defects - investment casting
TRANSCRIPT
Defects
• Defects – By definition an imperfection, blemish, fault or
deficiency.
• Often leads to REWORK or SCRAP.
• To correct all you need are:
• Exceptionally knowledgeable driven employees that can
identify the right root cause of the defect and then
implement the corrective actions without affecting some
other part of the process.
• This often involves senior management
Defects
• Root Cause
• Identifying the root cause can be difficult due to the
amount of possible variations in each process and sub
process.
• Requires a good understanding of the entire process
• Can even change form foundry to foundry
Defects
• Defect documentation:
• From the start Sure Cast has maintained a documented
defects log data base.
• With any data base it is only as accurate as the
information entered.
• To aid in identification we developed a training for our
defect log, shown next.
NON-CONFORMANCE TICKET
OAF# : Melter/Oven: Notes:
Job# : Qty Required:
Run-Lot# : Qty Inspected:
Customer : Qty Rejected:
Alloy : Code:( ) Qty Approved:
Emp 1: Emp 1 Emp 2
Emp 2: First Knock Out Damage KO
Date: ____/ ____/ ____
Stamp
1 Stamp 2 Final Broken Part BRK
Shop Cut-Off Damage CO
Emp 1 Emp 2 Emp 1 Emp 2Over Blast OB
Wrong Pattern PAT Poor Burnout BO Over Grind OG
Bad Pattern BP Shell Runout / Blowout BLO Straightening STR
Torch Burn TB Shrink SHK Handling Damage HD
Wax Drip SU Hot Tear HT Machining Errors MACH
Wrong Set-Up WSU Gas Holes GH Mag Failure MAG
Broken Wax BW Slag / Dross SLG Penetrant Reject PEN
Broken Shell BS Non-Fill / Cold Shut NF X-Ray Reject XRAY
Shell Lift SL Chrome Pitting SD Non-Gauge NG
Shell Buckle SB Short Pour SP Dimensional Error ENG
Excess Metal EM Wrong Alloy HI Stock STK
Ceramic Inclusion CI Misc. Inclusions IN * Other OTH
* Explanation for Other:
Form QA-NCT-101 Rev 0
Defects
• Defect documentation:
• From there you can point to areas of the log and get
information on how to complete it.
• For instance, the upper left hand corner is our plant
identification information.
• Selecting it would pull up a slide or slides on where to
get that information
This area of the scrap ticket is for part
identification information, including
OAF Number
Job Number
Run & Lot Number
Customer
Alloy Name & Code
Defects
• Defect documentation:
• When you selected a defect area it would pull up slides
on that defect
• For instance Torch Burn
• When you selected this it would bring up the following
information and hints
This happens when the person doing
set-up brings the flame of the torch
across the part while sealing the gates…
Causing a melted spot on the
wax pattern…
Which will be found around the gate
area or were a part is near the gate
of another part on a tree
This is were the wax was melted
Note its closeness to the gate This is what the part should look like
Defects
• Defect documentation:
• This helps them identify torch burn over non-fill for
example by pointing out its proximity to the gate and the
gate seal operation.
• This is how process understanding can aid or in lack of
understanding fault the true identification or root cause
Defects
• Root Cause
• The same can be said for a partial casting from a broken
wax or a broken shell.
• The part can be very close but the root cause far away
This happens when a wax pattern is
broken before shell is applied …
Causing an incomplete part to
be produced…
Which will have clean lines across
the broken area
Pic 3.51 height, 1
space in from edges
Pic 3.51 height, 1
space in from edges
Here is a comparison of a
broken shell to a broken wax
The broken shell on the left
has a ruff depression at the
break
Were the broken wax on the
right has a smoother
protruding break
Shell
Wax
You can see
the grain
structure of
the wax were
it has broken
Pic 7.01 height, Centered
with arrows and notes
The surface texture of the break tells you when it happened
This happens during the dipping process
when a piece is broken off of a part…
Causing an open hole in the
shell after de-wax…
Which is filled with to prevent metal
from leaking in casting
Pic 3.51 height, 1
space in from edges
Pic 3.51 height, 1
space in from edges
The application of ram causes
the cast part to have ruff
depression inward at the
break and a fine thin edge
around the break
Here is a comparison of a broken
shell to a broken wax
Note the broken wax on the right
has a smoother protruding break
Pic 3.51 height, 1
space in from edges
Pic 3.51 height, 1
space in from edges
Shell
Wax
Pic 7.01 height, Centered
with arrows and notes
The surface texture of the break tells you where it happened
Defects
• Back to finding our Root Cause
• While our system was good for assuring they found the
right cause, it wasn’t good for identifying one. It was
more to let them know when the found the wrong one.
• Still requires a good understanding of the entire process
• Some defects could still change form foundry to foundry
• Our answer to this was a picture category where you
could scroll through thumbnails to find a similar defect
and then pick the defect training.
Defects
• Each time we addressed this it improved but each
system was made by people that had a lot of base
knowledge, and each system was still relatively slow for
those newer in the industry.
• The time spent on our internal systems shows the need
to develop a better industry wide system that can be
used to train employees and in some cases customers.
• The ICI has come up with such a system to better
identify these defects. And with that I turn this over back
to them