead requires less force to cut.
    Shorter cooling time before sprue is cut means itís easier to cut.

    The movement cylinder provides about 30 lbs of force based on the average pressure used by most of the customers that use my panel (70psi)
    But some have had to run 100psi which is is 40lbs of force.

    Like I said this all is dependent on the variables listed above.

    On the air setups we use flow regulators to slow the speed of movement while still keeping the pressure(force) up.
    The Ďslammingí of the mold carrier to release the boolits is due to the molds not being polished and additional force needed to release the boolits from the mold.
    Even when i operate it manually I have had to slam the handle down to release stuck boolits.
    I polish all my molds now to make the drop easier.

    Look at this video -> https://youtu.be/B0TWNmgEMnM

    Look at the 3:30 mark. He uses tappers to release the boolits.
    If your using a gear motor your gonna need rappers for your setup too.
    Don't like being hammered by the Cast Boolits Staff, then don't be a nail.
    The rules are simple to follow.

  12. #12
    Boolit Grand Master popper's Avatar
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    Steppers and torque motors slip when torque is exceeded but they overheat if drive is not reduced.
    Whatever!

  13. #13
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    HATCH's Avatar
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    Tappers
    Autocorrect got me
    Don't like being hammered by the Cast Boolits Staff, then don't be a nail.
    The rules are simple to follow.

  14. #14
    Quote Originally Posted by HATCH View Post
    Tappers
    Autocorrect got me
    Has anyone ever sourced these tappers? They look like some sort of solenoid with a pretty long travel.


    Sent from my iPhone using Tapatalk

  15. #15
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    I never located them and the German guy is useless when it came to information about them.
    He paid someone to automate his machine.
    Don't like being hammered by the Cast Boolits Staff, then don't be a nail.
    The rules are simple to follow.

  16. #16
    Boolit Mold
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    Thanks Hatch for chiming in.

    In the mean time I nearly started a small machine shop for converting all my moulds, bought an X2 type mill. I acquired a Left hand torque wrench and found a source of Step motors and appropriate drivers. I believe the step motors can be programmed to do a back-and-forth shaking at the end of the stroke. I assume this would be sufficient if combined with polished molds, time will tell.

    I know I advance very slowly but I am committed to convert this machine - family and work occasionaly get in the way. I definitely will not pay an external company.

    Thanks all for your ideas.

  17. #17
    Boolit Master
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    Please do keep us updated with how you go with this project, i'm interested in seeing how you go about this. I hope to one day complete a project i started of building my own version of a bullet master, thses systems may help do it.

  18. #18
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    Quote Originally Posted by Pebbles View Post
    Thanks Hatch for chiming in.

    In the mean time I nearly started a small machine shop for converting all my moulds, bought an X2 type mill. I acquired a Left hand torque wrench and found a source of Step motors and appropriate drivers. I believe the step motors can be programmed to do a back-and-forth shaking at the end of the stroke. I assume this would be sufficient if combined with polished molds, time will tell.

    I know I advance very slowly but I am committed to convert this machine - family and work occasionaly get in the way. I definitely will not pay an external company.

    Thanks all for your ideas.
    so its been a little while, where are you at with your progress?
    I did sell a panel to a guy in Belgium last year or was it the year before.
    Don't like being hammered by the Cast Boolits Staff, then don't be a nail.
    The rules are simple to follow.

  19. #19
    Boolit Mold
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    Not so far, I had an urgent renovation at the house. But in the mean time I used the left handed torque wrench on one of my bigger diameter molds and found out the torque that would stall the motor is at +/- 14Nm when operating properly and a bit more if I let the mold cool down too much, like when I start up the casting process and find out I have an adjustment to make while the cold mold cools even further down.

    So now I found out what size stepper motor I need to buy. And I think I will use another way instead of the solenoid for operating the pour.

  20. #20
    Boolit Master
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    Urgent house work is never fun.... I'm trying to finish mine so i can put it up for sale

    Glad you have managed to calculate the torque needed, i wonder if there is a figure you should work with, as you don't want to spec the motor too low, or too close to that figure, just in case. Do you add 50% to the required torque? Different lead mixes will give different torque requirements to cut the sprue, bigger is generally better in these situations, to an extent. You don't want so much power that if it was to jamb up, that it pulls the machine apart.

    I saw another way that they did lead pour, you can use a stepper motor for that too, set it up to a cam, so you move it fast, it drops for a short time, turn it slow, it pours longer, it's an option?

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