Back to the future - A 3D-printed thumbslug

[VLe]

After getting tired to plug’n drill - hit or miss experiments with ADT, wikifit and all the other methods I have gone through I thought I need some easier method to play a little with my thumb angle and shape. I don’t have my own pro-shop equipment so I must drive around 70km to make a new drilling for my ball and it will quickly become costly.

Well, easier might not be the thing I came up with but at least more customizable and consisted design – A 3D-printed thumslug. I have noticed many benefits that can be achieved with this design. I have included some photos of my first experiments and prototypes with the design. The material that I have used with this is PETG which is close to the material used in the plastic bottles. It can be sanded and buffed to very smooth surface if necessary and it is very wear resistant. The surface can also be made very rough. I have also added a special venthole from the bottom of the hole to the top which can be seen in the pictures attached.

I have tested various different shapes for the thumb. The shape is a bit based on a tiered taping-system that I have used and I must say it is very comfortable. With this system there is almost no limits on the desired shape of the hole so it is a huge advantage comparing to the “normal” methods.

I haven’t tested this on a bowling ball yet but I will make my first 3D-plugball soon when I get everything ready. I will also test this system for the finger holes. The first model is for installing the slug with glue directly to the bowling ball, but I have also planned to modify this to an interchangeable version.

If I know the thumb pitches I can make the top layer so that it will match the radius of the ball surface. Therefore no drilling/sanding etc. after the installation of the slug is necessary. I will also add a little mark to the top which can be used to install the slug to correct oval angle on the ball.

This is still a bit of an experiment but I thought to share some information with other bowlers as I proceed. If anyone have any ideas or opinions for the design, please take off your tin foil hat and share it with others! And forgive me for bad english, I live in Finland.

[bowl1820]

Idea:

Use a 3D scanner to get the thumb shape/size for the hole.

[JimH]

What an excellent idea. I wish you the well in developing it.

By the way your use of English is very good, I would say it is better than very good.

[Dustin]

Very cool idea!!! Please keep us posted on the progress. As Jim said best of luck!!

[stevespo]

Very nice work! Last year, I printed a couple of oval test slugs (in PLA), but never got around to installing them. I was not nearly as clever or creative as you were with the shaping and the vent holes. Those are both very nice ideas and should add a lot of value over the standard tapered oval.

My own personal concerns were around the integrity of the printed slug and whether there was anything in the USBC rule book that might disallow them (perhaps not a concern in Finland).

I do believe that they are pretty well fused into a solid mass, but I'm not sure I'd consider them monolithic. Are they strong enough to withstand the shock of hitting pins at 17+ MPH? My understanding is that the interchangeable systems have to be tested or at least approved by USBC before using in competition.

Another small concern was getting the interior smooth enough. Tape would help on the front and back, but I'd also like to get rid of the ridges and make it very smooth without changing the shape dramatically. A design that worked with one of the removable systems would also be great!

I also wondered about being able to scan a thumb and use that as the basis for the slug. I have some ideas that wouldn't be too hard to prototype using 123D Catch (or similar software) and a digital camera. I'd be happy to share ideas and files.

I was also thinking about generating a parametric thumb model using OpenSCAD that would take a few parameters and produce a usable model without a lot of CAD work. Keep the ideas coming...

Steve

[VLe]

I would not worry about whether the material (PETg) is strong enough. It is also glued in to other material. Well, if for some reasons it break there is many other materials to print (nylon for example). For the interchangeable thumb design in the future my plan is to use the existing frame, drill the 1 1/4" "slug" out of it and then glue this printed slug in to it. If this works it would be a good way to recycle the old thumb pieces...at least for testing new shapes for the thumb.

A 3d-scanner is something that I have thought of but there is also downsides using it. Lets assume that I will be able to get a perfect 3d-model of my thumb. If I print it even with little extra space on every side, it may be that my thumb would not come out of the slug because the shape of the thumb is not cylindrical (the first joint is usually wider etc). Therefore there would still be some tweaking afterwards. I have done a lot of cad-work and it is not a problem for me to model the thumb shape. I use Solidworks for modelling. When I model the thumb shape from sketch, it is easy to make adjustment to it afterwards. It is also easy to modify the hole dimensions if I want to make this to another person.

One way to simply determine the shape of the thumb is to use a normal copyscanner for the hand and then measure all the details from the paper. You can add also a small grid on top of the scanned thumb before printing. I have actually tested to measure the span with this method a few times and got a pretty close values but this is off-topic. The scanned image must be confirmed to be in real scale. I personally still prefer using caliper and some other tools when fitting my own thumb but it would be great to have some sort of baselines to follow as there are for the tiered oval-system for example.

There is still some study to make with the shape of the hole. I am "out of the office" for a few days now but will get back to this in a moment. I will also post some other ideas, guestions and pictures.

[stevespo]

My experience is with PLA, and it seems quite durable. There are also many materials with different characteristics (rubbery, metallic, carbon fiber, etc) so it seems very likely we'd find something durable enough with good carving and shaping as well. I did not have good luck sanding the PLA as I could never really get the surface smooth enough for my liking. Nylon or ABS might be better.

My simple TinkerCAD generated oval slugs -

printed-slugs.jpg

With a scanner, I imagined automating some boolean operations to create the final slug shape. The scanned thumb itself would not be enough. I do think you're right that a CAD model can be manipulated easily and tested fairly quickly. If you were doing this for other people, perhaps you'd have a few common sizes and then make small changes to customize from there.

Steve

[VLe]

It seems that my few "days" out of the office have turned into weeks. I've been very busy lately so it has slowed down these experiments. Yesterday I went to the local bowling center and we filled/drilled my thumb hole to a straight 1 3/8" hole so i can start testing these printed slugs.

PETg is my go to material for first tests since it can be sanded nicely and is very strong. I would not use PLA since it is more like a brittle material and not so sandable.

There are lots of materials to use and many ways to archieve very smooth surface. One of them is using ABS and then smoothing it out with acetone. This should actually work for some manufacturer's PLA also. Here is some quick demonstration of the process:
http://airwolf3d.com/2013/11/26/7-steps ... s-acetone/" onclick="window.open(this.href);return false;

There are also coatings for different kind of materials that smoothen's the surface it is applied to. I would still use PETg and smoothen it by sanding for first tests to keep things simple. The surface can be sanded up to very smooth as I mentioned earlier.

For the designing part I have used layers that are measured on the required parts of the thumb. This is a bit like in the tiered oval-process, but I will be able to shape the design more accurately. Attached I have included one picture with visible cutting planes for the thumb hole.

I will update more information about the modelling procedure and first results soon.

[LittleTiger]

Another Finnish geek did this one already


First I created TOPS 3 (http://bowlingknowledge.info/images/sto ... _3_btm.pdf" onclick="window.open(this.href);return false;) shaped switch grip for myself.
Then I sent that one to local 3D modeling company where they drew that one using CAD and made 3D printer version.

Now I have been two identical 3D printed "switch grips" in use couple of weeks already.

More information how that was done you can found from 3D modeling company's blog:
https://www.playfulpixels.com/en/custom ... nd-printed" onclick="window.open(this.href);return false;

My own personal concerns were around the integrity of the printed slug and whether there was anything in the USBC rule book that might disallow them (perhaps not a concern in Finland).

Finnish bowling rules are based on USBC rules but I cannot see any problem with these.

Page 4 on this rule book: http://bowl.com/uploadedFiles/Equipment ... ACTIVE.pdf" onclick="window.open(this.href);return false; says like this:

Devices Movable devices are not permitted in a ball except that a device for changing the finger span or the size of finger and thumb holes may be inserted, providing the device is locked in position during delivery and cannot be removed from the ball without destroying the device. (Excluding tape in a gripping hole.)

Removable devices shall be permitted provided:
1. Such devices are used for changing the span, pitch, or size of the gripping holes
2. Such devices are constructed of a non-metallic material
3. Such devices are locked in position during delivery
4. No device shall be employed for the purpose of adjusting the static balance of the ball
5. No voids shall be permitted under the device
6. Density does not exceed 1.5 g/mL

There is no any requirements that these devices should be tested and approved by USBC like they do for bowling balls, etc.

[Spartacus]

This thread is almost 8 years old now, I found it looking for a CAD model for an "ultimate" inner sleeve.
Anyway... my answer to the topic here is YES.

I and 2 others have been bowling with FDM printed thumb slugs locally, several 300's (not me!) on them. PETG or Nylon have been great. PLA is good too but 2nd place to PETG or Nylon bridge filament.

ABS didn't last long - I only tried a single brand of ABS and don't remember what it was. MG Chemicals PETG, Hatchbox and oddly the cheap Chinese translucent PETG's are GREAT. I have blue/yellow/orange thumbs + spares in different sizes and pitches in the bag.

Materials are <$1 so experimentation is cheap. I have some smooth, oval, round, Velcro insert (like Ron's Magic Carpet).

One friend asked for a curved thumb interior. OK. That did not work as you can imagine!

Another usage is to change a span slightly. The smaller your thumb is, the more area you can move it obviously.
All so far have been the "Turbo" style - which is why I was looking for CAD/dimensions on the Ultimate for a ball just gifted to a friend.

[nipravsky]

hi you all
been away for some time
dose anybody have an stl file to share
thank you
yossi