Small pieces are often a problem for conveying technique and especially with regard to the machine discharge by means of reject chutes, because they get stuck easily.
In case of cleanroom conditions, there are two further requirements: consistent prevention of abrasion and easy cleaning facilities.
For this case, MTF has developed a new reject chute and already applied for patent for it. The chute is not equipped with changover flaps but with a rotating center shaft which is tiltable in three directions.
The rotating shaft is designed without any gaps, as the runoff plate and the lateral guidings are fixed together.
This effectively prevents deadlocks and abrasions and allows simple cleaning, as the rotating shaft is positioned within the gear drive and the ball bearing outside the chute body.
In order to discharge good parts, QA-parts and sprues separately, usually a pneumatic drive is chosen. If the switchover process has to be done very quickly (e.g. for separating good parts and sprues ejected at a delay) a servo drive is feasible.
As an option, the product contacted parts of the selection switch can be equipped with a teflon coating (FDA-approved), in order to have a smooth slide of parts into the lateral shafts.
In this example, medical plastic parts are produced in cleanroom conditions. A 3-way-chute serves to conduct the parts in 3 directions:
- Good parts are conveyed via an angled conveyor to a buffer station.
- Sprues and rejects are dicscharged centrally downwards into a box.
- Quality shots are directed to the operating side.