Date: Oct. 21, 1994
Author: Bill Shepard, Sr. Development Engineer
RE: Slit-Mask "Cutter"
RFO: Laser Based. Slit Mask Machining Tool
The intent of this document is to provide the information required by vendors to produce a quote for a Slit-Mask "Cutter", primarily with laser based technology in mind. The following major areas must be addressed:
1 Task Description
The Slit-Mask Cutter will be used to process Slit-Masks by making the following:
In other words, pre-processed slit-masks are brought to the slit-mask "cutter", set up and then the above user defined characteristics are added to produce the completed slit-masks. The machine must be able to produce 10 masks in one 8 hour shift.
The following are also required as defined in the sections below; --capability for electronics interfacing or slit-mask "handler interfacing" --throughput rate for the overall process including the production of several slit-masks and set up time for each mask in a production-like manner.
1.1 Slit Mask
A sample slit-mask is illustrated in the attached drawing, D1705.A.
NOTE: We will consider alternative materials to the 0.003 thick stainless steel if the mechanical and optical properties (and cost) can be discussed and evaluated before hand.
One or two small holes for alignment purposes may be required. These may be treated as additional slitlets on the mask with the capability to orient one slitlet perpendicular to the other. Alignment method for each mask must allow for the future plan to fully automate the process -- (via the handler interface).
1.5 Handler Interface
The electronics controls needed to perform the following will be required:
By "handler interface", a set of electronic 110 signal lines are expected to be provided by the vendor. Opto-isolated inputs & outputs are preferred. Some beginning & end of shift operator tasks may be required even with the fully automated mode of operation. For example, this might include: check cooling water, turn on system power, turn on lamp power, start up some control program at the user interface of the mask-cutter.
The requirement of the fully automated running capability is to enable the basic system to complete a shift of 10 masks without any human intervention after some initial standard operating procedure and before some final operating procedures at the end of the shift. The handler interface to enable this mode is the vendor's responsibility and the actual mask handler with inputs for the interface is UCO/Lick Observatory's responsibility.
Documentation for all handler interfacing and instrumentation/controls electronics shall be included. The intent here is to enable design interfacing, troubleshooting, and maintenance planning as well as implementation. This should include:
1.6 Throughput Rate
2 Operator/Machine Environment
The typical operator will have no special training with the use of laser equipment. Many operators will be occasional users of the system. While some advanced programming interface capabilities are desired, a user friendly interfaceP'GUI" is also preferred.
2.1 Normal Operation
The system will be used on a daily bases to produce 10 masks at a time. The masks are for installation and loading into the telescope instrumentation immediately after completion on site. Operator required procedures such as wiping off debris or poking out any residual material by hand is highly undesirable and will probably lead to the selection of an alternative process.
2.2 Standard Maintenance
Since a single observing date is planned well in advance, the loss of a few hours of nighttime observing time is a major failure and the loss of a full day is catastrophic.
2.3 Laser Safety
2.4 Weather/Altitude Conditions
The machine will be operated and maintained in Mauna Kea, Hawaii at approximately 14,000 ft. above sea level - at the Keck Observatory. Where or if applicable, options such as high altitude brushes will be required (for dc motors with brushes). The weather is mostly consistent throughout the year, at about 0 Deg. Centigrade. However, we can readily provide water that is as warm as about 20 Deg. Centigrade, (if necessary).
2.5 Reliability/Down Time
NOTE: "Similar applications" here refers to the task of cutting 0.003" sheet metal &/or cutting optically critical apertures out of a large spherical surface, etc. (The customer need not be using the system for telescopes or observatory instrumentation.)
Facilities requirements for our intended site are required to ensure that we can begin using the machine as soon as possible after it is installed.
Cooled water is readily available for system cooling. We will need to know the temperature, flow rate, and BTU/hr required.
4 Samples/Process Demonstration
We will provide a small sample of "bumped" stainless steel to test the process. The vendor will then produce a sample subset with about 18 slitlets and a record of timing data & machine parameters used to produce it. Any options/special equipment such as "auto focus" required to achieve the desired results should be used for the sample. If not this should be noted and explained.
Areas of particular concern are as follows:
The sample will be used to demonstrate that the proposed process can achieve the desired results as outlined here, regardless of these concerns.