Worm Drive Grounded Delta Printer

Tks for the update!
If time permits, I would really like to see a video of the movement, that you would like to correct with the parallelogram linkage.

@Jon: I am not sure what is meant by a parallelogram linkage. Are you talking about something like THOR Simpson? It would only work if you do that to two arms. However, I would advise you to figure out what the weak link is and beef it up. (Mathematically, your position should be constrained so it is just a matter of sizing all the components to get acceptable rigidity.)

I know this would be annoying to do but the the worm needs to be registered with a pair of bearings and some thread clamps.

I would also consider splitting the shoulder gear and adding a torsion print as a backlash removal attempt.

Note: My apologies if you have already done some of these things.

Good luck!

Edited 1 time(s). Last edit at 12/09/2013 06:03PM by nicholas.seward.

Quote
nicholas.seward
@Jon: I am not sure what is meant by a parallelogram linkage. Are you talking about something like THOR Simpson? It would only work if you do that to two arms. However, I would advise you to figure out what the weak link is and beef it up. (Mathematically, your position should be constrained so it is just a matter of sizing all the components to get acceptable rigidity.)

I know this would be annoying to do but the the worm needs to be registered with a pair of bearings and some thread clamps.

I would also consider splitting the shoulder gear and adding a torsion print as a backlash removal attempt.

Note: My apologies if you have already done some of these things.

Good luck!

I agree, finding the weak link is the most prudent course. I have been working on a more beefier effector, the pivot arms are fairly small and could be the source of the flexing. I have been getting some grief printing the thicker parts in ABS. If that didn't solve the issue, then I was considering replacing one arm with a parallelogram like with the THOR simpson.
Here is a vid

Youtube

Edited 1 time(s). Last edit at 12/10/2013 12:15PM by Solidus Labs.

@Solidus Labs: I think I know your main problem.

Test: Move the extruder to about 100mm above you surface. Press down and see if it is more rigid.

If it is more rigid, you just need to move your shoulder joints down so you stay far away from the planar singularity. (Your extruder is much closer to the joints than mine is.) That and beefing up your long arms should get you there. The shoulder looked good to me. Remember you don't need to add much plastic. You just need to add dimensionality to the arms. The rigidity is a function of b*h^3. If you just turn your arm on its side you will get 4 times the rigidity by my estimates. My theory is to go big with low infill.

Love the sound track
Tks for taking the time to post the video, love the eye candy!

A few ideas to consider.

Shoulder joint support structure:
I don't see a bottom triangular base tying the three shoulder joints together, ie. boxing in the structure.
Without a bottom base boxing in the shoulder joints, I can envision that the top plate is flexing (oil canning) downward, and the shoulder joints splaying outward.
Adding a bearing at the top and bottom of the rotational shoulder joint (Z axis), separated by as much space as is available will help with rigidity.

Quote
nicholas.seward
@Solidus Labs: I think I know your main problem.

Test: Move the extruder to about 100mm above you surface. Press down and see if it is more rigid.

If it is more rigid, you just need to move your shoulder joints down so you stay far away from the planar singularity. (Your extruder is much closer to the joints than mine is.) That and beefing up your long arms should get you there. The shoulder looked good to me. Remember you don't need to add much plastic. You just need to add dimensionality to the arms. The rigidity is a function of b*h^3. If you just turn your arm on its side you will get 4 times the rigidity by my estimates. My theory is to go big with low infill.

*face palm* Ahh you’re right. Without even testing I can tell you it is more rigid.
I move the horizontal pivot point up on the shoulder for more clearance but that also moves the horizontal singularity up.

Thanks for fresh pair of eyes.

Awesome +1

Printereing some new shoulders
youtube candy

How are things going? How do the new shoulders work out? Did they get rid of that singularity?

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AbuMaia
How are things going? How do the new shoulders work out? Did they get rid of that singularity?

Sorry there has not been an update for a while. I was really busy over the holidays. The new shoulders have improved the flexing on the singularity quite a bit. I am currently rebuilding the hot end to extend farther down and get further from the singularity. The prototype I built has very good position stability but has heat zone and jamming issues. Lowering the nozzle has cut into the z height so I need to reprint longer upper arms as well.
- Jon @ Solidus Labs

Yay! First “successful” print. There are still some flaws in the printing but I think I can fix that with some small tweaks in the calibration.

