On the last day of the residency, we [Residents Janet and Rob; Guest Zach; Coordinator Phoebe] ran a Make & Take event where we helped ten community members turn their drawings into linoleum block stamps. The workshop was GREAT! Everybody made at least one stamp, while some made two and one made six; the machines were cooperative; the designs were outstanding; the participants were wonderful; the conversations were fascinating; and the resulting imprints were beautiful.

above, a small selection of the stamped imprints we helped participants make during the workshop. Most started from tiny hand drawings, but a few were designed in the digital domain.

[TODO: image from workshop? Anyone manage to get one?]

Our goal here was to gently introduce participants to CNC machining without any of the fussy computer-centric steps usually required, like parametric modeling and the CAM doldrums. The core drawing-to-stamp mechanic leveraged two tools: mods, a browser-based digital fabrication workflow from CBA, and a pair of Carbide Nomad 3 desktop CNC machines we brought up from the TPZ Fab Lab in Boston. We also used a combination of on-phone image editing tools and Photoshop to prepare the images for mods. This documentation is focused on the Haystack workshop; for detailed instructions on the workflow, head over to the TPZ tutorial.

Fixturing

Our standard stamp machining process uses a 1/8” flat end mill for roughing and a 1/32” flat end mill for finishing; this provides sufficient detail while dramatically cutting down on the time it would take to do the entire job with the smaller bit. We initially considered devoting one Nomad to each step and moving work from one to the next, but decided this would require far too much fussy file transferring and would be prone to mistakes. To facilitate quick loading, we designed and fabricated a pair of quick clamps sized for the linoleum stock we brought which allows the machine operator to quickly and repeatably lock fresh stock to the bed of the machine.

above, installing a fresh ~2” linoleum block on the Nomad bed using one of the 3D printed clamps we developed and fabricated at the Haystack Fab Lab. So speedy!

Zach hastily pre-cut 40 linoleum blocks before heading up to Haystack and the resulting cut tolerances were not great; some blocks were nearly 1/4” smaller than others. This meant the clamp design needed to accommodate a range of sizes while still locating the bottom-left corner of the block to the origin datum. By representing the full size range in the Onshape CAD model of the clamp, we were able to ensure the clamping cams would sufficiently smush every size.

above, checking clamp range using models of the largest and smallest linoleum block we brought plus a bit of wiggle room on either side.

In order to prevent binding and ensure that clamping forces were consistent for all blocks, the cams were designed to have a logarithmic profile, somewhat like climbing safety gear. This curve results in a constant cam angle along the entire rotation. The CAD process produced a useful nugget: if you want to make logarithmic spirals, simply draw a helical spiral around the surface of a cone and project the result onto a new sketch plane.

above, a helix drawn onto the surface of a cone is projected onto a sketch plane to form the logarithmic face of the came.

If you’d like to make a set of clamps for your machine, you can 3D print a set from the *.stl files below, which are designed for ~2” blocks, or you can modify the Onshape design as needed for your size stock. Print the two heptabolts with 100% infill; the base and two cams seem plenty strong with 15-20% infill and normal PLA filament. The two clamp sets (white-on-black, black-on-white) we made for the workshop remained at Haystack to be used for future events, if desired.

• expand-y for clamp-y

Prior to the workshop starting, we installed the clamps with heavy-duty double-sided carpet tape to the MDF machine beds, inserted a linoleum block, eyeballed the X/Y zero point, and used the built-in zeroing probe to set the height for the evening.

Throughput

One of the reasons we feel the workshop was a success is that we were able to move some serious linoleum, so to speak. By looking at the *.nc file creation times from the workshop, we can get a pretty good idea of the total machine operator time needed to help a participant produce a stamp, including getting the drawing image from the photographer (Phoebe) or the digital designer (Rob); thresholding and cropping the image in Photoshop; toolpathing the two passes in mods; and actually running both steps on the Nomads using Carbide Create:

We started a bit after 5, so figure ~20ish minutes for intros, material distribution, instruction, and stamp drawing. Phoebe floated with an iPhone to capture drawings, perform initial image edits, and Airdrop them to machine operators; Rob did the same with students that preferred to use digital design tools like Illustrator. Zach and Janet each ran a Nomad set up back-to-back on a wide table, allowing them to share the linoleum bin, a small battery-powered vacuum, and a crucial de-fuzzing brush.

above, machining a stamp for a participant near the end of the workshop, and showing off a delightful build-up of linoleum debris on the Nomad.

It would be possible to run this workshop in an hour, but two hours seems to be a great tradeoff of stamp production vs long-workshop-exhaustion. The cycles are fast enough that it probably doesn’t make sense for a single operator to take on two machines, but with a few parallel machines and sufficient assistants it would be easy to support a relatively large group.