NOTE This is still a work in progess, it is currently printing quite well.
This work was originally derived from wolfmanjm/wolfhbot although since then it has diverged significantly and probably has very little in common now, although I retain the fork as provenance.
A large build volume 3D printer based on the CoreXY concept.
It uses 4040 generic extrusions for most of the frame.
- The X carriage runs on Makerslide from Amber Spyglass Ltd
- The Y carriages run on Makerslide from Amber Spyglass Ltd
- The drive uses GT2 pulleys and belts
- the Belts have no cross over, they are stacked on top of each other instead
- build volume is large 300x1200x300 mm
- The Z platform has three stepper plus ballscrew Z actuators running on two 2040 Makerslides with cast aluminium carriage. It runs on 1204 ballscrews.
I used an Alligator Board with some modifications. Details of the board are here: jsr38/AlligatorBoard
My expansion board to allow alternative stepper drivers can be found here: jsr38/crocolulo
I'm currently running Repetier firmware on the Alligator. My fork containing the current configuration is here: jsr38/Alligator-Repetier-Firmware
The two end idlers are 2x flanged bearings back to back, and another pair separated with a washer above it, Then two of the idlers on the X Gantry are raised to keep the belt riding level. I avoid the cross over of the belts by running the two belts one above the other in parallel.
The new Z actuator is a length of 500mm of 2040 VSlot, with a printed carriage and v wheels. Driven by a McMaster ACME 1/2" leadscrew with 10TPI, Bearing blocks using 608 at top and bottom and a Nema17 with 5mm/0.25" flexible coupling. The bottom bearing block isolates the flexible coupling from taking any weight and compressing. As the 1/2" leadscrew is pretty big it has no wobble as far as I can tell and having bearings top and bottom seems to be very stable. I also used a printed Leadscrew nut printed in PLA and it seems pretty snug and smooth. I also used a half height leadscrew nut and spring to implement antibacklash which appears to be necessary.
There is a length of 2040 that spans from the Z actuator to the other side of the frame where another 500mm length of 2040 VSlot has a vslot mini carriage which is bolted to the end of the 2040 beam. Halfway along this beam is a short piece of 2020 perpendicular to it, this provides the third attachment point for the bed.
The most important part of this design is the moving knot, which is attached to the top and bottom and runs over 4 v groove bearings on the cross beam, This keeps the beam level while allowing a single actuator on one end to move it up and down. This is the far end, and here is a view of the whole assembly.
The bed is attached to the cross beam at three places to provide three point bed levelling. I use a scheme where a 4mm stud is screwed into the tslots, and a 25mm length of aluminum rod, tapped to 4mm is screwed onto that, this can be turned to move up and down the stud. At the top of the aluminum is a cut out that the glass bed fits. Next to this, and also bolted into the tslot, is an M4 bolt with a conical spring bolted to the top, this pushes the glass at the three attachment points up into the slots on the aluminum rounds. This keeps the glass flat without deforming it, and allows it to be leveled at three points by turning the aluminum rounds. Some jam nuts are used to screw up to the aluminum rounds to stop them unscrewing once levelled.
So this adds several printed parts... The Carriage, a bracket to hold the leadscrew nut, and bearing blocks. Also some lathe work to cut a thread into the center of some 1/2" aluminum round, and lathe a groove at the top that the glass can slot into. (If the bed is not heated this could be a printed part).
Aluminum parts are from Misumi with Misumi part numbers
- 10x 500mm HFS2020 20mm extrusions - frame
- 16x HBLFSN5 corner brackets - frame
- 2x 550mm HFS2020 - X Gantry sides
- 2x 85mm HFS2020 - X Gantry sides (Note it's cheaper to buy 2x 1000mm of 2020 and cut these yourself)
- 2x 540mm Makerslide - Y Rails
- 4x HBLFSNF5 brackets - X Gantry
- 1x 500mm HFS2040 - Z Bed
- 1x 250mm HFS2020 - Z Bed
- 2x Shapeoko motor mounts https://www.inventables.com/technologies/upgraded-shapeoko-motor-mount - Y carriages
- 12x VWheels https://www.inventables.com/technologies/dual-bearing-v-wheel-kit or http://openbuildspartstore.com/delrin-v-wheel-kit/
- lots of M5 nuts and bolts
- lots of M3 nuts and bolts
- 2x Nema 17 Stepper motors (preferably Kysan or equivalent)
- 10 meters GT2 belt
- 2 x GT2 pulleys 20 tooth
- 12 x 5mm flanged bearings for the idlers
- 1x motor-bracket-l.stl
- 1x motor-bracket-r.stl
- 1x x-carriage.stl
- 1x Nema 17
- 1x lead screw (McMaster 1/2" 10TPI ACME)
- Two printed Leadscrew nuts and a collar for the anti backlash
- 5/8" diameter spring for the anti backlash
- 2x 500mm 2040 VSlot
- 4x solid V Wheels http://openbuildspartstore.com/solid-v-wheel-kit/
- 1x printed Z carriage, plus leadnut holder
- 1x mini vslot carriage and mini wheels http://openbuildspartstore.com/mini-v-wheel-plate/
- 4x v groove bearings, 2x turnbuckles, two lengths of Spectra fishing line for the moving knot
Getting the top of the frame square is essential, measure each end of the Y rails to make sure they are parallel. Next the belts need to have exactly the same tension to keep the X gantry straight, this was introducing non-square prints for me. Loosen the X gantry on both Y carriages so it sits loosely on the Y carriages, then measure the distance of each end of the X Gantry to the front corner of the frame. Now tighten one or other belt until the X Gantry is square to the Y rails, then tighten it down to the Y carriages.
If you find cylinders print out oblong or squares are not square this is probably the problem.
CC BY SA
WolfHBot by Jim Morris is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
Based on a work at https://github.com/wolfmanjm/wolfhbot.
