[Concepts_Design]

As far as I know, the customer in this case is an engineer working on her own time on a side project (I'll find out more when she comes to pick up the part). So for all I know, if the bids to make this were $1k+, then it might never have been made. Certainly not a rush item to keep a line running. The customers I make parts for tend to be inventors working on prototypes, and the shops around here typically don't really want that business anyway. But I couldn't live off this kind of work alone--I have the shop because I'm working on my own prototype, and these projects help offset some of that cost, teaches me new things, and helps to ensure the IRS sees this as a business and not just a hobby.

I did consider grinding--I thought about rigging up my Dremel on a spindle mount to do a finish pass after milling, but the finish from milling alone was decent. If you wanted a hardened screw, I'd think the way to do it would be to mill close to net shape in the annealed state, heat treat, and then grind to final dimensions. But what the heck do I know?

Sans,
are you from Massachusetts? I don't think heat treated screws would fair well since they are constantly being heated, they will just fracture. I think the only time they are needed is for glass filled or other abrasive types of resins.

[sansbury]

Concepts, yes, I'm in the Marine Industrial Park in Boston, right near the Harpoon brewery if you're familiar.

It is a torsional load, so yeah, hardening probably isn't particularly advantageous, but again, you could fill books with what I don't know about the subject.

[Concepts_Design]

Concepts, yes, I'm in the Marine Industrial Park in Boston, right near the Harpoon brewery if you're familiar.

It is a torsional load, so yeah, hardening probably isn't particularly advantageous, but again, you could fill books with what I don't know about the subject.

Oh man, that's a great spot to be, except I'd get nothing done after lunch at the brewery. I'm out in Leominster, about 40-45 minutes out route 2 west. Boston is a great city, but too damn difficult to get around down there

[mactec54]

sansbury

This is very small screw, ask when she picks it up if it's for a 3D printer, a screw like this, if it is for plastic, needs to have a mirror finish, then a nitride treatment, then a finish polish, for testing like it is would be ok for a prototype, if it gets to be for a production machine,& is for plastic's, then it would need to have a nitride treatment & polished

I made some that were 40" long & 5" diameter, with the pitch & depth that changed over 30" of the screw, they get real tricky to program when you have to have the pitch change, straight pitch like you have done is very easy to program, like you have said, Good job though for your first try at something like this

[Concepts_Design]

my educated guess would be that it is a prototype for a resin specific grade for micro molding. you're correct in that most of them are nitride, but by no means do they have to have a mirror finish. every resin is different, some like polished finishes and others like rough surfaces such as bead blasts or an edm finish

please let us know what she says it's for. I am curious to know. the 3d printer might be a possibility, I would think it would be a high end printer as all the ones I have seen just use a heated extrusion nozzle and spooled filament

[sansbury]

My guess would be an extruder to create filament from scrap plastic.

[mactec54]

my educated guess would be that it is a prototype for a resin specific grade for micro molding. you're correct in that most of them are nitride, but by no means do they have to have a mirror finish. every resin is different, some like polished finishes and others like rough surfaces such as bead blasts or an edm finish

Surface finish is a critical part of all plastic screws, no matter what the material/resin you are using, usually when you see a screw, that has been bead blasted it is on it's way out, you will never find an EDM finish on a screw, unless it has been a repair, & even then it would be stoned & polished

I have made 4 different screws this year, similar to this one for 3D printers, & 1 for a filament extruder, there are a lot of people into trying different ways to use 3D printer, not only just for plastic materials

When a screw for Plastic Injection molding is manufactured, it starts out, by being turned, milled then goes to grinding ( sometimes to stress relieving before Grinding ) then micro polishing followed by the nitride treatment, & a polish after treatment if needed

Photo of ( 1 ) of my molding machines, in my home workshop

[Concepts_Design]

Surface finish is a critical part of all plastic screws, no matter what the material/resin you are using, usually when you see a screw, that has been bead blasted it is on it's way out, you will never find an EDM finish on a screw, unless it has been a repair, & even then it would be stoned & polished

I have made 4 different screws this year, similar to this one for 3D printers, & 1 for a filament extruder, there are a lot of people into trying different ways to use 3D printer, not only just for plastic materials

When a screw for Plastic Injection molding is manufactured, it starts out, by being turned, milled then goes to grinding ( sometimes to stress relieving before Grinding ) then micro polishing followed by the nitride treatment, & a polish after treatment if needed

Photo of ( 1 ) of my molding machines, in my home workshop

this is not true, yes you wont find an EDM finish on them, I was just using that as an example along with bead blasting. But all screws do NOT require a mirror finish. While the majority of screws do have a HIGH, not mirror, finish they are coated with many different coatings now. nitriding, hard facing, various chrome platings, etc. and yes, some of them do in fact have bead blasts and some are even finish turned or ground. I know this for a fact as I have been working in injection molding for 24 years and I have had to work with vendors to spec out screws for specialty engineering resins, With the development of new resins happening everyday, also comes the developments in molding machinery.

