Tuesday, 19 May 2015

Whooper Update - Getting thingings on track

Reason I went in the direction I did;

The machine is a Roland MDX40A with the rotary axis making it a 4axis mill.

Ultimately I went with CNC over 3D printing. While 3D printing has come along way its still in its infancy. What 3D printing can do is no briner output, great when you want to quickly iterate something but its held back by poor surface face quality and post production clean up which when you want something with fine detail is a no no. Then the other stumbling block is the cost the best of the best you are looking at astronomical prices (I was hitting £1000mark). 3D print pricing is universally squared on size, a few extra centimetres would add hundreds to the price. 3D printing is very much like the dot matrix printers in the 80's its a long way from finished product at an affordable price maybe in 10 or 20years.

CNC on the other hand is a mature industry that due 3D printing taking a chunk of its market, costs for machines have come down. Where CNC excels is finish, fit and variable costs. Details can be 0.25mm, surfaces can be smooth as you can model them, price is loaded onto fixed cost material is relatively cheap, fit is exact (parts don't warp like big 3Dp parts). Then why isn't everyone CNC'ing their models? well this is the rub CNC requires machine access over hangs and internal spaces are a physical impossibility. This requires the user to break the model down into a way which can be machined and that's why an upload and output service couldn't happen.

Setting up and design;

So as with anything new and this complicated it took a while to get going. First I had to install the machine which meant a new bench set up for the workshop but it also meant I had to tidy the workshop as over the winter with no car in grew into huge dusty mess. Finding a place for everything when you have none spare space is tricky (basically play musical chairs for 2weeks).

With that sorted I could focus on getting the machine running CNC software is not plug'n'play. All I had to go on was a 4hr demo about 8weeks before the MDX40A was delivered. There lots of variables to consider and tbh I was feeling around in the dark for a while till I started to understand what processes did what. The good thing about the software is once you get the basics understood its easy to build on your understanding. It also has a helpful simulation render of the final output which helps you spot any oversights.

As you can see I picked the MWO lighting fighter to make it provided a number of challenges The part is very small this section is only 35x5x3.5mm it has small details, thin sharp edges, long compare to its thickness and has a joint so I can check too see how seamless the fit is. Its small size meant if I messed up I didn't waste a huge amount of time or material.


I purchased some model board from a site it said 'for fine detail' because it was quick to buy. But tbh its porous meaning the surface wouldn't be that smooth (something I could fix with by giving a post production gloss)

It took 6 attempts to get to a finished model, first attempts the plunge depth on the tool was too much, the original supports were too weak and I also thought I'd save time making the body and the thrusters together but that just meant the section was too long and was prone to snap. I also was delayed waiting for fine end mills (bits) to arrive and when they did found 1/8 mill ends didn't fit in a 3mm collet so I need to order and wait for a 1/8inch collet. Once those were sorted we were cooking.

As you can see I'm quite youthful looking for a 33yearold

0.5mm ballnose mill working into the under wing crevice

And the finished output

I also made a fan too blow the chips down and away. I bought an offcut of nylon on ebay doesn't machine too well but it'll never shatter.

And we're @ the present where I have to make a choice on model board (the stuff that gets milled). to help I made a test model that would represent what I would be making

Left to right high grade to low grade. 

 After I gave them a black base coat (so those pretty colours don't created illusions) to see which has the best surface finish. The blue and the red were pretty much identical but the red did better in the snap test so I think for the sake of a few pence more probably worth it encase of a mishap like dropping a part.

Only downer is you have to buy a big sheets of the stuff 800x400 which is like buying 2 years supply upfront. Once this is order and delivered and some mill ends for the USA arrive I'll be able to start work outputting parts of the HBK.

So that's us all up-to-date. The good news is unlike with 3D printing where there are big gaps between having something to show, with the new machine I'll be able to machine the parts as they are finished so there be more updates.


  1. Impressive stuff. Do you think you'll loose some detail in comparison to 3d print?

    1. most detail 3D printing can do is 0.3mm you also will always have one lower rez axis (this is normally the one that gives the print lines)

      CNC can do 0.25mm slots and 0.002mm sharp points/thin sections. Getting those details down is mostly about cleaver sectioning of the part. Everything made out of plastic comes from a CNC'd metal mould so you can get see the level on detail is near perfect. While investigating plastic injection moulding it put me on too CNC as a better solution than 3D.

      I've just sectioned the HBK foot for CNC'ing once I've machined it out I'll have a post going through the process. Although the foot lack details (in the game) MWO feet are very complicated structures with over hanging bits and toes so its a good example to show how you'd divide a part to allow access.

  2. Sounds like a better process on the whole then really. I find some detail is inevitably lost during the clean up process of 3d printing anyway.
    I'll look forward to future posts :)