These pieces are designed to provide the Tevo Tarantula Double Z axis from one engine. As it's complicated I won't go into the pros and cons here. No motor couplers so makes things more easy! It is a little more fiddly than motors, although requires no electronics.
They're remixed from the excellent brackets by thingirob. These components have been remodeled by me so that they do look slightly different. Please note I've added tolerances where the first parts had none, these should print fine without scaling.
You need 2 of the Z Nut holders. X2 has been included by me but just to remind you.
Please note is v1. I've updated the designs since then to improve them based on my own experiences.
You'll need the following parts to put it together. Lots of the screws etc. were spares from the kit, or left over from other changes I've made for the printer.
- 900mm closed loop GT2 belt. I found a vendor on AliExpress that made these very cheaply. If they stop selling them link may disappear.
- 4 x 608 Bearings
- 2 x 400mm lead screws. Threads will need to match. Also require brass nuts.
- 2 x 8mm bore 20 tooth pulley. Seller I used
- 5mm bore 20 tooth pulley for engine. Seller I used
- 2 x Smooth Idler Pulleys w/ 16mm diameter. I had these so no vendor, although commonly offered. Same pulley used on other axes of Tarantula.
- 2 x 25mm M5 Screws. Can be longer.
- 2 x Nylon spaces or nuts.
- M5 washers (to use to distance idlers correctly. I used 4).
- 2 x M5 nuts, ideally nylock nuts.
- Nema 17 engine from original Z axis.
- 4 x M3 screws to mount Motor (should already have these with original mounts).
- 8 x M3 screws and nuts to mount brass nuts.
- M4 T Nuts and screws. I won't include the numbers, however I'd suggest using a minimum of 8 on each bracket, and 2 for all the Nut holders. This could be 44 of every.
Optional 2 x 8mm lock collars. The screws are held in place by gravity, but it is possible to add lock collars beneath the bearing bracket. They are not used by me, as in case the print head crashes into bed, the screws lift out of the bearings and protect against damage.
Putting it together
Brackets and Lead Screws
- Put together the printer with the mounts as normal. Take care to try to align the brackets as best as possible.
- Insert bearings into applicable spaces in brackets. Should fit well, although may require some sanding depending on your printer is set up.
- Add brass nut to Z nut holders. Use M3 screws and nuts to fasten that is securely.
- Attach 8mm bore pulleys to end of lead screws and tighten grub screws well.
- Insert Lead screws through upper bearings, then thread on Z nuts, finally push lead screws into bottom bearings. It is just supported by this posture at each end, if using none of the screw, 400mm screws will come out the other side.
- Secure z nut holders to X axis. Care must be taken here to measure the distance from every side to a predetermined point on the frame (bottom or top, not the bed), to ensure it is square. Utilize the screws that are lead to adjust down and up manually. It is easiest to have the T nuts in the slots but leave them loose while adjusting, and tighten at the end.
- Attach stepper motor to motor mount. M3 screws should still be a little loose, letting the engine move.
- Mount should then be attached to frame. Position as centrally as possible.
- Add pulley to Motor and try to par with pulleys on direct screws. A straight edge like a ruler can be useful here.
- Push M5 screw through applicable hole for idler pulley. Add the nylon spacer (or nut if using instead), then add washers (2 for each). Put on the pulley and add nylock nut that is closing. These have to be assessed for height against the pulleys. You may have to remove or add washers to get the heights right.
- When the X axis is right now, it is possible to attach the belt. This ought to be threaded as show in the images around the pulleys. The pulley can be a little tight because of limitations in the frame, but should move over without too much trouble.
- Tension the belt by pulling the Motor back in it's slot then tightening the screws. Given how this works having higher tension is not as critical as it is on the other axes.
- Manually rotate the motor pulley (with care!) To make sure the mechanism does not bind up, and moves freely.
You need to reverse the Z motor direction from the firmware for this to work properly. That's the only change you will need to make (unless you have changed thread pitch at all).
It's been pointed out to me that unless alignment is ideal, having the screws supported on the end will result in binding. I don't have a problem with this in the event that you do, the best thing is to simply pop the bottom bearings out and not use them.
As with any modification to a printer, make sure you test through the range of motion of the Z axis to make sure it moves freely and does not bind.
You may need to up the present to the Z motor since it is currently working a little harder than it was.
I needed to buy a Motor wire because of moving the Z axis. Depending how you mount your electronics, you may not have to do this.
I appreciate any feedback you have! I am delighted to help where I could for those who have an problems.
Improvements from v1
- Removed some material to improve strength.
- Additional ribs to upper mounts to improve strength.
- Fixed an alignment issue with a few holes.
- Adjusted hole spacing under bearing blocks so all previous holes present.
- Increased travel for engine to allow more belt tension if required.
Recommend Concentric supports for brackets more easy to remove. Z Nut holder does not require supports.
Unlike thingirob brackets, I've enabled tollerance in these parts where required, so ought to have the ability to print at 100% scaling.