And the 3d printer is a very good possibility, I was just saying that the ones I have seen were not like that. But I have never seen the inner workings of a higher end printer before and it very well good be for a printer. Or as Sanbury speculated, it could be a extruder for making filament from scrap plastic.

Hopefully he will find out from his customer. But in the end, he did an amazing job and did it for an outstanding cost for his customer, so I'm sure that customer will continue to do work with him for a long time

[CNC-Dude]

So what is the problem if the screw is not polished? Does the plastic sticks to it and causes jams? I imagine the cylinder bore where the screw resides must also be of perfect diameter and polished as well? I am just curious on these items as I have always wanted to make one of these extruders but if it is going to require so much specialized equipment to make, chances are it will drop to the end of my wish list for a while.

[Concepts_Design]

So what is the problem if the screw is not polished? Does the plastic sticks to it and causes jams? I imagine the cylinder bore where the screw resides must also be of perfect diameter and polished as well? I am just curious on these items as I have always wanted to make one of these extruders but if it is going to require so much specialized equipment to make, chances are it will drop to the end of my wish list for a while.

certain resins stick to certain finishes. In a mold the surface finishes are for appearance and release after the parts are molded. Within the barrel it's not so much that it will jam as the barrel is heated and the screw is creating shear heat further melting the resin. But you don't want the resin to stick to the screw or barrel as it will further degrade and cause issues such as burnt material in the molded part, black specks, and other appearance problems, but more importantly the more the resin gets degrading, it loses it's properties and the molded parts could fail in the field due to issues like cracking

[LeeWay]

I know hobby 3D printers do not use polished extruders. Simply a brass tube. Now they are smooth of course, but not polished. The extrude pressure on them is the plastic itself. It is pushed into the hot end by force from the extruder wheel. That is one of the calibrations that has to be done when setting them up is how much force it takes to keep up the extrude volume. I am sure even the big boys need that calibration, though it is probably automated or automatic on those. Logically you would think that a polished finish would yield better results.Plastics are so varied though in makeup and properties that you really can not categorize them all as plastics any longer.
They IM lots and lots of different materials. Each has it's own requirements. I have helped with repairs being made to screws in a bone grinder in a render plant that I worked at when I was young. We added layer after layer of heavy weld on them . We had a specific template that we had to use all the time. Took us a couple weeks to repair one. It would last 6 months to a year before needing repair again. We simply ground down the welds. No polishing. The bone grinding action takes care of that. They are highly polished after a little use.

I am already working on two side project machines for my production, but plan to make an IM too to make some of our parts that take us so long to produce. That is our thermoformed dust ports on our blade guards. I could double our production with a machine that does that. There is quite a bit of waste in the process too. 4" polycarbonate tube is not cheap.

[CNC-Dude]

certain resins stick to certain finishes. In a mold the surface finishes are for appearance and release after the parts are molded. Within the barrel it's not so much that it will jam as the barrel is heated and the screw is creating shear heat further melting the resin. But you don't want the resin to stick to the screw or barrel as it will further degrade and cause issues such as burnt material in the molded part, black specks, and other appearance problems, but more importantly the more the resin gets degrading, it loses it's properties and the molded parts could fail in the field due to issues like cracking

Concepts, thanks for this insight. Makes perfect sense and it helps to envision what are some of the pitfalls. Of course in any manufacturing environment this is all of crucial importance, specially when the product has to last as designed on customer's hands. So it seems that for hobby use it would be OK if the finishing is not the ultimate. Plus I am not a polymerologist, so I would have no idea which finish to use for what resin. Heck, chances are I would not even know which resin I would be using! I guess milk jugs or PLA, Maybe ABS? But you know, these are generic names and chances are there is a zillion grades of each depending on chemical composition and manufacturing process.

Anyway, fascinating topic! Keep it coming!

[mountaindew]

Sansbury!
Nice work, to do this with no cam software is awesome.

Would like to also comment on the use of such devices! Archimedes screw is or can be used for many different applications besides injection molding ! I mentioned in another thread there are a dozen food manufacturing plants in this area that make all kinds of different products. I can almost guarantee every one of them have an Archimedes screw somewhere in the product line. I have experience with 6 foot in diameter and 50 ft long screws years ago we built a sewage treatment plant that uses these devices to move stuff around "common design and your city would have them also" . Anyway a great device to mix, convey, pump, lift ...................................
md

[mactec54]

this is not true, yes you wont find an EDM finish on them, I was just using that as an example along with bead blasting. But all screws do NOT require a mirror finish. While the majority of screws do have a HIGH, not mirror, finish they are coated with many different coatings now. nitriding, hard facing, various chrome platings, etc. and yes, some of them do in fact have bead blasts and some are even finish turned or ground. I know this for a fact as I have been working in injection molding for 24 years and I have had to work with vendors to spec out screws for specialty engineering resins, With the development of new resins happening everyday, also comes the developments in molding machinery.

