How to tell: Shoot a purge shot – look at plastic stream as it comes out.
Mechanical blockage in the Nozzle (chunk of metal perhaps) How to tell: Mechanical screw position indicator does not show screw moving to forward position (cushion position).Ī.
Other way – install a nozzle tip that has been welded shut – pick up a shot and inject. How to tell: Easiest way – screw rotates during injection. #2 - Plastic slipping around or through the check ring. Damaged check ring – Not very likely damaged in a way that prevents flow of plastic…but it could feasibly be stuck closed.Check ring or 3 piece valve assembly blocking plastic flow during screw recovery.Back pressure too low, or non-existent because of a faulty back pressure valve.Screw floating or skipping backwards during plasticization cycle.
Material slipping around or through the check ring.Not enough material in front of the check ring.I will not be addressing any process issues that can cause these defects and focus only on what machine conditions can be attributed to them.īasically caused by 1 of 3 machine related things: This will not be all encompassing, but hopefully there will be some things that I have seen over the years that may be helpful in troubleshooting the root cause for some of these defects. I have recently been tasked to list our a few machine related issues that can be attributed to some common injection molded part defects. What we must remember is we are all should have common goals to make our organizations profitable and make quality product for our customers. This phenomenon can be the cause of much finger pointing between your Maintenance team and your Processing team. Anyone who has participated in a root cause analysis exercise could attest that there are few defects that do not have duplicate occurrences on method and machine legs of a fishbone diagram. The thing with injection molding that can be conflicting is the numerous possible causes for many of the common part defects you may see. Short Shots and Contamination (burning, black specs, discoloration) If interested, please pm me.Machine related issues that can cause two molding defects that are predominantly thought of as processing issues. I also have various other textbooks for Engineering drawing, AutoCAD 2010, AutoCAD vba, etc. The Dynisco Injection Molders handbook: $20 The small booklet (15 pgs) is in decent condition as well and covers some general info about spinning, $30 for the pairĩ. Metal Spinning (Regan and Smith) & Metal Spinning (Boice Crane Booklet): The brown hardcover book is an original copy in very good condition. The Home Shop Machinists - Projects Seven: excellent condition, $15Ĩ. This is a really great old book old book on sand casting. Foundry Work: very good condition, some wear on corners of cover, but all pages are excellent. The complete handbook of Centrifugal Casting: excellent condition, soft cover $12Ħ. Lathe operation and Maintenance: near nwe condition, soft cover $20ĥ. Basic Machining Reference Handbook: new condition, hard cover $15Ĥ. Machine Tool Technology Basics: new condition, hardcover text book $20ģ. Audel Machine Shop Basics: new condition, $12Ģ. If your interested in something, just pm me with your address, and I'll determine the best shipping method and provide a cost.ġ. If you want to buy more than one book, I may ship using a different method, depending on weight. I would probably ship these USPS book rate, which is typically reasonable. Here's a list of books I'm clearing off of my book shelf.