Tag Archives: milling

Robot Gripper Mounting Bracket

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This is a gripper mounting bracket for a robotic application I made a few years ago.  I have since made three others with the same basic configuration.  It was made from two 1/4 inch steel plates welded to a 2 inch x 1/16 inch thick square tube.  The round end bolts to the robot arm.  The square end has a symmetrical bolt pattern with bolt holes and pin locating holes for mounting the gripper mechanism.  The bracket was TIG welded using my Miller Dialarc welder (it’s old and huge but works great – And has a water cooled torch!).

Preparation

The bracket mounting plates were made from plain square flat stock.  After drilling the bolt and pin hole pattern in the robot mounting bracket, it was turned round in a lathe so that its outer diameter would be a close match to the diameter of the robot arm mounting flange.

The square tube was cut slightly over length and the ends were squared in a mill so that both end bracket surfaces would be very close to parallel after welding.

Robot Mounting Flange

IMG00353The round flange is on the end attached to the robot arm.  It was made it first so that I would have a jig locating surface and mounting holes to attach to so that the gripper mounting flange end could be accurately machined.  Notice the hole in the center of the round plate.  It’s there so that the bracket can be mounted in a lathe.  Why?  The flanges warp when they are welded to the tube and the mounting surface must be squared so that it will lay flat against the robot mounting surface.  For me, it was much easier to mount the bracket in the lathe and turn the surface true than to mount it in the mill and machine it flat.

Welding The Bracket

IMG00354Alignment marks for positioning the square tube were scribed on the robot mounting flange.  Note that the position of the square tube and even the position of the gripper mounting bracket did not have to be perfectly aligned.  Why?  The gripper mounting surface and mounting holes were yet to be machined.  The hole positions are relative to the locating pins in the machining jig as seen later in this post.  It doesn’t matter so much where the gripper flange is as long as it’s not too far off position.

IMG00355The tube was placed in between the bracket flanges and clamped with a long ratcheting squeeze clamp.  The corners of the tube were tacked first, starting on one side and moving to the opposite side for the next weld.  When welding a bracket such as this I try to stagger the welds in small even amounts so that the warping and stress in the part is spread out as evenly as possible.  After all four corners of the tube were tacked I finished by welding slightly farther past the corners of the tube.  The same basic procedure was used for both bracket flange ends.

Machining The Gripper Flange

IMG00356A jig plate was made from 1/2 inch aluminum bar stock.  Clamping bolt holes were drilled and tapped and pin locating holes were drilled to align the robot flange end of the bracket.  The jig plate was then bolted to the mill bed and aligned square to the x and y axes of the mill.

The mill has a DRO (digital read out – for those unfamiliar) which was used to locate and set a known zero point at the center of the jig mounting holes, which was also the center of the bolt pattern of the robot flange plate.  The bracket was then mounted on the jig and a light skim cut was milled on the gripper flange to eliminate the previously mentioned warping.  Next, the mounting holes and locating pin holes were machined in the gripper flange.

Inaugural Post: Drill Mill X-Axis Crank Handle Project

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How can I adapt the crank handle to the x-axis shaft?

I bought a used drill/mill but it was missing the original left side x-axis crank handle.  A handle from a different machine was included with the purchase but it needed to be modified to fit.  As you can see in the first pic, the facing end of the shaft has triangular slots.  Unfortunately the crank handle only had a set screw hole.  Also, the bore in the crank handle needed to be enlarged to fit the center shaft.  I don’t have a pic of it here, but I mounted the crank handle in my lathe and bored the hole to the correct diameter.

IMG_0129How do I hold the crank handle for machining?

The next interesting problem was figuring out how I could hold the handle to machine the slots.  I have an older Craftsman rotary index table that has a circular bore in the center of the top of the table.  I used a piece of aluminum with one end turned to the size of the hole in the index table and the other end turned to the size of the hole in the crank handle.  That way I could locate the centerline of the handle through the centerline of the index table, thus enabling me to easily index around the center of the crank handle hole and machine the slots at the correct angles.

IMG_0122Holding the handle down was a bit tricky, but fortunately there was a step on the back of the handle shaft.

IMG_0123Machining

I first used an indicator mounted on the mill spindle to locate the centerline of the crank handle.

If you look at the end of the z-axis shaft in the first pic, you should notice that the edge sides of the steps pass through the centerline of the shaft.

IMG_0125 One edge of the cutter was offset so that it passed through the centerline of the handle.  This was done three times, with the rotary table being indexed 120 degrees for each of the second two passes.

IMG_0126Now you should be able to see the outline of the three steps.   Next the extra material between the steps was removed and the handle was deburred.

IMG_0127Finishing Touche’

The slots were a bit too tight, so after a bit of hand work with a file…

IMG_0128Vwaa laaa.  Now I have a crank handle for each side of the mill.  The last step was to drill a hole in the end of the shaft for a 1/4-20 screw to hold the handle.