Retromaster’s Electronics Projects

…related to old computers and other assorted stuff…

PCB Drilling with the MF70 CNC

Posted by retromaster on January 11, 2010

Over the weekend, I worked on getting rid of the backlash in the MF70 CNC. I’ve made new delrin nuts that fit much more tightly in the nut housings and I’ve tightened the stop nuts on each side of the X axis to make sure that there remained no play in the ball bearings. As the first photo shows, this resulted in a huge improvement in the backlash situation, although I had to reduce speed as the X axis became more difficult to move. Also, something I noticed before but I neglected to mention in my previous posts is that the X axis endplates do not seem to sit perfectly flat on the sides of the table. This may be because they are getting bent when the mounting screws are tightened. I think I may have to try rebuilding the endplates using aluminum twice as thick.

In addition to fixing the backlash, I greatly increased vertical speed for drilling and shortened the extension of the drill bit to just a few millimeters below the chuck, eliminating most of the problems due to wandering and flexing of the drill bit. But even these improvements were not enough to get a perfectly drilled PCB. It seems that warpage of the copperclad introduces a significant error as well. So significant in fact, that the holes in the top board in the first photo above did not align properly with the printout of the PCB layout. I also found out that I needed to have the hole locations mirrored since I was drilling from the copper side (this is a single-sided board). So I came up with the drilling setup in the right photo to fix the warpage issues and I had the hole locations mirrored, and I managed to have a drilled copperclad that matches the PCB layout very well.

The PCB I building is for testing the new axis drive circuitry that I mentioned in the previous post. In a few days, I expect to finish making and assembling the PCB. After a little bit of PIC coding, I’ll at least have an idea of the torque increase I’ll get from the new drives. If it turns out to be as worthwhile as I think it’ll be, I’ll build a new board with all drives for all 3 axes and then go back to improving the mechanics of the machine.

4 Responses to “PCB Drilling with the MF70 CNC”

  1. Vegard Paulsen said

    Brilliant! I just bought my self an mf70 to build a cnc version to drill holes on photoresist pcbs for my circuitboard prototyping.
    Very interested in how this works out for you!
    Where did you buy your cnc mod steppermotors and motor mounts?

  2. retromaster said

    Thanks. I had already bought the stepper motors a few years ago, I already had them when I started the conversion project.

    The mounts I manufactured myself, using a previous version of my MF70 CNC-conversion. You can see photos of the older versions in my older blog posts.

  3. Vegard Paulsen said

    Great. I found them.
    What kind of milling bits are you using to carve out aluminium?
    I plan on using the mf70 mostly for drilling pcbs and draw my own pcbs with cadsoft eagle.

    What software do you use to make the gerber files into something understandable for the cnc software and what cnc software do your recomend?
    By the way i guess i end up with 3 steppers and driverboards from http://probotix.com/index.php?view=product&path=30&product_id=88
    they have a nice offer and the steppers seems to be big enough for the job.

  4. retromaster said

    Well, I think you can find the answers to your questions (and perhaps other ones) at my https://retromaster.wordpress.com/pcb-making/ page.

    And that kit looks quite nice for the price, by the way.

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