First Experiences: Form 1 Resin Printer

I’ve been looking for a printer to help with small model railroad details for a long time. When I'd bought Makerbot's first 3d printer, the Cupcake, back in 2010, I'd hoped it would be useful for making parts and details for my model railroad. My early cupcake was still too coarse and tempramental. I've also sent parts away to Shapeways for printing in their Frosted Ultra Detail. Those parts came out beautifully, but waiting multiple weeks to see whether a design worked is annoying.

My new 3d printer, a Form Labs "Form 1", is a lot closer to what I've wanted for model-making. It has between 3 and 10 times the resolution of the filament-based printers and starts getting close to injection-molded detail. It's got drawbacks: even small parts take a long time to print, designing detailed 3d models requires a new set of skills, and its print material is expensive and easy to mess up. But I think I've found a 3d printer that will be more useful for HO scale modeling.

The Form 1

The Form 1 is a resin-based 3d printer. It uses a photo-sensitive resin to make the parts, shining a laser on the part to harden new material as the partial object is pulled upside down out of the resin bath. Each layer on the Form 1 can be 0.1mm, 0.05 mm, or 0.25 mm thick (.004 in, 0.002 in, 0.001 in). Layers are visible to eye in final object, but are small enough so they can't be felt on the final model. Unlike the ABS extruder printers (Makerbot, etc), layers are made optically, so the Form 1's prints don't have the characteristic ridging caused by plastic squeezing out under the heated nozzle. Layers are anywhere from 3-10x smaller on the Form 1 than the ABS extruder printers.

The experience is completely different. The Makerbot Cupcake was a wonderful DIY project made from laser-cut plywood, but the nice wooden box made the printer particularly noisy, resonating as the stepper motors moved the object and print head.

Form 1 printer. Mine isn't in as clean a setting.

The Form 1, by contrast, feels like a solid professional tool with a very cool modern look. It has an aluminum case with a orange plexiglass box covering the print area and protecting the resin from stray night. The printer has a single button for control and a large display showing the name of the print, time left, and layers to do - information that was on the computer on the early Cupcake. The Form 1 is also quiet, with the only real sound coming from the stepper motors peeling the layer, and even that is quiet. Unlike the Cupcake, I can imagine working in the same room with the printer. (To be fair, the Form 1 is also four times the price of my original DIY Cupcake, and comparable in price to Makerbot's latest professional printers.)

The Form 1 does have its own temperamental nature; I suspect it needs to be in a darker room to avoid curing unused resin in the printer. The potential for spills of resin definitely makes me banish it to the garage. The resin, gloves, and alcohol make for a slightly messier workspace; I'm waiting for some resin spills on the laptop driving it.

The software is pretty simple with few settings: load models, change orientation, add supports for delicate or overhung parts, and print. The computer model of the object downloads completely to the printer upon printing so that computer can be disconnected within a few minutes. I don't have to worry about whether the computer will run out of battery power or fall asleep halfway through a print run and mess up the print. I also can start working immediately on setting up the next model.

Post-processing is more work. Prints need to be pried off the build plate, agitated in alcohol 2 minutes, and soaked in alcohol for another 10 minutes. The resulting parts feel gummy and rubbery at first, but start feeling more like plastic after a day. Support structures can be annoying to cut off.

Design Guidelines

One of the unspoken weaknesses of 3d printers is that the 3d models often need to be redone for each kind of printer. The ABS extruder printers like my older Makerbot might not have been good at fine detail, but could make solid objects efficiently. Large internal areas would be crosshatched to provide adequate support, save plastic and print time. For best results, models needed to be designed for multiples of the extruded plastic width so details could be added with a single line from the nozzle.

The Form 1 has similar design rules that need to be followed. Resin printers aren't as efficient for large, solid objects; the resin is expensive and solid fills are slow. Hollowing models out with 3d software saves money and time.

Freight door model printed on Form 1. It took a few tries, but check out those supports holding the door to the track!

