Working With Plastics

Plastiblocks

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WDG

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I have a very old antique Coke machine that I'm turning into a Kegerator. I have made a wooden door and have about 1" between the door and the machine for insulation. I want to make a cover over the insulation out of ABS because I want to bend it. Also, I want to use some on the inside to match up with the door to make a tight seal. I'm looking at .125" or .187" to work with. My problem is that I will have to drive to Atlanta to get it so I'm thinking of getting some extra sheets to have as they aren't expensive. To have them shipped here would cost way more that the sheets. (4'X8') Anyone have an information that might be helpful before I jump into this. I was thinking of making a mold and using a heat gun to bend it. The door part would be one piece but the inside would have to be open to put the keg in. It would have a 4" or 6" side that would be slanted to shut the door.
 

vocatexas

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How about some info on machining plastics? thanks
Yes, and maybe a bit of info on selection of plastics for different applications. I need to make some suspension bushings for my Polaris Ranger and I'm not sure which plastic to use.
 

Plastiblocks

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Plastiblocks

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Yes, and maybe a bit of info on selection of plastics for different applications. I need to make some suspension bushings for my Polaris Ranger and I'm not sure which plastic to use.
I highly recommend to check out this source: Basics of Plastic Selection for Machining

We are also starting videoing how-to machine plastics videos and will have them posted starting mid-end of October.
 

Profkanz

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Some people are not very familiar working with plastics.





So we will continuously be adding useful info about plastics, here are few first ones we put together:

Joining and Gluing ABS

Painting parts with molded-in colors - a great partnership.

Your Guide To ABS

Drop us a note if you find this info useful.

If you have more questions/topics you'd like us to cover in future posts, please respond to this thread or submit suggestion on our website using this form
Attached is a plastics machining data sheet I acquired at a trade show some time ago. It includes cutting tool angles and cutting speeds for various machinable plastics.
 

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Southerner

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The question I always have is how to identify a particular plastic. I usually need this information so that I know what adhesive to use to fix the piece or join the piece. I have seen nothing definitive on that. Most of the time CA super glue does nothing and neither does epoxy and often acetone or Weldon #4 or #4 also do nothing. Does anyone know of a guide to identifying a particular plastic for the purpose of joining it?
Thank you.
Jim
 

BenzB

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Boedeker has some very useful machining guidelines: https://boedeker.com/Technical-Resources/Technical-Library/Plastic-Machining-Guidelines
Also, Quadrant Plastics and Eppinger both have guidelines and recommendations. I have been involved with machining of plastics and composites for 4 years now at Lehigh Valley Plastics. Some are very pleasant to work with (acetals, PVC's, unfilled nylon) and behave very nicely.
Nylon is hygroscopic and will change sizes depending on how wet it is. It can also be very abrasive especially if glass filled. But it is very strong and wear resistant.
Acetals (think Delrin but there are many different types) are very nice to work with, hold sizes well and are very stable. Slippery and makes for a decent bearing.
PVC is easy to work as well, holds sizes well.
UHMW's are easy to work with but difficult to get good finishes and hold tight tolerances. Especially on larger parts. Super slippery. Excellent bearing material. Nothing sticks to it.
Teflons are similar to UHMW's.
PEEK's are extremely tough, can be difficult to work with but excellent surface finishes and very tight tolerances are possible. Diamond tooling is preferred. No stringy chips, machines a bit like cast iron.
Polycarbonates (Lexan) and Acrylics (Plexiglass) are more brittle and tend to chip out easily. Especially when drilling.

There are so many others that they don't spring to mind at the time.

Rule #1: Heat is the enemy of plastics!!!
Thermal expansion is a problem and coupled with the fact that plastics don't dissipate heat like metal presents some unique challenges.
use a water based coolant whenever possible.
Look for tooling designed to cut aluminum.

Use positive tooling on a lathe. negative tooling doesn't work well. Except maybe on PEEK.
I use 600SFM with carbides as my base line and adjust from there based on behavior at the machine.
For feedrates start with .01 IPR and adjust as needed.

For drilling I usually use 150 to 200 SFM due to rule #1. Peck a lot, get the chips out or they will bind and create friction and therefore heat and melting and burning WILL happen. Chiploads are similar to those used in drilling metals.

For milling with carbide start with a baseline of 600 SFM and .003 to .007 IPT to start. For HSS tooling maybe try 200-300 SFM. Light depths of cuts with fuller radial engagement is preferred especially on routers.

