Have you ever tried to print multicolour with the Velleman K8200? By saying multicolour print, i actually mean swaping the filaments during the print. This can't be done though, if you won't make this upgrade. The main problem is that there's a huge gap, about 2 cm, between the gear that pulls down the filament and the hole that drives the filament into the hotend. The other problem, is that even if you fix that, you'll have to predict when to change the filament. The only solution, for now at least, is to predict when to make the change by calculating how many centimetres of filament is used for every layer for example. In my occasion, when i print tags or signs, i calculate the centimetres of filament used for every layer and i can predict when to make the swap. It's most based on experience i think, the more prints you make this way the better the results you'll have after time. Of course this is not the most accurate way to print with more than one colour, but anyone could make it. Moreover, the Velleman K8200 itself is not even designed for multicolour printing.
Step 1: Materials Needed
To begin with, you will need to have: a lighter, a 1cm spring with 3mm diameter and a pliers. The pliers will only be neede to place the "hot" spring into the base of the extruder.
Step 2: Dismantling the Extruder
You have to dismantle the extruder, so that you can have access in the inner side of it. You heat up the spring and by applying the spring into the base of the extruder as show in the picture, you melt the plastic and embed the spring to it. I suggest that you shouldn't stabilise the spring by using glue, because glue reacts with heat and it will not work. Beware that the spring should go into the plastic for about half centimetre, no more no less.
Step 3: Reassembling the Extruder
After you embed the spring into the plastic base of the extruder, you have to reassemble the extruder. Notice that the spring height should be right beneath the gear that pushes the filament downwards.
Step 4: Testing the Extruder
Now that you have reassembled the extruder is time to test it. Please do not install the motor until you finish this step. Insert the filament from the upper hole and watch it's direction. To work, it should insert right away the spring and slide into the hotend for melting. To be more accurate, as soon as the filament passes the upper hole and through the gear that pulls it downwards, it should immediately go into the spring and eventually in the hotend.