Any ideas how to scan and trim this part....

[Normsthename]

I have been given a job to make a small batch of vacuum formed parts. They already have the mould made by a another company so the forming part is dead easy.
I also have a original sample part
But I need to trim the formed part to the shape shown in the attachment. One part of it is a half circle, but the other half slopes down at an angle.
I want to trim the part on my CNC Router using a 1/2" Cove cutter for instance
I drawn the part in my 3D CAD system and I then transferred the plan view into my machining software and the CNC router will machine the shape with the 'Z' set at a constant level. I thought about tweaking the Z Movements of the part that slopes down, but it sounds very hit or miss.

Any ideas?

TIA

Andy

[Kiwi]

As you have drawn the part in CAD, why do you need to scan?
Is your router 3D?
Are hoping to machine the full edge with one setup?
With two setups and both face machined flat, would this be accepable?

[Normsthename]

Is your router 3D?

My Router is a homebuilt steel router with 3 axis X,Y & Z so that is only 2.5D?

As you have drawn the part in CAD, why do you need to scan?

I am struggling to work how to actually machine the edge, all the software I have would machine the whole object out,
The only other software I have is V-Carve that will machine the profile, but only in one plane, so any ideas much appreciated!

Are hoping to machine the full edge with one setup? With two setups and both face machined flat, would this be accepable?

I was going to just machine the part in one go, which was not ideal. Your suggestion of machining with two setups sounds good.
The company only want it machining on a CNC to make it uniform shape.

Thanks for your input.

Andy

[holbieone]

you will have to surface mill that slope with a ball end mill

if you need a hand programing let me know

[srmaietta]

I would make a jig that holds the part (half dome) at the required angle to allow the cutter to just move left-right and slice the piece off. You could even do this on a table saw if you make a jig. CNC seems like a bit much.
What type of accuracy do you need?
~Steve

[Kiwi]

If your router has 3 axis motors which can all be run at the same time, your machine is 3D.
What are the dimensions of your part?
If you are unable to do in your CNC I wonder if you could make a jig and machine with a handheld woodwork router.
Maybe tricky to make the jig but you could have a path perpendicular to the edge.

[vacpress]

hey!

a '3-axis' machine is '3d'. this isnt a very scientific terminology. does a machine with a rotary table become 4D or 3D+ ?

i have cut lots of vacuum formed parts using different methods. the best and most common is to use a drill press or mill with a.... 'horizontal mounted miniature circular saw blade' - if you want i can post a picture of this tool...

to me, it looks like they a)moulded the part with some extra 'flashing'
b) cut it on the first axis with a plain guide bar and above described tool.
c) set the angle of the drill press to that angle (it looks like a straight cut in the illustration - just at an angle)
d) cut it again at this new angle...

a band saw may work also, but i think the drill press and horizontal blade works great, at least if you account for it in the mold, and leave some extra space.

this could take about 30 seconds per part, total... correct me if i am wrong, i am moderately intoxicated having just arrived home from various bars and nightclubs.


-Robert

[Kiwi]

Your right, 3D isn't the correct term.
I was trying to establish if Andy's router was motorized 3 axis (XYZ) or 2 axis (XY) with manual Z axis.

[Normsthename]

I would make a jig that holds the part (half dome) at the required angle to allow the cutter to just move left-right and slice the piece off. You could even do this on a table saw if you make a jig. CNC seems like a bit much. What type of accuracy do you need?

I think the company only want the part to look uniform when finished, it is very visible and the edge need to be good.
The company who did the last batch used a CNC machine to trim the part.

What are the dimensions of your part?

The part is approx 180mm (7") diameter and about 200mm (8") long
One thing I did'nt mention was that the part is made from 2mm ABS plastic.

i have cut lots of vacuum formed parts using different methods. the best and most common is to use a drill press or mill with a.... 'horizontal mounted miniature circular saw blade' - if you want i can post a picture of this tool...