I'm not sure what part is not true, you are starting to say what I have already posted, but say it's not true??? for someone that has spent 24 years in the plastic industry, your exposure to screws & barrels, must of been very limited

The industry standard finish before any treatments, is a Surface finish roughness Ra.01 to 0.4μm this just happens to be a mirror finish, which is easy to achieve done on a machine similar, to what machined it

The PDF will also give those interested, more information on what & how plastics are processed, every plastics manufacture already have the spec's for what kind of screw is best to use for their material so this information is readily available

Some photos of standard screws, which can be found using a simple Google search

Yes she could be making pasta with a screw like this, although it would not have quite as much compression for food products

[mactec54]

Concepts, thanks for this insight. Makes perfect sense and it helps to envision what are some of the pitfalls. Of course in any manufacturing environment this is all of crucial importance, specially when the product has to last as designed on customer's hands. So it seems that for hobby use it would be OK if the finishing is not the ultimate. Plus I am not a polymerologist, so I would have no idea which finish to use for what resin. Heck, chances are I would not even know which resin I would be using! I guess milk jugs or PLA, Maybe ABS? But you know, these are generic names and chances are there is a zillion grades of each depending on chemical composition and manufacturing process.

Anyway, fascinating topic! Keep it coming!

Don't be intimidated, by what is being posted, it's a lot easier than you think, to achieve what is needed, for molding plastic, there is so much information available for this industry, just a little search & reading, will get you on track, to do what ever you want to do

[Concepts_Design]

I'm not sure what part is not true, you are starting to say what I have already posted, but say it's not true??? for someone that has spent 24 years in the plastic industry, your exposure to screws & barrels, must of been very limited

The industry standard finish before any treatments, is a Surface finish roughness Ra.01 to 0.4μm this just happens to be a mirror finish, which is easy to achieve done on a machine similar, to what machined it

The PDF will also give those interested, more information on what & how plastics are processed, every plastics manufacture already have the spec's for what kind of screw is best to use for their material so this information is readily available

Some photos of standard screws, which can be found using a simple Google search

Yes she could be making pasta with a screw like this, although it would not have quite as much compression for food products

I don't claim to be a process engineer, however I have worked with a lot of knowledgeable ones. Are you a process engineer? Do you have a doctorate in Plastics Engineering? I am primarily a mold designer, and I have worked for a few medical device molders that are leaders in their field. I am certainly no expert in screw and barrel design, but I do know the basics.

Ra .01 to 0.4 is a surface ROUGHNESS, not finish, and this can be produced by milling, turning or grinding. Not even the most seasoned tool maker can provide a mirror finish with any of these processes. The "mirror" finishes you're seeing in these pictures are the coatings.

Also, you pulled up a information sheet from 2007, there have been major advancements in resins and processing equipment in the past 7 years. And they even state this in the conclusion.

Not to mention that these are standard screws, there are many custom builders out there that will build anything you want and there are plenty of injection molders out there with their own proprietary designs for all kinds of processing equipment.

So to sum it up, I've forgotten more about injection molding in the last 24 years then you will ever know.

And, yes there really is a lot more to injection molding than what you can Google. There is a reason that it's called Scientific Molding....

[sansbury]

Don't make me pull this car over! Just kidding Lots of interesting information there.

Met the customer this morning and as I guessed it is an extruder to make filament for a 3D printer.

[Concepts_Design]

Don't make me pull this car over! Just kidding Lots of interesting information there.

Met the customer this morning and as I guessed it is an extruder to make filament for a 3D printer.

Nice job, I bet she was extremely happy with the results

[LeeWay]

I know there are many of these machines out there already, but is she working on a hobby version for production or just a back yard project? I sold my 3D printer a few years back, but I always thought the filament was very high. It has become much more reasonable lately. IM guys certainly have many contracts to fill, but somewhere some of those guys are wondering how we can make cheaper money.
With 3D printers needing filament, that area should get even more competitive than it already is and the price will drop even further. That is why I do not think such a machine would be that profitable if it were to be marketed. I had originally thought maybe a scale or working model for teaching classes.
With the proper advertisement, that might piggy back on the hobby side to be a valid market venue.

[sansbury]

I'd guess it's a production possibility? I didn't dig in too hard, she was a bit introverted--I work with a lot of engineers so know the type well.

I think the intention with this isn't to be a full printer (though maybe?), but rather a machine to produce filament, perhaps from scrap. I don't pay a ton of attention to the 3D printing scene, but I think filament production from used material is a thing that hasn't been widely done yet. While open-source filament is a lot cheaper than the stuff Stratasys sells, it's still relatively expensive, especially if you're at the edges of the first-world supply chain. Being able to recycle prints or say chop up a bunch of used milk bottles and turn them into filament could open some useful doors.