Positioning accurately: jigs, camera and series production
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A beautiful design is of little use if it sits two millimetres off centre. In UV printing, the object lies loose on the print table, and the printer does not initially know where it is. How accurately the design lands depends on how you align the object and the file to each other.
The origin point
Every flatbed printer has an origin point, usually a corner of the print table. From there the software counts the position of your design. If the object lies exactly at this spot, the design also lands where you placed it in the software.
This only works if the object has a fixed stop. A stop is an edge that you push the object against. It can be an acrylic angle, a piece of adhesive tape or a strip. What matters is that it does not move and always sits in the same place.
A simple trick without tools:
- Fix a piece of paper or card on the table
- Print the outline of the object on it
- Place the object exactly in the printed contour
- Print the actual design
Positioning with a camera
Some machines have a built-in camera, such as desktop machines like the eufyMake E1. The software then shows a photo of the print table, and you slide the design directly onto the object in the image. This is quick and convenient, especially for one-off pieces. The camera has limits, though: on the E1 it works up to an object height of 60 mm; above that, the software guides you through a manual origin alignment.
A few points to bear in mind:
- Calibrate the camera: After changing the print plate or after transport, the image can be slightly offset. The calibration is described in the manufacturer’s manual.
- Perspective: Tall objects appear slightly shifted in the camera image because the camera looks at them at an angle. With flat parts this is barely noticeable.
- Series: For many identical parts, a jig is usually more accurate than realigning each time.
Jigs
A jig is a plate with cut-outs into which the objects fit exactly. It sits fixed at the origin point. Each object thus has its fixed position, and you only have to insert the next one.
| Material | Advantages | Disadvantages |
|---|---|---|
| Acrylic, laser-cut | very accurate, flat, quick to make | laser needed, may reflect UV light |
| Plywood or MDF, laser-cut | inexpensive, good for flat parts | can warp with moisture |
| 3D-printed | also for round or irregular shapes, holders with depth | slow for large plates, check flatness |
| Foam board, card | quick, no machines | less durable |
3D-printed holders are ideal for lighters, pens, golf balls or phone cases, which would roll away or tip over on a flat plate. You will find the basics in the 3D printing section.
What to watch out for:
- Dark, matt surface: Light-coloured or reflective jigs can throw UV light back towards the print head. This can cure ink on the nozzle plate. Trade media and manufacturers therefore recommend dark, matt materials.
- Height matched to the object: The jig should not be higher than the printing surface of the object. Otherwise the printer measures the jig as the highest point.
- A little clearance: Plan the cut-outs a fraction of a millimetre larger than the object so that it is easy to insert but does not wobble.
- File to match: Create a template in the software for each jig, with the positions of all the cut-outs already entered.
Height and print distance
The print head only works sharply within a small distance from the surface. Mimaki, for example, recommends keeping the difference between the lowest and highest point of the printing surface below 1.5 mm. Larger differences lead to blur and ink mist.
Many machines measure the height automatically. They go by the highest point. If several objects of different heights lie on the table, the flattest object comes out blurred. So print only objects of the same height per run, or equalise the height with spacers.
Even a single object can cause problems: a curved phone case with a camera bump, a notebook with a raised corner. More on this under Blurred UV print and ink mist.
Several objects per run
With a jig you can print many parts at the same time. This saves time because the printer does white, colour and varnish in one go instead of approaching each part anew.
- All objects the same height and equally well fixed
- Enough space between the objects so that ink mist does not fall on the neighbouring part
- Before the first series run, make a test print on paper over the jig and check that all designs sit in the centre
Variable data: names and numbers
Personalisation often means: same design, but each part with a different name. With 20 key rings, you do not want to create 20 files by hand.
- In the printer software: Some programs can automatically insert text from a list or table into the positions of a jig.
- In a graphics program: Illustrator, Affinity Publisher or InDesign have data merge functions. You build a page with all the positions of the jig and fill it from a CSV file.
- Manually with a template: For small quantities, a file with all positions is enough, in which you swap the names one after another.
Check every name for typos before printing. A misspelt name is the most expensive mistake because the part cannot be saved.
For business
For recurring products, the time for a good jig almost always pays off. It makes rejects due to misalignment rarer, speeds up loading and allows you to use inexperienced helpers too. Include the production time for the jig in your costing; it is spread across all later orders.
Continue with: Preparing print data and Printing on round objects.