Injection Molding Q&A With Bob Hatch

By Bob Hatch

Related links: EDM | Polycarbonate (PC) | Polyethylene (PE) | Polypropylene (PP) | Polystyrene (PS) | Polyetheretherketone (PEEK) | Polysulfone (PSU)

You won’t find a molded part on these pages this month; instead, we invite you to imbibe the words of wisdom from IMM’s 12-year Troubleshooter.

Those who have saved their copies of IMM over the years may wish to pull out Bob Hatch’s very first Troubleshooter article, which appeared in the March 1996 issue. Although times and technology have changed, many of the problems Hatch sees today are the same ones molders and moldmakers struggled with back when he started writing this column. We thought that arriving at his 100th Troubleshooter column merited a pause from the usual problem-part analysis, to allow some reflection on how far basic technical skills in the industry have come and where they need to go now.

IMM: Have you seen progress in terms of tool designer skills over the past 10 or 15 years?

Bob Hatch: Yes and no. I’ve seen progress in using and understanding software and newer equipment, but we’re losing ground in the old-timer skills due to retirement and health problems.

IMM: What area is most in need of improvement?

BH: Toolmakers still don’t understand the processing side. They are better at communicating with engineers but not much better than 10 years ago at communicating with customers and molding department people. The toolmakers seem to have improved little in the areas of sprues, runners, gates, and vents—maybe a few have but not enough to make much of a dent.

IMM: What’s a common mistake that seems as bad now as ever?

BH: Lack of material shrinkage numbers! A shrinkage number of 0.005/0.007 in/in for shrinkage does not mean to use a 0.006-inch shrinkage number for both the flow direction and the cross flow or transverse direction; it means the shrink is 0.005 inch in the flow direction and 0.007 inch in the cross-flow direction. However, one thing that has improved a lot is that toolmakers are buying hot runner mold hot halves from recognized hot runner manufacturers instead of trying to build their own hot halves.

IMM: What are the most common tooling design errors you’ve encountered over the last decade or so?

BH: First, moldmakers still allow quick disconnects to be installed and waterline jumpers to be used on the molds they build, both of which are easily responsible for 50% of part rejects and many of our slow cycle times.

Second, cold runner systems are not being sized correctly for the material being run. Toolmakers still like to use small-diameter sprue bushings, runners that are all the same size or incorrectly sized, and gates that are too small for the material being run. Runners are not vented correctly (or not at all) and the number of part vents is far too few for the parting line length.

Finally, toolmakers like to make many of their own components, such as unscrewing mechanisms for threaded parts, instead of buying components right out of the mold component suppliers’ off-the-shelf catalogs.

IMM: What’s the biggest technology change in moldmaking you’ve seen?

BH: EDMs, especially wire EDMs, make the toolmakers really smile. Between these and toolpath software that almost does the thinking for them, it’s hard to figure out which they like best. Nearly every toolmaker I discuss toolroom improvements with mentions both of these with the same hushed tones. Maybe a third great improvement for the toolroom would be better moldfilling software that gets easier to use with every upgrade.

IMM: Are there specific materials that molders seem to have more problems with than others?

BH: Many molders are good with commodity resins such as polyethylene, polypropylene, and polystyrene, but when it comes to PEEK, polysulfone, and even polycarbonate, they get gun-shy and forget about the basics of molding conditions. These materials must be vented a lot more than other materials. Use big runners and gates for stiffer-flow materials and check the material manufacturers’ recommendations for barrel and mold temperatures. Lastly, use a well-maintained material dryer for those materials that need drying.

IMM: Has there been any progress in concurrent engineering? Are part designers more often working with tool designers at the front end?

BH: I see part designers and tool designers working more closely now than ever before. What I don’t see is tooling engineers working with the toolmakers or molders to improve their procedures and avoid constantly reinventing the wheel. Who is teaching the tooling engineers what size the sprue bushing, runners, gates, and vents should be on a new mold? Many of these engineers get embarrassed about not knowing what to do, but the fact is that many of the old-timers in the department don’t know, either. Sure, they could contract with someone to come in on a few projects to find out the correct sizing criteria, but custom molders often don’t have the resources for this and captive molders don’t want to admit they need help. So the answer from where I sit is, we haven’t made a lot of progress in these areas—maybe in another 10 or 15 years.

IMM: Are moldmaking suppliers—machine makers, steel companies, components—being more helpful to tool designers and moldmakers than in past years?

BH: Not that I’ve noticed. They sell the equipment or components to the toolrooms and molding shops and with few exceptions, the suppliers go back to their offices and wait for the next call. Naturally, I can’t see all that is going on in this area but if training is occurring, I am not aware of it. Training in all facets of the injection molding industry is critical to our future.

IMM: That’s a good point—an acknowledged problem in the industry is the lack of a systematic approach to transferring knowledge—basic troubleshooting know-how—to the next generation. How do you think this can be addressed right now?

BH: For the 40-plus years I have been involved in injection molding, this area of knowledge transfer has been accomplished mainly through on-the-job training and it just isn’t enough to bring our molding people and toolmakers along with the speed they need to keep up with new mold designs and molding equipment.

I remember when the big news around the industry was reciprocating screws replacing plungers in our molding machines. Then it was vented barrels, then process controls, then hot runner systems, then . . . well, you get the idea.

Years ago we were like the village blacksmith: We would build whatever we needed to make our molds and machines run better. Now, we have molding machines and toolroom equipment built by some pretty smart people and we need a lot of training just to keep up. We have to send every one of our employees out for training every month or two, not just once in the lifetime of their career and then only for a one-, two-, or three-day seminar. Continuous training for our employees is the only way we can keep up with other toolmakers and molding shops.

IMM: Would you advise a young person today to go into the moldmaking business, or plastics in general?

BH: I don’t see why not. A toolroom apprenticeship will give them higher hourly pay sooner than working as a molding technician, but over a 10- to 15-year period, the training for each should balance out the pay. If I had my choice, I would spend seven or eight years in the toolroom, become a journeyman toolmaker, and then switch to managing a molding shop. Many of the best people I deal with are those who have followed such a path. All they would have left to learn is the business side of the entire molding operation. Education is priceless and it does pay off in job satisfaction as well as in the old billfold.

IMM: How has your job changed over the years?

BH: After 20 years working in a custom molding shop, learning many facets of the business we are dedicated to, learning to speak the language of the toolroom and dealing with difficult customers, I took the position of technical director for a major material distributor. The next 20 years with the distributor gave me access to an amazing group of technical people who were hidden away, often just waiting for early retirement or something else that might come along.

Good guys long on knowledge and short on time were a tremendous asset for me to tap into. Some were from here in the States, some from Europe, some from Asia, and so on. I think I learned more in the first 10 years of being able to access these guys than I did in my 20 years in the molding shop. This probably isn’t all that unusual, but the learning curve was pretty steep for a few years.

The question now is probably whether or not I could go back to the small operation after seeing the big world of plastics. I probably could, but I enjoy my new life; being a teacher seems to suit me just fine these days. I get to meet a lot of nice people, see the latest and greatest molding operations, and even get involved in helping material manufacturing operations do their thing. Every day is something new and I am having fun. This has been a great career for me.

April 2008 - Reprinted with permission from Injection Molding Magazine. Copyright © Canon Communications LLC.