Assembling the Nimble¶
Before we begin¶
Because of the process used to make the plastic parts (SLS) there is a possibility of powder remaining inside some of the smaller openings. For instance, there might still be a little powder left in the holes for the mounting bolts. This is the moment to inspect the parts and to make sure they are all powder free.
- You will use the Worm bearings (part P) and both the shell housings (parts A and B)
- Insert one bearing into each of the shell housing.
- This can require a little force. If you cannot get it right, you can use the Worm (part G) to push the bearings in properly.
- Do this for both the bottom and the top shell.
- To assemble the gear shaft take the following parts:
- Gear shaft bearings (Part Q) 2x
- Gear shaft/Hobbed wheel (Part J)
- Gear wheel (H)
- Notice that on the end of the plastic part of the gear shaft we have included a little indicator to show you that the gear is turning. The shafts are so smooth that you would not be able to see it otherwise. If you want you can use a permanent marker to colour the top surface of the indicator to make it more visible.
- Insert the Gear shaft into the Gear and make sure the flat parts match. This needs a little push as it is supposed to be a close fit.
- Now fit the Gear shaft bearings on both sides and hold it together while going to the next step.
- To keep the Nimble closed and together, you can place the Breech block (part E) into the housing. This will lock into place with a click. To do so, keep the breech block horizontal, place the shafts into the bottom grooves of the housing and rotate the breech block upwards, between the upper “forks” until it clicks into place.
- Mount the Nimble on your printer. If you are using an adapter, have a look at the adapter page to see if there are any specific instructions for that adapter.
- When mounting the Nimble, make sure that you insert the PTFE tube into the hot end. The length of tubing will depend on the mount you use. The length should be so, that the Nimble or the top of the adapter locks it in place.
- The overall procedure if using the Groove Mount Adapter (Part D) is to have the Hot end in place, place the Groove mount adapter over the top of the hot end and place the Nimble on top of that, making sure the little tabs fit inside the “forks” of the Nimble. This locks the Nimble to the hot end and keeps it centered.
- For now use only 1 bolt (part T) to bolt the Nimble to the adapter or printer. This is done to lock it in and keep everything together while you prepare the drive cable and sleeve. You might need the M3 nuts here.
Do not overtighten these M3 bolts. Simply finger tight and then 1/4 turn is enough.
- Mount the stepper to your printer frame. The image shows it being mounted to a 20x20 aluminium profile. Other methods can be; mounting it to the base, attaching it to a bracket and mounting that to your printer or any other way of fixing the stepper to your printer.
The mounting hardware is not included with the Nimble.
- Take the Sleeve Clamp (part C) and slide the Drive Cable Sleeve (part F) in the top, as far as it will go. There is a little step in the bottom of the sleeve clamp to make sure the sleeve goes in just to the right depth.
- Clamp the sleeve using the M3 screw (part Z) and the Half nut (part W). Tighten the screw nice and tight. There is a little ridge inside the sleeve clamp to prevent you from squeezing the sleeve too far and jamming the drive cable.
This could need force, we designed it to be tight.
- If it takes too much force, use a adjustable wrench or something for the first time.
- It needs to be tight as the surface of the clamp smooths out over time.
- Now, take the drive cable itself (part L), both ends have square sides pressed into it. Even here it is reversible. Slide one end into the Drive Cable Sleeve and thread it all the way through. It will slide into the Coupler. Slide it all the way down and clamp it using the remaining 4 set screws (part Y)
- Back to the Nimble side.
- Slide the Sleeve, now containing the drive cable as well, into the next Sleeve Clamp (part C) and push it down as far as it will go. Use the M3 screw (part Z) and the half nut (part W) to clamp the sleeve.
After mounting the Nimble in place, you can loosen this screw a little to adjust the direction of the drive cable. Allow it to have a relaxed and free arch to the stepper.
- Insert the drive cable into the worm and then slide it down. To place the sleeve clamp correctly, make sure you line up the tabs with the 3 slots on the Nimble and in such a way that when locked, the screw in the next step fits inside the notch. This can take a little push the first time. As long as you make sure it is aligned properly, this is not a problem.
- Feed filament through the Nimble into the PTFE below the Nimble and make sure the breech is closed before tightening all the mounting bolts, this will ensure the correct alignment and that the breech will close easily.
- Now use the remaining screw (part T) and perhaps the remaining M3 nut, to bolt the Nimble to the printhead or effector. The Nimble is now installed. Have a good look to see if it all looks the way you think it should look and correct any things that do not look right.
Do not tighten these M3 bolts too tight. Simply finger tight and then 1/4 turn is enough.
- This is also the moment to adjust the direction of the drive cable, so that it forms a nice arch to the stepper, as mentioned in step 17. So loosen the short M3 screw from the half nut until you can just rotate the drive cable sleeve. Once it is in position, make sure it is seated properly by pressing down and then tighten the screw again.
Using the Nimble¶
First run the extruder a minute or two, with no filament clamped. Just to bed the gears and drive cable in. Extrude and retract a few times. (You will have to switch off the temperature control as most controllers will not move the extruder stepper unless the hot end it up to temperature) Use M302 P1 on RepRapFirmware to switch cold extrusion on (allow extrusion while cold) and M302 P0 to switch it off again. For other firmware use M302 S0 to switch cold extrusion on and M302 S170 to set extrusion to a minimum temp of 170C.
To insert filament, open the breech block. You do this by squeezing together the “ears” of the breech block and pulling outwards. You can leave the shafts of the breech block in or, for better visibility, take the whole breech block out.
Now you can see the top of the hot end (usually, depends on the adapter used) and slide the filament in. If the hot end is up to the correct temperature, you can purge the old filament by simply pushing down on the filament and feeding it into the hot end. After the old filament is cleared you can close the breech block.
this is is an excellent way to get a sense of the efficiency of your hot end. You can feel the resistance of the hot end and how easy it is to push the filament through.
To close the breech block, place the shafts into the slots of the “forks” on the Nimble, rotate until vertical and the ears click into place. The Nimble is now ready to use.
If the hot end is up to temperature, you can now test the extrusion. Simply extrude about 10 mm and observe how the filament comes out of the hot end. It should be a neat straight line.