Just because it is plastic is no excuse for a poor setup so like all materials consider cleanliness and rigidity. If working in a chuck or vise get a good grip.

I can't stress this enough: HEAT IS THE ENEMY OF PLASTICS!!!! KEEP YOUR TOOLING SHARP!!!

I hope this helps.
Benz
 

Plastiblocks

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Following a number of inquiries about our plastics including what type to choose and how to use them, we decided it would be beneficial to create an information hub from which we can share our knowledge and experience with you. We have chosen to start a YouTube channel as videos are an excellent way to show, in detail, the many aspects of machining plastics that you may not have previously known or considered. While text and pictures have their own advantages, videos allow you to focus on the nuances in a way that these other forms cannot accurately convey.

YouTube is not our first foray into the information sharing realm.
You can find simple articles here and in a Knowledge Center on our blog, along with a section devoted to projects .

While we have a list of previously asked questions, we cannot guess what you need/want to know. We count on your help to suggest topics we should cover in our videos and we will do our very best to create a coverage for questions asked.

Looking forward to everyone’s participation. Hopefully you will be interested to subscribe to our YouTube channel.
 

Hit-N-Miss Tom

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Can you suggest a plastic type that is "gasoline" resistive for items like a funnel, etc, ABS, PLA....? Would not be used to store gasoline, but for poring etc.
 

mcostello

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A suitable plastic for making parts immersed in Gasoline would be helpful to know about.
 

Mwags

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A suitable plastic for making parts immersed in Gasoline would be helpful to know about.
HDPE (High Density Polyethelene) would be suitable from a chemical resistance standpoint. Lacking knowledge of any further design/cost implications it would be my go to suggestion. GLTY
 

Plastiblocks

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Mwags

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I have a very old antique Coke machine that I'm turning into a Kegerator. I have made a wooden door and have about 1" between the door and the machine for insulation. I want to make a cover over the insulation out of ABS because I want to bend it. Also, I want to use some on the inside to match up with the door to make a tight seal. I'm looking at .125" or .187" to work with. My problem is that I will have to drive to Atlanta to get it so I'm thinking of getting some extra sheets to have as they aren't expensive. To have them shipped here would cost way more that the sheets. (4'X8') Anyone have an information that might be helpful before I jump into this. I was thinking of making a mold and using a heat gun to bend it. The door part would be one piece but the inside would have to be open to put the keg in. It would have a 4" or 6" side that would be slanted to shut the door.
Keep in mind that ABS is a Hydroscopic plastic, over time and depending on the humidity it will absorb water from the atmosphere. I'm assuming the 4 x 8 sheets you're considering are "warehouse stock" and therefore difficult to determine shelf time. If possible I would lean towards use of a nichrome wire as heat source for the bend line. A slow soaking type heat is what you want to minimize potential surface blistering from any moisture absorption. There are sheet extrusion Co.s that run several "reds" on a fairly regular basis (Grain patterns ?? IDK) you might see about asking to get some samples. Look at a Spartech/Royalite color No 2018 red GLTY
 

Tinker2

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What kind of plastics are used for firearm grips, ie; the plastic pistol grips and forearm grips on an Uzi? Or the backstrap on the Mac 10/11? Or the grip panels on the AMT 380?
 

Plastiblocks

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What kind of plastics are used for firearm grips, ie; the plastic pistol grips and forearm grips on an Uzi? Or the backstrap on the Mac 10/11? Or the grip panels on the AMT 380?
Plastic grips for firearms can easily be machined from PVC or ABS. Both are good choices.
PVC is often used for machining grips with intricate designs. The use of a flexible PVC to bond to areas of the grips to enhance handling and/or to further decorate the part. Interesting opportunities to do excellent inlay work are possible because PVC and ABS do not significantly absorb water, twist, shrink or deform over time as long as they were a machinable grade material initially. Not all ABS and PVC materials are the same.
Look for machinable stress relieved grades.
 

Tinker2

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Plastic grips for firearms can easily be machined from PVC or ABS. Both are good choices.
PVC is often used for machining grips with intricate designs. The use of a flexible PVC to bond to areas of the grips to enhance handling and/or to further decorate the part. Interesting opportunities to do excellent inlay work are possible because PVC and ABS do not significantly absorb water, twist, shrink or deform over time as long as they were a machinable grade material initially. Not all ABS and PVC materials are the same.
Look for machinable stress relieved grades.
Thank you sir. Would the ABS blocks you sell on your website be suitable for this purpose [ie; machineable stress relieved grade]?
 
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