2. Ducommun, Inc.
• Publicly Traded (NYSE: DCO)
• Oldest Company in the State of California;
Founded in 1849
• Three Business Units
– Ducommun AeroStructures (DAS)
– Ducommun Technologies (DTI)
– Miltec
• 2007 Combined Sales $367M
• $1 B Sales in 2012
4. • Company Headquarters – Gardena, CA
• 2007 Annual Sales > $215m
• Centers of Excellence:
– Gardena, California
– Monrovia, California
– Orange, California
– El Mirage, California
– Parsons, Kansas
– Guaymas, Mexico
DAS Fundamentals
5. DAS Centers of Excellence
Monrovia, CaliforniaGardena,
California
• More than 1m sq. ft.
• 6 facilities
• 1000+ employees
Orange, California
El Mirage, California
Parsons, Kansas
Guaymas, Mexico
6. 70,000 sq. ft.
Center of Excellence – Chem Milling and
vertically integrated processes
El Mirage, CA
7. El Mirage, California
• Aluminum Chem Mill
5 Tanks – up to 24 ft deep
• Titanium Chem mill
9 Tanks – up to 15 ft deep
• Steel Chem mill
10 Tanks – up to 6 ft deep
Size: 5,000 gal to 50,000 gal
13. Chemical milling is a milling
process by the use of chemicals
to achieve intricate structural
features which may not be
easily obtained by mechanical
milling.
17. Chemicals involved in this process are:
HF, Hydrofluoric acid
HNO3, Nitric acid
Dissolved titanium
Surfactants
Water
18. During the chem mill process, titanium metal
reacts with warm aqueous hydrofluoric acid solution
to form soluble titanium hexafluoride and hydrogen
gas and heat.
Ti + 6 HF → Ti F4 ∙ 2 HF + 2 H2 ↑ + Δ
titanium hexafluoride
19. Titanium alloys have strong tendency to adsorb hydrogen gas and render
the chem milled parts brittle.
In order to remediate the hydrogen embrittlement of titanium during chem
mill, nitric acid is added in the solution to remove the hydrogen gas as
soon as it is formed.
2 HNO3 + H2 ↑ → 2 H2O + 2 NO2 ↑
21. Also, in the presence of nitric acid, the chem milling
rate of the solution is reduced.
Therefore, it is important to maintain a certain ratio
of nitric acid to hydrofluoric acid (free acid) to
achieve good chem milling results.
22. Considerations in Chem Milling
1. Type of alloys
Ti-6AL-4V
Ti-Beta 21S
2. Fabrication methods of parts
3. Geometry of parts
4. Parts racking/orientation
5. Parts movement
23. 6. HF, HNO3 and Ti concentration
7. Tank temperature
8. Tank mixing
9. Operator
25. Titanium 6AL-4V
• Typical alpha, alpha-beta Ti 6AL-4V,
etchant performs well with etch rate about
0.8 mil/min.
• The free acid is between 2 - 5 N,
• Fluoride 3 – 8 N,
• Nitrate 0 - 3 N
• Dissolved Ti < 90 g/L
• 95 F
26. Titanium Beta 21S
• Etchant works well with etch rate about
0.3 mil/min
• Free acid 6 - 14 N,
• Fluoride 2 – 7 N and
• Nitrate 4 - 9 N
• Dissolved Ti < 40 g/L
• 95 F
28. SPF Titanium
• Etchant gives good result with etch rate of
0.8 mil/min.
• Free acid 2 – 5.5 N
• Fluoride 3 – 8 N and
• Nitrate 0 – 3 N.
• Dissolved titanium < 90 g/L
• 95 F
32. • Sheet (vertical straight down, mid of tank
depth wise).
• U-shape long blade, open end up and
slanted.
• Cylindrical, small opening down when
etches outside.
• Avoid gas trapping
• Past experience
43. • Etch rate increases as temperatures increases.
• Etching process is an exothermal reaction that
means heat will be generated during the process
• Tank size
• Surface area to be etched
• Etching rate
• Agitation/mixing of the solution
• Depth of cut
47. • Any procedures no matter how carefully
designed and written serves no purpose if it
is not prudently executed.
• Dedication
• Open minded
• Observance
• Accountable
• Integrity
• Always positive
Ducommun inc. is the oldest company in California found in 1849.
Publicly Traded (NYSE: DCO)
Currently it has three Business Units
Ducommun AeroStructures (DAS)
Ducommun Technologies (DTI)
Miltec
2007 total revenue of $367M
Ducommun AeroStructures has six centers of excellence. 4 located in southern california, one in kansas and one in mexico.
It is headquartered in Gardena, California with sales in excess of $215 million.
The 70,000 El Mirage facility is part of our chem mill center of excellence
In El Mirage, the main focus of operation is chemical milling of Al, Ti & Steel parts.
Currently, in El Mirage, we have 5 tanks dedicate to Aluminum alloys etching, 9 for titanium alloys and 10 for steel alloys etching with tank sizes varies from 5000 to 50,000 gal.
I’ll only focus on ti chem mill today.
But if you have questions related to Al & steel chem mill, I’ll be glad to answer it at the conclusion of this presentation.
Ducommun AeroStructures is one of only two companies that has perfected this waffle duct pattern of chem milling.
F-16 F-110 engine waffle duct in the etchant line. This is an ortho grid, versus the pattern on the JSF duct. Ducommun AeroStructures can do both isogrid and orthogrid, which differentiates our chem mill capabilities from other companies. The PVC rack in this photo is a rotational fixture used to ensure equal material removal while in the etchant tank.
Titanium part that has been descaled. It’s being checked to verify scale removal. Check with Art on these – this is Pauline.
Now let us talk about chemical milling of titanium.
As the name indicate,
Typical chem milling processes include ……………
Today, I’ll only focus on chemical milling and the related issues.
The desired results for titanium chemical milling can be summarized in here.
After define the goals, let us look at the reactions in the titanium chem mill process.
First let us find out what is in the chem mill solution.
Among these chemical, HF is responsible to perform the chem milling of the alloys.
All other chemical is either used to facilitate the removal of titanium or the by product of the chemical milling.
It looks like a very simple reaction.
Notice the formation of hydrogen gas.
If leave it alone, the hydrogen gas will penetrate the parts and increase the hydrogen content of the resulting parts.
By adding nitric acid, which is a strong acid, in the system, a much more complex situation is developed.
Depend on the type of titanium alloys, all these soluble molecules can co-exist in the solution in unknown proportion.
Once we are familiar with the reaction. Now let us take a look at what we shall pay attention to when performing Chem milling.
Based on the experience we accumulated, at least 9 factors need to be consider when perform chem milling.
In this picture, we can notice the uniqueness of chem milling
A close-up of the structural detail.
Structural detailed at an angle.
Here is the cross-section profile of the web.
With this approach, we be able to reduce the total weight by 2/3 of the original weight and retain good structural integrity.
This result was obtained by repeat masking, scribing, chem mill, masking scribing and chem mill processes.
The fixture enable the parts to spin and rotate at the same time.
The actual concentration limits are trade secrets.
Mixing homogenize temperature and the acids in the tank.
