We offer deep draw stamping up to 315 tons with steel, stainless, aluminum. Holds ±0.05 mm, in-house tooling, laser cutting, welding, assembly. ISO 9001, inspection reports per batch.

Deep draw stamping up to 315 tons in steel, stainless, aluminum. Forming, annealing, trimming, piercing, finishing. DFM support, documented inspections, subassembly. Consistent ±0.05 mm tolerance across production volumes

1. What Deep Draw Stamping Really Is

Deep draw stamping isn’t just “metal stamping with a deep shape.” It’s a cold forming process where a flat blank is pulled into a die cavity through a series of reductions. The blank holder or draw pad controls metal flow so the material thins predictably instead of wrinkling or tearing. When the depth of the drawn part exceeds its diameter, we call it deep drawing.

We use the process when a part needs a seamless, hollow shape—think cups, cans, enclosures, housings, deep shells. It’s the right call when you need:

One-piece construction instead of welded assemblies

Superior grain flow for fatigue resistance

Tight thickness distribution (±0.02 mm can be achieved with proper ironing)

High production rates once tooling is proven

It’s the wrong process if your part has heavy side features that require extensive post-piercing, if your volumes are only a few hundred, or if your budget can’t handle the upfront tooling cost. In those cases we’ll tell you to look at CNC machining or fabricated sheet metal. I lose a few jobs that way, but I don’t get returns.

Deep draw vs others – quick comparison

One thing nobody tells you: a lot of parts designed for deep draw actually start life as machined prototypes. The prototype works great, so nobody revisits the design. Then when you try to deep draw it, the corner radius is too sharp, the draw ratio is impossible, and the flange cracks. That’s why I always ask, “How was the first sample made?”

2. Real-World Applications by Industry

Over 20 years, I’ve watched deep draw stamped parts show up in places you’d never expect. Each industry has its own pain.

Automotive

sensor housings, fuel pump shells, solenoid bodies, heat shields. Corrosion resistance and thermal cycling matter. Stainless steel and aluminized steel are common. Tolerance creep here can cause a warranty recall. We supply Tier-1 and aftermarket.

Home appliance

washing machine tub flanges, refrigerator hinges, oven burner bowls, dishwasher spray arms. Cost is brutal, but the shape must be right or the assembly line jams. We hold 0.1 mm on large drawn stainless flanges because we use hydraulic cushions, not just springs.

Furniture & shelving

chair bases, table pedestals, display racks. Often tubular or conical shapes from galvanized steel. The surface finish IS the product. A scratch from poorly maintained tooling kills a retail sale.

Industrial equipment

filter bodies, pressure vessel ends, motor end bells, conveyor rollers. Thick material, often 3–5 mm steel. That’s where the 315-ton press earns its keep. Many shops can’t draw 4 mm CRS into a 200 mm deep shell. We can.

Medical & food equipment

seamless stainless trays, containers, panels. Sanitary finish. We sometimes do post-draw passivation and electropolishing in-house.

If you don't see your industry, send the print. We’ve done parts for everything from boat cleats to solar inverter housings. The physics of metal flow doesn’t care what label you put on the product.

3. Materials Selection Guide – And the Mistakes That Cost You

Choosing the wrong alloy is the single most common reason deep draw parts fail. Here’s what I wish every buyer understood.

Common mistakes I see every month:

1. “We’ll just use 6061 because it’s what we know.” 6061 work-hardens and cracks in deep draw unless you anneal between draws. Tooling cost doubles. Use 5052 or 3003 instead.

2. Specifying stainless 304 for a part that only sees indoor use. It’s 3× the cost and 2× the tool wear of cold rolled steel with powder coat. I’ll tell you if you don’t need it.

3. Ignoring material thickness tolerance. Chinese mills often deliver “2.0 mm” that measures 1.85. That 0.15 mm is the difference between a good draw and a wrinkled flange.

4. Designing a part that needs deep draw but also needs sharp external threads. Deep drawn shells are best coupled with welded inserts or secondary machining. Trying to thread thin drawn walls is a recipe for stripped fasteners.

4. DFM Advice – Designing Parts That Actually Draw

I spend a lot of time fixing designs that should have been reviewed before tooling was cut. Here’s what you should check on your drawing right now.

Draw ratio (blank diameter / punch diameter)

For steel, keep under 2.0 for a single draw. Higher ratios need redraws or annealing. Too aggressive, and the bottom tears out.

Corner radius

inside radius should be at least 0.8 to 1× material thickness for steel, larger for stainless and aluminum. Sharp corners are stress concentrators.

