clearance issue for bonsai grafting pincher

Discussion in 'Design and Modeling' started by billJankeys, Aug 12, 2013.

  1. billJankeys
    billJankeys New Member
    Hello All!

    I am new to 3d printing and I love this stuff. I have been trying to create a very small device to try a an experimental technique to create grafts from existing bonsai trees. As you might imagine, from the image below, the two edges are intended to be very precisely touching one another. Unfortunately, no matter how long I tinker with this in google sketchup, I am unable to get the device to actually precisely "cut" or "squeeze" the tiny branches that I hope to squeeze; the two "cutting" or "pinching" edges do not actually touch even when there is nothing between the two edges.

    One friend on here made the following comment: "Though it may work perfectly in Sketchup a little bit of clearance is needed to compensate for the printing inaccuracies. This happens to be a common problem that is pertinent to all manufacturing methods, not just 3D printing, and most high end CAD software have commands for automatically checking the clearances of parts in attempts to avoid the problem of not seeing interferences. You need to check the clearance between the two parts, where they slide against each other. The cutting blades should be zero clearance, but everything else should have a little clearance so that they can slide against each other without binding. If you need help with adjusting the clearance you can add your model as an attachment and one of us will be happy to add some clearance for you."

    Since I am new to this, I don't know how to add the clearance. Would one of you guys be able to explain to me how to add this clearance in sketchup or what I need to do?

    Thanks so much!

    Attached Files:

  2. denali3ddesign
    denali3ddesign New Member
    Hi Bill,

    What your friend is saying is, you need to remove some material from all parts that touch except the blade. Ho you accomplish this really depends on the geometry of the part. In some cases you could use the Offset tool, and in others you could use the Scale tool. There isn't an automated way to do it in Sketchup.

    If you don't mind sharing the SKP model, I'm sure one of us could take a closer look at the model.
  3. billJankeys
    billJankeys New Member
    Hi denali3ddesign,

    Thanks so much for your input! I love this forum

    Will these files be enough to add the needed clearance?


    Attached Files:

    JACANT Well-Known Member
    Hi Bill,

    I see you haven't sorted your model from your original thread. Or is it a different model?
    As @denali3ddesign said, the only way to do it is to make either one part bigger or the other smaller. Or a combination of both. Taking into account the tolerances for the material you want. The clearance for WSF is 0.5mm. It is only the parts that are touching each other that the clearance should be applied

    Just seen your last message. STL files are not suitable for what you want. You will need to adjust your original SKP file.


    Last edited: Aug 13, 2013
  5. denali3ddesign
    denali3ddesign New Member
    Thanks for the links, Rob - I hadn't seen the original thread.

    Bill, as Rob says, we'd need the original Sketchup model, but I'd tell you the same advice you got in your first thread. These guys know their stuff! :)
  6. billJankeys
    billJankeys New Member
    Hi Rob!

    Thanks for the feedback. I tried to address the issue which you discussed earlier and I have tried to do so in the attached skp file. Do you think this is adequate? Should this be changed in any way before I try printing again?


    Attached Files:

  7. denali3ddesign
    denali3ddesign New Member
    Hi Bill,

    I've attached your model with some notes added. From there you should be able to figure out the rest, keeping in mind your design intent.


    Attached Files:

    JACANT Well-Known Member
    I'm a little confused on how you expect this to work. I understand how it fits together, but once it is together there can be no movement to open the 'jaws'. Even now the parts are overlapping each other. So it would not fit together properly to start. See image.
    Very nice and cleaver but there is no need for the clip to be so shaped. There are too many faces touching to enable the clearances to be applied.
    I would design it without the clip feature you have designed. I would incorporate into the design a 'spring' which should keep the 'jaws' apart. The spring would fit into a cylinder which would become part of the clip fitting. One cylinder would fit inside another cylinder where the clearance can be applied. The spring would go inside these. There are a number of ways to accomplish this.

  9. billJankeys
    billJankeys New Member
    Hi guys.

    Thanks a ton Denali! I will work on making those changes.

    I appreciate your input too Jacant. I am having a harder time understanding what you are describing though. What I want is a clip that can be locked closed with the two cutting edges touching each other perfectly and then opened at the will of the guy caring for the plant. My intent is that by squeezing the little clip's sides the locking mechanism can be unlocked and the plant graft released. You are correct in stating that once it is locked it can not be unlocked; the printed physical model would not come undone and this is a problem. I am surprised that you could have predicted this from the sketch up file alone. I suppose I am going for the simplest possible design without springs.

    Would you be willing to change the model in the ways you are describing so that I can understand better what you are talking about?

  10. JACANT
    JACANT Well-Known Member
    Hi Bill,

    Here is an example of how you could make it work with cylinders.
    The green part has a clearance gap to fit the blue part.
    The red part has a clearance gap around the blue part. It is also a tight fit into the green part.
    It will move by the amount the blue can slide inside the red.
    The spring could be printed but I would use a propriety spring to suit.
    Your original file had a few anomalies, so I have cleaned it up.

    I have included an stl file to explain further. It is hollow in case you want to print it as a test.


    Attached Files:

    Last edited: Aug 16, 2013
  11. billJankeys
    billJankeys New Member
    Thank you Jacant! (sorry for the delay in response. I was out of town)

    I appreciate your assistance.

    The cylinder model is rather intriguing. I might print that out as you suggested and get back to you with thoughts.

    I hope you had a lovely weekend....

  12. billJankeys
    billJankeys New Member
    Also, Jacant, I tried converted the skp file you sent to an stil and uploaded it to shapeways for printing. Oddly the sent me a response that said that there is a problem with the submitted design. Any thoughts on how to most easily fix this?

    Their message stated: "Advanced Printability Failure Message:
    Automatic rescale failed. Model is not within acceptable bounds in mm (1.3859 x 8.85361 x 5.72008), inch (35.20185 x 224.88165 x 145.2901), or meter (1385.89966 x 8853.6084 x 5720.08301)."
  13. JACANT
    JACANT Well-Known Member
    What size is it supposed to be? I work in mm.
    Give me the width and I will scale it for you, inches or mm
    This model does not have any clearances applied.

    I just noticed on the model, that you have not done the cuts as I explained were needed in the earlier thread. I will apply them and rescale and send you new files.
    Last edited: Aug 19, 2013
  14. billJankeys
    billJankeys New Member
    Hi Jacant,

    Thank you for your assistance! I would like the width to be 25.4 mm. Do you think that is large enough to allow for satisfactory resolution of the printing of the small parts?

  15. JACANT
    JACANT Well-Known Member
    Sent PM