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Thursday, 8 February 2018

How to cut Clock Frames on a smaller CNC table.- Part 2

In the previous post I looked at 4 ways to in which you could cut profiles that were longer than the working area of your CNC machines table.
This time I shall look at a single method that can be used to simplify the operation using the Cut2D software from Vetric

To start this we need fill out the Job Setup Dialogue in the top left hand corner of the screen, the blank size and thickness to be used , along with the Z datum and the XY Datum which importantly should be set in the bottom left corner of the blank, the red dot marking the spot.

Next we load the DXF file and centre it in the blank using the F9 key after highlighting all of the parts. Now draw on a horizontal line across the centre of the blank and draw on two holes near the ends of the that line as shown, and a further two holes on the bottom edge of the blank vertically aligned with the first two holes. The first two holes are the index holes in the blank and the bottom two are the location pin holes to be drilled in the spoil board on the table.

Having completed that we can generate the first tool path to drill the holes in the Spoil board, I have used a Ø3mm cutter for this, same as is used for all the other cuts. These two holes will be used later to fit location pins into when the blank has to be moved. Save this tool path and generate its gcode so that you can drill the holes in the Spoil Board later.

Now we can  generate the next tool path to cut the two holes on the centre line using the same cutter.

The tool path for all the holes is generated next, followed by the tool path for the outside profile cuts.

So far the tool path generation has followed the normal path, and at this stage you would be ready to generate the gcode for the rest of the cutter paths. We do however need an extra couple of steps now to generate two separate paths with a vertical displacement of the blank in between.
We do this using the Tool path Tiling Manager as indicated below, this brings up the dialogue box shown on the left. We need to select 'Feed through in Y' under Tile tool paths and the Tile Height to half the blank length. The first tile is shown as the bottom half of the blank and is marked T1, clicking on the Active Tile box  changes it between Tile1 and Tile 2.
You need to keep this Dialogue box open through the next steps.

With both 2D and 3D windows open on screen un-tick the 'Draw tool paths in original position'  and set to Tile 1. Now Tick the bottom 3 tool path box's so that they will be included in the generated gcode and save the tool paths.

The next step is to generate the code for the second tile, click on the Active tile box to change it to 'Tile 2' and also un-tick the 'Drill holes on the centre line ' box in the toolpaths window, as we don't want to cut into the location pin that will be fitted in that position, now save the tool paths.

The final step is to actually cut out the Backframe on the CNC machine, so step 1 is to cut out your blank and place it on the spoil board with the bottom edge of the board near the bottom of the table, mark the bottom left-hand corner of the board onto the table and then set up the Datum XY on the machine itself by moving the cutter to that location and zeroing it. Move the blank out of the way and Zero the Z height to the table top and load the gcode for drilling the two holes into the table, now cut the two holes.
With that preparation complete return the blank to the top of the spoil board and fix in position with the bottom left hand corner on the Datum XY mark and fix in position, zero the Z height to the top of the Blank if necessary .
Now load the tool paths for Tile 1 and cut the holes and profiles.
With that complete release the blank, fit two dowels into the two holes drilled into the spoil board and locate the blank over them and fix the blank down in its new position, load the tool path for tile 2 and complete all the cuts.
Thats it your done and hopefully have a perfect Backframe completed.

Thursday, 1 February 2018

How to cut Clock Frames on a smaller CNC table.

For several years I worked with a CNC machine that had a small 400mm x 250mm working area, not anymore, now I have a Stepcraft 600 with 600mm x 400mm working area and life is so much easier.
It did, however, make me realise that during all the times I struggled to cut those clock frames I had found a number of different ways to get around the problem so this article will describe 4 of those ways.
None of these is really simple and all require that you are able to use CAD software to manipulate the files, the first two can be done on 2D CAD using the DXF files whilst the last two require the use of 3D CAD to work with the STP or IGS files.

Method 1 - Vertical displacement of the Blank.

The first step is to download the DXF files and load it into your CAD software.

Once loaded you will need to draw a large rectangle around the Clock Frame and centre the frame within it, this represents the size of the actual wood blank you will be cutting the Frame from. Next draw in the two holes on the horizontal centre line of the blank shown above ringed in purple. 
Now draw two rectangles to form two virtual blanks, these join over the centre line of the actual blank. Now draw in the second pair of holes at the bottom shown here as half holes as the fall on the edge of the blank and will be drilled into the Baseboard only. 
The second pair of holes needs to be vertically aligned with the pair in the middle of the Blank, the size of the holes is up to you to suit whatever location pins you have to hand, and spaced widely apart. 

When the Virtual blanks and the holes have been added then you can save the virtual Blanks as two separate DXF files, as shown above, these are then ready to be loaded into your Cam software to generate the gcode. The blanks should be the same size as each other so that when you bring them into the CAM software you can make XY Datum position at the bottom left-hand corner of the blank.

The next step is to create a drilling operation to place the 2 bottom holes into your baseboard, then create another drilling operation for drilling the top holes in the top of the virtual Blank of the bottom section (green above). 
This preparatory work completed you can carry on and prepare all the cutting steps for both the virtual blanks.
The next step requires you to load the actual blank onto the CNC machine and place the bottom left-hand edge on the XY Datum, then clamp the blank in place and proceed with the cutting. 
When the cutting of the bottom section is complete you can fit two location dowels in the holes you previously drilled in the baseboard and then locate the holes drilled into to centre of the blank over the dowels, clamp down and complete the cutting operations on the top of the frame.

Method 2 - Radial displacement of the Blank.

The procedure for this method is pretty much the same as the Offset method but instead of moving the blank vertically between cuts we swivel the whole thing around 180 °.

This time load the DXF files into your CAD software and create the large outer rectangle that represents the actual blank and then the 3 location pin holes on the centre line. The centre hole is on the vertical centre of the blank and the two outer holes equally spaced each side. When completed the virtual blanks can again be saved as separate DXF files to be used in the CAM software.

The same procedure as before drill the 3 holes into the baseboard, making the Datum XY on the bottom left-hand corner of where the blank will fit, then load the blank with the bottom left-hand corner of the blank on the Datum XY, clamp in place and complete the drilling and cutting operations for the bottom section.
Now remove the blank from the baseboard, fit the 3 location pins and refit the blank rotated 180° and complete the cutting.

Method 3 - Make frame in multiple sections.

These next two methods require the manipulation of the 3D CAD files to cut the IGS or STP files into segments and then generating the DXF files from those new parts.
The files are loaded into your 3D software and then cut into 3 parts using a Z shape spline or surface to generate a Half Lap joint on the ends of the parts.

After the 3D model has been cut into the sections these sections are used to Generate new DXF files that can be used in the CAM software to generate the gcode for cutting the parts.

Method 4 - Simple split with Biscuit.

In the 3D  model cut out a pocket in the back of the frame between two holes and then cut the frame into two halves, see below.

After the 3D model has been cut into the sections these sections are used to Generate new DXF files that can be used in the CAM software to generate the gcode for cutting the parts.
With this method, it is also possible to make the changes in the 2D files by drawing the pocket and the split lines onto the 2D drawings files and creating two new DXF files that are used to generate the gcode.

Sources of 2D and 3D software

If you need 2D/3D CAD software you can try these sources

Autodesk Fusion 360  2D/3D CAD  free versions available.

Free CAD CAM software  for free software

Vetric Cut2D   Excellent for  CAM $149 / £110