Project Plasma CNC
Notes on re-working the existing Grote_CNC_freestafel into a Plasma CNC cutter with our new PlasmaCutter
Rough Plan
- Find a proper 8x5 flex-tube to Euro2 pneumatics coupler for the main box.
- Wire up Aart his [plasma torch 'pen' style using one of the spare mounting plates for the CNC machine.
- It seems to have an extra pilot wire/HF capability.
- It has a spacer ring.
- We have no spares yet.
- Re-use the existing pneumatics
- Current is 6mm OD v.s. cutters 8mm OD -- so we need to check the flow. And otherwise increase diameter for all
- Make it easier to swap heads (wood v.s. plasma).
- We have nice quick release plates - but the bold is a bit hard to get to
- We currently do not have easy connectors for the earth-wire; alighnment lasers and the air.
- The power connectors are a bit of a mess
- We have several unused wire runs in the flex-chain.
- The current emergency stop buttons pick up interference from the plasma cutting - which upsets the FGPA/embedded CPU and the keyboard of the PC.
Todo's
- find out what sort of air/current connector is used on the unit (M12?, conical?)
- find out what type of earth connector is used on the unit.
- confirm exact sizes/threads of the current pneumatics used. Including the HBM ones (in at least one case a 1/8 was sold as a 1/4).
- understand how hard it would be to build / use the extra HF /pilot arc wiring we have on the plasma pen:
I am a bit confused as to the naming - it seems that the industry now calls the spark-gap starting HF; and the HF pilot arc; and the true pilot arc something like separate pilot arc.
So if we have an expert - or someone enjoys becoming one - yes please !
- find 20-30 meters of shielded cable & rewire all emergency buttons in a ‘star’ configuration (all to one point as opposed to a loop).
- ask our resident electronics experts very nicely to make us some `opto’/something separation for these long wire runs with a relatively solid voltage/current through the switches. (Bonus point if you manage to do the entire thing optical; including the buttons themselves!).
- see if we can get enough flow through the existing 3.2x6mm tubing of the gantry; and if not upgrade that to a 5x8 diameter. Which is not entirely trivial as the current CNC has a solenoid. And it has to be flexible.
- bit of a tedious (but rewarding) task of removing all the old wires/no-longer-used wires from the energy cable trains and feeding the new ones through.
- find a handful of small size quick release pneumatic connectors that match above. And while we do that - also connectors for the alignment lasers and the grounding wires.
- find some flexible wire suitable for 40A / few kWatt / 20m-ish? (and ask our resident electronics / physics experts if it helps if this is shielded).
- move the current dangling connectors to a small box/plate on the Z-axis so we can swap heads. Do something clever with the suction pipe to make it fast/easy release.
Volunteers
Dirk will be looking at the pneumatics, fittings, gaskets, solenoid and the connectors in the next couple of days.
Specs
- Table size: ruim 2m x ruim 1m ?
- plasma cutter
- max 40A, few kWatt ?
- trigger switch is wired to 'CB mic' style two prong connector (male on unit; female on end of wire).
- Around 150 Liter/minuut air usage: implies 5mm tube inner diameter is fairly minimal
- air inlet hose plasma cutter 8x5 (Outer diameter, Inner Diameter) - pressure generally 5 Bar or about there.
- air hoses on the CNC machine now: ~6mm outer diameter
- CNC torch
- Outer diameter around 29.5mm
- air seems G1/8 inner thread
- second brown wires goes to tip -- HF/pilot starter?
- Should get away with 2.5 mm^2 copper wiring: 10m 2.5 qmm Cu is 0,07 ohm -> 2,5V verlies bij 40A according to Aart. May be a bit more if we need to add a connector.
Notes, links
- Most CNC heads seems to use magnet easy-come-loose couplings to protect the head as the steel can 'point up' during cutting.
- Exact metric sizes of G1/4, G1/8: https://www.festo.com/wiki/en/Threads_in_pneumatics
- Current pnematics connectors we are using https://www.hbm-machines.com/producten/luchtgereedschap/snelkoppelingen-en-insteeknippels/hbm-euro-insteeknippel-14-uitwendig
- https://www.hf-electronics.nl/CB-Plug-Female-2-Polig
- Torch that is more like 'our' current LIDL torhc: https://nl.aliexpress.com/item/PT-31-LG-40-plasma-cutting-straight-lance-head-40-0-degrees-pen-gun-head-LG40/32674455800.html
Ordering
- Small set of spares for head. https://nl.aliexpress.com/item/26-Stks-set-Plasma-Torch-Snijmachine-Accessoires-Tips-Voor-LTP5000D-LTPDC2000-Lastoorts/32835947680.html
- CB plug; female, 2 polig
- 5mm outer, G1/4 outer coupler for 8x5 tube to Euro insteeknippel
- Right euro insteeknippel
- Suitable earth connector (e.g. yellow banana plugs/chassis) 1x female, 3x male)
