Thanks agaoin for your interest and your points, they are very much appreciated.
Well first off I am a real fan of the Maslow CNC concept, low cost being the ultimate aim. However the world of CNC has changed a great deal since the first vision for the concept. GRBL electronics & software are now prevalent and low cost, certainly unless I am mistaken a good quality GRBL board can be purchased for around $30.00 and GRBL software in many circumstances is free. So the first aim is to introduce a lower cost electronics kit, coupled with a good software source.
The chain drive concept fitted the time period of the availability for hardware to create a low cost CNC machine, even at 8x4 area. Now there are available many other low cost ideas for linear rails. I am a fan of openbuilds and I do create my own CNC designs based on the openbuilds concept.
2nd aim, well, it is now entirely feasible to create a linear sled that comes in at around the same cost as the Maslow sled, but removes a lot of the restrictions placed on the machine and with respect to the Maslow concept introducing a more readily available source of hardware will encourage better design ideas that ultimately arm the user with an easier to use machine. Low cost is feasible also.
Addressing your other points, the Maslow II forum post was where my interest was piqued, this is a very similar design to a machine that I had made for a client only a few months ago, but this was a ‘traditional’ 8x4 horizontal machine. As part of the design and with a vertical machine in mind for the future I designed a linear sled for this client that I could use on smaller machines such as 4x4, the sled would fit both, even a 4x2 bench machine could utilise the sled, no further design required.
Then I saw the Maslow II post and I realised that a similar less equipped, less technical, lower cost linear sled could be designed to fit the Maslow timber frame quite easily. So this is were I joined the forum, with the intention of discussing this idea.
My client only wanted to cut 2D stuff, from ply and MDF, and she had no need for a typical Z axis, she was only ever going to cut a maximum of 1" (25mm) width materials, which means a much lower Z axis can be applied, possibly even one with a similar principal as the Maslow sled, one which slid on the surface of the material.
This brings me to your next point, that the Maslow sled touched the work area, so Z is always zero. I differ with your view that this is a better solution, for a couple of reasons, the first reason is that if the material to be cut is warped in any way then the edge of the sled will lift with the warp, thus lifting the tool at the same time no matter how small the warp and a large warp would tilt the sled and the tool. A heavy weight or spring based sled which pushed the Z onto the material may make some difference but that is the wrong approach, that is adding to the complexity of the machine needlessly. Finally, the Maslow sled is deliberately large diameter, so the base can slide over existing holes or pockets without dipping into them. A raised linear stage can be much, much smaller so again aids in lowering costs, so for this reason I dismissed the sled touching the bed idea.
Your next point about the vertical axis is correct, a standard stepper motor would indeed not be locked if there was a power cut so a belt or chain drive would not be an option unless a gear motor was used. Unless a lead screw was used, such as a TR12x3, the motor would not move, the sled would remain in position in the event of a power cut. Once again another hardware option is available, a low cost TR12x3 anti-backlash Delrin nut is available so expensive ball screws do not have to be used, and in time, yes the Delrin nut would wear, but can easily be replaced with another low cost nut. So on the Maslow Linear sled I will incorporate a vertical lead screw. Yes there may be issues with balance & weight of the sled head with gravity but a balanced pulley system could be introduced to combat this or a more powerful Nema 34 motor used, I would need to investigate further for this.
Rigidity would be built into the linear stage so aiding the Maslow sled to move in a smoother fashion giving more precise cuts, there would be no judder or friction kick steps on a raised linear stage.
Another point is that the Maslow timber frame is now a proven design, and with a wheel based (or other linear slide method) linear sled this timber frame can still be used. So for those who want to keep this low cost frame to create a large CNC cut area the frame can be slightly adjusted to incorporate a more standard linear XYZ stage. For new users the complexity of the Maslow V design sled and associated chain drive system would not then be an issue.
Of course I am open to having all of these points discussed further, that is the point of my post.
My ultimate main aim is to help the guys out there who want a low cost, large area, wall based CNC cutter to be able to build something that is based on a traditional XYZ system but is still affordable and maybe not as complex to get their heads around as the chain drive system