LISA Simpson vinhdinh posted about whether [url=http://forums.reprap.org/read.php?178,267007,267007]threaded rod could be used to make a Rostock style printer[/url]. I made a lengthy post about the reasons you wouldn't want to do that. If any of you know me then you will know that I hate to be critical. So I started to feel bad and I decided to see if I could design a decent threaded rod bot. I got a glimmer of an idea and even though it doesn't fully fit with my design asthetic I decided I had to at least mock it up. I would be delighted if someone wanted to take the idea to completion. Design goals: *Make a Rostock style bot that is capable of high speeds with a threaded rod. *Minimize the number of components. *Eliminate all spherical joints in favor of 608 bearing joints. *Eliminate the smooth rods and linear bearings if possible. *Look cool. *Mount the steppers as low as possible. *Eliminate all unnecessary supports. [img]http://forums.reprap.org/file.php?178,file=21243,filename=LISA.jpg[/img] Behold LISA Simpson. (LInear Simpson Alternative) As drawn she uses [url=http://www.mcmaster.com/#99030A400]1/2"-8 8-start ACME precision ground threaded rod[/url]. I was pleasantly surprised at the price of $56. (That is not cheap but remember I got rid of all the linear rails and bearings.) This setup will move the shoulder nuts at 240mm/s. If you desire more structural stability you can upgrade to [url=http://www.mcmaster.com/#99030A112]3/4"-6 2-start rods[/url] for almost the same amount of money. (However, that upgrade will downgrade your top speed to 80mm/s.) [img]http://forums.reprap.org/file.php?178,file=21244,filename=tension.jpg[/img] However, even with the skinnier 1/2" rods you can use some simple string to increase the rigidity of the bot. I don't see any reason to get fancier than this. I would test the rigidity without the strings first to see if the strings are even needed. [img]http://forums.reprap.org/file.php?178,file=21245,filename=volume.jpg[/img] The build volume as drawn is 6L. Biggest cylinder that fits in the volume is 165mm diameter x 200mm tall. The inverse kinematics on this are pretty close to the kinematics for the Rostock. However, the carriage rotation in coupled with its translation so you will have to do one trig calculation for each arm to adjust for that. That should be no biggie for an fast ARM processor. Rough Vitamin List: *6' [url=http://www.mcmaster.com/#99030A400]1/2"-8 8-start ACME precision ground threaded rod[/url] $56 *12 [url=http://www.amazon.com/Shielded-Bearing-R8ZZ-inch-Bearings/dp/B002BBGXZM/ref=sr_1_9?s=industrial&ie=UTF8&qid=1384584666&sr=1-9&keywords=r8+bearing]R8ZZ bearing[/url] $34 *12 608 Bearings $3 *4 6702 Bearings $4 ******* VERY LOW COST ITEMS ****** *12 M3x5 *14 M3x20 *36 M3x16 *52 M3 Nyloc Nuts *6 M8x55 *6 M8 Nyloc Nuts *3/4" MDF Flatstock Concerns: *Backlash could be a problem then again it might not. If it is, I have some ideas on how to make the printed shoulder nuts wear compensating. *Friction. Lubrication is a must. I will need to figure out what grease is PLA safe. Future Explorations: *Design the hub pieces to be able to side step the threaded rod by an extra 25mm. This would give you a 50% bigger build volume. This would allow you to print a cylinder that was 210mm in diameter by 200mm tall. (Without this mod you can only print a 165x200mm cylinder.) *Play with mounting the extruder stepper on the hub. https://reprap.org/forum/read.php?178,267835,267835#msg-267835 Mon, 08 Jun 2026 00:48:23 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?178,267835,897419#msg-897419 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,897419#msg-897419
I’ve tinkered with delta-style printers before, and one thing I found is that minor tweaks in arm geometry or joint spacing can drastically affect rigidity and backlash. Using string or tensioned cable to stiffen the frame is a neat trick you might be surprised how effective it is without adding weight. For lubrication, I’ve had success with PTFE-based greases on PLA moving parts, which reduces friction without degrading the printed material.

