Robotic Engineering of a Part
Marking Work Cell

Robotic Engineering

This project did not start out as a robotic engineering exercise, but as a manual operation, as described, on the page-Direct Part Marking.

The customer's business, has increased to the point, that an operator was utilized, for 8 hours per day, loading and unloading, the simple fixture, for direct part marking.

The part mix lead us to believe, that a fully automatic, robot cell, could be justified, along with keeping the existing system, for the shorter runs.

An examination of the parts being produced, revealed that there are 4, high production parts, with average batch size, of greater than 50. The cost of small, Scara robots have fallen dramatically, recently, making many more applications, financially viable.

Initial discussions with the customer, established a budget of $60,000,for this project. A system, that could be loaded with parts, and run, un-attended, for, a reasonable amount of time, was the prime requirement.

The Robotic Engineering Solution

It was decided to custom design, a robotic work cell, with myself responsible for machine design and project management.

The first task, was to select the hardware, best suited for the application.

The Epson 2S654S

The choice of robot, was quite wide, but eventually, Epson was decided upon. This robot has been used before and local representation was available, making after-sales-service, readily available.

The Epson robot selected, was a model E2S654S, with Vision.

The Technifor Unit

The direct part marking system chosen was Technifor. Their unit interfaced well with the robot and the overall robotic concept.

The Technifor unit selected was a model-CN212Cp

The Epson vision system was chosen, to simplify the location of the parts. In order to maximize the run time, of the cell, it is necessary to place as many parts as possible, inside the robot work envelope. It was possible to locate 7 special trays, in position.

Each tray can accommodate up to 52 parts, randomly placed. The vision system will guide the robot, to the final part position. Note that the trays are hard black anodized and the parts are natural aluminum, in color, thus giving good contrast, for the vision camera.

Machine Sequence and Estimated Cycle Time

  1. A batch of parts, will be placed in the trays and the trays placed in the cell (trays are pin located). Trays are sensed to be in position by proximity switches, tapped into the table plate. Please note that all parts must be the same, in all trays.

  2. The cell doors are closed, and the program selected, to suit the part, via the operator panel (MMI).

  3. The robot moves to the first tray, and the vision guides the gripper to it's final position, over a part. Estimated time-4 seconds.

  4. The gripper moves down, inside the part and expands to grip. (note that the gripper fingers have 4 different diameters, at 4 stepped heights, to suit the 4 selected parts, thus the robot moves to the correct height, to suit the part selected.) Estimated time-4 seconds.

  5. The robot moves the part, to the Technifor part marker. Estimated time-4 seconds.

  6. The part is marked, around it's periphery, as it is rotated. Estimated time-6 seconds.

  7. The robot moves the part to the unload chute, where the gripper is released and the part slides out of the cell, into a shipping box. Note that the part is sensed by a through-beam photo-cell and the part count is displayed and recorded. Estimated time-6 seconds.

ESTIMATED TOTAL CYCLE TIME-24 SECONDS PER PART

Safety and Guarding

Any robotic engineering project must address operator safety. The Scara robot is small but can move at very high speeds and cause serious injury!

Square Mechanical Tubing,(1 1/2in. square) was used, on this project, to construct the frame and clear Plexiglas was bolted in.

There are a total of 6 doors, on 3 sides of the cell. Each door has a "Schmersal" switch, mounted. These switches are specifically designed for guarding and are recommended, to be seriously considered. Click here to visit their site

Project Management

As soon as the robotic engineering was complete, 3 quotations were obtained, from local machine shops and electrical panel builders.

The chosen suppliers (based upon delivery, prior similar experience and price) were advised. Requisitions were then issued to the customer, who then generated purchase orders.

Requisitions were also issued, for the robot, the part marker and all other purchased items required. It was then possible, to detail a schedule, showing final delivery of the completed robotic cell.

The total robotic engineering hours, were approximately 150,with a further 50 hours of project management time. The total elapsed time, from initial customer talks to final delivery, was 4 1/2 months.

Project Conclusion

A very successful robotic engineering project but a few things were learnt re vision system lighting. A constant, independent light source is essential for any vision system. A minimum of shadows and constant light density is mandatory!

The concept of using vision to locate the parts. prior to picking up, worked very well, once the lighting problems were solved by placing independent light sources, overhead.

Cad Drawings

Cad Drawings

This Autocad drawing, by the author, shows the general arrangement of the machine. If you click on the image, you will have access to a PDF file. that can be easily printed, for your reference.

Photo Gallery

Part Marking Work Cell-Front
Part Marking Work Cell- Side
Part Marking Cell-Front
Part Marking Work Cell- MMI





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