May 22, 2014 Photos

Current Build Progress

Sometime between May 31, 2014 and Jan, 2015...

May 31, 2014

Just a little video of the x and y axis moving

A picture of this current build

May 22, 2014

Another picture of the current build progress from a different angle...

 A snapshot from the motor end of the machine looking through the middle.

The linear rails and ballscrew can be seen from this picture

A picture of the motor and the reinforced  beam...

 A close up of the one of the linear rails...

An image of the ballscrew attached to the pillow block

The view in between the two extrusions...oo look, its a shaft coupler!

THE BUILD!!!

May 22, 2014

Currently we have built the base and aligned all the linear motion components for the x-axis (ballscrew, linear rails, ballscrew mounts, etc.)

1) The assembly began with the the two base beams and four legs. Each base beam had two legs mounted perpendicular at each end. Perpendicularity was maintained by an L bracket on the inside corner.

2) Next the second level of the frame was added in order to connect the two halves mentioned above. The extrusions were cut to specific dimensions so they would create a rectangle with 90 degree corners.

3) The the linear rails, ballscrew mounts, ballscrew, and the gantry beam were added. Alignment of the gantry beam was achieved by first mounting the beam at the free end of the ballscrew called the "ballscrew free end mounting beam". Then a the gantry beam, which was loosely attached to the linear rails by t nuts and hex screws, was pushed flush against the ballscrew free end mounting beam. Then the screws and nuts that attached the linear rails to the gantry beam were fastened.

 The ballscrew was one of the most difficult components to align. The ballscrew pillow block was mounted roughly in the center of the gantry beam first. The setup, minus the ball screw, in the picture above was assumed to be aligned correctly before the ballscrew alignment was attempted.

The ballscrew nut was moved to different points along the screw and the gantry beam was moved to match the ballscrew nut position. If there was any misalignment, the ballscrew nut would not fit smoothly into the pillow block. Minor adjustments to the position of the bearing blocks on each of the ballscrew would be made in order to adjust the orientation of the screwn. This process would be repeated until the pillow block could be slid over the ballscrew nut at the center, left, and right side of the screw without having the ballscrew nut rub against the walls of the pillow block.

Jan 17, 2015

It has been a while since I have updated the blog since school got busy back in June 2014 and also being away for four months in the fall right after spring term ended. Anyway, the machine has been full constructed and here is a picture of how it looks.

The only thing that needs to be completed is the wiring and also drilling more holes into the table to for mounting. 

3D CNC Designs

Our goal throughout designing this machine is to maximize cutting area to CNC size ratio in order to get the "best value" out of our machine. We obtained aluminium extrusions as a donation and decided use these for the framework. It would have been nice to use a wide aluminium plate (like this) for the legs of the gantry to provide better resistance against a moment around the y axis (y axis the direction is parallel to the rails mounted on the gantry in the pictures below). However, blowing hundreds of dollars on two aluminium plates (2ft x 2ft x 1/2 inch aluminium plate = approx $120) for the legs of the gantry did not seem practical since we have aluminium extrusions readily available. 

Slim Mils Gantry Design 0.1:

This was our original gantry design but the development for this design was discontinued after noticing some difficulties that would come during manufacturing and assembly of the ballscrew. It is visible in the picture below, but there is a bearing block that is inside a hole (in the aluminium extrusion) behind the motor mount plate on the right hand side. This would require a mill to make a square hole for the bearing block and also weaken the aluminium extrusion. Also, if future upgrades took place, the aluminium extrusion with a hole in it would be harder to reuse in other applications. 

However, this design does optimize the length of the linear rails and ballscrew and maximize y direction travel. Some concepts were taken from this design and used in the following designs.

Slim milS CNC 1.0:

This was version 1.0 of the our CNC machine. The gantry design has changed so that the crossbeams are removable which allows for heigh adjustment. Also, none of the aluminium extrusions have any slots milled into them, only small holes along the front face to mount the linear rails. Minimal alterations to the extrusions equals to a higher re-usability factor. The crossbeams also have big gusset plates joining it to the gantry legs. The previous gantry allowed for a 15 Series 4334 4-hole inside corner gusset while this newer version allowed for a 15 Series 4338 8-hole inside corner gusset. 

Although this design improved upon some of the old gantry design weaknesses there was still room for improvement. The major flaw found in this design can be seen in the bottom center pictures. The router(9.3lbs approx) is about 22cm from the center of the gantry leg which will create a large moment around the y-axis and cause a slight bending of the gantry leg. If this design was implemented and began to cut material, cutting forces in certain directions would add to this moment force and increase error to the machining operation.

Also the base show in the top center picture has a slight weak point, the beam which the motor is connected to. All the axial force in the x-axis direction is eventually channelled to this beam. The aluminium plates, having a relatively small thickness in comparison to the extrusions, would be the component that deforms the most.

After recognizing these weak points, a 2.0 design was set into motion. 

Slim milS CNC 2.0

The major changes from version 1.0 to 2.0 is that the gantry obtained another set of legs for more support at the base. Also there is a aluminium beam that runs across the top of the two aluminium extrusions in the base (middle right picture). 

Now the machining begins...