Hello, like the title explain, I would like to have more depth of cut with the Z axis. Currently I have 60mm and I would like to add 100mm. Does some of you already made it with an OX? As I have some twist (like this thread Axis twist!!! Solution?) I would like to have some feedback from people who already did it. I guess if it's higher I will have more twist. I would like to only change the X plates (on the Y rails). Plywood for start and test if everything is ok then 10mm aluminium. I'm also maybe thinking to buy C-beam instead of 60x20, will it change a lot ? Thx, David
Coming from a production CNC machining background I'm sorry I didn't discover Openbuilds until a few weeks ago. I toyed with the idea of springing for a Sherline mill but the cost for what you get seemed high. Openbuilds puts the pricing into something that I feel is more appropriate. Upon reviewing the available kits it seems the z-axis travel is on the short side compared to the proportions of a something like a Haas mini mill. Sure I understand an Openbuild mill is more of a hobbyist tool rather than production but if using small step overs while side milling you could eliminate a lot of the flexing that probably takes place because of the inherent design of an OX build and longer travels would be OK wouldn't it?
@davels That 40mm increase is something like 60% increase in distance on the part of the machine that has the greatest leverage effect. 10mm plate would also be overkill as the wheels will disintegrate long before the gantry plates flex. And before that, your extended Z will destroy the part. The C-Beam will help in two ways. 1) It's taller which provides a better area to counter the torque. 2) It's a single piece which negates the twisting due to separation. What people do with the stock 2060 doubled piece is bonding them with bolts. @Sprags Using a full stepover does not reduce the load. 25-40% seems to be the norm depending on material and machine. In fact HSM is based off of a much lower stepover with a deeper DOC. A full stepover can be mechanical suicide in some situations. At the end of the day, you have to build for what you need. If you need a deep cut, consider a moving spindle instead of a moving Z axis. Once you are able to clear the work piece, the rest is up to the end mill's DOC. With a moving gantry, no matter what you do, your DOC will always be half of what a fixed gantry (moving spindle) can do. That is purely a result of clearance.
I should have specified a smaller stepover (10-40%) compared to a larger stepover (55-60%) using the same federate will put lower side cutting forces on the spindle/z-axis which in turn will probably reduce flexing of ALL axis of motion.
Thank you for your answer So 6mm aluminium plate will be enough (like originally on the OX) I mill the plywood, I have to test it now. I will "link" both 2060 rail and see if it change something about twisting, if not, I will buy a c-beam. As I'm new to CNC world, I still have a lot to learn/understand
I have another question before start the update. Now, the eccentric screw are on the bottom of the X plate. Could those eccentric screw put on the top? It should be easier to adjust them
I would say no because having the top ones all at the same position will keep it level. The eccentrics can be finicky and you may not get the gantry perfectly level. If they work themselves loose, the gantry could lower causing inaccurate cuts. But, this is all just my opinion.
