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Re-Pumping a Chiller Unit for Laser Engraver

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awemawson:
I went to use my Chinese Laser Engraver to make a label only to find that it was reporting an error on the water circulation. Now these things come as standard with a small immersible pond pump, and you provide a bucket to put it in  :clap:

Now I have to use anti-freeze as my laser is next to the roller shutter, and I didn't want an open bucket of poisonous antifreeze on the floor in case the dogs took a sip, so I got an enclosed 'Chiller Unit'. These things are essentially very simple - they have a reservoir tank, and a circulating pump that pumps coolant through the laser tube, and returns it via a pair of aluminium tube radiators. There is a thermostat controlling a fan cooling the radiators, and a flow sensor coupled to an alarm sounder. Finally there is a thermometer display showing tank temperature. They are quite expensive for what they are, but I was fortunate enough to pick a used one up for less than half price on eBay. It has served me well for a year or so until this incident.

Examining it it was obvious that the pump wasn't running. It's a brushless 24v DC 25 watt jobby. The exact identical item is available on various Chinese web sites, but at quite a price and a very long lead time.

Time to see what else will fit. Several small 24 V pump available in the UK on ebay - but with different mountings and different inlet pipe diameters, but I was sure that could be overcome  :clap:

Ordered one and the postman delivered it this morning so here goes :

First remove the old pump. Mounted nicely on a rubber vibration mount, but the wet side was intriguing to say the least. It seems they've used soft silicone tube with silicone sealant and tywraps to hold it all together

awemawson:
The replacement pump was a nice close match in terms of its electrical characteristics and flow rate - actually it's flow rate was slightly greater. However it's mounting was completely different.

A bit of cogitation resulted in me bending up a bracket from 1.6 mm galvanised plate to adapt the new pump to the original holes that were in the chassis.

The differing input port sizes was easily overcome by a bit of reinforced pvc pipe that happened to have both the right i/d and o/d  :thumbup:

awemawson:
So I popped the new pump in and re-made the electrical connections, and re-filled the tank with the antifreeze solution. Sure enough, things are back to normal, no alarms  :ddb:

However I'd noticed when I drained the tank that there were bits floating about, so had filtered the coolant through a spray painting filter on the way back in, and filtered out some fibrous 'stuff' that was sufficient to block the filter. Now as the pump circulated coolant through my 'test loop' I realised that there was still quite a bit that must have been in the radiators.

Time to drain down again and re-filter  :bang:

awemawson:
So I left it running on the test loop for a while to prove out it's potential for leaks, then put it back together and returned it to service on the laser. Perhaps I can make those labels now  :scratch:

wheeltapper:
have you taken the old pump apart? it might be the same crud stopping it working.

Roy.

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