How to Select an Automatic Pick-and-Place Machine

Reading time ( words)

This is the third in a series of articles designed to help buyers analyze and select SMT equipment for PCB assembly, and examines automatic pick-and-place machines, the most complex component in a circuit assembly operation. Because of this complexity, the next few columns will address different functions in this process.

Automatic pick-and-place machines are much more common than manual or semiautomatic machines, but they also have the greatest range of capabilities and cost. This column will focus on features and capabilities and include some cautions regarding reliability of low-cost machines, including:

• Production volume ranges (CPH)

• Accuracy and repeatability specs

• Pick-up and centering methods

In future columns, I will address size, machine accuracy, encoders, feeders and mechanical positioning methods.

When starting your evaluation process, there are two defining factors to keep in mind, which determine what category fits your machine needs. The No. 1 principal factor is components per hour (CPH), and the secondary factor is machine capability.

Production Volume

As in the previous column, it’s constructive to start by addressing production ranges for various types of machines, since this is the No. 1 factor in your evaluation process. For purposes of comparison, since all circuit boards vary in size and complexity, we talk about volumes in terms of components per hour, or CPH. The following table offers a general guideline of machine categories defined by their CPH.

Machine Capabilities

This is the second defining factor in helping choose the correct auto pick-and-place machine for your needs. Here, we will only be talking about two aspects of machine capability: accuracy and repeatability, and pick-and-place centering methods.

Accuracy and Repeatability

For production machines, we typically recommend looking for a machine with accuracy of +/- .0001” and down to fine pitch capability of 12 mil on a repeated basis. Less expensive machines often don’t meet this spec. 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.

Pick-and-place Centering Methods

There are four methods for pick-up and placement:

1. No centering mechanism

2. Mechanical (jaws)

3. Laser centering

4. Vision centering

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. Obviously, this is 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.

• Pros: Low cost

• Cons: Low accuracy, repeatability and long-term reliability, no options, or spare parts

• Size range: No definable tolerances

Read The Full Article Here

Editor's Note: This article originally appeared in the March issue of SMT Magazine.


Suggested Items

Exceeding Customer Expectations

02/26/2018 | Stephen Las Marias, I-Connect007
Aculon Inc. commercializes unique surface coatings leveraging nanotechnology and other surface modification techniques. The company’s original focus was the optical industry, developing treatments of prescription eyewear, sunglasses and other optics.

Three Reasons to Use PCB Panel Routing Techniques

10/12/2017 | Duane Benson, Screaming Circuits
Most PCBs are individually routed—meaning they're not panelized. That doesn't mean that, sometimes, sending them to a PCB assembler in a panel isn't a good idea or even required. Generally, assemblers don't require panels, but there are some cases when they do.

The Need for 3D AOI

06/05/2017 | Stephen Las Marias, I-Connect007
While the coplanarity of height-sensitive devices such as BGA packages and leaded components can be inspected in 2D using multi-angled colored lighting and side-angle cameras, these will be susceptible to an increase in false calls, a need for additional programming and cycle time, and possible escapes. These factors underscore the need for 3D technology in inspection strategies.

Copyright © 2018 I-Connect007. All rights reserved.