Monthly Archives: March 2015

Rebuilding a LPKF Protomat 93s Circuit Board Milling Machine

Worth keeping. I acquired a dead twenty-year-old LPKF Protomat 93s circuit board etching (milling) machine. This machine, when working, makes circuit boards by mechanically etching, rather than chemically etching, the circuit board traces on a copper-clad board. It’s essentially a special-purpose milling machine. The special advantages of the Protomat, compared to a regular desktop milling machine, are: 1) it has a high-end high speed spindle (60,000 rpm); 2) it has a mechanical depth limiter to control the cutting depth of the milling bits; and 3) it is massively built with precision components. I thought it was definitely worth keeping; but, unfortunately, the electronics on my machine were bad. There are a couple of circuit boards in the machine; and it would have probably cost around $1,000 to replace the main board. That was way too much money for me, so I decided to replace all the electronics.

Goal: to rebuild as a Mach3–controlled CNC machine. My idea was to completely junk the existing electronics, and rebuild the Protomat as a Mach3 controlled CNC machine. It turns out that it was fairly easy to do, so if you have an old machine like this, you might be able to bring it back to life for a few hundred dollars.

Here it is working:

And here is what I did to get it going again.

The stepper-motor controller. The Protomat electronics controls three things: 1) the stepping motors that move the milling head in the X and Y directions; 2) the solenoid that pulls the milling head down to cut and drill the circuit board; and 3) the high speed spindle controller. Getting the stepping motors going again was straight forward. The steppers are bipolar NEMA 23 steppers, and I already had a stepper motor controller using Mach3, so it was just a matter of wiring up the stepper motors. My controller box is the Gecko G540–based STDR-4C system produced by Jeff Birt at Soigeneris, using the ethernet SmoothStepper. The only thing that gave me pause was setting the current limit for the steppers. There were no nameplates on the Protomat steppers. Motor nameplates usually give the current limit. However, by looking at other similarly sized motors, I concluded that 1.5 amps would probably be safe. As it turns out, at that setting the motors have not gone up in smoke, they do not run hot, and they run fast enough, so I think I made a good guess.

The solenoid-controller. To control the milling head solenoid, I had to first figure out the solenoid voltage. I guessed that it would be a standard solenoid voltage, either 12V or 24V. I connected various DC power supplies to the solenoid and found that 12V was too little to pull the solenoid, but 24V worked. I also noted that the original electronics had a toroidal transformer with a 24V tap, which I take as confirmation that it is a 24V solenoid. I also discovered that the solenoid has a diode across it. Next, I had to figure out how to control the solenoid. But that was easy since I already had the controller box, which provides a Mach3–controlled relay. Ordinarily this relay would be used to control a coolant system, but instead I used the relay to control the current to the solenoid. I’ll describe my software arrangement in a later post, but for now I’ll just note that I use a M8 g-code (coolant on) to energize the relay and solenoid, and a M9 g-code to release the solenoid.

The spindle-controller. Replacing the spindle control electronics was the biggest challenge. Initially, all I knew was that it was a three-phase motor because it had three wires going to it. But fortunately the spindle was marked, so at least I knew what I was dealing with. It’s a Jager 33–1 W02 spindle, with a maximum RPM of 60,000. I found the spec sheet online, which indicated that it had a maximum voltage of 21V, a maximum current of 7 A, and maximum driving frequency of 1,000 Hz. It took me a few days searching online to find something suitable. Most of the VFDs I found did not have high enough driving frequencies; and if I found one with a driving frequency that went up to 1,000 Hz, it was for motors with much higher operating voltages. Eventually I discovered the Sunfar E300 inverter, sold by Automation Technology as the “KL-VFD03 Mini-type Integrated Universal Inverter (VFD), 2.2KW.” And it was only $199.

This VFD has a maximum driving frequency of 1,000 Hz, which is just what I needed. It has dozens of user-adjustable operating parameters, but the key one here is the maximum output voltage, which is 25–250V. The spindle has a maximum operating voltage of 21V, but I figured that setting the VFD maximum voltage to its lowest value, 25V, would be close enough. So I purchase the VFD, connected it up, and it worked. I keep checking the temperature of the spindle to make sure that it is not overheating; and so far, so good. It is possible to control the spindle speed from Mach3, but I’ve been doing it manually.

220V supply. One small wrinkle is that the VFD needs a 220V supply, and I don’t have a 220V line where the Protomat is located. But I did have a spare 110V-to-220V step-up transformer. The one I had was 750 W. The spindle is only 170 W.

Circuit board quality. When I finally got the rebuilt system going, I was able to make some really nice boards:


I also took a close-up. The isolation cuts are very sharp:


Replacing the software.
The downside of replacing all the electronics was that I could no longer use the LPKF BoardMaster software to control the machine. I eventually worked out a tool chain to do that, which I will write about next time.

Hanging Suns

By |March 25th, 2015|Visual Design|0 Comments

So now all the snowflakes in my front window have been replaced by suns. I strung them up with fine fiishing line — lots of knot tying. To get the spacing right, I made the simplest of jigs — two nails hammered into a 2 x 4:


I had trouble getting a good picture of the 3D-printed suns hanging in my window, so this will have to do for the time being:


I’m ready for spring now!

3D-Printing 4-Dozen Suns

By |March 20th, 2015|Visual Design|0 Comments

This week I’ve been 3D-printing “suns” for my window display. It was sort of like baking batches of cookies. I “baked” the suns four at time. Here they are on the “cookie sheet”:

suns on baking sheet

I made two dozen yellow suns and two dozen orange suns:

pile of suns

Next, I have to drill holes in them to string them up. That’s 96 holes. It will take me a little while.

Welcome to the blog

By |March 15th, 2015|News|0 Comments

Welcome to the Daniel Bogen Design blog! It’s taken three years to get my design studio in order; but now that all the essential pieces are in place, it’s time to start cranking out the projects. It took about a year and a half to find a property for my studio, renovate it, and move in. And then another year and a half of machine setups, repairs, and upgrades. And finally, the last major hurdle — just completed last week — was getting all the necessary software together.

Going forward, I will be writing about various projects I’m working on and sharing some of the design methods I’ve developed over the years. Some of the projects will be open-source, some will be commercial, some will be educational, and some will be recreational.

Today’s project is updating my studio window display. We’re on a commercial street here, mostly retail and restaurants, and the shops tend to have seasonal and holiday displays in their windows. Although I do not have a retail operation, I like to support the local merchants, so I put some seasonal decorations in my window, too. I’ve had some laser-cut acrylic snowflakes hanging in the window since December. Here’s the CAD version of a snowflake:


And now it’s time for something more spring-like, so I’m in the process of 3D printing some sun-like decorations. Here’s the CAD version of a “sun”:

I’ll be printing them out in yellow and orange.

Welcome to Daniel Bogen Design

By |March 4th, 2015|News|Comments Off on Welcome to Daniel Bogen Design

Our new design studio in South Philly is up and running … finally!

Working on assistive technology and other projects. The Blog will begin soon.