What is a micro-joint?
A micro-joint is a tiny uncut tab that holds a laser-cut part in the sheet until it's unloaded, also called a tab, micro-tab or nick. It stops small or thin parts tipping up or falling through the bed, and leaves a small nub on the edge where the part is snapped free.
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What does micro-joint mean in fabrication?
When a laser cuts a part's outline, the part comes free the moment the cut closes. Small parts can then drop between the bed slats, and thin parts can tip up and catch the cutting head as it passes. A micro-joint prevents that by pausing the cut for a short distance, leaving a bridge of metal between the part and the surrounding sheet (the skeleton).
Micro-joints are tiny, usually a fraction of a millimetre wide on thin sheet and wider on thick plate. They're added when the job is programmed and nested, and a part might have one or several depending on its size and weight.
How is a micro-joint used?
After cutting, the whole sheet is unloaded with the parts still in it. Operators break the parts free by twisting, tapping or knocking them out, and the skeleton goes to scrap.
Where the joints go matters as much as how many there are:
- Put them on edges that will be hidden, welded over or folded, not on a cosmetic face.
- Keep them away from tight-tolerance edges and holes.
- Use as few as will hold the part safely. Bigger, heavier parts need more.
Customers can ask for no micro-joints on visible edges. That's worth knowing at quote time, because it changes how the job is programmed and handled.
Why does a micro-joint matter?
Micro-joints protect the machine and the job. A tipped part can hit the cutting head, causing a collision that stops the machine and can damage the head or nozzle, and a part that falls through the slats is lost or damaged.
The trade-off is the nub. Each micro-joint leaves a small raised witness mark that usually needs filing, grinding or deburring off, and on a run of hundreds of small parts that adds up to real labour.
Undercut micro-joints
An undercut micro-joint sits slightly inside the part's profile, so when the part is snapped free the leftover nub sits below the finished edge instead of sticking out. That can remove the need to grind the joint off, which suits parts going straight to assembly or coating. The catch is a small notch in the edge, so undercut joints suit edges where a notch doesn't matter.
Micro-joints and quoting
Micro-joints are set when the job is programmed, so they don't appear on a quote. The time they create does: breaking parts out of the skeleton and cleaning the nubs. On jobs with lots of small parts, price that handling and finishing in. In Tempus Tools, deburring can be added to the quote as a secondary process, priced per part, by area or by weight, alongside the cutting.
Further reading: Are secondary processes costing you money or adding to your profit?
Quote the whole job, not just the cut
Tempus Tools prices cutting, material and finishing work like deburring on one quote, built from the customer's drawing, so the time spent after the laser gets paid for too.
FAQs
Why are micro-joints used in laser cutting?
To hold parts in the sheet while cutting, so small or thin parts don't tip up into the cutting head or fall through the bed.
Do micro-joints need to be removed?
The part is snapped free of the skeleton, leaving a small nub. It's usually filed, ground or deburred flush, unless the edge is hidden or welded over.
Where should micro-joints be placed?
On edges that are hidden, folded or welded, away from cosmetic faces and tight-tolerance features. Use only as many as you need to hold the part.
What's the difference between a micro-joint and a tab?
Usually nothing: tab, micro-tab and nick are other names for a micro-joint. A bridge is different. It's material left inside a part to hold a floating interior, like the centre of a letter O.
Do micro-joints affect cost?
Indirectly. Each one leaves a nub to clean up, so jobs with many small parts carry extra finishing time.