I printed off another plate of Mendel parts the other week, including two more Z-axis drive screw blocks. This time I increased the height of the support layer (7 slices rather than 4) to better accommodate the slight sloping of the glass foam base. I was more careful in removing the large parts this time, and tried first to peel the HIPS support off of the glass foam as the first step, rather than trying to remove the ABS parts from the HIPS right away. I found that using a pocketknife to lift up the HIPS at a corner worked very well, and I was able to remove all the parts with no breakage. The HIPS is still bonding to the ABS more strongly in some spots on the tray than in others (the bonding in the rear right corner still being the strongest), and I’m at a loss as to why.
I decided to try printing one of the large toothed pulleys this time around to see what the resulting quality would be like. While it’s certainly functional enough for the goals of a self-replicating rapid prototyper project, I think using traditionally manufactured off-the-shelf pulleys when possible is a much better solution – no need to cripple precision in the name of purity. You’ll also note the helical looking object at the far right – this was the first non-Mendel part I had tried printing. It’s a screwable jewelry box that I found on Thingiverse. Unfortunately, I was a bit eager when putting the two halves together, as I should have lightly sanded the surfaces first. The fit is rather tight, and now I can’t get the two pieces apart.
With this latest batch of parts complete, I had a look inside the dry box on the Stratasys to see how much filament I had left. Very little, it turns out – perhaps 7 turns each of ABS and HIPS. I was expecting my shipment of filament from New Image Plastics to have been here over a week ago, but in doing a little digging, it appears they can be slow to ship to their hobbyist customers. I can’t blame them – the big industrial orders that actually keep them in business get priority, and it’s very kind of them to take the time to deal with RepRap users at all. I suppose a bit of patience is in order.
So, what to do with a Stratasys FDM 1600 that’s just sitting idle? Have a look at the innards, that’s what. I could find no real information on what is inside the FDM machines other than illustrations in Stratasys patents, and what I can see inside the build chamber. However, the Stratasys 1996 10-K filing notes that the “sole current supplier of the X-Y stage for the FDM 1650, FDM 2000 and FDM 8000 benchtop systems is Asymtek.” It was a solid bet that I’d find some Asymtek hardware inside, and likely other off-the-shelf parts as well (as commodity 1/16 DIN temperature controllers were used on the front panel rather than a more integrated system). The manual cautions against removing any panels, as it could wreck the calibration. The side panels do look rather beefy, but I’m guessing there’s not a great deal of interesting machinery or wiring behind them. The upper cover, on the other hand…
The front of the machine is to the left – you can see two of the thermocouple wires that run to the temperature controllers on the front panel. There’s a DIN rail for power distribution at the top left of the photo, and as best I can tell, the white box underneath the large circuit board on the right is just a power supply. Just out of view in the upper left is the LCD keypad interface, which is an Intelligent Instrumentation CTM150B-00. The big beige box in the lower left is the Asymtek controller, model A-201 (for which I found the operation manual and the service manual). Asymtek manufactures fluid dispensing equipment generally used in manufacturing circuit boards, and the A-200 series appears to have been specifically targeted at OEMs to use as a turn-key motion control system. This looks to have been a very shrewd choice by Stratasys – rather than having to build a motion control system from scratch, they found an off-the-shelf system that was extremely well suited to the task. Given the wording of the 10-K filing, I’m guessing that the X-Y mechanics were all from Asymtek as well (looking inside the FDM build chamber, it easily looks like an upside-down A-100 or A-300 for the X-Y).
The big circuit board itself is what I assume to be a proprietary Stratasys board, as there are no company, brand or model names silkscreened onto it. The two ROMs are labeled as firmware 7.04 (which I think is the version the LCD panel displays on startup). The large square chip is a National Semiconductor HPC46003 16-bit microcontroller – no internal ROM on this version of the uC, hence the need for a pair of socketed ROMs.
I couldn’t learn a whole lot right away from the circuit board (though if I get a chance I’ll dump the contents of the ROMs), so I started looking into the Asymtek controller. I came across a paper on fractal fill patterns that used an FDM 1650 as a testbed (the late 90s must have been a great time for grad students to play with Stratasys machines – unlike newer models, these older units have a high hackability factor). The paragraph that jumped out at me was:
The Stratasys FDM 1650 machine used for the experimental tests is driven by an Asymtek A-201 digital motion controller. The A-201 controls the x-y movement of the depositing head, the z movement of the stage, and the rotation of the two electrical servo-motors mounted on the head that feed the thermoplastic wire into the two liquefiers. The controller uses Automove Control Language (ACL) for programming ; Stratasys has implemented a slightly modified version of this language, called Stratasys Machine Language (SML). It is similar to Hewlett Packard’s PCL used to control plotters and all commands are strings of ASCII text.
Another google search, and I found the Automove Control Language reference. Sure enough, the commands detailed looked just like the lines in a .SML file generated by Quickslice. I wondered what modifications Stratasys made to ACL to create SML, as a sampling of commands I pulled from a generated .SML file are all present in the ACL reference. In fact, I have a sneaking suspicion that the “Stratasys Modeler Language Programming Reference Manual” noted in Øivind Brockmeier’s thesis was hardly more than a re-labeled ACL manual (perhaps to hide the identity of a key supplier), especially as Øivind notes that the revision of his copy was 3.4 from May 1991, and revision 3.4 of the ACL manual was released on April 22, 1991. Sure enough, in tracing the RS-232 cable in the FDM 1600, I found that it runs right into the A-201 – the brains of the FDM are Asymtek, not Stratasys!