There's also the question of what detail can be shown. The Form 1 prints detailed enough that I need a magnifying glass to look at the detail, but I still found myself trying to get smaller detail than even it could print. On my sample prints, I was able to get detail down to 1 HO inch (0.015 inch) with few problems, but haven't gotten it to print sub-inch bolt and screw detail. The freight door pictured is 10 feet x 8 feet HO, not including the track extension. The track hanging the door is one inch wide, and its long length seems to have some problems printing straight and complete. Bridging empty space is a challenge; the original door handle and track hangars on the freight door wouldn't print correctly until I made them a bit thicker. Again, I needed the magnifying glass to check out the detail.

Seth Neumann's lights, printed on Form 1 with supports. Cutting the part off was not fun.

For pieces with overhangs, the PreForm software can automatically build a model with supports. The supports and "raft" that sticks to the build platform can be bulky - around 15 cc for some of the parts, which is much larger than many of the parts I'm building. Using supports also means that the part needs to be carefully cut from the supports. It might be easier in some cases to redesign the part to reduce the need for supports.

Parts that printed well at Shapeways might not do as well with the PreForm supports. For example, my friend Seth needed 1990's era industrial lighting for warehouses on his model railroad. He's made a compact sprue of parts that prints well at Shapeways. However, the multiple layers of parts (diffusers and small lights) cause problems for the supports. Printing the part flat also means lots of support nubs to file off when preparing the part.

One solution to the support problem is to print objects straight on the build platform, which can work for parts with large flat surfaces and without overhangs. I've been printing most of my parts this way because many are already flat pieces. Printing on the bare platform works for smaller pieces like the freight door. I've heard concerns about warping from the extra laser light to secure the first bits of resin to the build platform, but the baggage doors were doing reasonably well. Building without support structures does mean that you can't have detail on the "wrong" side.

Operating costs

So how much are all those nice parts costing me? The Form Labs resin costs $150 for a liter bottle, or around 15c/cc. For the small parts, a non-trivial amount of resin ends up washed off the model or disappears in cleanup, so perhaps double that price. Machine time is the bigger factor for expensive equipment. Models appear to take about 30 minutes to get initial layers done (one minute per layer), with subsequent layers going much faster (sometimes seconds between peels.) Models with rafts take lots more time and space - a simple raft for Seth’s modern lights model took 20cc of plastic for a 3 cc piece, but the piece did print pretty flawlessly. At $3000/machine, and assuming I get 1000 hours of use out of the machine, that’s $3/hour to run the machine for a 3-4cc piece. Overall, that means that the Form is somewhat cheaper than Shapeways ($5.00 for setup and $2.39 per cc for frosted ultra detail), but not by a significant amount. I suspect I'd still use Shapeways for printing lots of parts when I'm pretty sure the parts will print well, and where I can wait a couple weeks for the part to arrive. The Form 1 will be much better for testing potential designs, for making masters for other ways of making parts (resin casting, perhaps), or when I want a part tomorrow.

Comparing The Form 1 Against Shapeways Frosted Ultra Detail

I've used Shapeways, a 3d printing service, to print parts for my model railroad. Shapeways's frosted ultra detail material is a perfect product for model railroad parts, showing lots of detail and being solid enough to use in real models. Their behind-the-scenes video suggests they're using a 3D Systems ProJet 3500-HD printer, which is a $90,000 machine. Like the Form 1, the ProJet hardens a resin with a bright light to make the model; unlike the Form 1, the ProJet prints the resin with an inkjet-like head, and shines a light over the part to harden it. It also has a nice feature of also printing out wax to support overhanging portions of the parts. The wax support makes the ProJet better for multiple layers of parts or parts with significant overhangs.

Shapeways part on left, first try at part from Form 1 on right. Warping and thinness is my fault; just notice that detail is close.

Here's an direct comparison of a first attempt at printing my Victorian stick-style details against the part at Shapeways. I printed this part badly; I should have made it a bit thicker to help it stand up to being printed from the build platform, but it's still possible to see the detail is comparable. The Shapeways part with frosted ultra detail is a better part without any of the needed cleanup work, but it did have a multi-week turnaround. Having a printer handy when trying to design a part like this is really great, especially as you’re getting acquainted with the material and its limits. The freight door I showed earlier went through multiple revisions that kept getting rejected by Shapeways after a week delay - definitely not fun when trying to design in fits and starts.

