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Thread: Laser cut ball lifter.

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    Master Inventor daverob's Avatar
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    Default Laser cut ball lifter.

    I've been playing around with ball lifter designs for a while now, and none of them have been particularly satisfactory. They have either required too much time and effort to make and so would be uneconomic to sell them at an affordable price, or have been compromised by using off the shelf parts that don't fit together well enough to prevent the ball lifter from jamming up all the time.

    After seeing the design of the Pibow case for the Raspberry Pi, and how it is made from a stack of laser cut acrylic parts, a little lightbulb appeared above my head and I wondered if it would be possible to make a ball lifter out of a stack of laser cut acrylic. That way the laser cutter can do all the hard work, and I'll just have a pile of parts to stack up and screw together along with a motor and a switch.

    Out came the CAD package, so I could sketch the concept out and see if it would work. The design is heavily influenced by the orange ball lifters from Japan, so uses a duplex gear. The design of the gear was the most complicated part, you want the balls to nestle nicely between the two halves of the gear with no gaps between adjacent balls, so there was a fair amount of maths involved in calculating the sizes and spacing of the teeth.

    drawing.png

    The parts were then laid out onto a single sheet and sent to my local plastics fabrication shop to laser cut. A small motor was ordered from an eBay seller and a microswitch was found in my junk box. A few nuts and bolts later and voila...

    Ball_Lift.jpg
    There are a few issues with the design, the motor isn't really powerful enough, it can just about manage to lift balls the full height of a pachinko machine, but it's really struggling and slows down to about half it's no-load speed. I was expecting this, and have already ordered a more powerful one from a seller based in China, but the one I've got was the best one I could get from a more local seller in a more reasonable delivery timeframe. The other benefit of a weak motor is that you are less likely to break anything if there's a jam.

    The main problem is that the acrylic gear isn't really robust enough, there are already signs of damage to the teeth. The heat from the laser cutting process makes the cut edges quite brittle and the hammering it gets when it's pushing a stack of balls the height of a pachinko machine is a bit too much for it. The next prototype I try will have the laser cut parts annealed (gently heating and cooling the parts to remove the heat stress from the laser cutting), if that doesn't work then I'll have to try making the gear from something a bit stronger (nylon or acetal/delrin).

    The plastics shop is cutting and forming a ball catcher/tank to sit behind the lifter, and with a bit of luck I should have that to play around with for the weekend, and I can get rid of the duct tape stopping the balls from falling out the back!

    A 30 second video of it running should be available on this YouTube link.
    Last edited by daverob; 03-06-2014 at 11:27 AM. Reason: Fix image tags

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    Goodwill Ambassador luckydog's Avatar
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    Default Re: Laser cut ball lifter.

    a neat job so far
    幸運わんわん Luckydog or Yukiwanwan in Japanese

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    Pachi Puro Moparformances's Avatar
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    Default Re: Laser cut ball lifter.

    impressive as always

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    I was thrown out of Top Gear Drunkenclam's Avatar
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    Default Re: Laser cut ball lifter.

    Sweet looking.

    have you tried expo tools, for motors,they do a range with different power/rpm and ones with gearboxes too,

    MOTORS, GEARS & PULLEYS
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    Master Inventor daverob's Avatar
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    Default Re: Laser cut ball lifter.

    Quote Originally Posted by Drunkenclam View Post
    have you tried expo tools, for motors,they do a range with different power/rpm and ones with gearboxes too,
    Just taken a look at their site, and the prices quoted are a little bit over my budget. The nearest equivalent motor to the one I'm using is £32.95 (~$55), and I don't think it'll be powerful enough to lift the full height of a pachinko machine. There's no data available on the dimensions/mountings or specifications, so I'd need to buy one just to find out if it'll work.

    I designed the lifter for a standard 37GB motor, as they're readily available from many manufacturers in a range of voltages, RPM and motor powers. The one I'm currently using was £7($12) delivered, the one I've ordered from China is £9 ($15). While the quality might not be as good at the cheap end of the market, they should be fine in an application like this, and if they wear out you don't have to find the one shop that sells them to source a replacement.

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    Blind Shooter matthew818ply's Avatar
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    Default Re: Laser cut ball lifter.

