Xinneng Battery Tray CNC Processing

• 1
  What a Battery Tray Actually Has to Do
• 2
  Which Features Belong on a Milling Machine
• 3
  Setup Strategy for Large, Thin-Walled Trays
• 4
  Material Choice Sets the Whole Process
• 5
  Tolerance Stack-Up: Where the Real Limits Sit
• 6
  When CNC Processing Is the Wrong Answer
• 7
  How We Run a Tray Job
• 8
  Tray Feature vs. Best Process

A new energy battery tray is not a box. It is a structural frame, a thermal interface, and a sealing surface at the same time. It carries the module weight through crash loads, keeps coolant channels or cold plates flat against the cells, and holds an IP-rated gasket line around the whole perimeter.

That combination is why the drawing looks the way it does. Wall thickness is set by stiffness, not by looks. The mounting bosses are set by the vehicle frame, not by the tray. The sealing groove is set by the gasket, which is usually a molded part with its own tolerance band.

Xinneng battery tray CNC processing enters the picture when those three jobs overlap on the same part. A stamped shell can be cheap and fast, but a stamped shell cannot hold a flatness band on a sealing land and a machined boss height in the same operation. Milling can.

The trade is cycle time. A tray that takes one stamping hit may take 40 to 90 minutes on a 5-axis machine, depending on size and feature count. That is the number to weigh against rework and leak testing.

Not every surface of a tray needs to be machined. The engineering question is which features carry a functional stack and which are only there to close the volume. Machining the second group costs money and buys nothing.

Sealing lands and gasket grooves are the first group. A groove that varies in depth by 0.10 mm will leak or over-compress the gasket, depending on direction. Face milling a groove to ±0.05 mm depth is routine on a rigid setup.

Mounting bosses and busbar pads are the second group. These mate with fasteners and busbars, so hole position and pad flatness matter more than surface finish. Drilling and spot-facing on a 4-axis mill handles this well when the tray is small enough to index.

Coolant channel covers and cold plate interfaces are the third group. Here flatness over a long span, not local tolerance, is the failure mode. A 0.05 mm bow across a 600 mm cold plate contact area is enough to open a thermal gap.

Lastly, cell stack rails. If the rails are extruded and then machined on the ends only, the mid-span stays as-extruded. That is usually fine. Machining full length is only worth it when rails double as compression stops.

Battery trays are thin-walled and long. Those two properties fight the cutting tool. Clamping force pushes the wall in, and release springs it back, so the part measures correctly on the machine and wrongly on the CMM.

The fix is to stop clamping on the sealing face. Use vacuum fixturing or dedicated soft jaws that locate on the outer frame and support the floor from underneath. Support spacing beyond roughly 300 mm without a support pad invites chatter on floor facing.

For trays up to about 750 × 1,150 × 550 mm, a 5-axis machine with a Ø400 mm rotary table can often do the whole part in two setups. Longer trays that fit our 4,000 × 400 × 150 mm travel need a different plan: machine one end, re-index, and control the joint with a common datum.

Roughing and finishing should be separated in time, not just in tool. Take 1.5 to 3 mm radial cuts in roughing at moderate feed, then let the part sit before finishing. Aluminum moves after roughing. Skipping that pause is the most common cause of a bowed floor.

Tool choice is boring but decisive. Three-flute carbide end mills for aluminum floors, high-feed cutters for pocket clearing, and a long-reach face mill only when the overhang is unavoidable. Long tools chatter, and chatter shows up as a Ra value out of range.

Most trays are 6061-T6 for a reason: it machines clean, welds acceptably, and holds strength after the thermal cycling a pack sees. 6061 is the default unless a corrosion or weight target pushes you elsewhere.

5052 and 5083 bend better and resist salt spray better, but they are gummier under the cutter. Expect lower feed and more built-up edge. If the design is mostly formed sheet with a few machined pads, 5052 may still win on total cost.

7075 gives the highest strength of the common grades, but it is not the right answer near coolant. It has poor stress-corrosion resistance in wet, chloride-rich environments. Use it for brackets, not for a wet tray floor.

Stainless 304 or 316L comes in when the pack sits in a marine or chemical setting. Stainless trays machine slowly, roughly one third the material removal rate of 6061, and they work-harden if the tool rubs. Feed must stay aggressive enough to cut, not polish.

Steel trays appear on heavy commercial vehicles. 4130 or 4140 after machining usually needs stress relief before finish boring, otherwise the bores move a few hundredths after welding.

A ±0.005 mm callout on a single hole is easy. The same number on a hole position relative to a sealing land 900 mm away is a different job. Position tolerance accumulates across the datum chain, and thermal expansion during machining adds to it.

Aluminum expands about 23 μm per meter per °C. A 900 mm tray that warms 5 °C between roughing and finishing can move roughly 0.10 mm if it is not temperature-stabilized. That is the number that decides whether you need a climate-controlled bay.

For most tray features, the practical callouts are: sealing groove depth ±0.05 mm, pad flatness 0.05 mm over 300 mm, hole position ±0.10 mm, and general machined surfaces at Ra 1.6–3.2 μm. Tighter values should be justified by a functional reason.

Sealing faces are the exception. If the gasket is a molded silicone profile with a 30% compression window, the groove depth tolerance must fit inside that window after coating. Anodizing adds 5 to 25 μm per surface, so specify masking or adjust the pre-plate dimension.

We hold ±0.005 mm on features that need it, and we will tell you when a drawing calls for it on a feature that does not.

Machining is a subtraction process, and trays are mostly empty volume. If more than 60% of the blank becomes chips, the quote will reflect it and so will the lead time.

High-volume trays, meaning tens of thousands per year, usually belong to die casting or stamping with a secondary machining pass. The tooling cost is real, but the per-part cost drops far below milling. The sensible split is: cast or form the shell, machine only the sealing land, the pads, and the bores.

Very large trays are a second boundary. Our largest travel is 4,000 × 400 × 150 mm, so a tray beyond that envelope has to be split into sections and joined, or handled by a different process entirely.

A third boundary is wall thickness. Below about 1.2 mm in aluminum, clamping deflection dominates and inspection becomes the hard part, not cutting. Thin walls can be machined, but the fixture design has to be solved first.

One more: prototypes and design iterations. Here milling wins outright. No tooling, changes applied by editing the program, and a first article in days rather than weeks.