On a slightly different note, thinking about build planning makes me wonder if anyone here has tried integrating design tools for printing complex shapes into a workflow. Something like a microplate layout planning guide
might seem unrelated at first, but the way it maps precise positions and tolerances could inspire ways to pre-check delta printer kinematics or ensure print volume is fully optimized before committing to a long print.

All in all, this design exercise really highlights how creative mechanical simplification can open up new possibilities. I’d be curious to see what others think about testing it with the 1/2"-8 rods first and seeing if the string bracing is necessary before moving to larger rods.]]> memaquin1231 Delta Machines Wed, 07 Jan 2026 02:30:08 -0500 https://reprap.org/forum/read.php?178,267835,763553#msg-763553 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,763553#msg-763553
One problem is the speed of rotation of the nut.
The best is a toothed belt between the motor and the nut, and bearings between the nut and the motorized trolley.
For the effector the bearings Ø 60 mm are not expensive, 6 € piece.
I begin the drawings ...]]> Pascal68 Delta Machines Fri, 21 Apr 2017 08:45:00 -0400 https://reprap.org/forum/read.php?178,267835,763004#msg-763004 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,763004#msg-763004
Motorized trapezoidal nut with Nema 17.
What gear?
How RPM?
How many volts?

I think 24 volts, 600 RPM, chevron gear, what do you think?]]> Pascal68 Delta Machines Tue, 18 Apr 2017 05:48:21 -0400 https://reprap.org/forum/read.php?178,267835,762893#msg-762893 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,762893#msg-762893
And now all say it with me. DeJAY ;) Actually the Y is silent, it's like Dejah :P]]> Dejay Delta Machines Mon, 17 Apr 2017 13:09:18 -0400 https://reprap.org/forum/read.php?178,267835,762861#msg-762861 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,762861#msg-762861 nicholas.seward Delta Machines Mon, 17 Apr 2017 10:15:04 -0400 https://reprap.org/forum/read.php?178,267835,762854#msg-762854 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,762854#msg-762854
I'm sure Nicholas can tell you better, but I think the mathematics are still the same. Any horizontal movement of the effector / arm screws each carriage up and down the lead screws. I don't think this is a big issue either way except for homing and probably homing and auto-calibration.

I too was interested in Lisa for a sturdier delta style assembly, and it looked to me like that too. But sadly it's not, except with a giant massive lead screws. Hmm well maybe it's time someone made a lisa with 3D printed lead screws? [i.imgur.com]]]> Dejay Delta Machines Mon, 17 Apr 2017 09:50:22 -0400 https://reprap.org/forum/read.php?178,267835,762853#msg-762853 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,762853#msg-762853
Here's how I see the arms, with forks.



The forks do not touch.

The trapezoidal nut in resin: 10% epoxy, 45% powder bronze, 45% graphite powder.

L'effecteur n'a pas de roulement, remplacé par le mélange résine + bronze + graphite.

La vis trapézoidale n'aura pas besoin d'être lubrifiée, grâce au graphite.

Plus qu'à dessiner les pièces qui reçoivent la résine.
]]> Pascal68 Delta Machines Mon, 17 Apr 2017 09:33:42 -0400 https://reprap.org/forum/read.php?178,267835,762225#msg-762225 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,762225#msg-762225 The trapezoidal screw 40x7 serves for the inner shape, the release is wax, to create the game.
The outer mold may be the part equipped with a toothed wheel, ready to be used after pouring the resin.

