[Williamlii]

Hi Peter - Oh you meant that the base had to be stiff, and not the rails... Yes, the base will end up very stiff indeed, no worries. Thank you for your explanation of drivers and motors peter, that settles it. I'll have to use two drivers for two motors, even though they are synchronized.

The I'll design the machine will not affect the shape of the gantry much depending on weather or not I use a single or two ball screws. But point taken, I agree that this should already be sorted out. It initially was, but you made a few good points that made me lean more towards using a single ball screw instead of two.

Ouhh, interesting paper. I really like these types of machines, but there's also a lot I don't like about them too. The paper introduced to quite a lot of new constructions in parallel kinematics that I have not seen before. I do hope these machines will get accepted in the industry in the future, all though it doesn't seem like it.

Regards William

[Williamlii]

Hello, I'm back with some design updates. I've been tinkering a bit around with some FEA and shape optimization in an attempt do design a rigid Z-axis/clamp. Again this has been designed for a material with a Yong's modulus of 50 GPa, and the results a rather impressive. For the simulations I have used a hollow tube to represent a 2.2 kW JGD-80 spindle (about 8 kg) , although I'm sure it will be a little stiffer than what I've made it in CAD. At the moment the Z-axis also functions as a Ø80mm clamp for the spindle, and it weighs in at just 7 kg. The idea with the current z-axis is that it's very damp as a composite, and I'm hoping it will do wonders compared to aluminium clamps. I'm not sure how well a composite material will grip the spindle when it functions as a clamp, therefore I could potentially cast a sleeve into the casting. I'll have to figure this out if this becomes the winning design. The screws for the clamp will of course have washers if this end up as the final design. Another very noteworthy thing to mention is that I've increased the initial z-axis travel so that it can travel 150 mm. The gantry will therefore also have to be higher than it currently is. The Z-axis clamp/plate is currently a bit tricky to cast, I'll have to sleep on it and figure out whether or not it would be worth it to go though the trouble. I do have a simple solution for casting it, but it does make the mould a little more complex.

Other alternatives and materials. I have multiple designs that I think could work well. The simplest of them all would be to buy a stress relieved cast iron plate and mount two generic Ø80mm clamps for the spindle. A more exotic method would be to laminate metals together using epoxy and glass veil as Peter suggested as an option. This would also be a more damp compared to solid aluminium. Some articles mention that epoxy granite has up to 10 times better dampening properties than cast iron. My composite material will made be made of aluminium and carbon swarf and will hopefully have a similar dampness to that of epoxy granite.

At the moment I really like the current design. It has superior damping properties compared to conventional materials, and I think it looks really cool and professional. I know pretty doesn't cut, but it makes me happy..

I'll return with some alternative solutions and compare the results.
- William