@Jon: As far as I know there have only been 4 individual Simpson style printers that have actually printed. (I hope this year that number goes to 100s) You are #4 with a unique design nonetheless!!!!!!!!

Excellent! Can't get much closer to the spirit of reprap than this! Almost everything is printed, only the motors, worm gear, electronics and hot end need be purchased. Well... a few bolts and bearings huh? But no belts, no long threaded rods, no metal cutting or shaping. I really hope you will release the files soon.

---

[www.linistepper.com] Open source stepper motor drivers.

@Jon,

Looks fantastic!
Got video candy?

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End effector Hub assembly:
I just noticed your hot end design/assembly!
It looks like you have a bespoke hollow threaded aluminum tube running down the center of your end effector hub.

Are you using the aluminum tube to sandwich the hub, and bearings tightly together so the assembly is ridged?
Are the 3 bearings touching each other, or is there plastic separating them?
The bearings look larger than 608's, what series are you using?



*****************************************

Redesign of the Hot end/end effector/hub:
To increase rigidity of the end effector I'm redesigning it to use a hollow threaded rod with bearings clamped in between.
Either an electric lamp fitting, vented SHCS, a vented stud, or your hollow threaded aluminum tube will be used.

A discussion about the end effector modification begins in the Lisa thread:
[forums.reprap.org]

Material suppliers:
Electric lamp fittings
[www.sizes.com]

1/4-27, Dia 6.35 mm (0.250"), 626 bearing 6x19 mm.
1/8-IP, Dia 10.29 mm, (0.405"), 6800 bearing 10x19 mm.
1/8-IP, Dia 10.29 mm, (0.405"), 6900 bearing 10x22 mm.
3/8-IP, Dia 17.15 mm, (0.675"), 6703 bearing 17x23 mm.
[www.bearingworks.com]

Lamp stuff
[www.profhdwr.com]

Lamp parts
[www.txlampparts.net]

3/8-ip nuts are 27 cents each at:
[www.iqlightbulbs.com]

M8x40mm, 7.41ea, Vented Socket Head Cap Screws
[www.mcmaster.com]

M8x50mm, $15.19ea, Vented Socket Head Cap Screws
[barnhillbolt.com]

5/16-18, $16.00ea, Hollow Threaded Studs
[www.mcmaster.com]

*****************************************

Hub offset:
I have a question about the end effector hub offset.
I want to design my arms to be inline with the end effector hub/pivot axis,
but I'm unsure if I'm violating the laws of physics.

In this image I can see that your end effector bore in the hub is offset relative to the arm.
Is this to prevent a singularity, or is it for some other reason?




Tks!

Excellent! And it has the stiffness to carry the extruder on top of the hub, that's amazing. Definitely deserves some videos. . .

@Jon,

I'd like to verify that we have the newest version of the g-code preprocessor, is the math still the same?
What software language is this code written in?
tks!

double La_1;
double La_2;
double La_3;
double Da_1;
double Da_2;
double Da_3;
double Ra_1;
double Ra_2;
double Ra_3;

Ra_1=sqrt(sq(cartesian[X_AXIS]-V1_X)+ sq(cartesian[Y_AXIS]-V1_Y));
Ra_2=sqrt(sq(cartesian[X_AXIS]-V2_X)+ sq(cartesian[Y_AXIS]-V2_Y));
Ra_3=sqrt(sq(cartesian[X_AXIS]-V3_X)+ sq(cartesian[Y_AXIS]-V3_Y));

La_1=sq(Ra_1-Nx+Sx)+sq(cartesian[Z_AXIS]-Sv+Nv1);
La_2=sq(Ra_2-Nx+Sx)+sq(cartesian[Z_AXIS]-Sv+Nv2);
La_3=sq(Ra_3-Nx+Sx)+sq(cartesian[Z_AXIS]-Sv+Nv3);

Da_1=((sqL1L2-La_1)/theta_CEND);
Da_2=((sqL1L2-La_2)/theta_CEND);
Da_3=((sqL1L2-La_3)/theta_CEND);

if (Da_1 <-1 || Da_1 > 1)
{
    Da_1=floor(Da_1);
    SERIAL_ECHOPGM("Arm Limit X\n"); 
}
if (Da_2 <-1 || Da_2 > 1)
{
    Da_2=floor(Da_2);
    SERIAL_ECHOPGM("Arm Limit Y\n"); 
}
if (Da_3 <-1 || Da_3 > 1)
{
    Da_3=floor(Da_3);
    SERIAL_ECHOPGM("Arm Limit Z\n"); 
}
delta[X_AXIS]= acos(Da_1)*rad2ang;
delta[Y_AXIS]= acos(Da_2)*rad2ang;
delta[Z_AXIS]= acos(Da_3)*rad2ang;

