Punch and die clearance...fail - Page 3
Close
Login to Your Account
Page 3 of 3 FirstFirst 123
Results 41 to 52 of 52
  1. #41
    Join Date
    Oct 2011
    Location
    West-Central Illinois, USA
    Posts
    1,278
    Post Thanks / Like
    Likes (Given)
    2026
    Likes (Received)
    582

    Default

    Following Red in post#25, you can get away with some flakey stuff with aloneymum… Consider what is possible in the first attachment below. I have no idea what the shear edge would look like at the largest tested clearances...

    Then “Condensed Aids” lists “shearing strengths” for blanking pressure in the second attachment.

    Number 3&4 are bliss (use a ruler for the answer) charts for blanking and then angular shear effect.

    Good luck,
    Matt
    Attached Thumbnails Attached Thumbnails aluminum_blank_jones_122.jpg   shear_tons_sqin2.jpg   shear_bliss_log.jpg   shear_bliss_angles.jpg  

  2. Likes winklershop, sfriedberg liked this post
  3. #42
    Join Date
    Jan 2005
    Location
    Houston
    Posts
    5,689
    Post Thanks / Like
    Likes (Given)
    533
    Likes (Received)
    2481

    Default

    I gotta admit....if you are making aftermarket auto parts at $2 each (why so cheap?) and only 500 of them....that's $1,000 per year. Most people can come up with that 'income' by laying off the Starbucks or cigarettes or Astroglide.

    The aftermarket automotive world is a tough one...as others noted, people have come to expect very nicely finished parts. I agree with the comment that a punched part is gonna be a dud compared to a water jetted part. Don't forget, there are Chinese 11 year olds with water jets...

    But back to the $2 but - very few parts of that size are sold for $2. There's something you're not covering but I'll assume you mean you need to produce it for $2 in order to make a killing type of profit.

  4. Likes digger doug, winklershop, Philabuster liked this post
  5. #43
    Join Date
    Jun 2019
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    323
    Post Thanks / Like
    Likes (Given)
    98
    Likes (Received)
    285

    Default

    Quote Originally Posted by GregSY View Post
    ...by laying off the Astroglide.
    Hey now! Let's not go overboard here! I couldn't talk the bank into at least giving me a reach-around, but I did at least get some lube out of the talks.

  6. Likes winklershop liked this post
  7. #44
    Join Date
    Oct 2014
    Country
    CANADA
    State/Province
    Ontario
    Posts
    1,216
    Post Thanks / Like
    Likes (Given)
    690
    Likes (Received)
    930

    Default

    Given the time/investment in the die, the need to sit in front of the machine and run it, and the need for post-processing parts it seems like a bad deal to me...

    For $10k or so you could put a used VMC in your garage and have it making small batches of parts while you sleep. Setup rows of aluminum bars on a fixture using pitbull clamps, go inside watch TV and have a beer, come back to 20-30 finished parts, rinse and repeat. If you need to change the part a little just change the program and get back to it, no need to make another die.

    You could definitely hit your price per part this way (excluding the setup as previously mentioned) because you barely have to account for your shop rate if you're running unattended, especially running the machine in your garage. And at the end of the process you'll have a VMC, which is a very flexible piece of equipment that you could leverage into many other products.

  8. Likes winklershop liked this post
  9. #45
    Join Date
    Aug 2017
    Country
    UNITED STATES
    State/Province
    Washington
    Posts
    27
    Post Thanks / Like
    Likes (Given)
    30
    Likes (Received)
    0

    Default

    I appreciate everyone's input, a lot of things well said, i am here to learn, a lot of you have a massive amount of experience and knowledge.

    I wanted to see how this part would come out with what i have done so far. After work i put it on the 50 ton electric over hydraulic press. the ram moves at a snails pace compared to a punch press, so i don't think this is a fair analysis of my die set, but its all i have...results are in and its not pretty. i didn't bother with running the hole punch operation, just focusing on the blanking operation at this point.

    the strip warped and got stuck in the bridge stripper so i had to unbolt the stripper plate to get the strip out

    the shear line is only about 1/16" the rest is all break, that tells me the clearance is still wrong (after i changed it from .024" to .048" per side)

    the corners on the strip left nasty burrs, i think i have done something wrong with the radii of the punch and die

    there is a small burrs on the blank....wow look at the side angle of the blank

    If this was put in a 75 ton punch press, what would the results be?

    here are the pictures:

    Punched - Google Drive

  10. #46
    Join Date
    Oct 2011
    Location
    West-Central Illinois, USA
    Posts
    1,278
    Post Thanks / Like
    Likes (Given)
    2026
    Likes (Received)
    582

    Default

    Quote Originally Posted by Mike1974 View Post
    Also, my die makers handbook doesn't say anything about constant clearance over xx thickness, or that I have seen. However, they do recommend 12.5% clearance per side since Dayton did a study on this along time ago proving 12.5% produced a cleaner hole with less breakout. If you tighten the clearance up (unless you are just doing an edge trim op) the material bulges around the punch then snaps back into place creating a dragging/galding effect.