    How are you progressing so far. What kind of motor did you use, and where did you get it? I am in the process of making a ball lift as well made from acrylic. I am just having problems figuring out the motor aspect of it.

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    Master Inventor daverob's Avatar
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    Default Re: Laser cut ball lifter.

    Quote Originally Posted by matthew818ply View Post
    How are you progressing so far. What kind of motor did you use, and where did you get it?
    I figured I'd need a 30rpm motor, and wanted to run it from a 12v power supply, so I just plugged in '12v 30rpm motor' to eBay and looked to see what came up.

    The first motor I bought was one like this. It's a standard size motor with common mounting points and available in several sizes from different manufacturers. The motor itself is too small and not powerful enough. But I got it quickly from a local seller and it was good for testing the initial design of the lifter as the lack of power meant that I didn't risk breaking any of my acrylic parts. In my lifter design it was good for lifting the balls about a foot to 18", but you could hear it start to slow down as the stack of balls got any higher than this.

    At the same time I ordered one of these motors from a Chinese eBay seller (not the same seller in this link though). I chose this particular one as I found the manufacturers site and could download a datasheet with the full specs of the motor (It's a ZGB37RG 12v 30rpm). This one is plenty powerful enough and was working well lifting balls the full height of a pachinko machine without any stress. But the first time the gear got jammed, it broke a couple of teeth completely off.

    I haven't had much spare time to make any more progress on this, but I'm working on a revised design with some spring loaded sections of the ball guides, so that if there is a ball jammed in the gear, the ball guide springs out of the way and allows the jammed ball to move to the next gear tooth. I'll also be cutting several spare gears on this sheet of acrylic!

    I'm also planning to make the gear in nylon (or Delrin) as I think acrylic is too brittle for this part, especially after the heat stress put into it by the laser cutting process. But I'm probably going to have to wait until I can afford a small CNC router as it's a pretty complicated part to make on my manual milling machine.

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    Blind Shooter DaveCapps's Avatar
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    Default Re: Laser cut ball lifter.

    Nice!!! About the gear, what about aluminum? Should be soft enough not to damage the balls but undergoes no dramatic structural changes under laser cutting.

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    Default Re: Laser cut ball lifter.

    Got .stl files? (or just about any other 3d format, for that matter)... wouldn't mind giving a try printing with PLA or ABS. If the plastic fill is the right orientation, the teeth could end up pretty strong... But even then, the best idea would be to have it back off at jams. Sense current... Too much current = back off for a few seconds?
    Last edited by Chumsize; 04-29-2014 at 05:14 PM.
    Woof!

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    Master Inventor daverob's Avatar
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    Default Re: Laser cut ball lifter.

    Quote Originally Posted by DaveCapps View Post
    Nice!!! About the gear, what about aluminum? Should be soft enough not to damage the balls but undergoes no dramatic structural changes under laser cutting.
    I'm not sure about aluminium, it might be too soft and the repeated hammering of the balls could cause the gear to permanently deform. I'd prefer a plastic with slightly more elastic properties, hard enough to resist most deformation, but will 'spring back' into shape after the jam has been removed. Acrylic is too brittle, but I think nylon should be a good fit (or an acetal such as Delrin if nylon isn't tough enough). However the local shop only has a low-power laser cutter, so I'm currently limited to the small selection of plastics they have in stock.


    Quote Originally Posted by Chumsize View Post
    Got .stl files? (or just about any other 3d format, for that matter)... wouldn't mind giving a try printing with PLA or ABS. If the plastic fill is the right orientation, the teeth could end up pretty strong... But even then, the best idea would be to have it back off at jams. Sense current... Too much current = back off for a few seconds?
    No .stl files, I drew all of the parts with 2D CAD and figured out the assembly in my head. When I first learned to use CAD (Medusa on a Sun3/60 workstation) everything was 2D and I haven't had the opportunity to update my knowledge since then. I'm just getting back into mechanical design, so I'm starting by simply refreshing what I already know just with slightly more modern tools.

