Repair (or get rid of) the faulty extraction fans for the laser-cutters

[amcewen]

As a side-effect of #1978 and #184 we've now got two broken fans for the extraction of the laser-cutters. We should see if they can be repaired - either both, or making one good one out of the two broken ones - so we've got a spare on hand; or if not, we should get rid of them.