Tag Archives: custom jaws

  • Customized Workholding Makes Perfect Parts Possible

    DSC_3583When our customers take delivery of one of our chucks, it is already outfitted with the proper clamping devices that hold workpieces firmly in place for machining. Sometimes, our standard products are good to go right off the shelf. But, more often than not, the workholding has been custom-machined to be a perfect match with a particular part. To maintain control of this process, ensure quality and reduce delivery times, this is done in our own machine shop at our company headquarters in Wheeling, Illinois. We call it the “Prototype” shop because each piece is a “run of one.” On any given day, the shop will turn out a variety of jaws, grippers, part stops, locating and positioning components.

    Designed for a Perfect Fit
    The process begins when a customer sends their workpiece to our Engineering Department for evaluation. The engineers determine the proper chuck for the part and then design the workholding components that will actually grip the workpiece. The manufacturing team will discus the plans with the engineers, select the proper operation sequence and machine tool(s) in the Prototype Shop and start cutting. Time for the process depends on the detail, complexity, tolerances and manufacturing difficulty.

    DSC_3580 copy 2The Right Equipment for the Job
    To meet the everyday challenge of turning out intricate and detailed workholding devices, our Prototype Shop is well equipped with a variety of high precision lathes and milling centers. We have one 5-axis machine and a number of 3-axis verticals, as well as turning centers with live tools for flexibility, along with the usual band saws, grinders, etc. We can handle a wide range of workholding from 24” diameter down to components that are only 1/16” in diameter.

    Since most of the parts machined in the shop are one offs, a premium is placed on cutting down set up times. One of the best time-savers in the shop is our own APS Automatic Positioning System, which can reduce the setup process by up to 90%. We use it for turning, milling, measuring and grinding operations.

     

    Our SinterGrip inserts also shave minutes off sintergripof set ups. They can bite into a piece of stock as little as an 1/8” in and lock it solid so we can work the whole piece without the risk of mismatching caused by manual indexing. “Teaming SinterGrip inserts with our 5-axis machine saves a ton of time,” said CNC Supervisor John Jurney.

    Personalized Attention to Each Component
    “Our machine shop is run by a highly educated and motivated team who have been given top-of-the-line machine tools and software to work with,” John said. “That is why SMW Autoblok is able to provide our customers with the ultimate in workholding customization for any application.”

    If you’re not satisfied with the results from your workholding, please contact us and we’ll put our Prototype professionals to work for you.

  • Jaw Design: The Proper Hold for Each Application

    Selecting the right jaw design for high quality turning is a little more scientific than it might appear. The wrong choices can reduce machining speeds, result in poor surface finishes or deform parts. Our engineers consult with you to find the jaw combination that works best for each unique application.

    Jaw Design 101

    CSI_4002The muscle in most turning workholding is provided by the chuck and the jaws. The chuck is the foundation that provides the power. The jaws bolt onto the chuck and are actuated to press against the workpiece. A serration can be machined into the jaw or bolted on as a separate component, which we’ll refer to in this article as a gripper. This “bite” creates additional friction if higher cutting forces are being used.

    The Gripping Formula

    The correct jaw design is always based on the application. The variables boil down to this calculation:

    (clamp force + friction ≥ cutting forces x 1.5 safety margin)

    In other words, will this jaw (or jaw and gripper combination) hold the part with enough pressure to clamp it firmly with a force greater than that exerted by the cutting tool? This must be done without deforming the workpiece and at rpms that will generate maximum productivity and profit. If the cutting tool is exerting more force than the jaw, it could grab the part and pull it out of the machine, so for extra precaution, a safety margin is added as a multiplier.

    Screen Shot 2017-08-24 at 10.48.56 AMFinding the Right Combination

    The combination of jaws and grippers are as endless as the number of innovative workpieces our customers machine. It all depends on the application. Using too much mechanical clamping force can deform a part. Grippers add friction so less force can be used, but if they are too aggressive (sharp), they will leave marks on the workpiece. Aggressive gripping is usually not a problem with raw materials in the rough stage of machining. The marks will be removed in the finishing process. So, clamp it tight and rev up the rpms (but remember the safety margin).

    Another Design Solution

    Another technique we use to apply the right force without deformation is to increase the number of jaws in the chuck. Moving from a 3-jaw chuck design to a 6-jaw model spreads the force over more contact points. By increasing the jaws, pressure can be reduced at each contact point, thereby reducing the risk of deformation.

    A Word About Grippers

    Grippers themselves vary greatly. While sometimes it is unavoidable to machine serrations right onto the jaw, most often, stock gripper pads are bolted on so they can be readily replaced when worn. When a customer shows us the work piece they want to clamp, we first look to see if a standard gripper will fit the bill. While there are 5-10 standard grippers we regularly recommend, each one can have over 40 different variations. Sometimes we can adapt an existing model for a particular application. If these options don’t work, custom-built is the only way to go.

    Easy Does It

    After the roughing stage, more finesse is required when using grippers. Most embed deeper as more force is applied. Controlled depth grippers never go any further than a pre-determined depth, no matter how much pressure is used. They are an excellent choice to clean up the workpiece during interim stages or when hard turning. Selecting a controlled depth gripper involves careful experimentation to find the perfect depth, but we can sometimes get the right combination of depth and force in an off-the-shelf model.

    CSI_3963The Finishing Touch

    Obviously, marking isn’t acceptable in the final finishing process. At this stage, a bored jaw option may be preferred to perfectly match the diameter of the workpiece. This smooth jaw has no “bite” at all and uses friction alone to keep the part from spinning.

    The Best Way to Get It Right

    The surest way to give our customers the best results on high precision machining jobs is to custom design a jaw that matches the specification of their particular application. We usually craft two to three custom workholding systems each week. That’s how critical the characteristics of the combination are.

    The fact is many of our customers depend on the knowledge and experience of our engineers to select or build the best combination for them so they get the finest finish on their workpieces at the highest speed – without resorting to guesswork.

    If you would like to discuss customized solutions for your workholding applications, please contact us.

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