[www.ebay.fr]]]> Pascal68 Delta Machines Fri, 14 Apr 2017 04:29:26 -0400 https://reprap.org/forum/read.php?178,267835,761929#msg-761929 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,761929#msg-761929 Pascal68 Delta Machines Wed, 12 Apr 2017 15:09:23 -0400 https://reprap.org/forum/read.php?178,267835,761842#msg-761842 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,761842#msg-761842 I do tests in PLA but it's not easy.]]> Pascal68 Delta Machines Wed, 12 Apr 2017 07:53:02 -0400 https://reprap.org/forum/read.php?178,267835,760409#msg-760409 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,760409#msg-760409
If this solution can work, the arms must be very rigid in torsion.]]> Pascal68 Delta Machines Tue, 04 Apr 2017 07:05:31 -0400 https://reprap.org/forum/read.php?178,267835,760392#msg-760392 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,760392#msg-760392 nicholas.seward Delta Machines Tue, 04 Apr 2017 04:43:25 -0400 https://reprap.org/forum/read.php?178,267835,760390#msg-760390 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,760390#msg-760390
If the arms go from the axis of the screws to the axis of the effector, the deviations will be eliminated.

Mathematics will surely be simplified.

For the arms I thought of the carbon tube big diameter, with at each end a fork fixed to the big bearing.

It takes 3 rolls superimposed in the effector
The fork of the arms must be twisted before attachment to the effector So that the arms do not interfere.
The XYZ limit switches will have an offset equal to the superimposition of the bearings of the effector.

Mathematics should no longer need offset since it works from axis to axis.

My hypothesis is perhaps not good, and perhaps you have already thought of it?]]> Pascal68 Delta Machines Tue, 04 Apr 2017 04:05:05 -0400 https://reprap.org/forum/read.php?178,267835,759851#msg-759851 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,759851#msg-759851 There may be solutions for the geometry of the arms, to reduce the deviations.
I write them as soon as possible.]]> Pascal68 Delta Machines Sat, 01 Apr 2017 04:49:25 -0400 https://reprap.org/forum/read.php?178,267835,759261#msg-759261 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,759261#msg-759261
One solution is to have two screw on each axis with two or three spinning nuts. This will allow you to use the standard 6 arms. However, that is just a more complicated way to do the original.]]> nicholas.seward Delta Machines Wed, 29 Mar 2017 14:27:44 -0400 https://reprap.org/forum/read.php?178,267835,759234#msg-759234 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,759234#msg-759234 For the rigidity of the LISA, one can apply what I did on my kossel quoted in the link.
The tube is 2020, and the rods are diagonally threaded in M10.
And it's very rigid.

Remains mathematics not easy for me ...]]> Pascal68 Delta Machines Wed, 29 Mar 2017 12:59:59 -0400 https://reprap.org/forum/read.php?178,267835,759217#msg-759217 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,759217#msg-759217
Agreed that the rotation of the nut is low inertia but now the carriages have larger inertia. I don't think this will be a problem. In fact, a nut with backlash will perform much better when the carriages get heavier by having gravity peg the carriages to one side of the thread.

I personally would go huge with the screws. I found this.

I am not exactly sure what a PAP motor is? I think I know what you are talking about but can you provide a link.

Now for the bad news, rostock style deltas have a ton more rigidity than LISA. (Let me say that again...LISA is not very rigid.) There are things you could do to make LISA more rigid but the geometry is just inherently less constrained than the standard configuration.

Can smoothie do this? Sure. It won't be too hard. I already know the math. (I have solved the inverse kinematics. I don't remember if I solved the forward kinematics. That might be a trick.)

One thing you might have never thought of is homing. The interdependence of the axes cause this to be a tough computational problem. I might suggest a simple solution. Some controllers like the DUET (I think) can turn down the current and just run the carriages into a wall. Otherwise, you are stuck manually homing or an iterative approach with a decreasing backoff.

Sorry to say that LISA just isn't super practical. However, it has style so I would be glad to help if you want to keep going down this path.]]> nicholas.seward Delta Machines Wed, 29 Mar 2017 11:43:58 -0400 https://reprap.org/forum/read.php?178,267835,759182#msg-759182 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,759182#msg-759182 [www.igus.fr]

On the other hand, the IGUS screws are expensive, the quality having a price, 154,08 € piece, better to try this other reference of screw:
[www.ecmu-csr.com]
To 44,78 € inc. VAT piece.

