Arcdroid CNC Plasma Robot in Rapid Prototyping Processing
The Arcdroid is a compact 2-axis CNC plasma table that turns a hand torch into a cutting machine for plate parts. This page explains what it can hold, what it cuts well, and where a prototype should leave the plasma table and go to milling or turning instead. Written for design and manufacturing engineers who need flat metal parts fast.
What this page covers
One topic: plasma-cut flat prototype parts, and the point where the process stops being the right choice.
What the Arcdroid actually is
The Arcdroid is a two-axis CNC arm that mounts a handheld plasma torch and moves it over a steel table. It is not a gantry router and it is not a machining center. Two stepper axes drive the torch in X and Y; the arc does the cutting. The whole machine fits on a bench and runs from a normal single-phase supply, which is why small shops buy it.
Because the torch is a plasma torch, the cut is thermal. Metal is melted and blown out of the kerf by the gas stream. That gives you a fast, low-cost way to make flat plate parts without tooling. There is no cutter to load, no fixture to clamp beyond a few hold-downs, and no spindle to program.
Speed is the main selling point. A 300 mm bracket in 6 mm mild steel cuts in well under a minute of arc time. Set-up is a DXF file, a pierce point and a lead-in. On a short prototype run, that is often the whole job.
The trade-off is dimensional quality. Plasma leaves a tapered edge, a heat-affected zone and a rougher surface than milling. If your drawing calls for ±0.005 mm and Ra 0.8–1.6 μm, this machine will not deliver it, and no amount of parameter tuning will change that.
- 1Good fitFlat plate brackets, gussets, mounting plates, weldments
- 2Poor fitAny part with pockets, bores, threads or tight tolerances
- 3Typical tolerance±0.2 mm on thin plate, looser as thickness climbs
- 4Edge conditionDross on the bottom, slight bevel, oxidized cut face
Thickness, kerf and the limits of a plasma cut
Cut capacity depends on the torch, not the table. A small handheld torch on the Arcdroid handles roughly 1 mm to 12 mm mild steel cleanly; beyond that the arc struggles and the edge quality drops fast. Stainless and aluminium behave differently. Both conduct heat away faster, so you need more current for the same thickness, and aluminium tends to leave a heavier dross layer.
Kerf width is the gap the arc burns away, typically 0.8 mm to 1.5 mm on a small torch. The CAM step offsets the toolpath by half the kerf, so the finished part comes out at the drawn size if the kerf value is right. Get it wrong and every hole in the batch is off by the same amount. Measure one test coupon before running the plate.
Hole diameter matters more than most people expect. A plasma arc cannot cut a hole much smaller than the plate thickness and still hold a round, usable edge. On 6 mm plate, plan for holes of 8 mm and up. Smaller holes are better drilled after cutting, or the part goes to a mill.
Heat input is the other constraint. Thin plate warps. Long straight cuts on 1–2 mm sheet can bow the part as it cools, and two parts cut close together may pull out of tolerance. Leave a wider nest spacing on thin material and let the plate cool between passes.
Plasma cut versus CNC machined prototype
Same part, two processes. Pick by tolerance and geometry, not by habit.
| Factor | Arcdroid plasma | CNC milling |
|---|---|---|
| Geometry | Flat 2D profiles only | 3D, pockets, bores, threads |
| Tolerance | ±0.2 mm typical | ±0.005 mm |
| Surface finish | Rough, oxidized edge | Ra 0.8–1.6 μm |
| Plate thickness | About 1–12 mm | Any, up to 4,000 mm travel |
| Prototype lead time | Same day, in-house | 3–5 days shipped |
| Best use | Brackets, gussets, weld prep | Mating faces, bearing seats |
Running a prototype batch on the table
Start from a clean DXF. Closed contours, no duplicate lines, no open paths. Plasma CAM tools fail on open contours more often than on any other input error. Check the file in the nesting software before you load plate.
Nest with the grain in mind if the part will be formed or bent later. Cut direction affects which side of the kerf carries the dross, so on visible parts run the torch so the dross lands on the hidden face. On thin sheet, alternate cut direction between adjacent parts to spread the heat.
