More thoughts on the Stratasys and RepRap

A nice long holiday weekend is a great occasion to tinker around with a rapid prototyper.  Well, all right, any weekend.  Or weekday for that matter.  There’s something enthralling about watching your creation emerge slowly, slice-by-slice from the build platform.  POV-Ray enthusiasts will know the feeling well – watching your file slowly transformed into an image, one line of pixels at a time.  Although in the case of a rapid prototyper, the transformation is subtly different – you know exactly what the output object will be (unlike in POV-Ray, where you have to alternate between adjusting your scene description file and rendering that file until you achieve the effect you want – enjoyable, yes, but lacking a direct translation of vision into result).  A rapid prototyper on the other hand, allows a leap between the digital domain and the physical one.  Perhaps not as exciting in terms of watching the process, but more profound in concept (as evidenced by the abundance of ‘replicators’ in science fiction).

I’ve done a lot of research into the Stratasys machines and RepRap lately, especially as I now have to feed this beast which I posses.  While I have a decent amount of filament, the cost of getting more has kept my use of the Stratasys to a bare minimum. Bolson Materials charges $250 for a 4 pound reel of filament, which is probably a great price, considering that the HP-branded Stratasys units recently released for sale in Europe have filament cartridges that are (as of this writing) $987.94 each after currency conversion. And you thought buying inkjet consumables was bad.  Given that this is only $12.06 less than what I paid for the machine (yes, I practically stole the Stratasys for a cool grand, and everyone I speak to agrees that I basically won the  Craigslist lottery), I began looking into the filament itself.

The first step was to determine exactly what material I was dealing with. I knew that it was ABS plastic, but I didn’t know if there was anything special about it (I know almost nothing of plastics engineering, but I know that numerous formulations are possible – Lego bricks, for example, are not pure ABS, but a custom formulation). I knew Stratasys wouldn’t be keen on divulging this information (imagine the response at a KFC counter when you ask precisely which 11 herbs and spices are used – okay, not the best analogy, but bear with me). I had discovered many years ago that MSDS sheets are an excellent window into proprietary information, divulging industrial secrets by virtue of safety legislation. So I did some searching and found that the MSDS sheet for the modeling material indicated that the filament was essentially pure ABS, with perhaps a tiny amount of mineral oil, tallow, and/or wax thrown in for a lubricant.  Similarly, I discovered that the breakaway support material appears to be nothing more than HIPS (High-Impact Polystyrene).

Obviously, buying Stratasys branded filament would quickly become prohibitively expensive (the classic razor and blades business model in evidence).  It’s generally a bad sign when you go looking for a product, but can’t find a price for said product.  Yet diligent web searches led me to stumble onto this post. Given that New Image Plastics could apparently supply smaller diameters than the 3mm RepRap standard (I needed .070″ for the FDM 1600), I figured I’d give them a shot. I called them up and inquired about getting a few pounds of ABS and HIPS in a .070 filament size.  Unexpectedly, I was speaking with James Waring, owner of the company.  He told me that a number of customers were using .070 ABS filament from them in Stratasys machines with no problems, and that for newer Stratasys machines that had chipped cartridges, he is aware of someone who is successfully reloading cartridges and will hopefully be revealing the technique once perfected.  Anyhow, I ordered 5 lbs. each of ABS and HIPS, and James said that he’d have it scheduled for production this weekend!  I can’t imagine a more phenomenal response time from a vendor.  If the spools feed through the Stratasys without issue (shouldn’t be hard – the current ‘lobster red’ spool appears to be about a decade old from the tag information, so they’re not exactly prime material), I’m sure I’ll be ordering lots more.

Meanwhile, I also tried my luck with contacting Stratasys to see if any spare parts or other service was still available for the unit (not that it appears to need any, but I wanted to be prepared).  Their tech support department told me that no parts or service were available for the FDM 1600, and they couldn’t direct me to any third parties that did service on the unit.  I also asked about the availability of a document called the “Stratasys Modeler Language Programming Reference Manual” that I found referenced in a thesis I came across.  The thesis covers the building of an automated build platform loading/unloading system, and the document appears to detail the format of the .SML file that gets uploaded to the printer.  Unsurprisingly, the person I spoke to knew absolutely nothing about the document.  Getting updated software required speaking to the software licensing department, which I called next.  I found that the last version of software to support the FDM 1600 was Insight 6.3, and that yes, I could certainly get a copy.  However, that would mean paying $2000 for an annual software support contract.  Oh, and the FDM 1600 is being dropped from support at the end of the year, so it would essentially be $2000 for 6 months of software support.  I declined to sign up.

Friday I decided to try and tackle the offset between the ABS and support material.  The manual explains the procedure, but references a calibration filename that doesn’t exist in my software version.  After opening a few different similar files, I finally found the one I needed – one that would print out a square of ABS and then deposit a single circuit of support material on top.

I’d run one, estimate the offset, then launch the tip calibration program to upload the offset to the FDM 1600.  After a few iterations, I finally was pleased with the path matching and decided to try a larger print to run overnight.  I grabbed the Mendel SolidWorks file and created an assembly with some of the larger parts that don’t lend themselves well to machining easily. This step is needed because Quickslice can only work with a single .STL file (whereas Insight can work with multiple objects). In order to print multiple parts, I have to create a SolidWorks assembly of how those parts are to be printed, and then export the entire assembly as a single .STL file.  Quickslice churned through the slice and road generation slowly – I’m guessing this old software was far from optimized.  Once done, I uploaded the file to the FDM, hung around for a little while to make sure the base layers were being laid down correctly, and left the machine to its business for the night.

I wasn’t sure what to expect the next day – RepRap machines seem to still be at the stage of needing a lot of monitoring during a build, and I worried that I’d come back to find a giant birdsnest of filament occupying the build chamber.  But no such disasters had happened – I had a beautiful print waiting for me:

It took a bit of coaxing to remove from the foam, but I could then admire the work.

I’m not sure why Quickslice decided to run supports up on the left – the teardrop holes on the Mendel parts are less than the overhang support threshold in Quickslice, but perhaps a rounding error tipped the scales.  This print took 14 hours, so the FDM is no speed demon.  I think a Mendel could probably run the job in half that time, although RepRap currently bypasses bases and supports, and has a coarser output due to the 0.5mm nozzle orifice.

I’m pondering whether or not to actually build the Mendel right now, but I’ll probably pass the parts over to Chuck so that he can have a crack at the project.  I’m still interested in the RepRap project, but if I were to build one, I’d probably redesign the system into something that looks more like the FDM, but has a larger working envelope.