Homemade Multi-Drill

Discussion in 'Power Electronics' started by Cosmosus_, Jul 7, 2018.

  1. Cosmosus_

    Cosmosus_

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    Hi,
    I'm thinking of making a multi drill for wood drilling, that uses anywhere from 6 to 9 9V or 12V DC motors. These motors would be wired in parallel, with one battery source. I'd mount a drill chuck on each of the motors shafts for a drill bit. Now, I need a little bit of help from you. Do any of you have an experience in doing such a project?
    My main concerns are drilling torque so that I could drill holes effortlessly in about 5 centimeter thick wood frames. Also, Another concern is battery life and how many volt batteries should I get? With same voltage as the motors? Are DC motors prone to overheating by working close to their full potential? My goal is to have reliable and long-lasting contraption for drilling.

    Thank you very much, I wish you all a good day!
     
    Cosmosus_, Jul 7, 2018
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  2. Cosmosus_

    kellys_eye

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    What's wrong with battery portable drills? That's what they're made for!
     
    kellys_eye, Jul 7, 2018
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  3. Cosmosus_

    BobK

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    I think he wants a rig that drills multiple holes at once.

    Bob
     
    BobK, Jul 7, 2018
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  4. Cosmosus_

    Cosmosus_

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    Thank you for your message.

    I was thinking anywhere from 6-8 drills, spaced about 5 centimeters apart. I would like to be able to use smaller aswell as bigger drill bits, like 10 mm.
    Maybe batteries are more of a hassle than I thought. After more thinking about this project, the best option would be 220V power supply rather than battery, since this machine would only be needed in garage. In this case, a transformator should be wired before the circuit (motors). Would I need anything else, like voltage regulator? My main goal with this project is being as straightforward and simple as possible, with enough DC motor torque to drill thicker pieces of wood and without motors overheating.

    Here's what I'm trying to achieve:
     

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    Cosmosus_, Jul 7, 2018
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  5. Cosmosus_

    kellys_eye

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    You would - literally - need battery-powered drills (as per the stuff DIYers use) to drill holes at 10mm diameter! Using motors as small as the ones you show (which seem to be ex-battery drill motors imho but without the gearboxes) you WILL need a gearbox reduction to attain a 10mm capacity.

    There are many old battery drills on eBay - drills that have passed their useful life but are otherwise 'working' but come without a battery (or, at least, without a working battery) and their innards are fairly standardised.

    If you could aim at a particular model and get some used versions to strip down you could get the motor, gearbox and chuck to mount as you see fit.

    Once you decide on the motor (size, quantity and maximum load you want to run) you can then size a PSU to match.

    The alternative would be pulley-driven chucks with variable spacers and a single motor drive.
     
    kellys_eye, Jul 7, 2018
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  6. Cosmosus_

    Cosmosus_

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    What would I need for pulley driven chucks with one motor? Do you think this is the better option?
    After some thinking, I decided to use house supply, 220V instead of battery.
    About Power units, should I buy transformer and rectifier separate or all in one? Looking for cheapest option I can get, under 10 bucks if it's possible (for example some rectifiers can be bought for under 1$. I don't need independent motor control, nor any kind of speed and torque control for any of the motors.
    About drill bits, I asked the people that need this machine what size of bits they would use and said that only smaller ones, like 4-5mm. If I would buy multiple motors, I'm looking for ones strong enough to drill with 4-5mm drill bits, but still cheap, like 10 bucks a piece or less from China. One guy at another forum suggested these two:
    https://www.ebay.co.uk/itm/Electric...5?clk_rvr_id=1590899362551&afsrc=1&rmvSB=true

    https://www.ebay.co.uk/itm/10-1-Gea...PM-Encoder-Gear-Motor-37Dx49L-mm/183147703801

    First one's got only 470RPM but has 10:1 gearbox, what do you think? Can something for even cheaper like 10bucks get me enough speed and torque to use 4mm drill bits?
     
    Cosmosus_, Jul 8, 2018
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  7. Cosmosus_

    duke37

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    For drilling wood you need speed or very sharp tools to get a good finish.
    Routers typically use up to 20000rpm and produce dust rather than shavings.The smaller the drill, the faster it should run. There is a best speed measured in m/s depends on the wood. Think of it working like a grass trimmer on a small scale.

    All drills must run in the same direction so will need to be linked with a chain and tension sprockets or gears with idlers. Look at grass cutters with multiple rotors.
     
    duke37, Jul 8, 2018
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  8. Cosmosus_

    kellys_eye

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    There is no really reason to use multiple motors - a single motor driving a load of shafts/collets would be easier to implement but you'd be 'stuck' with the shaft separation (distance) you design it for i.e. you won't be able to alter the distance between holes.

    Drill chucks are easy enough to source, as are individual motors but getting the rpm/torque correct is harder. Torque can be found using gearbox reduction whilst rpm is easily (readily) controlled - up to the maximum the motor/gearbox can tolerate of course.

