Part 2 Print or Print 2 Part?

I SUBSCRIBE TO A magazine called Design2Part. It’s like an old time Playboy or Playgirl magazine for manufacturers, prototypers, backyard tinkerers, full of stories and sources for companies in the USA that still manufacture things. Lots of exotic looking parts with explicit photos and illustrations and yes, I read it for the articles. The ads, too, because they’re a smorgasbord of small and large services for domestic manufacturers, specialized fabricators and finishers and providers of parts, and yes, even some screenprinters. These are electronics and industrial printers, labeling housings and control panels, or producing circuits, sensors and HMI components.

A recent install and training contract at a metal fabrication plant gave me the idea for Episode 30 of Art, Ad, or Alchemy? They had been sending parts out. Part 2 Print. Now they wanted to bring the Print 2 Part in house.

I thought it might be of interest to readers to learn a bit about this area of the screenprinting universe. If you’ve been printing t-shirts all your life, and wonder about printing in the 3rd dimension, maybe it’s a direction you could take to find some new clients in your region — small manufacturers — who in many cases need a printer who is up for a challenge. Anybody can be a DTF ‘printer’ these days and decorate a t-shirt. It takes a heat press and not much more. You are competing with every bozo in town or online, and the price you can charge is limited by your competition, not your costs.

Printing on 3-dimensional objects (NOT 3D PRINTING) presents unique challenges, but it can be very profitable – or economical, depending on who is doing the printing: Contract printer, or in-house. And screenprinting brings distinct economical and process advantages over other printing or labelling options:

• Screenprinting is faster than digital on production runs
  In one color printing, which is the bulk of industrial applications, screen printing throughput is significantly faster than digital printing except in short runs. If you are printing hundreds or thousands of a product, this gives you a competitive advantage, as well as faster delivery times.
• Screenprinting is more durable than digital or labels
  Heavier/thicker ink deposits with appropriate ink last longer. Labels can come off or fade or wear. Direct printing looks professional, a label looks temporary.
• Screenprinting allows for the use of specialized inks
  Unlike other processes, screenprinting allows the use of a wide range of inks including epoxies with catalysts for hardness, or inks formulated specifically to the product, not the printer. See square peg, round hole.
• Screenprinting is easily adaptable to substrate material and oddball part shapes and sizes

  If a part has a flat area to print, and you can hold it still and fit it under a screen, it can usually be screen printed. Digital printing of parts doesn’t provide this flexibility. And depending on the part, screenprinting allows a choice of material-specific inks that will bond and last, where others fade, scratch off, or wear off through continued use.

All of this adds up to screenprinting being the method of choice when compared to or competing with other printing processes. This becomes your unique selling proposition, or whatever marketing buzzword you want to attach to it. Of course you have to be able to deliver the goods.

The challenges for a screenprinter who has never printed anything other than t-shirts or flatstock aren’t too bad … if you can make a good screen.

The screen is usually 230 or higher.

Your stencil has to be resistant to the ink

Easy, right? Now the hard part(s).

A typical screen printing press designed for parts printing. The main difference is the ability to reset the height and off contact. The jig is attached to a slotted base, which can be height adjusted. Screen fits in the holders, the head raises and lowers for the print. (Photo courtesy RH Solutions)

• PRESS: The press installation referred to above was a semi-automatic, with a special jig table which could be raised or lowered depending on the thickness of the part and the holder. This is one of the fundamental differences to ‘regular’ screenprinting. You can also make a setup for manual printing. Same idea, have the screen adjustable above your printing base, so you have the ability to place and remove the part, and the screen can come down and stop with a little off contact.
• STOCK: Whatever the material, you need to match an ink to it. For metal parts, or parts with powdercoating or enamelled or ceramic surfaces, the go to ink will be an epoxy. Other materials will require a different type of ink to adhere and bond.
The stock must be uniform. In height as well as width and depth, because once in the jig or holder, it must present to the screen in the same place if you want to print multicolour, or even single color in register.
  