Seth’s light fixtures also come out close, though the holes in the diffusers weren't fully opened, and cutting the parts off the support structure was a real challenge.

Hints for New Owners

I've done six prints so far; generally, the parts that were larger and simpler printed well, and the parts where I was trying to be clever - printing small parts on the build platform, or aiming for tiny detail - came out less well. So far, I'm feeling very good about the Form 1.

One helpful hint: you don't need to fill the tank deep to be able to print parts. When the build platform initially comes down, it fills much of the tank space and highlighting why the maximum fill mark is so low. I've been worried about the resin curing between prints in our warm weather, and keeping less in the tank gives me some confidence I won't waste too much resin if that occurs.

Future Projects

So what am I going to do with this new printer? I've got a list of projects, but I suspect I'll be adjusting that list as I find what prints well and what prints badly.

One thought: how about making HO figures? Having a "model railroad club" set modeled after my friends could be a nice example of what can be printed. The real people scanned by Fredini over at Thingiverse could serve as great source material.

I need a bunch of HO SP flat cars for the lumber business on my layout. I've been hoping to find a good plastic car, but why not print some? I'd been planning on printing something similar to a plastic kit with a solid deck, but another modeler showed a flat car model on Shapeways where he only printed the underframe and metal parts, and glued a wooden deck on afterwards to complete the model. (See the GSC flat car model at Shapeways.)

Borcher Brothers building, North First St., San Jose

And finally, I want to use the printer to make architectural details I can't buy at the hobby store. The freight doors pictured above match a particular real building, and I've got a model waiting for six of those doors. I also want to build a model of the Borcher Brothers building supply. The real building, built in 1926, had an italianate design, but the terra cotta details are impossible to model. With a bit of care, I might be able to make those parts on the Form 1.

I may not be posting about the Makerbot here much, but it still gets occasional use for model railroading. Check out my latest experiences over at my Vasona Branch blog to see how I'm using the 3d printer for model railroading, or look at all the 3d printing related articles there.

Final results for the Shapeways part

And just to prove that I'm not just making up stories about repairing hundred-year-old furniture for the page hits, here's a picture of the repaired table, with the fixed caster in the center.

The table has a pedestal base that splits in the middle; each side of the base has three casters, and a central post with a caster supports the table when it's pulled out to its largest size. Here, you can see two of the original casters as well one the repaired one.

My wife mentioned this weekend that she'd always been really frustrated by the broken caster, but never had the stamina to complain to the refinisher and get him to find a replacement of the correct size. She was ecstatic that we could fix the table, and even happier that we'd learned some new techniques to make the replacement part.

Once again, thanks to Shapeways for the replacement part, and Makerbot for making me trust that I could make a correctly-sized replacement part!

...Wherein the Author Repairs a Hundred-Year-Old Caster...

Man, that Shapeways stainless steel is pretty.

I got my second delivery from Shapeways today, and it had the two metal parts: the screen door catch cast in stainless steel, and the dining room table caster printed in stainless but with a bronze finish. Both are well-finished, precise, and smooth - although the photo might make it look like the parts have print lines, the parts actually feel smooth. The larger latch piece is 1.5 inches long, so that'll give you a sense of how fine the metal 3d printing can be.

First step: reassemble the table caster. The part's pretty much perfectly finished straight from the box, but I sized the axle hole a bit small so I could drill it to the diameter of the axle. I was a bit worried about this; stainless steel is usually a horrible material to drill or machine because the metal at the surface hardens as it's cut; if I cut the stainless steel evenly removing a bit each time the drill spins, it'll drill fine, but if I don't advance the drill bit far enough, the metal will harden because of the pressure of the tool, the tool will stop cutting, and I'll have to push lots harder to drill through the casting. Traditionally, this is described as a weird "ka-thunk!" with the drill not cutting, then suddenly grabbing on the metal when enough pressure's added to cut the metal.

