Milling sheetmetal

In prototyping we often need sheet metal parts on a quick turnaround.

The basic premise: Glueing down the sheetmetal onto an aluminium carrier to cut out the parts with an endmill.

In this case the sheet metal is hardened stainless spring steel, with an aluminum AW5083 tooling plate as the sacrificial plate. The tooling plate is very nice for this purpose, as it is already reasonable flat. The superglue used is not very critical, any thin viscous superglue will work, in this case I use a rubberized shock resistant glue, similar to Loctite 380 Black Max:

The sheet metal and the sacrificial plate get cleaned with scotchbrite and washed down with clean acetone. After layout out where to put the sheet metal, superglue is applied in a more or less the whole needed surface on the sacrificial plate. After adding the sheet metal on top, it can be floated in position for a short period of time.

The next step is optional, clamping or weighting the sheet metal down. This is mostly important if more than simple 2D shapes are needed, like chamfers, steps or slots with a precise depth. In this case I added a large steel piece to weight the sheet metal down.

Curing time can be anything between a few minutes and multiple hours. As per experience, 15 minutes are usually fine – But with critical or expensive materials I will leave it over night to cure.

All that remains is to clamp the sacrificial plate with the sheet metal glued to it to the table off the milling machine (or in a vice):

For cutting out the parts I prefer a small endmill, between 1mm and 2mm diameter. In this case I used a 1,5mm endmill:

The waste can be ripped off after cutting out the parts:

To release the parts from the sacrificial plate, you have different options:

• heat
• mechanical
• solvent

Superglue remains can be removed with acetone.

In this case I used a knife to lever the parts off the sacrificial plate.

Washed off with acetone, deburred with a cratex stick and scotchbrite:

Small parts cut from spring bronce, the cutter used was a 0,6mm three flute endmill. The parts where released with a scalpel blade from the sacrificial plate.

Regarding the machining process:

• the whole contour is cut as a continous spiral, about 0,05mm pitch
• no roughing/finishing, I cut the contour to final dimension right away
• Small endmill (I like three flute with a corner chamfer, between 1m and 2mm. Speeds and feeds are very forgiving, no matter the material, I will run it at about 12000-15000rpm, 1200mm/min and 0,05mm doc in a continous spiral toolpath)
• Definetly cut trough the sheetmetal into the sacrificial plate - That way you negate cutter wear and clean, square sidewalls on the parts are a result.
• Depending on the material, cutting oil can be a very good idea. But many materials like hardened spring steel or stainless steel can be cut dry.