    When I first started having thoughts about ball lifters the idea was to get a small sign making CNC engraver/router and cut all the parts from flat sheet (as I could manage the 2D CAD and G-code generation from the skills I learned in my apprenticeship days in the machine shop). A lack of funds to invest in the CNC meant everything was put on hold for a while. The local plastics shop getting a laser cutter reawakened the idea at a more affordable prototyping cost, and so I can try to prove the concept in laser cut acrylic before making the investment in equipment.

    I had thought about making a small motor drive board that would reverse the motor if it jammed, but it does add to the complexity a bit. I'd like to keep the electronics as simple as possible and sort the jamming problem on the mechanical side of things on this build. Besides I have another completely different ball lifter concept bouncing around inside my brain. This one will definitely require a microcontroller based driver circuit and it's calling out for me to build a prototype just so I can determine if it's genius or garbage (most likely the latter!).

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    Eye Shooter chmer01's Avatar
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    Default Re: Laser cut ball lifter.

    This looks great! I'm sure it will be just as good as the dongle you designed. Can't wait to see the completed product.
    Eric C.
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    Default Re: Laser cut ball lifter.

    Howdy Folks

    Great job on the design I do have a online site for motors and cool stuff but to get the stuff to you in the UK a Member here has to ship it to you for some reason they don't ship to the UK

    Motors-Electronic Goldmine
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    Master Inventor daverob's Avatar
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    Default Re: Laser cut ball lifter.

    Can't believe it was 3 years ago that I started this project, it doesn't seem that long ago!

    Just got myself a new toy to play with.

    Laser_Cutter.jpg Sprocket.jpg

    I've just finished setting it up and cut my first bit of acrylic with it.

    Once I've properly got the hang of operating it, expect to see some progress made on this project...



    ... but don't expect it to be too soon, as from the 3 year wait it does appear that I work at a glacial pace.
    Last edited by daverob; 07-13-2017 at 01:52 PM. Reason: trying to fix the images :(

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    Scowlin' Jean Hornigold hanabi's Avatar
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    Default Re: Laser cut ball lifter.



    sorry there is an issue with the images since some updates were done, hopefully it can be resolved soon



    Just have to click on them for now
    Angie ...
    Pachinkos, Pachislos, Coffee, Papercraft Ninja, Pinball

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    I was hiding in a room in my mind...
    You crush the lily in my soul...



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    Default Re: Laser cut ball lifter.

    Acrylic is not brittle. You made it brittle by laser cutting it.

    The intense heat of laser cutting creates stresses in the acrylic. To remove those stresses, the part would have to be annealed, which is accomplished by heating in a controlled oven and gradually lowering the temperature. You can read more here: https://en.wikipedia.org/wiki/Poly(methyl_methacrylate)

    There are probably better choices of material than acrylic. I was going to use acetal when I got around to making mine. But I would investigate the properties of any material before laser cutting it. If for no other reason, to find out what toxic fumes you're inhaling during the laser cutting process.
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    Master Inventor daverob's Avatar
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    Default Re: Laser cut ball lifter.

    Quote Originally Posted by browne92 View Post
    Acrylic is not brittle. You made it brittle by laser cutting it.
    I believe I mentioned something similar in the first post on this thread.

    The issue with cutting and then annealing to remove the internal stresses, is that I'm thinking of this as a production engineer (rather than from a simple design standpoint). Annealing (done properly) takes an oven with fairly precise temperature control, and requires a cycle time of around 12 hours. The cost in terms of investment in equipment, energy to run the oven, and time taken add up to more than simply selecting an alternative material to work with.

    Acetal/Delrin produce formaldehyde gas when laser cutting, and is also quite flammable. So I need to make sure that the fume extraction is working perfectly and I'll probably wait until I get the 'air assist' hooked up to my workshop compressor, as the small compressor provided with the laser cutter may not be able to provide enough airflow through the cutting area to prevent combustion. Either way, there is always an extinguisher nearby in the workshop.

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    Sandwich Shooter browne92's Avatar
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    Default Re: Laser cut ball lifter.

    Quote Originally Posted by daverob View Post
    I believe I mentioned something similar in the first post on this thread.
    Sorry, missed that. I'm so used to dealing with people that jump into these technologies with any research, that I assumed. My apologies!