Wall thickness

expect 20–30% thinning in stretched areas. Don’t put critical mounting holes in those zones. We can redistribute material with proper blank development, but physics limits how much.

Hole locations

never place holes near the die radius or flange edge where metal flow is unstable. They distort. We pierce after drawing whenever possible.

Flange width

minimum 4× material thickness for a flat flange. Narrow flanges curl and lose flatness. We add extra trim stock and then finish-trim.

Material flow

use draw beads or blank holder steps to control wrinkling, but be careful: too much restriction increases thinning and scrap.

Cost drivers

deep drawn parts with large open areas (like a wide, shallow pan) waste material. Better to reduce flat areas and leave them for a secondary trim die.

If you send us a 3D model, I’ll give you a redlined DFM report in 24 hours. Not just a “looks good”—I’ll tell you where it will tear, where it will wrinkle, and what it will cost to fix. No charge for that.

5. Our Deep Draw Manufacturing Process – And Why Each Step Matters

When we take a job from flat sheet to finished part, here’s the sequence. If a shop skips one of these steps, the cost pops up later.

1. Material inspection

we verify thickness, hardness, coating weight, and certificate of analysis. If the coil doesn’t match the spec, it goes back.

2. Blanking

laser or shear. Blank shape is calculated from finite element methods or from years of trial. A 2% blank shape error can cause a 20% thinning variation.

3. First draw

forms the basic cup or shell shape. We control punch speed, blank holder force, and lubricant film thickness. The 315-ton press gives us enough force to hold the blank flat without starving the corner radius.

4. Redraw(s) 

further reduces diameter and increases depth. Between draws, we may anneal (stress relieve) stainless or hardened steel. Without annealing, the material cracks.

5. Trimming

removes the wavy edge (earring) to create a precise rim. Done in a trim die or with laser cut for complex shapes.

6. Piercing

holes, slots, louvers. Always after drawing so holes don’t distort. Progressive dies can combine some steps, but we sequence based on the part.

7. Annealing (if needed)

heat treatment to restore ductility before the next forming step. We control temperature and time to avoid grain growth.

8. Surface finishing

deburring, cleaning, oil removal. Then whichever coating the spec requires.

9. Assembly

we weld brackets, press in studs, or attach hardware. Done on the same campus so nothing gets lost in transit.

10. Final inspection & packaging

full dimensional report, surface inspection, then customized packaging to prevent transit damage. You receive the inspection data with the shipment. No hiding bad CMM reports.

6. Tolerance: The Truth About ±0.05 mm

Many tooling shops will tell you they can hold ±0.05 mm on a deep drawn part. That’s true on one part, on one day, on one machine. Holding it across a run of 20,000 pieces is a completely different animal.

What breaks tolerance in production:

Tool wear

stamping dies wear. A sharp corner erodes, material flows differently, dimensions shift. We track tool hits and measure every 500 pieces. After 50,000 strokes, we resharpen or replace.

Material variation

different coil heats have different yield strengths. A softer batch flows more, walls get thinner, OD changes. We test incoming material and adjust process parameters.

Temperature

the press, dies, and parts heat up. Thermal expansion of 0.01 mm per 100 mm is typical. On a 200 mm diameter, that’s 0.02 mm. We run a warm-up cycle before production to stabilize.

Lubricant film

too much lubrication causes floating, too little causes galling. Both affect final dimensions. We maintain consistent application.

When we quote, we include exactly which features will be held at 0.05 mm and which will have ±0.2 mm because of the metal flow. We use CMM and optical measurement to verify. The report goes to you. If a feature drifts, we stop and adjust—not wait until the order is done.

7. Surface Treatment Selection for Deep Drawn Parts

A deep drawn part usually needs protection or a cosmetic finish. Here is how we help you pick.

Powder coating

good for steel and aluminum; durable, many colors. Not for tight-threaded areas. We pre-treat with phosphate or chromate for adhesion.

Electrophoresis (e-coat)

great for complex shapes and inside cavities. Uniform coverage, excellent corrosion resistance. Used a lot in automotive brackets.

Anodizing 

aluminum only. Hard anodize for wear, decorative for appearance. Note: anodizing adds dimension (half the coating thickness).

Galvanizing

hot-dip or electroplate. For outdoor applications. Watch for distortion on thin drawn parts due to heat. We often send out after forming.

Passivation

stainless steel. Removes free iron, restores corrosion resistance. Mandatory after welding or forming.

Oil coating

temporary rust prevention. Good for parts that will be further processed. Cheap but requires cleaning at the next stage.

Black oxide 

mild steel. Minimal dimensional change, nice matte black look. Not great for corrosion alone; usually needs oil.