Even on a length of 1m50 one should not have bending.]]> Pascal68 Delta Machines Wed, 29 Mar 2017 09:20:09 -0400 https://reprap.org/forum/read.php?178,267835,759167#msg-759167 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,759167#msg-759167 Pascal68 Delta Machines Wed, 29 Mar 2017 08:02:45 -0400 https://reprap.org/forum/read.php?178,267835,759152#msg-759152 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,759152#msg-759152
Thank you for answering so fast.

For the nut, it will have less inertia in rotation than a screw that rotates.
For the standard pitch may be sufficient by changing the PAP motor to screw ratio.
For the bearing it can be replaced by 3 bearings placed on the periphery of the nut.
For the size of the screw I was thinking about a Ø 30 mm, ensuring the rigidity for 1 m 50 of height.

The advantage of the LISA is to have a heavy effector without problems, that's what interests me.
I currently have a Kossel 1 m 50 and I can not implement complex effector :
[forums.reprap.org]

For the cables of the motors I thought of the cable in tablecloth.

But for python mathematics, can we use them with Smoothieware firmware ?
I think we need to put the mathematics program in Repetier, but I'm not sure.

Excuse me if my translation is not very fair, I am French.

cordially]]> Pascal68 Delta Machines Wed, 29 Mar 2017 06:11:37 -0400 https://reprap.org/forum/read.php?178,267835,758987#msg-758987 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,758987#msg-758987
Quote
Pascal68
Hello,

If the problem of precision is due to the rotating screws, why not turn the carriage nuts, each equipped with a PAP motor.
It allows to have screws of very big section, and more rigidity.

I thought about using something like this.

The main problem is the screw wobble so this is a great solution. The secondary problem of having horrendous kinematics isn't really an issue these days. I initially shied away from this approach because one of my main guiding design principles is to have a static stepper if at all possible. I will have to think about this some more. Maybe LISA has some practical potential.

Problems I see with this approach... (none of them are bad but I felt I should delineate them)
*Large enough screw that will double as the support will be heavy.
*Nuts for those screw will be quite large requiring very large bearings. (weight and cost concerns)
*Friction will be higher for this design especially if we do some sort of anti-backlash.
*Wire fatigue.
*Large dynamic mass.]]> nicholas.seward Delta Machines Tue, 28 Mar 2017 12:17:00 -0400 https://reprap.org/forum/read.php?178,267835,758965#msg-758965 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,758965#msg-758965
If the problem of precision is due to the rotating screws, why not turn the carriage nuts, each equipped with a PAP motor.
It allows to have screws of very big section, and more rigidity.]]> Pascal68 Delta Machines Tue, 28 Mar 2017 09:55:56 -0400 https://reprap.org/forum/read.php?178,267835,384493#msg-384493 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,384493#msg-384493 www.marginallyclever.com]]]> simspeed Delta Machines Thu, 17 Jul 2014 14:57:39 -0400 https://reprap.org/forum/read.php?178,267835,384393#msg-384393 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,384393#msg-384393
The print volume actually goes up as the size of the hub increases to a point.

LISA is not a super rigid arrangement. A traditional arrangement is what you need for a mill.]]> nicholas.seward Delta Machines Thu, 17 Jul 2014 11:42:58 -0400 https://reprap.org/forum/read.php?178,267835,384289#msg-384289 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,384289#msg-384289
Quote
cozmicray
did you get some of these ball screws?

Hi, sorry no I didn't order them. Although I am tempted, I'm not sure if I want to build a LISA. I like the concept and would like a delta printer that is strong and sturdy enough for a multi direct extruder and light milling, I'm not sure if this is the way to go. I guess the main problem is that any forces acting on the effector (acceleration / deceleration but for milling also buffets) directly act on the precious ball screws. Like Nicholas said, as soon as they bend it's all over. So it's not really something that helps me with what I ultimately want (print large scale simultaneously with 3-4 different materials).

I thought about stabilizing the leadscrew but it's difficult because of the rotating carriage. I guess the best way would be to go back to the delta design and have a wheeled carriage on an extrusion and use the ball screw instead of a belt. But that is just much more expensive.

I'm still trying to get my first printer (Kossel Mini) working but I try to build a "wheel screw", a rubber wheel on a precision steel rod.