    Quote Originally Posted by daverob View Post
    Acetal/Delrin produce formaldehyde gas when laser cutting, and is also quite flammable.
    Which is why I plan on machining. I've never machined acetal, but I have nylon. It cuts like hot butter. I'm hearing that acetal is similar.

    I am curious. You said that you are stacking layers of acrylic. What thickness, and what type of power required to cut? I've been looking for a chart that shows power required to engrave and cut various materials at various thicknesses. I speak pretty good Google, but haven't found anything yet.

    And for the record, machining acrylic is no dream either. I was CNC cutting parts using a 1/16" 90 degree point end mill. I liked using the mill because it let me put a nice chamfer around the edge of the part. But when cutting, I kept ending up with a ball of melted acrylic on the end of the cutter. And no amount of playing with feed speed and spindle speed seemed to help. Which left me standing over the thing with a can of WD-40 constantly wetting it down. What a mess. Not worth the trouble, so I gave up.
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    Default Re: Laser cut ball lifter.

    Not terribly knowledgeable, yet, when it comes to laser cutting but what about PETG? Or are the fumes still bad on that.

    Hopefully will get access to my university's laser cutter here in the future to experiment with things.

    100 machines and counting...

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    Master Inventor daverob's Avatar
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    Default Re: Laser cut ball lifter.

    Quote Originally Posted by browne92 View Post
    Sorry, missed that. I'm so used to dealing with people that jump into these technologies with any research, that I assumed. My apologies!
    Definitely not jumping into this, had two years to research while I was saving my pennies for the laser cutter. I've worked with plastics a lot in the past, so know a fair bit about their properties.

    The prototype ball lifter was all made from 3mm (~1/8") acrylic. Now I have my own laser cutter, I'll probably use a few different thicknesses, as I won't have to pay set-up fees to the shop for each sheet.

    With most plastics, the laser only melts the plastic and the 'air assist' blows it through the hole you've just melted, so you need to have the power to melt all the way through in one go. With acrylic, you literally vaporize the material at the cut point, so if you go slowly enough you can cut quite thick material with even the low powered lasers. The limiting factor with lowest powered laser cutters is the focusing of the laser beam, if the material is too thick the beam will be nicely focused near the top face of the material but will diverge as it approaches the lower face and as the laser is now spread over a bigger out-of-focus spot, it may not have the power to melt/vaporize the larger area.

    Most laser cutter guides say to run a few tests on your own machine to determine what speeds and powers are appropriate for each material. This is because there's a lot of different types and qualities of laser cutters, and the laser tube 'ages' and loses power as it gets older. For example my machine is one of the cheaper 'generic' Chinese machines. It claims to be a 60W laser, but in reality it is an overdriven 50W laser tube, so if you run it full power at 60W it will burn the tube out in no time. Also the quality of the optics can make a large difference to the amount of laser power that actually gets delivered to the material. So a guide that gives accurate figures for one model of laser cutter wouldn't necessarily apply to mine.

    Acetal cuts like a dream on a lathe/milling machine/CNC. In my experience it's probably the nicest material to work with. Acetal cuts in small chips which clear away from the cutter with ease. It's also not as fussy about feeds and speeds as most plastics, and even an inexperienced machinist should be able to get a good surface finish.

    Acrylic is one of the worst for machining. Only ever use brand new tooling on acrylic. It has to be super sharp, any hint of dullness and it will melt and stick to the cutter. So if you've previously cut any metals with the end mill, buy a new one for acrylic and make sure it's a decent quality one! I use solid carbide single flute cutters and reserve them strictly for plastics. Cutting with lubrication can help, but with good tooling once you've got the feeds and speeds set up right, you can get away with simply blowing air from an airline to clear chips and keep the workpiece cool.

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    Chicken Fried Steak takethecastle57's Avatar
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    Default Re: Laser cut ball lifter.

    Why not take the Orange or the Silk ball lifter gear and get the measurements from it and cut a new one out of that white Plastic kitchen cutting board material ?


    Or make a multiple piece mold and cast the lift gear ?
    Last edited by takethecastle57; 12-04-2019 at 10:38 AM.
    When things don't go right the 1st time , Step back ,Take a break and come back renewed. RGS

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