Colt 1911 project update

[NewAgent45]

Setup

Top

Bottom

I’m a novice and new to CNC. I have only had my CNC Shark Black Diamond about a month now. I’m experimenting and learning something every day. One of my projects is carving a pistol in 3D. I actually started my project before I saw the James Bond PPK posted on the Vectric web site. I'm taking some similar approaches.

I’m importing an un-textured model into Cut3D creating and running the toolpaths, after setup

I’m running the following sequence of toolpaths.
1. Rough – Top
2. Rough-Bottom
3. Finishing – Bottom
4. Finishing – Top
5. Cut Tabs

For now I’m using two 8 X 10 inch pieces of ¾ MDF laminated together for my blanks so my thickness is 1 1/2. I checked the thickness after gluing and it is remarkably close to 1.50”.

My first picture shows my setup. I extended the 5/16 dowel pins so they would be visible in the photograph.
The second and third pictures are the top and bottom view of my first complete carve. There are definite quality issues with my final product. These issue are what I would like to discuss and hopefully get some good advice.

Issues:
1. The finish cuts did not quite cut all the way through and left a thin fin behind. It made removing the finished carve from the support frame very hard. I see I specified and overcut distance of 0.0 on the Cut3D material size page. Is this the correct parameter to correct this problem? I also see also see a cut plane position in model. This is currently unselected and don’t seem to be pertinent for my issue.

2. The finished carve had a small (~0.100”) offset between the top and bottom cut. This is to much error. I think that this problem is because I choose to reference the left-hand corner (top view) when the dowel holes are referencing the center. My blanks aren’t exactly true. I’m thinking of changing my reference point to the center to fix this issue. Can you comment on this? I'm also interested in use of offsets. Again! Right now I’m referencing the center of my blank for both the dowel pin holes and the slotted step drill mounting holes. So it seems like I should use the same reference point for the Cut3D tool paths. But this reference is sacrificed in the carve. Does it matter?

Have a great day and thanks for your input.

……….. Rod

[Mike-S]

Can't help with your questions, but I really like your hold-down method.

[NewAgent45]

Mounting hardware

Bits

Bits

Mike-S:
Thanks for your interest in my hold-down method. I stole this from my spoil-board. I try to avoid the use of clamps when possible. I build my spoil-board entirely on the CNC machine. So I decided to use the same features for mounting.

For the spoil-board I first run a drilling tool path using a step drill (5/8 x ¼) then a profile path with a ¼ end-mill to slot the ¼ holes. The slots allow you to easily slide your spoil-board or you’re carving blank in the T-slots. After this I mount the spoil-board to the CNC table and run the T-Slot profile followed by a surface planning profile.

I included a picture of the bits I use and my hardware.

The Nylon hardware was ordered online from Master-Carr and its much cheaper ordering in packages of 100 than the local hardware store. I couldn’t find a suitable step-drill so I purchased an attachment for a ¼” drill. I purchased the attachment and the slim square nuts online from Jamestown Distributors.

I’m still looking for advice on my 3D carve, But there don’t seem to be any takers here. So I’m back to experimentation.

Have a great day!

…………. Rod

[zeeway]

Hi Rod,

I am not sure I followed the entire discussion, but if I were cutting that project (neat model, by the way). I would rough and finish the first side, then flip it over, locating on the dowel pins...they are cut into your table right? It wasn't clear to me if you were truly locating on the dowel pins. The way you are doing it, when you rough, flip, rough backside etc...when you go to finish side one, you are pushing against a non-solid back, and that may be throwing you off. Or maybe I misunderstood...?

Flipping and locating on dowel pins that are cut into you table should locate the first and second sides within .010 inches of each other.

Angie

[NewAgent45]

Angie,

Thank you very much for your reply. I'm already processing in the order you suggest (rough-top, rough-bottom, finish-not & finish-top) and flipping twice on the dowel pins. I don't think the issue is with the mounting/locating system. The offset I'm seeing is a shift in x. When I created the tool paths I use lower left corner for my reference and I. Noticed a small shift of the edge of the blank from a mark I put on the table. I think I should have reset my x reference. I'm thinking I might be better off referencing the center which can easily be marked by diagonal line on both sides of my blank when I start.

I'm also interested in your comments on my cut through problem. I writing this on my phone would you mind reading about this issue in me original post?

Thanks again!
....Rod

[zeeway]

Hi Rod,

Your reference point can stay in the lower left - it is okay either way. Here is probably more detail than you want...if I were doing this model...

First for the design I would set the zero point in the center, and model the top with the dowel pin holes on the horizontal center line and of course, equidistant from the vertical centerline. Center the model in the material in the design. The design for the bottom would be horizontally flipped, with the same dowel pin locations as top. You can play with the models, flipping one and copying to the other to make sure they are aligned.

I would then reset both origins to lower left (just a personal preference) and for the top model I would zero z to the top, and on the second model zero z to the bottom (table top). Recalc. Set material, do rough and finish on first side, cut dowel holes. Remove material, zero to table top, cut dowel holes in table top. Set dowel pins. Flip material and locate on dowel pins. Rezero to table top and run second side rough and finish.

Any offset from top to bottom model should be at most the clearance in the dowel pins. If you have more than that, you have a machine or modeling issue.

You could also zero to the table top for the first model, and tell the design you have 1.5 inch material, with the model located at the top of the material. If your material was a little thicker than 1.5, this would eliminate any issue there.

Hope this is clear - this process usually works for me...unless I mess up.

Angie