Luckily, the Shapeways sintered metal cut drilled smoothly and easily, so getting the axle hole square and the right diameter wasn't hard.

The original axle (only a hundred years old!) was bent, so I knew I needed a new one. The old one had both ends of the rod hammered wide to hold the wheels on, meaning that the caster couldn't be disassembled without cutting the axle. Instead, I wanted to make sure I could remove the axle if I needed to disassemble the caster. Because the wooden wheels are 100 years old (and already have flat spots), I suspect I'll need to replace those some day. For the replacement axle, I borrowed a 3/16" diameter stainless steel pin intended for trailer hitches; one end already had a wide head, and I shortened the pin with my trusty hack saw and cut a slot with my lathe for an E-ring to secure the wheels on the axle using a parting tool. I then drilled out the axle hole just larger than the axle. The axle got reassembled - pin, wheel, printed part, wheel, and E-ring - and out broken hundred year old caster is ready to go back onto the table.

Pics of the fixed table later.

The caster broke when we refinished the dining room table a few years ago. The guy doing the work was apologetic, and searched for a matching caster without much luck. I remember thinking at the time that I could probably machine a new part, but I knew it would be a challenge to get the dimensions right and get the work suitably precise. I'd even thought at the time I ought to learn about bronze casting, but really didn't need an excuse for another hobby.

Fast forward three years, and access to the Makerbot and Shapeways made replacing the part easy. Without the Makerbot, I wouldn't have been able to experiment with shapes and test that the printed piece would fit and function correctly. Without Shapeways, I wouldn't have been able to print the new part in a material strong enough to hold up the table. Without both - a handy, personal 3d printer, and a way to print in exotic materials, we'd still have a broken table.

Thanks, Makerbot and Shapeways!

First Shapeways Part!

I got a delivery from Shapeways today - a nice box shipped all the way from the Netherlands to California and containing only the tiny screen door latch. The metal parts must still be in process.
The new part is coated in a matte black finish and feels very light; with the rough finish, it feels almost like dense foam. It's a bit lighter than the original injection-molded piece and Makerbot-made piece. I worried a bit about the part's strength (I printed it in Shapeways's "black, strong, flexible" plastic), but it seems robust enough to be handled when locking the screen door. The bit of white visible on the part shows the underlying plastic color; I used a countersink to cut the depression for the flathead screw attaching it to the door.

The great news is that the Shapeways part exactly matches the original, broken latch in overall dimensions. Although a bit pricey at $6.88, it required none of the sanding and finishing I've done for my Makerbot-printed parts.

The three-latch picture shows how the part compares to the original latch and to my Makerbot-printed part. One surprising difference is in wall thickness. I'd designed the original model to print on the Makerbot, and to simplify printing, I sized all the walls 0.74 mm (or the thickness of two extrusions.) By doing so, the Makerbot didn't try filling between the extrusions and fouling on extra plastic. The Makerbot-printed walls end up at about 1.4 mm, close to the thickness of the original parts. By contrast, the Shapeways part walls came out exactly 0.7 mm thick - half as thick as the original. It looks strong enough, but the part seems surprisingly thin.

Now, I just need to wait for the metal parts to arrive!

Differences between Models for Makerbot and Shapeways

I just sent my first parts off to Shapeways - a couple replacement pieces for our sliding doors, and the replacement casting for the dining room table caster. As productive as the Makerbot is, using an outside printing service works for these items. Two of the parts (the caster and a catch for a screen door) need to be printed in metal for strength. The third, a latch for our screen door, will be printed in black plastic. I'm curious how the latch prints; I've been able to print lots of these latches on my Makerbot, but the part requires a lot of sanding to make it as smooth and shiny as the original. I'm looking forward to seeing how the Shapeways's final product looks.

I'll post details once the parts come in.

