Very high tool masses

Discussion in 'Tool heads & ToolChanger' started by Sneaky_Tank, May 16, 2021.

  1. Sneaky_Tank

    Sneaky_Tank Member

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    I want to put a 7kg Dyze Pulsar pellet extruder on a toolchanger.
    and I want to move it at 1000mm/s, max loading of something like the following:
    156 / 30 N
    6.18 / 4.02 m/s^2
    Y / X axes respectively.
    (should this be entirely unrealistic, I could shoot for something else)

    This would be on a 16mm ballscrew, and with 2 carbon fiber linear guides that should collectively handle the loading well.
    any reccomendations for how to make that happen inside the toolchanger environment?

    I'm thinking about adding a secondary or tertiary set of changers connected to the tool, and matching tool-plates on the X axis main toolchanger.

    If I give the extra changer(s) a decent spacing from the original, would that offset the mass limitations of the standard changer?
    If so would an axial offset, along the same plane, or a 3-dimensional offset be sufficient?

    If anyone has info on what the designed Safety Factors were for the toolchangers, I'd appreciate it, so I can use that as reference, and avoid reinventing the wheel with something like the bootleg toolchanger XXL?

    Specifically, any help from E3D staff would be greatly appreciated, since I'm trying to go just short of actually breaking the toolchangers involved.

    For background information, I'm a mechanical engineering student just finishing my second year of courses, so I can do the engineering work and calculations myself for anything up to and including mechanics of materials.
    I've been using 3D printers for 11 years, started on a mendel 90, and have been using a Prusa Mk3 for the past few, with volcano upgrades added for speed and volume.
    This design has the goal of actually printing at 1000mm/s, utilizing toolchanging, and printing from both filament and pellets; all to build a testbench prototype for general testing before a redesign and final polish.
     
  2. Greg Holloway

    Greg Holloway Administrator
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    I'm not sure what you are asking here?

    The ToolChanger / Motion System has a rated max tool loading of 1kg, and then you'll have to slow things right down to avoid any problems.

    Putting a 7kg tool onto the Motion System would be a very bad idea. Moving it around at 1000mm/s would be almost impossible without abusing the laws of physics.
     
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  3. Sneaky_Tank

    Sneaky_Tank Member

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    I figured that, and I want to do it anyway, but not on the Motion system designed for the toolchanger
    Here's an annotated screenshot of the design so far, for context.
    The whole point of this design is to <strike>abuse the laws of physics<strike/> be robust enough to properly carry out these movements, hence the 40-4080 extrusions and carbon fiber linear guide tubes on the X axis.
    Also the AC servos on the Y and X axes, and corresponding ball screws* since belts will melt and leadscrews will just implode inwards.

    My goal still stands, in that I'd like to make this happen without re-inventing the toolchanging wheel, rather just using more wheels to account for the limitations of using one wheel.

    ball screws* : hollow ones with cooling, god help me and the shriveled up husk of affordability I was shooting for.
     

    Attached Files:

  4. Greg Holloway

    Greg Holloway Administrator
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    Write down a specification. Decide exactly what it is you want to do. Then look at ways of going about doing it.

    Those ballscrew motors look waaaaay too big for the applciation. You're not moving a lot of mass, so don't overspec the motors, they have an electrical mass which will bog things down too. Consider the pitch of the leadscrews. You will get greater speed by having a higher pitch, but it comes at the cost of resolution. Consider the material throughput of the extruder too. No point going 1000mm/s if the extruder / hotend can't keep up.

    Like I say, write down what you want, be as exacting as you can be. Then figure out how you are going to do it.
     
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  5. Sneaky_Tank

    Sneaky_Tank Member

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    You make a good point, I think I might be failing a sanity check here.

    I've been working from a feature set and goal standpoint, and been doing many calculations to optimize for different tooling, and the only one that can somewhat close to keep up to the design speed of the motion system so far is the Dyze Pulsar extruder at 500mm3/s, so about 0.5mm3 every mm of travel.

    Noting that, I think that this may simply be a situation where I have to reconsider my design goals since they don't match up to reality.

    Reducing goal print speed to 500mm/s, rather than 1000, doesn't limit the speed I can print at with the Pulsar, but it does lower the RPM and lead requirements for the screws, and If I only have to get up to 0.5m/s then achieving that within 10% of the machine's range of travel per axis becomes a lot easier.

    Thanks for the advice, I'll screw with my spreadsheet calculations to see what this change might look like.

    I'll still be wanting to mount a 7kg tool on a tool changer plate or N tool changer plates. Any preliminary advice on that? since it'll be undergoing similar loading situations albeit of a lower magnitude and for shorter durations?

    (attatched are a couple screenshots of the calculation spreadsheets I've been using to assist in designing well.)
    upload_2021-5-17_13-37-5.png upload_2021-5-17_13-37-27.png upload_2021-5-17_13-37-52.png
     
  6. Albert Curmi

    Albert Curmi Member

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    Hi there, this is my first post here so please let me know if I break any rules!

    Question: If we do not consider accelerations and the general movement systems, can the kinematic coupling, as set-up, withstand more then 1 kg, whilst maintaining respectable repeatability (not necessarily 5 ┬Ám) for a large amount of cycles? If no, what is the main limiting factor? The clamping force of the stepper motor mechanism or the accelerated wear caused by the extra loading on the kinematic coupling?

    I also would like to add that I greatly appreciate the work carried out by E3D to deliver this system, at a very respectable price, from an industrial perspective. Thanks a lot and good job!
     
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  7. Greg Holloway

    Greg Holloway Administrator
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    I think you'll be ok with 1.001kg, maybe even 1.002kg. Is that what you meant by more than 1kg?

    The simple answer is I don't know. I've not put anything on it larger than 1kg because that is all it is designed for. If you go outside of the design specifications then you'll have to find a way to answer those question yourself because I don't have the answers.

    The spring is the 'weakest' part of the coupler. It was chosen to be able to lock 1kg or less onto the toolhead. You'll need to change that. Next you'll want to look at a larger toolhead stepper motor because it will likely struggle to operate with a stiffer and stronger spring. That then has a knock-on effect requiring that the carriage assembly needs to be enlarged to account for the bigger toolhead stepper motor. I'm sure the rabbit hole goes a lot deeper than that too.
     
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  8. John Meacham

    John Meacham Well-Known Member

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    If you build your tool "taller" so that it reaches over the toolchanger then you can probably go a bit heavier because it won't be pulling as much on the spring statically and you can slow down to reduce dynamic load. But yeah, you would need to test it.
     
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  9. Albert Curmi

    Albert Curmi Member

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    Thank you for answering my question :)
    I have done some work on the design as is and I can state that the rabbit hole IS deep.
     
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  10. Greg Holloway

    Greg Holloway Administrator
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    You may find your approach needs greater clarity; What is it you are actually doing, and why?

    Are you making a toolchanger that can manage tools >1kg? Are you making a tool that is 1kg that you just want to test?

    Do you actually need a toolchanger? Would an IDEX system work better?

    A better understanding of your goals should point you in the right direction regards machine design.
     
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