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  1. prdave00

    Supplier requesting switch over to new machine - watch outs?

    Our current supplier of a plastic molded thermoplastic polycarbonate urethane part is asking if we'd consider "upgrading" from a Arburg model 270S400-100 U press to a Arburg 270C-400-90. Differences provided by our supplier are listed below. We do not want to completely re-validate the process...
  2. prdave00

    (Poly)urethane spring design

    Can anyone point me to any good references for designing urethane springs or know of any applicable posts in other forums? I've found information in catalogs such as that provided by Sorbothane, but these seem to be geared to helping one decide what might work from their catalog and not how to...
  3. prdave00

    3D MODEL OF HUMAN PELVIS WITH SACRUM

    Try here: http://www.3dcadbrowser.com/download.aspx?3dmodel=48783 You should also look at the Visible Human Project at http://www.nih.gov/ for a fee. Or try SawBones for a fee. Good luck!
  4. prdave00

    Yellowing of polycarbonate urethane (pcu)

    Thanks for all your help.
  5. prdave00

    Yellowing of polycarbonate urethane (pcu)

    Chris & Pat: Obvious material degradation such as surface cracking hasn't been noted, but my recollection (and I'd have to check with my colleague) is that there was some permanent set after application of the loading cycles. The concern is that this yellowing is an indication that the material...
  6. prdave00

    Yellowing of polycarbonate urethane (pcu)

    I've noticed done yellowing on some tubes extruded from 80A pcu I've been evaluating. These parts are being cyclically compressed (5-10% strain) in a saline solution maintained at 90-100 deg F. The cyclic loading is being performed in a room with fluorescent lighting. I don't see this yellowing...
  7. prdave00

    Differentiating Grade 23 (6-4 ELI) from Grade 5 (6-4) Titanium alloy

    I have a part that is made out of a titanium alloy per an ISO standard. The issue is the ISO standard covers both the Grade 23 and Grade 5 alloy in terms of chemistry and mechanical properties. Unfortunately the supplier of this part is either not being forthcoming or doesn't actually know what...
  8. prdave00

    True position of sphere

    Now the attachment....http://files.engineering.com/getfile.aspx?folder=fa252168-9d19-45ef-a26b-6fffecce073b&file=deletemesoon3.PDF
  9. prdave00

    True position of sphere

    Belanger: I'm not sure I see your point. Re FCF B, doesn't the actual center of the sphere have to meet both conditions, i.e., lie within the a .1 diameter cylinder and within the planes separated by .05? In my head, I'm imagining a cylindrical tolerance zone that is .1 in diameter and .05...
  10. prdave00

    Basic dimension puzzler

    I'd speculate this is a way to distinguish some dimensions apart from the others. Maybe an "inspection dimension" or a dimension that changed from the prior revision of the drawing.
  11. prdave00

    Surface profile decision, allow less accuarte clocking

    The attached drawing is similar to a part I have. I need to control the profile of a detente on a spherical part (think construction ball locator with a shoulder) tighter with respect to the center of the sphere (datum D) and the bottom of the shoulder (datum B) to control the surfaces...
  12. prdave00

    True position of sphere

    I need to correct the post... Is there a difference between the following feature control frames (FCF) to control the position of a sphere using the attached intentionally incomplete drawing to put it into context? FCF A |TP|SØ.1|A|B| |TP|.05|B| FCF B |TP|Ø.1|A| |TP|.05|B| My instinct is...
  13. prdave00

    True position of sphere

    Is there a difference between the following feature control frames (FCF) to control the position of a sphere using the attached intentionally incomplete drawing to put it into context? FCF A |TP|SØ.1|A|B| |TP|.05|B| FCF B |TP|Ø.1|A|B| |TP|.05|B| My instinct is that they are equivalent - the...
  14. prdave00

    Plastic Spring Suppliers

    Will a rapid prototype work (SLA, SLS, etc.)?
  15. prdave00

    Reporting surface profile check with CMM

    I recently came encountered an "issue" with a supplier. A 3D surfaced feature with a profile tolerance is being checked using one of 2 CMMs depending on what's available. I should note that the entire sample population from each batch is checked using the same CMM (i.e., both CMMs cannot be used...
  16. prdave00

    Machining causing 316 SS to anneal???

    I've been able to source 316 drawn wire in the spring temper condition from a variety of places. Some even have it waiting on the shelf (although .010 was the smallest I came across in a quick search). Most of these places can also do secondary operations like straightening, centerless grinding...
  17. prdave00

    Hard Coat Anodizing Tapped Holes - Oversized Taps Available?

    OSG offers oversized taps - http://www.osgtool.com/product_list.asp?type=TAP&type2=SPIRAL%20POINT&list=280&Page=1. I've only seen metric or UN threads off the shelf and not pipe. This link explains about oversized taps designated as "H" taps meaning its pitch diameter is on the high side of...
  18. prdave00

    Creating a reference frame - options

    I have a part that I've dumbed down (considerably) and attached 2 options as to how to establish a DRF for purposes of discussion. The drawings are also intentionally incomplete. The part consists of 3 feet with a domed tip that will sit on an irregular surface. There is a also a spherical...
  19. prdave00

    Accelerating stress cracking in PEEK

    I have a PEEK part that is machined with intermittent stress relief heat treatment cycles per the suppliers reccomendations. This component is joined to another in the field using a thread cutting screw where a secondary stress relief cycle is not feasible. Anyone know of a way to accelerate the...
  20. prdave00

    PAEK vs. PEEK what are the differences?

    Polyaryletherketone (PAEK) is the name for the family of polyketone compounds including PEK, PEEK (a name branded by ICI under the Victrex name), PEKK, and PEKEKK amoung others. If it just says PAEK then it could be any those listed in that family.

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