That miniature circular saw blade sounds like a good idea, I could program the CNC router to cut into the side of the forming, and then work its way around on one plane. Then another setup to cut the other plane?....
If you have a picture of a 'miniature circular saw blade' it would put me onto the right track
Thanks for all the valuable input.

Thanks

Andy

[vacpress]

Sure.

The tool is called a 'slitting saw'. it is very simple and if you have an appropriate blade, you can make an arbor(holder) for it on a simple manual lathe with some steel, a bolt, and a washer...

i found a pic via google to save myself some trouble... if you cannot find the tool, again, let me know, and i will dig it out and do my best to determine the manufacturer..


mine has many small teeth, and is about 3" diameter. the arbor is probably 1/2 inch steel rod. it has been usefull for many random operations on the mill...

i never used the tool on a cnc machine, but i have an idea how you can do it easily...

1) make the mold with enough clearance for the blade in both cutting operations. form your parts so that they have a signifigant flat space to mount to a jig.

2) create a jig at the required angle, and cut the parts so that they are still held down by the material that is to be cut on a perpindicular plane.

3) remove jib, load part, make perpindicular cut...


again though, i could see lining these suckers up and using the machines manual control.. how many do you have to make? really the advantage of using a drill press is that the table can be set at an angle.. this has proven itself to me in the past, when i have spent lots of time making special holders for parts, then had a more experienced fabricator show me the slitting saw blade trick. i felt like a fool who cannot see past my possession of more complex equipment! one good reason to do this on a CNC mill is to learn some other ways of using the mill besides routing and engraving..

<img src="http://www.taigtools.com/Images/1110LA.JPG">
<img src="http://plsntcov.8m.com/Mona/Burner_005.JPG">

to finish your edge, a not so coarse sandpaper double-taped to the workbench works well.. then follow that with a finer grit if needed for part specs. when doing small runs of any molded object, i get very crafty to have good results without making jigs and fixtures.

[Normsthename]

The tool is called a 'slitting saw'. it is very simple and if you have an appropriate blade, you can make an arbor(holder) for it on a simple manual lathe with some steel, a bolt, and a washer... i found a pic via google to save myself some trouble... if you cannot find the tool, again, let me know, and i will dig it out and do my best to determine the manufacturer.. mine has many small teeth, and is about 3" diameter. the arbor is probably 1/2 inch steel rod. it has been usefull for many random operations on the mill... i never used the tool on a cnc machine, but i have an idea how you can do it easily... 1) make the mold with enough clearance for the blade in both cutting operations. form your parts so that they have a signifigant flat space to mount to a jig. 2) create a jig at the required angle, and cut the parts so that they are still held down by the material that is to be cut on a perpindicular plane. 3) remove jib, load part, make perpindicular cut... again though, i could see lining these suckers up and using the machines manual control.. how many do you have to make? really the advantage of using a drill press is that the table can be set at an angle.. this has proven itself to me in the past, when i have spent lots of time making special holders for parts, then had a more experienced fabricator show me the slitting saw blade trick. i felt like a fool who cannot see past my possession of more complex equipment! one good reason to do this on a CNC mill is to learn some other ways of using the mill besides routing and engraving.. <img src="http://www.taigtools.com/Images/1110LA.JPG"> <img src="http://plsntcov.8m.com/Mona/Burner_005.JPG"> to finish your edge, a not so coarse sandpaper double-taped to the workbench works well.. then follow that with a finer grit if needed for part specs. when doing small runs of any molded object, i get very crafty to have good results without making jigs and fixtures.

Thanks Vacpress
Very hepful instructions, I will go down to the store tomorrow and see what circular blade I can get. Then I will have a better idea what I am doing

Thanks

Andy

[vacpress]

you should probably try mcmaster.com or use-enco.com

i think mine came from enco. i have several.. i use them for lots of 'odd jobs' on the mill... for awhile i was even using them to cut sheet material as i didnt have a bandsaw...

-robert