Polymer suitable for maching thin walls

[offanon]

I’m looking for a material I can use to house an outdoor electrical device. The housing is to be machined. The housing needs to be 40mm deep to accommodate a 25mm deep semi-circular cut. This semi-circular cut has a 0.5mm wall at each end. We have tried nylon but the 0.5mm wall distorts beyond acceptable levels. Would FR4 accommodate this design? Has anyone successfully used a polymer to machine thin walls with a 25mm depth? Is this even achievable with machining?

 

[ornerynorsk]

Waterjet might be a suitable solution for this, at least for the through-profile portion of the part.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[1gibson]

That drawing screams "3D print me" when I look at it. Or make a master out of aluminum, then make a silicone rubber mold, cast with resin? If you do that, you might omit the smaller dia holes and drill those separately.

Maybe something glass filled would be more stable if you HAVE to machine it?

 

[btrueblood]

I'd doubt the part you show is even mold-able, much less machine-able. Why so thin?

You might think about machining the slot while the material still has a lot of wall left along the top edge, then pouring wax into the hole to act as support, then machining the top surface to size. I probably won't help much, but it's all I've got.

 

[offanon]

The housing holds a split CT, the distance between the cores is critical to the functionality of the circuit. I require a 1mm gap between the two cores. That gives 0.5mm each side.

 

[Pud]

You don't mention where in the World you are, but see if this stuff or equivalent is available: Tufnol.

The cotton fabric based is not the easiest to clean machine but the paper based stuff is. I see they machine their product as well - might be worth a RFQ as they will let you know if it can be done.

Cheers

Harry



www.tynevalleyplastics.co.uk

It's ok to soar like an eagle, but weasels don't get sucked into jet engines.

 

[mcgyvr]

Is distortion during machining the problem or just a "weak" feel in the end product?

I've machined some pretty darn thin features in type 1 gray PVC.. Of course its all about speeds/feeds/flute type,etc...
A "roughing" pass to remove most of the material (leave a 1.5mm or so wall) then a fine "finishing" pass to machine to final thickness should help..

 

[rickfischer51]

POM (Delrin and Celcon) are easily machined, and I think they have pretty good electrical properties.

 

[johnokelly]

We tried using Delrin but the wall distorted. Im not worried about the feel as the part shown is only half the assembly. The other half sits back to back with the thin wall so nobody will ever be able to feel it once its assembled. Its the distortion that I am concerned about. Ive requested a quote for the manufacture of the components from Tufnol. I'll also try the Type 1 PVC, thanks for the tip.
'

 

[ndsram]

HI try some Glass Filled Nylon material where it has good strength and machinability or Glass Filled Phenolic Material has good strength but machinability is little bit doubtful. Check if you can purchase some PEEK or PAEK if they are availablereadily

Regards
N D Senthil Ram

 

[chicopee]

I like 1Gibson and ndsram ideas, however, would dielectric strength be a factor?

 

[rickfischer51]

Machining a glass filled material is not a good idea if there is any stress on the part. The machining will cut into glass fibers and they will intersect the surface, resulting in stress concentrations. This will greatly reduce strength in general, and impact and fatigue strength in particular. Normally when a part is molded from glass filled material a neat surface layer several mils thick forms against the tool wall and prevents the glass from penetrating the surface. Machining removes that and cuts into the fiber.