What matters on this part
Two things decide whether a frame housing works: a continuous magnetic path, and a bore that stays concentric with the frame. Deep drawing gives both, because the wall is formed in one piece and the bore and the outside diameter are formed against the same tool axis. We draw these frames from DT4E pure iron, DC04 or magnetic stainless such as 430, on presses from 25 t to 350 t, with the tooling designed and built in-house.
What the part does
In a solenoid valve the coil produces a field, and the frame closes that field around it so the armature is pulled with enough force to move the valve. The frame therefore has three jobs at once: carry flux without saturation, hold the bore that guides the armature, and survive the assembly and the operating temperature without distorting. A welded or laminated frame introduces joints into the magnetic path; a drawn frame does not.
Grades we draw for magnetic circuits
| Grade | Why it is chosen | What to watch |
|---|---|---|
| DT4E pure iron | High permeability and low coercivity: the reference material for the magnetic path | Soft and easily dented; handle and store with care |
| DC04 low-carbon steel | Good formability with usable magnetic properties; the economical choice | Permeability below pure iron; confirm flux requirements first |
| 430 ferritic stainless | Magnetic and corrosion resistant where the valve sees moisture | Less ductile; flatter draw steps |
| 316 / 316L | Where corrosion resistance dominates and the magnetic duty is light | Austenitic, so essentially non-magnetic |
Why drawing rather than welding or stacking
- One piece, one path. A drawn frame has no joint in the flux path, so there is no air gap to close and no weld to inspect.
- Concentricity from the tool. Bore and outside diameter are formed against the same axis, so runout is a property of the tool rather than of how the part was clamped.
- Wall thickness under control. Where the frame has to be thin, the wall is reduced by ironing and held to tolerance instead of being machined away.
- Volume economics. Once the tool is built, the piece price falls with the batch; strip layout decides the material utilisation.
Our means
| Item | Range |
|---|---|
| Presses | 25 t to 350 t, single station, progressive die and transfer |
| Maximum draw diameter | Ø250 mm |
| Wall thickness (published housing configurations) | 0.25 mm to 1.00 mm, most commonly 0.50 mm |
| Tooling | Designed and built in-house, in the same plant as the presses |
| Documentation | ISO 9001:2015 processes; FAI and PPAP-compliant documentation; IMDS data for automotive part numbers |
Flux requirement, bore tolerance and wall thickness are confirmed against your drawing; where the magnetic duty is critical we would rather check the grade before quoting than after the tool is cut.
Frequently asked questions
Why not machine the frame from bar?
For small quantities, machining is a reasonable route. Once the part is a thin-walled frame in series, drawing wins: it removes the material rather than cutting it away, and it forms the bore and the outside in one piece, which is what keeps the magnetic path continuous.
Which grade should I specify for the magnetic circuit?
DT4E pure iron gives the highest permeability and the lowest coercivity; DC04 is the economical alternative with usable magnetic properties; 430 is magnetic and corrosion resistant but less ductile. Tell us the flux the valve has to develop and we will confirm the grade against the drawing.
Can the frame be drawn and then machined?
Yes, and it is often the right combination: draw the body, then machine the faces where a tight tolerance or a sealing surface is genuinely required. A drawn wall and a machined face belong to different tolerance classes, and the drawing should say which is which.
What documentation comes with the parts?
Dimensional and geometric checks are recorded in our own inspection lab; for series programmes the quality team releases first-article inspection reports and PPAP-compliant documentation, and provides IMDS data for automotive part numbers. Material traceability comes from mill certificates held against the batch.
Related pages
Written by the Balford technical team, Zhuji, Zhejiang. Last updated 8 October 2026.