The primary purpose of these visits, however, was to evaluate the wear on the mixer and to recommend small, inexpensive repairs that could be made to maintain mix quality and extend mixer life.

Unfortunately, there are not enough people climbing into your mixer on a regular basis to evaluate wear, so that responsibility, in most cases, falls onto you. I’m a big believer this needs to become a routine activity on the dairy. I suggest a physical inspection should be completed every 500 loads or two months, whichever comes first. It will only take about 10 minutes to complete, and it should be documented.

The best tool for documenting the mixer wear is the camera on your smartphone. It is very easy to evaluate wear when you can compare today’s pictures to pictures taken on previous inspections. In a perfect world, you would start taking the pictures when the mixer was brand-new, but today is also a good starting point.

I will focus on vertical mixers, but some of the same principles apply to horizontal auger machines and reel-style mixers.

First, you should try to do the inspection with a clean machine; it is hard to see potential problems when they are covered with mud or old feed.

Start with a quick walk around looking at the tires, undercarriage, hitch and PTO shaft. Make sure all the safety shields are in place. Inspect the scalehead and wiring, making sure there are no cracks in the scale head and it is still water-tight. Check wiring connections so they are watertight and there are no spots where the insulation is worn through.

Inspect the hydraulic hoses for cracks, cut or leaks. Look for oil leaks and check grease lines. I had a customer who religiously greased the walking beam on his mixer only to find the grease line was broken and none of the grease was getting to the bushing.

If you have a chain, check tension, chain wear, sprocket wear – and don’t overlook the sheet metal. Once the sheet metal wears through, you will be depositing little shards of sharp steel into the feed. Check for wear on the mixing vessel, particularly around doors and the bottom couple of inches of the sidewalls. Make sure to take lots of pictures.

It’s time to inspect the inside of the mixer but, first, you need to ensure your personal safety. First, open all the doors of the mixer and lock them so they can’t come down on you. Shut the tractor off, remove the keys, and put the keys in your pocket. When you enter the mixer, be very cautious because as mixers wear, the steel can get very sharp; a pair of leather gloves may be beneficial.

First, inspect the auger and knives for wear. Each manufacturer will have a different recommendation for clearances between the auger and sidewall, but normally if the gap between the leading edge of the auger wing and sidewall is more than the thickness of your index finger, some attention is needed.

Some mixer brands have a “kicker” mounted on the auger wing. This is an extremely heavy-wear item and is essential to ensure mix quality on those brands. Check the thickness of the augers; most augers start out between 1/2 and 1 inch thick. If the augers get too thin, the flighting will begin to bend down and negatively impact mix quality and increase horsepower demand. Inspect the knives; mixer knives are self-sharpening and don’t need any maintenance but, once they wear, they need replaced to ensure mix quality, feed quality, fuel usage and overall mixer wear. As your knives wear and you need to add mix time to get the desired mix, you are simply shortening the life of the mixer.

Now let’s inspect the mixing vessel from the inside. Look for any spots where welds are worn off or the wall has worn through. Pay particular attention around the doors, the bottom couple of inches of the floor, the inserts and where feed changes direction at the end of the sidewalls. If your mixer has a liner, thoroughly inspect the liner for loose welds or holes. A liner can extend the life of your mixer, but if you wear a hole in the liner and don’t quickly fix it, feed and silage juices will collect behind the liner and cause more rapid corrosion of the mixer wall.

With the inspection of the augers, knives and mixing vessel walls complete (and you have documented everything with your camera), you want to document the auger timing. I like to turn the front auger so the leading edge is in the middle of the front door and then check the other augers to make sure they are in the correct position. The auger timing will vary by brand and door location, so you need to make sure you are using the correct timing for your machine.

Your dealer should be able to provide you a drawing of the correct timing for your unit. You may ask why auger timing is so important: Having the correct timing impacts you in three ways. First, it helps with horizontal movement of feed during mixing. Second, it helps move feed to the doors to unload faster. Third, a mixer whose augers are out of time requires more horsepower.

Now that the physical inspection is complete, and you have documented it with pictures, replace the keys, start the tractor and close the doors (checking to make sure they are working properly). Start the mixer and listen for anything unusual, then run the chain (if equipped) and check its operation.

You should compare today’s pictures to previous inspection pictures and generate a punch list of anything you find, and then repair it as quickly as possible. Making small inexpensive repairs now because you identified problem areas early will help minimize ownership cost, maintain mix consistency and keep downtime to a minimum.  

Ed Jackman has spent 38 years advising dairy farms in the U.S. and Canada. Email Ed Jackman.