How To Select A Pick and Place Machine-News-Wave Soldering Machine-Soldering Machine | Wave Soldering Machine

Most pick and place machines will handle a fairly wide variety of board sizes, with a work table designed to accommodate boards up to 16” x 24”. There is also ease of control over the components, which aids in accuracy, along with a simple learning curve. In most cases, no training is required.

Don’t overlook electrical requirements. Make sure the machine you buy will plug-and-play in your environment without pulling in new wiring or else plan on an adapter/transformer.

We will start by talking about two aspects of machine capability – accuracy and repeatability, and Pick and Place centering methods.

For production machines, we typically recommend looking for a machine with accuracy of +/- .001” and down to fine pitch capability of 12 mil on a repeated basis. Less expensive machines often don’t meet this spec, so that’s something to be aware of.

Most low-cost machines will also not come standard with a computer or software which could help with the repeatability aspects if not the accuracy. While some may offer enhanced technology – most do not.

1. Method 1: No centering mechanism other than relying on the component’s pick-up point for placement. In other words, the part is not physically centered after being picked up by the tool head, and if it’s picked off-center on the tool, it will be off-center when placed on the board. This is obviously not a very accurate placement method because there is no definable tolerance. You can expect to find this method used by hobbyists or instructors, but certainly not in any type of precision production environment. There are not many options available either, and long-term reliability is questionable.

a. Pros: Low cost.
b. Cons: Low accuracy, repeatability and long-term reliability, no options, or spare parts.
c. Size range: No definable tolerances

2. Method 2: Mechanical centering jaws or fingers In this method, the component is picked up and moved into its center position in the X and Y axes on the pick-up head. Typically, this method is easy to set up and repeatable within +/-.001” accuracy. This centering method is generally found in low- to mid-range machines.

a. Pros: Easy to learn and set up; repeatable; one of the fastest method currently available; a true “on-the-fly” system; low cost.
b. Cons: Physically touches the component which may not be appropriate for certain types of parts, especially those with delicate leads.
c. Size range: 0201 packages up to 35 mm square.

3. Method 3: Laser centering In this method, the component is picked up inline with a laser beam which detects the component’s center position on the tool head and recalculates the zero point of the part according to its position in the X, Y axes and rotational position relative to the head for an accurate placement on the board.

a. Pros: Touchless; on-the-fly (similar to mechanical method).
b. Cons: It is less reliable. There are limitations on the types of parts it can handle, such as very thin components (If .050 thin, they may need to be reset because of part variations, even from the same vendor); requires longer setup time, since the Z axis (part thickness) must be defined; more costly than Mechanical Centering, but about the same as Vision.
c. Size range: cannot center parts below 0402 packages or larger than 35 mm square.

4. Method 4: Vision centering Here, there are two types, Look-Down and Look-Up. Look-down vision will view the top of the component prior to picking it up for its pick-up location. It then calculate its center, compares it to its image file from the stored database, then picks up the component and transports it to its position on the board.

a. Pros: True touchless centering; can handle odd-shaped and delicate components; Look-Down Vision Centering placement is accurate to +/-.004”.
b. Cons: Typically longer setup times due to the need to teach the vision system how to identify part images which are stored in the machine’s database; a slower method of centering due to time slice required for processing; Vision is more costly than the mechanical method; for Look-Down vision, the part may move from its pickup point to its placement on the board.
c. Size range: 0402 – 15 mm

The Look-Up Vision method is the most accurate centering method available. The component is first picked up from the pickup area, moved to a camera station that looks at the bottom of the component, and calculates its center position.

a. Pros: True touchless centering, handles delicate components; accurate down to +/- .001” positioning capability
b. Cons: Typically, a longer setup time due to the need to teach the vision system how to identify the image, stored in the machine’s database; a slower method of centering due to processing time; Vision is more costly than the mechanical method.
c. Size range: 01005 – 50 mm (can see smaller and more detail)

The Pick-Up and Centering Method you choose will have a great deal of influence on the quality and speed of your production needs, along with how to relate this accuracy back to the machine. But, that’s just the beginning.

As with any complex machine, there will be tradeoffs between cost and capabilities, some of which specifically relate to production accuracy and yield. We will address next:

To review, when starting the evaluation process, there are two defining factors to keep in mind which determine what category fits your machine needs. The first principal factor is CPH (components per hour), and the secondary factor is machine capability. While it’s constructive to start by understanding how production rates affect the type and performance of a pick-and-place machine, please refer to the prior two chapters for those ranges.

Machine capability is the second defining factor in helping choose the correct auto pick and place machine for your needs. In this chapter, we will address three aspects of machine capability that have a direct impact on final board quality and production yield.