I was a bit surprised at the changes needed to get a part ready for Shapeways. Take, for example, the latch. When I'd originally modelled this part, I'd drawn it in SketchUp as a solid object. To print it on the Makerbot, I run it through Skeinforge to generate the gcode file which describes exactly where plastic gets extruded. One of Skeinforge's neat tricks is to let the user decide how solid the object should be. Should it be 100% plastic all the way through, or just contain a cross-hatch which provides enough support for the object, but only fills 20 or 30% of the model with plastic? That decision both speeds up printing and cuts the amount of plastic being used. That cost isn't a big deal because the Makerbot plastic costs around $50 for five pounds, or around 10 cents a cubic centimeter.

[Four versions of the sliding door latch. Clockwise from left: original Arcadia screen door latch, injection molded in black plastic. Original model, drawn as a solid. New model, designed to be hollow for cheaper printing. Partially sanded latch almost ready to be used.]

Shapeways, by contrast, assumes that you want the object completely solid unless you design in hollow areas. Their price is also higher because of the better quality printing, the cost of the machines used, and postage. For plastic models, the cost of an object varies from $1.50 to $3.00 per cubic centimeter for plastic and nylon materials, and $10 per cubic centimeter for the sintered stainless steel models. So when I uploaded my original Makerbot-friendly design to Shapeways and asked for a quote for the object, I got a price of $5.63 for the 2.57 cc object, printed in the "White, Strong and Flexible" material.

Ok, time for a bit of thought. I'm a bit cheap, and almost $6 for the latch is on the edge of my tolerance. All that solid material didn't seem essential for the part - were there ways I could cut down on the plastic used? I looked at the original part, and saw I'd made my model a bit too large, so I cut down the shape a bit to match the original, and brought the price down to $4.79 for 2.19 cc of material.

But could I do better? The original injection-molded plastic casting, although cracked, was still around, and I saw that it was actually hollow. Injection-molded pieces pretty much have to be hollow, from what I understand. The plastic needs to cool as quickly as possible after being placed in the mold, and needs to cool evenly to avoid warping. I tried hollowing out my original piece, but found matching the non-right-angles with SketchUp's extrusion tool worked really poorly.

Instead, I started my design from scratch again, this time planning on hollow walls that were 0.7mm or 1.4 mm thick. Those numbers were chosen so I could make test prints on the Makerbot easily; 0.7 mm walls get built as a double shell of plastic filament, and 1.4 mm walls get built as four-thread shells. I extruded side-to-side to get the non-right-angle on the base, then filled in as appropriate to get support for the metal tab that actually moved the latch. It took me a few more hours, but I finally got the piece down to 1.62 cc and a final price of $3.93. I printed a couple on the Makerbot; the pieces are a bit rough, but definitely usable. I'll be interested to see how the final Shapeways parts work.

My other big lesson was why I like the idea of 3d printing complex shapes. The third model, the screen door catch, is a relatively simple design that can be fabricated with machining tools pretty quickly. The version pictured took me a good three hours of careful work (including tweaking the design when it didn't actually fit the existing screw holes). Unfortunately, one wrong turn could have ruined the piece. That three hours of work was also fine for a single model, but I'd hate to have to make three or four of those catches. Being able to make a single model and then print a bunch of parts is much more appealing appealing.

So, my key lessons for the last week:

* It's fun to have access to Shapeways to print final models. I'm looking forward to seeing the final parts.

* Different designs are needed for the cheap-and-Skeinforgeable models for the Makerbot, and the expensive-and-solid models for Shapeways. Sometimes the same model can be used in both places, but plan on a bit of tuning.

* It's often better to start the design again from scratch rather than try to tweak an existing solid Makerbot model because of the difficulty of changing faces inside the SketchUp model. I did have better luck when I switched SketchUp to show a wireframe, rather than solid, object.

* Even when I can machine a part out of metal, I don't think I'd want to make more than one or two of the same part. 3d printing in metal gives me an easy way to make duplicate parts.

It's Different When the Printer's Always There

There's always the decision of whether to buy some complex tool like a 3d printer, or just borrow time on one.  When I was thinking of getting a Makerbot, some friends in LA reminded me they sell high end 3d printers, and if I could send them an STL file, they'd be glad to print my part on the nice machine in their garage.  I've never taken them up on that offer. As I've seen when borrowing time on a metalworking lathe, having to *go* somewhere or wait for the opportunity to use a tool increases the chance I'll never do it. Having access to the machine at home makes it much easier to experiment in some spare moments, and try crazy ideas without the planning and commitment to go elsewhere to do my project.

