Defects - Investment Casting

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

This information is on the top front of the traveler – Areas shown in red

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

Torch Burn

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

Broken Wax

Pic 5.01 height, centered

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

Shell Break

Pic 5.01 height, centered

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