Edit for 2014: this article is now nearly 4 years old, and nowadays there are soft-close kits by Blumotion and others that make this process much simpler and cheaper!
In this instructable I will teach you how to retrofit the Blumotion soft-close drawer system (from their TandemBox line) to almost any drawer! Most people prefer to retain a consistent appearance in their kitchen, so replacing the drawers entirely is out of the question (not to mention very expensive.) The Blumotion system is one of the best, however it only works with the corresponding drawer system from the same company... or so they thought :)
Tools you will need:
- bolt cutter
- small flat-head screwdriver
- small hacksaw (I used a coping saw)
- some bolts (small thread, M2.5 or 0.1" thread diameter)
- some screws
- ruler & pencil
The only requirements for the existing drawer:
- approx 12mm (0.5") clearance on either the left or the right of the drawer (almost any rail system will have this)
- approx 9mm (0.35") clearance behind the drawer
The drawer can be made of wood or metal - doesn't matter.
Note about the small piston-type door buffers / dampers:
Before this project I attempted to use these to damp my drawers, but they didn't work well (drawers wouldn't self-close, or still slammed shut.) The Blumotion system with its long throw and spring+latch mechanism overcomes these issues. Thanks to adamazing for bringing this up in the comments.
Step 1: Obtain the Blumotion Mechanism
WARNING #1: IKEA also sell an AU$10 RATIONELL damper add-on kit. This will NOT work as it contains only the damper and not the spring-latch mechanism which is so crucial to the system.
WARNING #2: Don't buy the bigger drawers as they use a different damping mechanism which is much harder to modify.
Obtaining this kit from IKEA is relatively straightforward. If you need a salesperson's assistance when ordering the kit(s), you will probably be asked if you have the correct RATIONELL cupboard in which to install the drawer - a lot of people have obviously tried to screw their existing drawers onto the RATIONELL rails with little success.
Once you have purchased the kit, take out the 2 rails and set the rest aside.
Step 2: Extract the Spring and Latch Mechanism From the Rail
The spring is the key to the Blumotion system. It provides a closing force just stronger than the damper, resulting in a consistent closing motion every time, nearly regardless of the drawer load.
First, extend the slider (and keep it extended until the mechanisms are removed.)
Using a small screwdriver, pry up the metal tab holding the small end of the spring mechanism down. You don't need to bring it up all the way, just loosen it up as far as the screwdriver will naturally go. Once this is done, use a finger to hold the mechanism where it meets the spring (see note in pic.)
Keeping your finger there, turn the rail over and use the screwdriver to disengage the plastic tab. Release the small end of the spring mechanism by pushing down with your finger (i.e. towards the end of the rail) and you can then lift it off the metal tab. Gently let it come to rest against the large end of the spring mechanism.
Step 3: Extract the Spring and Latch Mechanism From the Rail (cont'd)
IMPORTANT: do NOT let the slide close when the large end is loose, or you will likely jam the whole thing up. Fixing that is not hard, but beyond the scope of this instructable :)
Step 4: Extract the Damper From the Rail
First, we need to trip off a protruding tab on the damper housing (NOT the one on the damper itself, we need that!) If we don't trim off the tab then the damper will not sit flush against the side of the cabinet later on. It is MUCH easier to trim this off while the damper is still attached to the rail, so do this first!
Then saw off the whole damper mechanism, taking care not to damage the tab on the damper itself. If you cut just next to the ribbed section (see pic) it will be over very quickly.
TIP: don't hold the rail where I'm holding it, as the saw will go straight to your hand after cutting through the damper!
Step 5: The Extracted Blumotion System
The only Blumotion component missing is a simple yet critical one - the pin on the rail which engages the spring mechanism.
Step 6: Install a Bolt in the Drawer Side
Before drilling a hole in the drawer, you need to know exactly where to drill not only here but also in the cabinet, which is where we'll be mounting the Blumotion springs and dampers. The easiest way to do this is to remove a rail from the cabinet, fit it to the drawer and mark your mounting points on the drawer (use masking tape) and measure your offsets from the cabinet front and bottom edge of the rail.
Note that if your existing drawer system closes itself under gravity for the last 5cm (2") of travel, then your Blumotion system will need to be installed at the same angle. In my case, this angle was 2.5mm (0.1") down for the last 5cm (2") of travel, or a gradient of 1/20. The pictures in the next step will make this clear.
Once you know where to drill, installing the bolt is quite simple. I recommend using a split ring washer or a lock nut to ensure the bolt does not come loose over time.
As for the length of the bolt, the aim is to miss the cabinet wall by about 2mm (0.08"). Choose a longer bolt and cut/file away as necessary.
I prefer to keep the bolts as hidden as possible, so I've installed mine on the far side of the kitchen. Note that the second and third pictures in this step are of drawers on opposite sides of my kitchen.
Step 7: Install the Blumotion System Into the Cabinet
After installing the spring mechanism, pull the clear plastic piece forward until it locks into place - this primes it ready for the pin and the drawer.
For the damper, the angle does not matter so much, as long as the tab is facing outward so as to catch the drawer when it closes. Note that the distance from the front of the drawer must be sufficient otherwise it may stop the drawer from closing prematurely. There will be more than enough plastic "ribbing" on the damper housing for 2 screws which will hold the damper in place nice and securely.
Step 8: All Done!
The great thing about this method is that you will now have a number of perfectly fine drawers left over, and you can install these wherever you like as per the IKEA instructions. They just won't soft-close/auto-close anymore :) (Although if you only take one Blumotion mechanism out of each drawer, they will)
A final note: please remember not to slam your friends' drawers - not everyone has soft-close!