I got reminded of the benefits of having a machine handy this week.  I've been running low on projects for the Makerbot lately.  Luckily, a friend sent a pointer about Jay Leno's  use of 3d printers to keep his classic cars running.  He'll design a part, print it, and if it fits correctly get a copy made in metal, or sometimes use the actual plastic piece when appropriate.

That reminded me of one of my lingering repair jobs.  Our dining room table dates back a few generations (and supposedly came around the Horn to California), but when we refinished it a few years back, the woodworkers broke one of the casters.  It's an odd design - finding the patent is easier than finding a modern reproduction - and the small (1" cube) bronze casting wasn't easily reproduced.  I think I could machine a replacement piece, but I know it would take a few hours work to make a piece, and I'd probably have to redo the piece a few times if it didn't fit perfectly.

Luckily, Shapeways is printing stainless steel these days at $10/cubic centimeter, so I realized if I could make an STL model of the piece on my Makerbot and test that it's the right shape, I could send it off and get a replacement piece.  Our table would then be ready for another hundred years of use.

The problem is that I wouldn't trust that I could get the design of the piece right on the first try... or tenth try, and I certainly wouldn't try making a replacement piece with a three week turnaround time and $40 charge each time. But I've got a Makerbot, and while it won't print in metal and might not be as precise as the expensive machines, I know it's available, and I can easily run through multiple design attempts in an evening. If the design works, then I might send it off to be printed.

So with a couple evenings of work in SketchUp and on the Makerbot, I'd printed four example pieces, found cases where my measurements were off, and tuned the design.

Helpful hints when trying to replace a mechanical piece:

1) The original piece was a bronze casting, and whoever made the original master had worked to make a beautiful piece: smooth curved shape, no sharp edges.  SketchUp, with a bit of work, can add such curves.  However, once the shape stops being a simple rectangle, it's really painful to adjust the position of axle holes and precise measurements.  As in machining, I learned to start by making a very simple shape, add the high-accuracy features, print a model, and test whether it fits and works mechanically.  Once the shape works, then I started playing with the design.

2) By hand, the easiest way to add curves to a SketchUp design is to draw a curve on a flat face, then extrude (or un-extrude) the shape through.  This only allows curves on one face since extruding doesn't work so well with curved faces or angled faces.  SketchUp also doesn't find intersections between curved faces automatically, so extruding (for example) a pair of intersecting holes through an object doesn't correctly handle the intersection.

The Rounded Corners SketchUp plugin might have helped here by letting me round or slope edges to better match the appearance of the original casting.  Note that the Makerbot renders 0.3mm thick levels, so having more than 3 faces on a rounded corner with radius 1mm wouldn't get me a better surface.

The Rounded Corners plugin only works well if I did all edges at the same time, and unfortunately it kept trying to round the drilled holes. I finally gave up, and used the grab tool to manipulate edges to round off the design.

3) I still need to figure out how to do the cupped socket in the casting.  I made the socket here using the "Follow Me" tool, but I'm also tempted to just get the 3d printed metal piece close, then machine the part with a ball-end mill to the precise dimensions.  Machining stainless steel isn't easy, but it might be easier than trying to get a smooth cupped surface at the correct dimension in the STL only.

Now I just need to get my courage up and ask Shapeways to print me a copy in metal. Heck, maybe one of the strong plastics would be enough to get the caster rolling again!

(BTW, Shapeways's price for this piece in stainless steel is $40 - probably worth it so I don't have to machine an equivalent piece. Interestingly, I'd thought their price was based on material used, but it looks like it's actually based on object volume. Because the casting measures in at 4.06 cc, I ought to see if I can get rid of that last 0.06 cc to drop the price $10.) (Bzzt. Ignore Robert's predictions about cost on his late night posts.)