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- From: jeh@cmkrnl.com
- Newsgroups: sci.electronics
- Subject: Re: PC masks from a laser printer??
- Message-ID: <1992Jul27.225040.606@cmkrnl.com>
- Date: 28 Jul 92 05:50:40 GMT
- References: <1992Jul27.065039.5734@lugb.latrobe.edu.au>
- Organization: Kernel Mode Consulting, San Diego, CA
- Lines: 53
-
- In article <1992Jul27.065039.5734@lugb.latrobe.edu.au>, MATGBB@LURE.LATROBE.EDU.AU (BYRNES,Graham) writes:
- > Dear Knowledgeable ones,
-
- that remains to be seen. :-)
-
- > Up until now I have made my PCB's using donut and tape transfers on
- > overhead proj film, exposing Electrolube +ve resist on the copper.
- > However, as I have now entered the compuer age and bought a cheapy
- > PCB CAD program, I need to produce masks from a laser printer.
-
- Questions along this line come up every few months or so.
-
- I'll leave the explanations of the exact methodology for doing PC masks on a
- laser printer to others, and stick to my own personal hobby horse:
-
- YOU SHOULD NOT ASSUME THAT A LASER PRINTER IS A PRECISION DEVICE!
-
- Specifically, you should not assume that your laser printer will lay down toner
- in the same place every time, not until you test it.
-
- Here's one test. Coax your printer to printing a 6" square grid of 0.1-inch
- squares. Print two such grids onto separate sheets of white paper. Find a
- light table or something similar, lay the two grids on top of one another, and
- see if you can make them match up *everywhere at once*. Never mind getting
- them to match up with the edges of the pages aligned -- that's not an issue,
- that's what the crop marks on your PCB pattern are for. No, I'm talking about
- getting them to match up *at all*.
-
- (If you really want to be shocked, copy one of these on an office
- copier -- ANY office copier -- and try to make the copy match the
- original. Especially do this if you are planning on using a reduction
- copier for doing reductions from the laser printer output for your
- PCB masks.)
-
- If they match up, great! No problem -- with your particular printer. Don't
- assume that other printers are as good.
-
- If they don't match up, you'll have to evaluate the degree of error and see if
- the results are still acceptable for your particular PCB work.
-
- (The usual reason for the problems I'm alluding to is that laser printers,
- especially low-cost ones, are not really precise paper-handling machines. Not
- only is the registration of the paper slightly different from one sheet to the
- next, but the paper will shimmy and shake a bit as it goes through the rollers.
- Hence there is usually some error along the line of travel of the paper.
- There is usually very little error in the dimension at right angles to the
- paper's line of travel, since points on that axis are spotted by the printer's
- rotating prism, or LED array, or LCD shutter, or whatever, and these mechanisms
- are usually fairly precise.)
-
- --- Jamie Hanrahan, Kernel Mode Consulting, San Diego CA
- Internet: jeh@cmkrnl.com, hanrahan@eisner.decus.org, or jeh@crash.cts.com
- Uucp: ...{crash,eisner,uunet}!cmkrnl!jeh
-