Here is your youtube candy:
[www.youtube.com]

re:End effector Hub assembly:

Are you using the aluminum tube to sandwich the hub, and bearings tightly together so the assembly is ridged?
Yes the aluminum tube is threaded and screws the effector arms together.
Are the 3 bearings touching each other, or is there plastic separating them?
There is plastic separating them. In the second picture you can see the hubs recess into each other.
The bearings look larger than 608's, what series are you using?
They are 6804.

re:Hub offset:
In this image I can see that your end effector bore in the hub is offset relative to the arm.
Is this to prevent a singularity, or is it for some other reason?
The dogleg forearms have an off center shift, this is just shifting them back.

re:Hub offset
I'd like to verify that we have the newest version of the g-code preprocessor, is the math still the same?
What software language is this code written in?
The formulas are still the same, I might have changed/added a few variables. The language is Arduino, which is more or less c++.

Tks!

I love the looks of your GDR, the extruder sitting on top makes it look very cool.

.2 layer and .4 layer sample print

Small update:
I printed new longer forearms which will give more printable Z area. After a bit of re-calibration, here are some photos.




I have ordered SLA prints of all the parts which I plan on using for master to make casting molds for short run production.
How does everyone feel about crowd funding the production?

Jon – Solidus Labs

Here is a pretty good milestone. I'm printing one of the GDR pieces on the GDR. Repraping...
[www.youtube.com]

Hello Jon

How precise are the parts comming out of your machine? Are they usable as mechanic parts?

Thanks

@SolidusLabs:

You have longer arms now, what is the size of the build envelope?

Can it accurately reproduce the arms, and worm wheel?

What is the print speed, and what do you think the top print speed will be after tuning the software, and calibration?

Quote
Guizmo
Hello Jon

How precise are the parts coming out of your machine? Are they usable as mechanic parts?

Thanks

The shoulder was fairly loose on the tolerances, it was probably 0.3 mm because of the low sub divisions. I was pushing the firmware pretty hard to get 16x microsteps and 50 sub divisions/sec at 60 mm/s. At this speed I was able to see some distortion on the faster curves.
The 16x microsteps works out to about .0037mm which is absurd. Setting the microsteps to 4x (.015) or 8x (0.0075) I can hike up the sub divisions to 200 and still maintain the higher speed.
The print fits into the upper arm after some reaming and cleanup so I think they are useable parts.

Quote
A2
@SolidusLabs:
You have longer arms now, what is the size of the build envelope?
Can it accurately reproduce the arms, and worm wheel?
What is the print speed, and what do you think the top print speed will be after tuning the software, and calibration?

I lowered the print head so the build envelope is approximately the same. 180mm diameter x ~100mm z useable. All of the GDR parts will fit in the build envelope.
I am printing the worm wheel now. I’m printing at .48 nozzle @ 150 micron layer height and about 30mm/s which will take about 4 hours. I normally print them with a .28 nozzle so we shall see how the teeth come out. I prefer slower and accurate instead of fast and have to print again. 60mm/s is printing now but I think I can get it up to 100mm/s

Yay parts. Enough for 2 more machines. Time to build some beta units!

Components look great!
I'd like to see a video with all 3 running

Have you decided on what electronics that you will be using?

Quote
A2
Components look great!
I'd like to see a video with all 3 running

Have you decided on what electronics that you will be using?

I am running with ramps 1.4 but im interested in the ramps-fd

After printing about 20 calibration circles I'm about 97% there. I'm still dealing with some spherical issues from my base plate. My router needs a tuneup.

@Solidus Labs:

It looks fantastic, I'm impressed, and it appears to be round, good job!

It looks like a joint shifted to create the step in the worm wheel tooth profile.

Will the cast resin parts include the extruder?

The standard appears to be RAMPS 1.4, + Arduino Mega2560 R3.
The ramps-fd looks great, but I don't have experience with any of them.