T3P3 Kossel Mini Kit Release 2

Assembly Instructions

Chapter 12 - Timing belt Installation

Creative Commons License

This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

Think3DPrint3D Ltd


1201 Parts needed

GT2 timing belt x 4m

100mm x 2.5mm zipties x6

NOTE: The motor pictures in this section still show the pulley fitted with the thin pulley flange at the end of the shaft. We have now reversed the pulley on the shaft for better  belt alignment - see Section 202 in Chapter 2 - so please ignore this difference. The correct alignment of the pulley is shown in this picture -->


1202 Fit timing belts

Cut the timing belt into three roughly equal lengths each > 1300mm long.

Pass the end of one length around the X-motor. It is easiest to insert the end on the right side of the pulley so it emerges from underneath on the left (face the belt so that the teeth can engage with the pulley).

Pass the end of the belt through the groove on the left side of the carriage, over the top of the idler bearings from left to right , and pull down until it reaches the carriage again.

Loop the belt around the top fixing peg on the carriage from right to left.

Adjust the length of the cut end to about 25 mm above the top of the carriage. Pass a 100mm ziptie around the belt, make into a loop and do up partly.

Push the looped ziptie down until the belt is tightly looped around the peg.

Tighten the ziptie, making sure that the belt teeth facing each other interlock to prevent future slippage,  and trim off the ziptie end. Do not trim the belt end yet.

NOTE:  Some customers have found it difficult to anchor the belts adequately with single zipties. If you are unsure of how well they are secured, then you can use a second ziptie to be on the safe side.

Check that the belt is properly engaged on the motor pulley.

Pass the other end of the belt around the bottom peg on the carriage, tighten so that the whole length of belt is under some tension, and ziptie as before.

Repeat for the other 2 belts, trying to get all 3 as near to equally tensioned as you can.

1203 Tension timing belts

Loosen the capscrews holding the top brackets in place on the towers slightly. Tighten the belt tensioners until the belts are all equally tight and make a low twanging note when plucked. If the top frame is badly out of level, so that there is a big variation (> 5mm)  between the lengths of extrusion sticking out of the the 3 top brackets, then it is desirable to correct this. Back off the tensioners,  level the top frame, cut a ziptie on the loosest belt and re-ziptie it with greater tension. Retension the belts as before.

Once the belts are tensioned to your satisfaction you can trim off any excess from the cut belt ends, but leave at least 5 or 6 teeth sticking out of the zipties. Finally retighten the capscrews loosened at the beginning of this stage.

Now go on to the next Chapter