Pierce on scrap, not on the part. A pierce blow-through leaves a crater roughly 1.5 times the kerf, and if that lands on the edge of a finished profile you will be grinding it later. Lead-ins of 3 mm to 5 mm on a straight segment solve this.
After cutting, expect a deburr step. A quick pass with a grinder or a tumbler removes dross and takes the sharp edge off. If the part is going to powder coat or paint, that is also the moment to check flatness, because coating will not hide a bowed plate.
When the prototype proves out, the same DXF usually feeds a laser or a punch for production. That is the real value of plasma prototyping: the drawing survives the process change, and only the tolerance band moves.
When to cut on plasma and finish on a mill
Many prototypes need both. A weldment bracket might be plasma-cut to profile and then have two bearing bores milled into it. That sequence works well, and it is cheaper than milling the whole plate from solid. Cut first, machine second.
The order matters for a reason. Plasma cutting puts heat into the part, and the part moves as it cools. If you mill the bores first and cut the profile afterwards, the profile cut can pull the plate enough to shift those bores. Cut the outline, let it cool, then set it up on the mill.
For parts that must hold a flatness callout, a stress-relief or a light face cut after plasma is common. A 0.5 mm skim off each face removes the heat-affected layer and gives you a clean datum. From there, normal milling tolerances apply.
GreatLight runs both sides of this workflow. We have 16 simultaneous 5-axis machining centers, 12 four-axis mills and 27 three-axis machines, plus mill-turn centers, so a plasma-cut blank can go straight onto a mill in the same shop. That avoids the shipping step and the re-datum risk that comes with splitting the job between two suppliers.
- 1Cut then machinePlasma the profile, mill the bores and faces after cooling
- 2Skim cut0.5 mm per face to remove the heat-affected layer
- 3One supplierFewer set-ups, one datum chain, one inspection report
Common questions
Can an Arcdroid hold ±0.005 mm like a CNC mill?
No. Plasma is a thermal process and the arc erodes the edge as it cuts. Expect around ±0.2 mm on thin plate, and looser on thicker material or on long thin parts that move as they cool.
If the drawing needs ±0.005 mm, the part has to be milled. There is no parameter set that closes that gap.
What is the thickest plate the machine can cut?
It depends on the torch mounted on the arm, not on the table itself. A small handheld torch cuts roughly 1 mm to 12 mm mild steel with acceptable edge quality. Past that, the cut slows down, the bevel angle grows and dross gets harder to remove.
Stainless and aluminium need more current for the same thickness, so treat 12 mm as a mild-steel figure and derate from there.
How small a hole can plasma cut?
A practical rule is that hole diameter should be at least the plate thickness. On 6 mm plate, plan for holes of 8 mm and up.
Anything smaller tends to come out oval or ragged. Drill or mill those features after the profile is cut.
Do I need to deburr plasma-cut parts?
Yes. The bottom edge carries dross and the top edge is sharp. A grinder pass or a tumbler run handles most prototype quantities.
If the part will be anodized or powder coated, deburr before finishing. Coating follows the edge and will not hide a rough cut.
Can plasma-cut parts be welded?
Yes, and that is one of the better uses for the process. The heat-affected zone is narrow on thin plate and a light grind on the cut edge is usually enough prep.
For structural welds, remove the oxidized layer first. It is brittle and can trap inclusions in the weld pool.
When should a prototype skip plasma and go straight to CNC?
Skip plasma when the part has pockets, threads, tight bores, mating faces or a flatness callout. Also skip it when the material is thin sheet that will warp, or when the geometry is not flat.
A quick test: if the drawing can be fully described by a 2D contour and a thickness, plasma is worth trying. If it needs a third dimension, it goes to the mill.
Send the drawing, get a process recommendation
Upload a DXF, STEP or PDF. We reply with a quotation and a DFM analysis within 12 hours, and we will tell you plainly whether the part should be plasma cut or milled.
12-hour quoteFree DFM analysisNDA on request100% inspection