Quote
VDX
... for a better DIY-able 'recirculating bearing' concept cylinders instead of balls are even better for linear bearings ... simple cut a smooth rod in short pieces and fill them into the tray ;)

I thought about this too in the thread. I wonder if you could actually use "rubbery" recirculating rods for a threadless lead screw? The rubbery mini rods would circulate in a spiral around the rod, having friction in one direction but rotating freely. Probably not feasible because when the mini barrels touch each other they would create high friction and also have friction recirculating back. Just another crazy idea :) In any case, the delrin balls are really cheap and precise. I dream about being able to print something like this completely assembled with 3 materials, low friction hard material, rubbery flexible material and easily dissolvable support material.

Quote
cozmicray
What are "these"
link is not right?
Please explain these recirculating ball screws?

Not sure why the link doesn't work, but FYI below are some more links. The link is simply to make a "DIY" printed linear bearing that runs directly on extrusions (like lm8uu bearings but for extrusions instead of rods). This saves you wheels and mounting them etc. Theoretically this could save time and money and space, practically it's probably a bit more hassle. I want to try to build this though because it's cool.

My idea was probably better explained as "lazy-suzan rings" (didn't know the name) to create "typical" delta effector platform that can carry multiple extruders. Basically a big bearing with effector in the middle the arms attached to the outside. This concept will likely not be bearing fruits (sorry for my unbearable puns!) since Nicholas multi extruder concept looks far easier to build. Also the problem that shoulder joint offsets and effector joint offsets need to be the same if I understand correctly, so the bigger the effector, the bigger your shoulder and you loose even more print space.

[github.com]
[github.com] (updated, easier to print version)
[www.flickr.com]
[youtu.be]

Sorry for the long post and noise!]]> Dejay Delta Machines Thu, 17 Jul 2014 08:17:35 -0400 https://reprap.org/forum/read.php?178,267835,384059#msg-384059 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,384059#msg-384059
Quote
Dejay
I guess an alternative might be to create a really big 3D printed bearing, similar to these, using delrin balls

... for a better DIY-able 'recirculating bearing' concept cylinders instead of balls are even better for linear bearings ... simple cut a smooth rod in short pieces and fill them into the tray ;)]]> VDX Delta Machines Wed, 16 Jul 2014 18:29:15 -0400 https://reprap.org/forum/read.php?178,267835,384029#msg-384029 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,384029#msg-384029
LISA is inherently bad because any error in the straightness of the screws will be doubled because of the rotation and could be even more than doubled if you go for high speed rotations. It was a fun concept but it doesn't fit in my value engineering vocabulary.]]> nicholas.seward Delta Machines Wed, 16 Jul 2014 17:12:31 -0400 https://reprap.org/forum/read.php?178,267835,384025#msg-384025 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,384025#msg-384025 What is the current state of LISA?

Current design?
Future?

On the back burner to your SCARA Robot design?

Tnx
:S]]> cozmicray Delta Machines Wed, 16 Jul 2014 17:05:19 -0400 https://reprap.org/forum/read.php?178,267835,384023#msg-384023 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,384023#msg-384023 did you get some of these ball screws?
How are they?

With 800mm length --- what would be the print volume dimensions?

Tnx

:S
Quote
Dejay
I've found some rather cheap ball screws on ebay 800mm and 1610 (apparently 10 mm lead), in the range of $60 with free shipping. These have less lead than the high lead screws, but they also have far less friction. Would this work / compensate so that you could use higher RPM on the motor instead of higher lead?
]]> cozmicray Delta Machines Wed, 16 Jul 2014 17:02:54 -0400 https://reprap.org/forum/read.php?178,267835,384021#msg-384021 Re: LISA Simpson https://reprap.org/forum/read.php?178,267835,384021#msg-384021 link is not right?

Please explain these recirculating ball screws?
:S

Quote
Dejay
I guess an alternative might be to create a really big 3D printed bearing, similar to these, using delrin balls
]]> cozmicray Delta Machines Wed, 16 Jul 2014 16:56:16 -0400