Take the train to Köln-Ehrenfeld. There are several cheap rates offered by Die Bahn: e.g. the Schöner-Tag-Ticket (27€ for 5 persons, but only inside NRW, and only on work-days) or the Gruppe&Spar (drive in groups with at least six persons, discount up to 70%). Also there is Dauer-Spezial - use this link to find out if you can use this service for your destination. If you're planning to come via train from abroad, simply check the homepage of your national train company.
The station Ehrenfeld is best reachable from Köln central station via S12 and S13 (direction ''Düren'' or ''Horrem'') from track 11. See the timetables for details:
At the station Ehrenfeld, take the exit '''Venloer Straße'''.
From here, it only takes some minutes on foot:
Cross Venloer Straße and follow Heliosstraße to its end.
Turn right and after some metres left again into Lichtstraße.
It's about 500m to the location, a red house indicated with a large sign '''Vulkan'''.