    Die Makers Handbook - Jerry Arnold - Google Books
    page 40-41
    THIS^^^^

    Quote Originally Posted by winklershop View Post
    the strip warped and got stuck in the bridge stripper so i had to unbolt the stripper plate to get the strip out

    the shear line is only about 1/16" the rest is all break, that tells me the clearance is still wrong (after i changed it from .024" to .048" per side)
    WE call it shear but what it really does → "is break". You built a nice looking tool, Mike thinks you need 12.5%, the stuff I posted from jones suggests you could be nearing 15% before your happy.

    Good luck,
    Matt

  11. Likes winklershop liked this post
  12. #47
    Join Date
    Aug 2017
    Country
    UNITED STATES
    State/Province
    Washington
    Posts
    27
    Post Thanks / Like
    Likes (Given)
    30
    Likes (Received)
    0

    Default

    i see

    basic diemaking book by D. Eugene Ostergaard refers to it as the cut band, says it should be about a third of the thickness, i have also heard that it should be about half the thickness

    here is a picture of an example of excessive cutting clearance which is what mine looks like

    20191125_210553.jpg - Google Drive


    maybe this is a factor of speed of the punch? hydraulic vs punch press

  13. #48
    Join Date
    Oct 2011
    Location
    West-Central Illinois, USA
    Posts
    1,278
    Post Thanks / Like
    Likes (Given)
    2026
    Likes (Received)
    582

    Default

    I fixed your picture & I hope you really don't want that edge radius on the part...

    When I said break the fractures migrate toward each other & meet at the center of section when all is right. Look at the second attachment.

    Good luck,
    Matt
    Attached Thumbnails Attached Thumbnails excessive_clearance.jpg   shear_break_200dpi.jpg  

  14. #49
    Join Date
    Jun 2012
    Location
    Tennessee USA
    Posts
    712
    Post Thanks / Like
    Likes (Given)
    353
    Likes (Received)
    418

    Default

    There are a lot of clearance numbers/formulas out there. Many of the published numbers express the value in terms of total clearance instead of the clearance per side (PS). The photos you posted exhibit the following:

    1) Minimal shear/burnish to break zone ratio
    2) Large roll-over edge
    3) Large burr

    To me, this shows an excessive amount of die clearance. You can even see the angle of the fracture plane when viewing the blank from the side. If you used the 12.5% formula as a per side clearance then I might suggest cutting another punch from mild steel (for test purposes) and trying this again but use 7.5%-8% of material thickness per side (PS). For future reference, always state whether your clearance numbers are total or PS to avoid confusion. Reducing the clearance will require greater tonnage so be wary of the stress this puts on your press, hoses, and support as the cutting force searches for the weakest component.

    Strip distortion should be less but due to using a bridge/box stripper this may be unavoidable. Strip distortion is a reflection of the cutting force and distance to nearest edge. This is one reason why spring strippers and pressure pads are used to control the distortion in a blank or strip. Your focus should be on the clearance right now, the distortion solution can come later. I also have to ask:

    1) Are you using some sort of oil on this? You really need to.
    2) How did you achieve locating the critical alignment of punch to die? It appears slightly off but it may be the photos.

    The ram speed of a mechanical press would change things a bit but not enough, in this case, to matter much. Ram speed has a greater effect on drawing a shell than blanking (unless it's Fine Blanking which this is not). Cut another punch from low carbon scrap with 7.5%-8% per side and see if things improve. Post results please. Good luck.

  15. Likes digger doug, Rewt liked this post
  16. #50
    Join Date
    Sep 2015
    Country
    UNITED STATES
    State/Province
    Tennessee
    Posts
    535
    Post Thanks / Like
    Likes (Given)
    257
    Likes (Received)
    421

    Default

    AD beat me to it.

    Technically, what you're referring to as a "shear edge" is called burnish. Judging from the photos, you don't have enough of it. Which means too much clearance. How did you measure your clearance?

    Using a true bridge stripper for that thick of material is not at all advisable. I undertand you were trying to skirt a fine line on tonnage but material is simply too thick for that kind of solution. Properly done, it would be with gas springs set to the amount of blanking and stripping force required. Bridge strippers rely on the reverse tonnage of the press to finish their work. Fine for thin stuff, not advisable for thick. Especially when clearance is not ideal, as in this case.

    Also, how did you set that punch to the die? Setting punches is a rather advanced skill, usually one of the last things we let apprentices do. As AD said, and only from looking at the strip, that punch doesn't look set correctly.

    Keep in mind, neither I nor it seems anyone here is criticizing, it's just that for us, it's not a hobby.

  17. Likes digger doug, AD Design liked this post
  18. #51
    Join Date
    Oct 2005
    Country
    UNITED STATES
    State/Province
    Pennsylvania
    Posts
    15,701
    Post Thanks / Like

    Default

    Quote Originally Posted by Rewt View Post

    Keep in mind, neither I nor it seems anyone here is criticizing, it's just that for us, it's not a hobby.
    Bears repeating.

  19. Likes AD Design liked this post
  20. #52
    Join Date
    Jun 2012
    Location
    Tennessee USA
    Posts
    712
    Post Thanks / Like
    Likes (Given)
    353
    Likes (Received)
    418

    Default

    "Keep in mind, neither I nor it seems anyone here is criticizing, it's just that for us, it's not a hobby."

    -I always thought it was for the glory and high pay.

    -To the OP: You're doing ok, some of the info has been slow in coming so you had a clear course of action to learn from. None of the posts have been criticism, we're all trying to help.


Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •