Tape Strip Holders

[GaryM]

Absolutely agree on ebay or AliExpress for hardware like spacers, screws, etc. I regularly buy these there in qtys of hundreds per item. Stainless metric bolts in buttonhead m3, nylon spacers, brass spacers etc. Quality is very good and price is low.

[mrandt]

I don't think $20 for feeders is a good idea. My target is $10 retail per feeder.

OK, that sounds more reasonable. When you mentioned the cost of fasteners * 5 + injection molding in your earlier post, I got a bis scared

I used pricing from McMaster, which I'm sure isn't the best price. I haven't spent time yet to find better sources, so I don't know how much I could get these prices down.

I think this is still a good approach and part of the iterative process. Buy standard parts from a source you know, which sells small quantities. Figure out what works for you. At a later point, you can always go to other distributors and discuss pricing for larger quantities - or even have the parts custom-made overseas.

I'm sure this design also won't be the final design. One thing I've learned from previous projects is that the DFM process is all about iteration. I'm not smart enough to come up with the best design on my first try, so I go through multiple iterations.

I bet nobody is. Good design always comes from reiteration. I wonder how many iPhone prototypes where scrapped before Mr. Jobbs was happy with it...

Talking about your new design: How do you intend to interconnect the sliding bars? I liked that in the previous design and don't understand how it is supposed to work in the new version.

One more idea: Instead of using bolts and nuts, you could also use flat pan-head screws for thermoplasts and screw them into the plastic directly, at least for some of the connections:

feeder_screw.png (65.44 KiB) Viewed 21464 times

Molding or drilling a hole with right diameter should be possible and you will save the cost for fine threaded screws + nuts. The screws for thermoplasts come very cheap and are often used in plastic parts, e.g. toys, household appliances, etc.

[JohnSL]

For both spacers and springs I'd recommend finding a Chinese vendor on eBay or Aliexpress that has something close to what you want and then ask if they do custom.

Thanks Jason. I did a quick search for threaded spacers, and indeed I was able to find a much less expensive source. Springs I think will take more work because, unlike "M3 hex spacer," it's hard to find a search term for just the right springs.

I don't have anything productive to add here. I just want to say that I really like the direction this is going!

Always nice to hear .

Talking about your new design: How do you intend to interconnect the sliding bars? I liked that in the previous design and don't understand how it is supposed to work in the new version.

Thanks for bringing this up--I completely forgot to cover this. During my testing with 3D printed parts, I discovered that it's very important for the two sides to push up by the same amount on the tape. I also discovered that slight offsets between the two parts in X would cause much larger differences in Z because of the 10 degree slope. A slight offset, therefore, could result in one side of the tape being tight, but a slight gap on the other side, allowing a little bounce in this tape. That's not good. Then I realized that they don't need to be connected. So in this version, each side has it's own spring, and therefore can move independently. This will ensure that both sides hold the tape tightly.

Molding or drilling a hole with right diameter should be possible and you will save the cost for fine threaded screws + nuts. The screws for thermoplasts come very cheap and are often used in plastic parts, e.g. toys, household appliances, etc.

I tried that originally, but ran into some space issues. Using a screw directly into the plastic required a post with an M3 (slight smaller) hole in it. And this post required that I increase the size of the angled slot. Increasing the size of this slot also meant that I had to move the screw head up a little, which reduced the maximum vertical size of the tape that I could use. So I went back to a screw and nut, which are really inexpensive anyway. The other option I could look at, I guess, is to switch from an M3 screw to an M2 screw. Right now the nut/bolt pairs used to hold the slider in place are M3, and the screw for the spring is M2 (mainly to allow fitting inside the loop of small springs).

-- John

[JohnSL]

I did some more work this evening. The first image shows the bottom. Here you can clearly see the two springs that allow each side to be tight against the bottom of the tape. You can also see that I now have just two spacers.

Version 5a.PNG (76.31 KiB) Viewed 21447 times

Here is a close-up of the springs:

Version 5b.PNG (198.16 KiB) Viewed 21447 times

I can't model the spring stretched out, so it's in the fully compressed position here. On the right side you can see my first attempt to create a hook for the other side of the spring. At this point I'm ready to make another set of 3D printed test parts to see how this works out. I think I'll need to get new springs that are about 1/2 of the strength, but I'll know more after I test this design.

[mrandt]

Hey John,

nice work - I like it. Thanks for the explanations.

Then I realized that they don't need to be connected. So in this version, each side has it's own spring, and therefore can move independently. This will ensure that both sides hold the tape tightly.

Makes sense; if each side has their own spring I am sure it will work nicely.

Molding or drilling a hole with right diameter should be possible and you will save the cost for fine threaded screws + nuts. The screws for thermoplasts come very cheap and are often used in plastic parts, e.g. toys, household appliances, etc.

I tried that originally, but ran into some space issues. Using a screw directly into the plastic required a post with an M3 (slight smaller) hole in it. And this post required that I increase the size of the angled slot. Increasing the size of this slot also meant that I had to move the screw head up a little, which reduced the maximum vertical size of the tape that I could use. So I went back to a screw and nut, which are really inexpensive anyway. The other option I could look at, I guess, is to switch from an M3 screw to an M2 screw. Right now the nut/bolt pairs used to hold the slider in place are M3, and the screw for the spring is M2 (mainly to allow fitting inside the loop of small springs).

OK, I get it. If diameter / screw size is a constraint, go for M2. Will still be strong enough but save you some space. Also, I suggest to turn the screws by 180°. It is easy to model a hexagonal cutout for the nut on the outside of the rail; I often do this on 3D printed parts. You can sink it just the right distance to fit a given screw. The screw head would then be on the inside and would probably make for a nicer "slider" (maybe combined with a washer) than the nut. Assembly might also be easier and quicker.

Do you have a link to the springs you are currently using? Maybe some people can help you search for alternatives.

Malte

[JuKu]

You have a hook for the spring in the brown part. If that is strong enough, wouldn't a similar hook work for the green part as well?
For the spring, we first need to find the specs for it. Then, we need to talk to someone in China that has a spring making machine. Once this goes in production, we'll need roughly a barrel of springs; the price will be cents each.

[JohnSL]

Also, I suggest to turn the screws by 180°

The nut that is in the drawing right now is a low-profile nut, which I originally chose because I was planning on having a indentation on the other side for the nut. However, even the low-profile nut is thicker than the head of the button head screw. In order to have the nut flush with the outside, the wall thickness between the nut and the inside would be 0.3 mm. Moving the nut to the inside gave me a wall thickness of 0.45 mm.

You have a hook for the spring in the brown part. If that is strong enough, wouldn't a similar hook work for the green part as well?

Because of mold geometry. I'm trying to keep the mold as simple as possible in order to keep the cost down for making the mold. Adding a hook to the outside part (green in the images) could be done by adding an opening to the outside for a boss in the mold. And I could certainly do that. But again, it might increase the cost of the mold itself.

For the spring, we first need to find the specs for it. Then, we need to talk to someone in China that has a spring making machine. Once this goes in production, we'll need roughly a barrel of springs; the price will be cents each.

Correct. I'll order some more springs from McMaster-Carr so I can find an appropriate force/in. From this I'll have the wire thickness, diameter, and number of turns that we can then use to order a "custom" spring.

[JohnSL]

I think I'm getting pretty close. Today I fixed a few small issues I found by making a prototype. I also finally added a pin for positioning the tape:

Position Pin.PNG (71.44 KiB) Viewed 21411 times

The magenta part should clip in place and provides the alignment pin that I had on my 3D printable version. In addition, it helps hold the outer parts at the correct spacing for the tape. Unlike all of the other parts, this part will have to be different for each tape width. This is also the only part where there could be some trial and error with getting the dimensions just right. I'm thinking that either I'll make these parts in a separate mold, or make them 3D printed parts. They're small enough that I could make the molds myself and run them on my desktop machine, so that's also an option. I'll have to see what the increment in cost would be to add these to the same mold as the other parts, and the cost for adjusting the mold before I'll know the best route.

Speaking of tape widths, I just looked at the specs again and realized I need to make a few small adjustments, as the maximum tape width is 0.3 mm greater than the specified width. In other words, for an 8 mm tape, the maximum width is 8.3 mm.

[instrukcion14]

Hey guys

I'm so glad seeing progress in design strip holder. Right now I'm also thinking about strip holder for my machine but it would be waste my time when I see what you did. I would like to be part of this design community.
I find your solution so clear and easy to produce but see there few possible problems and also have few suggestions.

Position pin is interesting but as you know it's small part and easy to lose and break. It's good consider if that pin is necessary.

There are a plate pressing tape upwards from bottom. Under tapes holes is nothing what can prevent making any shadow under tape in holder. There will be only free space inside holder with unexpected lighting which can cause "can't find circle" error. My suggestion is to make this plate a little bit wider to cover all tape holes from bottom side. Most of tapes are thicker on both sides and also in holes line and because of this you can make this plate as width as is width of the tape holes line.
You can then make also some reel holder and then it should be very powerfull part of liteplacer.

And at least my biggest suggestion is to let you inspired by shifting tapes in tray: https://youtu.be/XIKzpkfqq60?t=55s. This solution are totaly appropriate for liteplace. Easiest way how to make a automatic feeder, which can be next big progress for litplacer. There are also option to combine this 2 solutions and eq. you place 10 components and then p&p shift tape in tray to save more time. It's depend on pressure of spring you use in you modular tray system.

Thanks all for making our lives much easier

[JohnSL]

Thanks. I welcome ideas and suggestions.

Position pin is interesting but as you know it's small part and easy to lose and break. It's good consider if that pin is necessary.

The pin part is clipped into place when you assemble the strip feeder. Once installed, it would take some work to remove it as it snaps into place, so I doubt it would be lost. As to strength, the pin will not take that much force, plus the plastic is actually pretty strong. I've used this type of clip before and never heard of one being broken or lost. Here is a view that shows the snap action:

Pin Clip.PNG (43.83 KiB) Viewed 21400 times

There are a plate pressing tape upwards from bottom. Under tapes holes is nothing what can prevent making any shadow under tape in holder.

It's a little hard to see in the images, but the sliding plate under the holes is wider, and completely covers the bottom of the holes. Here is another view that shows it better:

Under Holes.PNG (58.51 KiB) Viewed 21400 times

Notice that the sliding plate on the right is wider at the top. I'm thinking of having these parts made in green so you get good contrast with both white and black tapes.

And at least my biggest suggestion is to let you inspired by shifting tapes in tray: https://youtu.be/XIKzpkfqq60?t=55s. This solution are totaly appropriate for liteplace. Easiest way how to make a automatic feeder, which can be next big progress for litplacer. There are also option to combine this 2 solutions and eq. you place 10 components and then p&p shift tape in tray to save more time. It's depend on pressure of spring you use in you modular tray system.

Peeling the tape is probably the biggest difference, and solving that would certainly increase the price. I think there is value in having both automatic and strip feeders, and I've often seen both in use on machines. As a result, I'm focusing only on the strip holders, with a target price of $10.