    I still think you'd be better off collecting a number of identical used battery drill mechanisms and driving them 'as one' from a single supply (controllable for speed) but you must use a motor/gearbox that suits the material you plan to drill through.

    If the battery drill isn't suited to 'whatever' then nothing you do will make it work the way it should.
     
    kellys_eye, Jul 8, 2018
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  9. Cosmosus_

    Cosmosus_

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    The problem with collecting drill mechnisms is that I want to make mutiple copies of this project, like 10 of them.
     
    Cosmosus_, Jul 8, 2018
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  10. Cosmosus_

    Cosmosus_

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    Cosmosus_, Jul 8, 2018
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  11. Cosmosus_

    Minder

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    Personally I would not use those or any SMPS (switch mode) power supplies for motors.
    It may cost a little more to just use a transformer and bridge rectifier, but only entails two components which are far more rugged for this application.
    M.
     
    Minder, Jul 8, 2018
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  12. Cosmosus_

    kellys_eye

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    Probably because they are constructed using below-spec parts and have outputs that barely (or safely) reach the stated maximum.
    The old adage 'you only get what you pay for' stands true everywhere.

    Whilst I don't doubt the Chinese suppliers can't deliver these items cheaply (mass production, cheap labour etc) and they do it very well for the majority of items you can get from China, when you're making devices that need reliability you have to use reputable suppliers who's quality assurance checks (should) ensure the item you buy is as it's stated to be, fault free and reliable.

    If use of the drill mechanism (when completed) is only intermittent then I'd suggest you use a battery with associated charging system. The battery (or batteries) will deliver the peak amperage required and the charger will maintain the system when 'off load'.
     
    kellys_eye, Jul 8, 2018
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  13. Cosmosus_

    kellys_eye

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    Well, depending on how determined you are (or how essential the system you want to build actually is) you could purchase NEW drill mechanisms.... our local Lidl/Aldi store often has battery drills for low, low prices - they come with NO BATTERY, the idea being you purchase one or as many batteries as you require.

    If you keep an eye on the DIY supplier sites you may also find bargains as 'end of line' items.

    Ebay occasionally has collections of the same type battery drill for 'spare or repair' - usually because the battery has gone dud and purchasing a replacement is often more expensive than buying a whole new drill!
     
    kellys_eye, Jul 8, 2018
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  14. Cosmosus_

    Cosmosus_

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    Thanks to all of you for helping,
    after prolonged research, I'm set on this DC motor: https://www.banggood.com/775-Gear-M...tail-top-buytogether-auto__2&cur_warehouse=CN
    This one is used in most battery powered drills, usually on 24V.
    I'll be using 6 of these motors, so if they are connected to 24V one motor draws 0.16A, then 5x0.16=0.8A with a deviation of a few Amperes.
    Onward, I've been looking and have been recommended this power supply: https://www.alibaba.com/product-det...pm=a2700.7724838.2017115.1.b3c83ab4qLUWpu&s=p
    Now this supply has output current 2.08A, is this maximum current? What if I connect these 6 motors, where there is 0.8A, can power supply go that low with providing less than it is made for?
    I've got another question; if power supply has for example output voltage 9-40V, does this mean that if I buy the motors (link), where voltage is 12-36V, that power station will fry the motors with full voltage or does it regulate it?

    Thank you,
    L
     
    Cosmosus_, Jul 9, 2018
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  15. Cosmosus_

    duke37

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    The picture of the motor shows a plain shaft or an output gear. It does not say what you will get.
    The power supply has a fixed output voltage. You will need to get the right supply to give the motor speed you want. Speed will be propotionate to voltage.
    So long as the supply can provide more current than the demand, then you will be OK. A soft start system may be advantageous to get the motors up to speed without over stressing the PSU.
     
    duke37, Jul 9, 2018
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  16. Cosmosus_

    Cosmosus_

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    So what do you say in practical values should power supplys output current be, if I use this motor (0.16A of idle current - how much current when in use?) ?
     
    Cosmosus_, Jul 10, 2018
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  17. Cosmosus_

    kellys_eye

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    Depends on the load on the motor - the current will be anywhere between the no-load value (160mA) and it's stall current (whatever that is). Only you can tell.
     
    kellys_eye, Jul 10, 2018
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  18. Cosmosus_

    duke37

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    The power supply has short circuit protection but it does not say it has a current limit, if the protection is activated, do you have to switch off to go again?
     
    duke37, Jul 10, 2018
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  19. Cosmosus_

    twister

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    Harbor Freight has a little rotary drill grinder that has a 12v transformer and also has three different size cottlets for less than 10 dollars. That would be perfect for you. Maybe you could hook two of the transformers in series if you only have 240v service.
     
    twister, Jul 18, 2018 at 10:39 PM
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