PATTERNMAKING

[bigk]

Is anyone using shopbot cnc to produce patterns for metal castings etc?

[beacon14]

This is probably not what you are looking for but you did say "etc." so here goes...


8645

8646

This was for a client who makes vacuum-formed industrial packaging.

[bigk]

Thanks,
We are small pattern making business looking for a suitable cnc machine
What we really want to know is if the shopbot is suitable for making patterns & vac form models etc. Can the shopbot has can machine draft angles (taper)? Seems that the vac form model in the photo has. Was it done with a tapered cutter or by multiple passes.
Any input would be appreciated.

[beacon14]

The draft angles can be done in two ways - with a 3D model and 3D toolpathing, machined in a raster format with a ball nosed bit, which can provide extreme detail if needed but typically takes longer, or using tapered cutters like the pattern in the photos. This one used a 10 degree bit which took two passes to get the required depth, you can see a slight burn/watermark at the top of the lower pass, probably caused by the bit angle not being exactly 10 degrees or by the non-cutting top of the flute rubbing - I never had to figure it out since this was a one-off and the customer actually liked the extra detail - it added a slight extra ridge to his plastic parts which increases the strength and it matters not a hoot what the form looks like, just what shape the resulting parts have.
The answer to your question is that the ShopBot can produce just about anything as long as it doesn't have "undercuts"
BTW these forms are some of my most profitable work - they are expensive but since the client is making thousands of parts from each mold his cost is only pennies (OK, maybe dimes) per part. He is much more concerned about quick turn around times - which the 'Bot is also perfect for.

[bigk]

Patterns for castings have draft angles on all vertical faces to allow them to be molded and are without any undercuts. A 3D model and 3D toolpath seems the way to go as patterns may require different degrees of draft on various sections
What progams did you use for 3d modeling & tool pathing ?
I have no experience in this area & would need programs that are easy to learn

[beacon14]

I don't do a lot of 3D work so I'll let the 3D experts chime in on that one. I do know that once you have a model (either homemade or purchased) Vectric's Cut3D will produce a toolpath very easily.

As long a you can find a router bit or end mill with each draft angle required you can do it all with either PartWizard or VCarve Pro. I draw everything in 2D in DesignCad and import into VCarve Pro for toolpaths.

[btk]

Kevin,

I do a lot of pattern making.
I mainly use Rhino3D and VisualMill/RhinoCam.
Depending on the tyes of patterns you are making, using Tappered Bits on steep angles will be a lot more productive than using a 3D strategy with a ball-end mill as the step-over will have to be very small to get good quality.



Brian

[bigk]

Hi Brian,
Are you using a 3 axis shopbot cnc?
If so could you give some feed back on your results. Maybe a photo or two of what you have done, if possible
On the matter of taper, most patterns we produce require only between 1 & 3 degrees of taper.
If the profile of the pattern is complex then maybe using a ball-end mill with small step over would be the way to go. If the profile is simple with common taper,tappered bits would be the better option. Thanks to all for the input,
Regards Kev

[btk]

Kevin,

Yes, I am using 3axis
Amana sells a 3 degree pattern making bit.
I also have some 1.5 degree tapered end mills.
Normally a project will require detailed work to be done with the ball end miill and just the long flat sides will be done with a taper bit to give the draft required.

Brian