  Beware of rounded edges. You can’t print air. Your art must fit that stock and land on a printable area.
• JIG: This is the trickiest part. Jigs can be made of wood, welded up in the machine shop, or built from foam core and D-tape, but they have some common criteria if they are going to work.
The part has to be held securely during the print. If it moves, it blurs.
The jig holder must be mountable to the print table. On the auto, it has a typical slot system, where the jig can be attached with bolts. I’ve had jigs with magnetic bases, that stick to the metal of the table top. And in a pinch, we’ve built a jig holder and guides from foam core or other materials, taped down.
  
  The other consideration when making a jig is easy to load, easy to remove the part. And because it’s fresh wet ink coming out, picking it up must be easy to do without smearing the ink.


The rest of the components are common to automated textile or graphic printing – squeegee, flood bar, screen, and ink. Controls determine stroke length and repeat, pressures and angles, flood pattern, speed, peel, etc.

• Levelling: As in all other screenprinting, the screen must be parallel to the surface being printed. If it isn’t, the off contact distance between one side of the part and the other can often lead to problems, either requiring uneven pressure on the squeegee, or missed portions of the print.


Printing multicolor on a round object presents unique challenges. These drums were also handmade, so had irregularities in height, diameter and material! This is a hand printing setup.






A typical job, labelling breakers, receptacles or readout windows on a sheet metal housing. We put a clear mask over the part before starting the print run, then it’s easy to clean and reprint while adjusting pressure or registration.

• Run-on/run-off: This is another defining difference in printing 3-dimensional objects. If you are printing close to an edge, you have to have a support equivalent to the height of the part, so the squeegee is supported when it crosses the edge of a part. Otherwise the squeegee will pull the screen down and contact the surface, either at the start of the print, or at the end. This will make the image blur. A smart jig builder uses this lip as a register point — the part is placed in the jig holder in between the run-on/run-off lips. Sometimes you can just cut a part in half, and use the two sides as your register edges, attaching them to the jig holder, the part dropping in the space between.
• Ink: Well, if the plastisol printers thought waterbase inks were hard to use, they’re going to love epoxy inks …These inks are activated with a catalyst, and once mixed, they start to harden. Depending on the manufacturer, their working time is around 4 hours. You can add retarders, but once the cure gets going, nothing stops it … and you better clean your screen before that happens. Some other inks clean up easier, but usually these inks are all ‘air dry’ So if you are on a long print run, you either can’t stop — get a helper to take over — or you will need to clean the screen.
  
  Bigger shops might look at UV curing — with these inks, it’s possible to start and stop production, much like plastisol. Whatever ink you use, it’s main function is to stick. So, always test. And keep in mind. Many inks take days to achieve full cure. Many epoxies will set harder when give a bit of heat in an oven.
• Handling: This was mentioned above, but it’s important. The time it takes to do one print is made up mostly of stock handling. Picking the part, placing the part, printing the part, removing the part. Of all these, the actual printing is the quickest. So if you want to be faster, the speed comes from handling. Make every motion efficient. Have the part clean, dust free, and easy to grab.
When placing the part, make the jig easy to slap the part in, correctly aligned. If you are using a lip for a stop, the part should rest against the trailing edge, so the squeegee is pushing the part against the stop.
  
  When picking up the printed part, it should come out of the jig easily, and your fingers should be away from the ink.
  Where you put the part matters too: Have your trays or conveyor or racks close by.
• Drying: This will be determined by the ink. As many of the inks are air dry, a rack system will be needed. If the parts are too thick for a standard rack, then a table top or trays work. Epoxies need an oven to cure quickly, although a t-shirt dryer could be used.

That’s about it. I love the challenge of printing 3-dimensional objects and parts. Personally, although I love posters and art prints, I made my best coin on printing plastic parts, housings, and faceplates for charging equipment and other industrial uses. Why? When you are the only one who can do a thing, you can charge what you want, within reason. The need is always there as long as some inventor or manufacturer wants to label their product or machine. And it’s a really special feeling to help some local company put out a better product and help build our manufacturing base. Screenprinting plays a big part.