If you are unsure which coating fits, tell us the environment (indoor, outdoor, chemical exposure) and whether the part will be touched. We will suggest a cost-effective option. You’d be surprised how often people over-spec a coating, adding 30% to the part cost for no reason.

8. Quality Inspection – More Than a Checklist

Our independent quality center is not a closet with one caliper. It includes tensile test equipment, CMM (three-axis), surface roughness testers, hardness testers, and a dedicated inspection team.

Incoming quality (IQC)

raw material certificates are verified, we measure thickness and hardness on every coil. We reject material that’s out of spec before it hits the production floor.

In-process (IPQC)

first-off inspection every setup; then periodic sampling every 500 parts. CMM data is logged and trended. If a dimension trends toward the control limit, we stop and correct.

Final inspection (FQC)

statistical sampling (AQL 1.0 or per customer agreement). We check critical dimensions, appearance, surface finish, thread engagement, weld integrity. Reports are signed and shipped with parts.

Material verification

for stainless and aluminum grades, we use handheld XRF analyzer to confirm alloy composition. You won’t get 304 when you paid for 316.

It costs us time and money, but it costs you far less than a container full of rejected parts at your receiving dock.

9. Common Purchasing Mistakes – Learn from Others’ Pain

I’ve seen buyers burn their budgets on these traps. Don’t be next.

Chasing the lowest quotation

the cheap shop is saving money somewhere: thinner material, softer tool steel, no annealing, no incoming inspection. Six months in, the parts mushroom, rust, or crack.

Material substitution

304 replaced with 201. 5052 replaced with cheaper 3-series. Unless you test, you won’t know until field failures. We provide mill certs with every coil.

Negative thickness tolerance

supplier takes the full minus tolerance (e.g., 2.0 mm becomes 1.85) to save material. A deep draw die designed for 2.0 mm will wrinkle with 1.85. We design for mid-range and don't allow full minus.

Ignoring tooling life

cheap tooling lasts 10,000 shots. Then dimensions drift. Amortize tooling over the projected life, not the first order. We build tools for 500,000 shots minimum.

Tolerances tighter than the process can hold

±0.02 on a deep drawn feature across a 300 mm part is not realistic without secondary machining. We will push back, but we’d rather you think we’re stubborn than ship bad parts.

Basing a purchasing decision on 5 samples alone.

Samples are hand-picked. Demand a capability study (Cpk/Ppk) from the production run, not the sample run. We provide that data upfront.



10. How to Choose a Deep Draw Stamping Factory – A Practical Checklist

Use this when you evaluate suppliers (including us):

1. Press tonnage and bed size

can they draw your future larger part, or will you have to re-source?

2. Tooling design capability

ask to see a DFM example. Does it address draw ratio, thinning, material flow?

3. In-house secondary processes

fewer handoffs mean fewer delays and finger-pointing.

4. Inspection equipment & records

ask for a sample inspection report from a recent similar part. No report, no control.

5. Material certification 

do they provide mill test reports? Can they verify alloy on-site?

6. Production capacity 

how many strokes per day? Can they handle your peak demand?

7. Communication

who will you talk to when there’s a problem? An engineer or a salesperson?

8. Visit the factory 

watch a tool change, see the first piece come off, check the scrap area for trouble jobs.

If a factory welcomes your quality audit and can explain their process in plain language, they are likely honest. If they get defensive about tolerances or hide the inspection room, walk away.

11. Why Buyers Work With RongHai Precision Metal

We are not the biggest factory. We compete on two things: engineering honesty and batch consistency.

• 20+ years of personal experience means I have seen most deep draw failures before you draw your part. I’ll tell you when your design needs adjustment, and I’ll fight to keep it manufacturable before you spend money on tooling.

• The 315-ton bed gives us headroom. While other shops are running their 160-ton press at 110%, we are at 70% and in full control. Less vibration, better part quality.

• Our ISO 9001 system is not a paperwork exercise. Every batch comes with a dimensional report. If the CMM shows a deviation, we will call you before we ship.

• We’re equipped to laser cut, CNC machine, and weld drawn parts. You get a finished subassembly, not a box of parts needing five more suppliers.

Send us your RFQ. I’ll personally review it, give you an honest assessment, and quote you a price that includes all the things that keep the part in spec over the long run.

Before you commit to a deep draw supplier, spend ten minutes on our knowledge base. We’ve written practical guides covering DFM for deep drawn parts, material selection for stamping, how to audit a sheet metal factory, and explanations of common forming defects. These aren’t marketing fluff—they are field notes from the shop floor to help you make better sourcing decisions.