recommend an electric switch plastic casting material?

Trying to figure out which plastic to use to cast the insulation insides around the brass metal contacts of a vintage DC rotating switch that does carry a lot of amps.  So the plastic has to be wear resistant against the brass contacts sliding across and resistant  to the heat created from the current being drawn thru the contacts.

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jjames394 years ago

Electric injection molding machines are coming into wide use in the case of injection molding machines with mold clamping forces of 1800t or less. In order to bring out to the maximum extent the excellent features possessed by fully electric injection molding machines, it is very important to carry out mold design giving attention to the following factors.
(1) Accurate positioning

In a fully electric driven injection molding machine, although it is possible to carry out at high speeds the opening and closing of molds, in order to prevent breakage or abnormal wear at the time of contact between core pins while carrying out accurate positioning of the cavities on the movable side and on the fixed side, it is recommended to install precision positioning guides.
The recommended Misumi standard components are:
- Tapered tweezers TPN, etc.
- Tapered block sets TBS, etc.
- Side straight block set TSSB, etc.

(2) Smooth operation of the ejector plate

In a fully electric motor driven injection molding machine, although it is possible to carry out operations of ejector plates such as high speed operation and multiple stage ejection, if the construction is not designed so that the operation of the ejector plate is smooth, biting of the ejector pin or biting of the return pin are likely to occur.
Therefore, it is recommended to use an ejector guide system.
The following Misumi standard components are being used widely:
- Precision ejector guide pin EGH, etc.
- Ejector guide bush EGBH (Plain type)
             EGBZS (Copper alloy non-lubricated type)
            EGBL (Linear type)
            EMBS (Ball slider), etc.

Further, it is recommended to install a switch for confirming the returning of the ejector plate.
For this purpose, the following are recommended:
- V-156-1A5-T (Micro switch)
- MGXL-8F (Contactless type)

(3) Smooth operation of the slide core

Smooth operation of the slide core is also important. In order to prevent biting, it is recommended to provide a lubricating groove in the guide rail, or to use a non-lubricating type material (oil free metal).
The following Misumi standard components are recommended:
- GR5SCM (Guide rail with groove)
- SRTL (Non-lubricating guide rail)
- CGZ (Non-lubricating center rail)
- STW (Non-lubricating slide plate). cck elisa kit

(4) Stabilization of the cavity surface temperature

In order to stabilize the molding conditions, it is very important to stabilize the mold cavity surface temperature. In order to achieve this, it is recommended to use the following standard components:
- HIP (Thermal insulation plate), etc.
- M-HTM3021 (For cartridge heaters)
- Mold temperature controller: PID control type

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iceng4 years ago

Try "Halar® (ECTFE)
- Ethylene-Chlorotrifluorethylene copolymer exhibits better mechanical
properties than many other fluoroplastics. But like other
fluoroplastics, its flame retardance, chemical resistance and low
dielectric constant remain constant over a wide temperature range. These
qualities make it suitable for use in such products as electrical
insulation, monofilament, tank linings, housings, and electrical
components. It may be usefully employed at temperatures from the
cryogenic range to about 330ºF."

Personally I like use Delrin because I can afford the cost and have access to scrap pieces.

Veewee111 (author)  iceng4 years ago
Thank you. Will put Halar on the list, but have not found it in a room temperature castable form to keep it from costing too much with low production.
We have Delrin also at work, will start picking up the scraps, but either way looks like will need CNC machining.
verence4 years ago

> "heat created from the current .. thru the contacts."

If there is any heat, your contacts are not good enough.

Veewee111 (author)  verence4 years ago
Totally agree, but if the switch gets a bit of corrosion in it, I do not want the switch to just melt down if some heat is generated.
Have seen same problem with repro fuse boxes vs originals. The originals hold up much better to heat.