Choosing Rotational Molders



rotational molders

When looking at rotational molders in deciding what company you want to mold the plastic parts for your project, it comes down to many criteria. We will look at these criteria and examine them to help you get the most desirable outcome.

1. Source rotational molders by geographic location

First off, you have to know the size of the mold/spider so the molder will know if his molding machines will be big enough to mold your parts individually on an arm or if the mold/spider is small enough that it could be put on a grate mount and run with other non-related molds or if they can’t run the mold at all. This is important to know because if the part is run by itself on one arm, the costing of running the machine’s arm is fully put on that part. If you have a part that has a resin that has a very tight processing window, this will have to be done anyway so the full properties of the resin can be realized and the full attention of the operator is on your mold. If your part isn’t as critical, you can take advantage of the split cost of the machine time among several other molds of having it run on a grate. Rotation molding can be flexible in these situations and the cost advantages should be taken advantage of if possible.

2. Identify rotational molders by the size of their equipment

Geographic location is something that needs to be looked at since generally, rotationally molded parts are large. You want rotational molders near you if you are shipping the parts from your facility. You don’t want to pay for shipping parts twice, from the molder to you and then to the end customer, if you can avoid it. If, however, you are having the molder package the part and they are drop shipping from the rotational molders facility, that issue is no longer the case. You could be located in California, but have a selection of rotational molders in the Midwest make more sense if the majority of your customers are east of the Mississippi or evenly spread throughout the US for that matter. Not all rotational molders offer the same services. You also need to know if your molder will do assembly if your molded part is part of a larger assembly. If it is, then the molder can do the assembly, package the part and then drop ship that assembly to your end customer. You will pay for that time, but it can make sense to have it all done in one spot.

3. Qualify rotational molders by quality and ability to hold tolerances

The next area to look at is quality. Is the surface finish what you want? Does the parting line have flash? Can they repair blemishes? Do they visually inspect the parts before shipping or boxing? Along with quality you may also lump in ability to hold tolerances. Rotational molders should have an inspection department that can okay the shipment of parts. Some of these inspection departments will have Faro arms to inspect the parts to make sure features, overall dimensions and the dimensions specific things like threaded inserts are in the correct location. You will need to know they can match up with whatever they need to matchup with. Not all rotational molders are able to generate an inspection report and if that is vital to the part you are having molded, you need to know that up front.

4.Comparing proposals from rotational molders, don’t always go for lowest cost

After you have the answers to many or all of these areas, you have to get quotations. It is recommended that you get more than one quote. Normally, you will find the quotes are in a narrow range of price. If they aren’t, it’s either because someone missed something or someone is just charging too much. Going with the lowest price is often not the way to go. Part quality can vary from rotational molder to rotational molder. You have to make sure you are getting everything you need. Quality can vary greatly from molder to molder. You own the mold, so you can take it to where you need to have it run, but you have to do your due diligence. Please take a look at the list of rotational molders I have listed on my website. These are some of the molders I have worked with and can recommend as very good molders. If you know of a molder and he isn’t on this list, it doesn’t me they aren’t a good molder. It just might be a company I haven’t worked with.