Disruptive Z Axis Carriage Design

[@Random3.142]

I love the fact that you thought of an idea, modelled it, tested it, and shared it. I find it really useful to see this, I've not thought of this concept and it's also useful to read the comments from experienced builders about the problems that you might encounter. Keep it up, I look forward to following your developments.

[@lucmartz]

Thanks for the support ✌🏼

[@VictorFS-eh3gr]

I don't know the dimensions but, that kind of bearing assembly and ballscrew should let you put the spindle closer to the gantry. It will be hard to have it all really parallel. I quite like that you use the linear rail as part of the structure of the Z component. Check the deflection gantry it seems that it will be huge. It would be better if you could make a square beam using aluminium plates (aluminium tubing has too little wall thickness) and have the same assembly procedure as you have right now. Because the gantry is not moving, you can make it as rigid as long as the table/floor can hold it. In my case, I wanted a compact and easy to tune CNC so I went with a moving gantry but that design has lots of problems. Like: chip management, sealing against dust all axis, limited mass on the moving axis, big enclosure, difficult to assemble, hard to water cool all of the moving members, 4 motors for 3 axis, 4 encoders, etc.

[@lucmartz]

Thanks for sharing your experience with your machine Victor. Yes, Y axis movement defined on gantry movement is challenging, it is interesting why the bunch of plasma/waterjet CNC routers on the market that use that configuration exist, maybe is because the tool is not applying forces in the X and Y axis? The movement of the spindle closer to the gantry is very good idea. In order to do not leave the rigidity responsibility to the linear guide rails I will replace the plastic spacers with a single steel piece, but now that you mention the square beam using aluminum plates... I think I will go on that direction. I'm working on a new video where I show the details of the FEA analysis and future changes of the design. Thanks for pointing the "spindle closer to the gantry" improvement opportunity.

[@tinkot]

Im certain you are going to see a lot of vibration issues with the design, especially when cutting deep. You should try to alter the design so there is a more rigid connection with the rails and the spindle, especially because its sticking out

[@lucmartz]

@tinkot that's a good observation, I'm planning to replace the current plastic spacers with a single piece of steel. I hope to post soon a video about the design process including some FEA

[@skrubol]

3 Issues I see with this design. 1: Wet noodle. When this is extended more than a few inches, you'll be able to move the spindle visibly with your own strength. I'd guess you need to stiffen this by at least a factor of 10 to have it usable for more than drilling. 2: Accuracy issues. Those types of linear rail are not guaranteed to be straight. They need to be screwed down and and held against a reference (flat) surfaces. 3: Not much clearance. In the configuration you show this most of the time, with the axis as far up as it will go without coming out of the lower block, the spindle shaft sticks a couple inches below the gantry clearance, and any tool inserted in it will just stick out further. If you move the spindle up the rails, then the rails will have to protrude below the gantry when at it's lowest position. Linear rails are not a good substitute for a real frame.

[@lucmartz]

I'm taking notes @skrubol thanks for the feedback. The idea is to keep it simple and explore options, I will release soon some FEA analysis that will help me to take the right direction in this project, the screw down and held against a reference surface is one of the changes, but the surface will travel :) I'm having "spacers" in between the rails, the change will be to replace the spacers by one single spacer in steel with machined datum planes, the next limitation is the force of the stepper, yesterday I tool some measurements those can only handle 5kg (49N) so that is part of the constraints to take in count.

[@kesor6]

Love it! Excellent concept and explanation of its advantages. Are there any new disadvantages to this approach over the more traditional ways to build Z-axi?

[@lucmartz]

Thanks @kesor6 . I’m currently doing some FEA studies in order to determine the max deflection on this concept and compare it. I hope to release the video in a couple of weeks.

[@amfcreations6894]

Ive made mine like that 25 years ago using a 16mm thick steel plate to suport the rails and its not as rigid as having the rails fixed to the gantry ,so i will change it for a fixed rail version. the max depht of cut in steel using a 10 mm end mil is about 1mm not good enough for me. So go for the fixed rail if you can its much more rigid.

[@lucmartz]

@amfcreations6894 oh well, you are more ambitious than me :) I hope to cut aluminum at the most with this machine because I have a constraint on the force that the steppers motors can provide, I have posted a #youtubeshort taking the measurement and it is 5kg at the tip of the spindle, so around 49N before loose steps on the steppers which is really bad. Could you explain if the 16mm thick steel plate is in between rails or it is holding the linear guide carriages? I appreciate your comments

[@amfcreations6894]

@@lucmartz the rails are bolted to rhe 16mm plate and the cariege is bolted to a 25mm plate., the cariage is locked and the rais move up/down with the 16mm plate

[@lucmartz]

@@amfcreations6894 That's relevant information, are you using 2 or 4 rails? I have the idea that if I have a box as you suggested I can use 4 of those rails instead of just 2...

[@amfcreations6894]

@@lucmartz 2 rails 15mm . it does not really matter using 4 rails it will be hanging far away from the suports cariage i will changing mine to 20mm rails.

[@khhabachi6018]

Did this for 2 years ago you will get vibration and a no rigidity

[@lucmartz]

Yes, currently the machine has a max deflection of 0.4mm at the max force that the stepper motors can provide, I will post tomorrow a short video about how I took the measurement. I have done plastic parts with this machine with some acceptable precision but only happens when use the appropriate finishing passes with the right depth of cut. I will post soon more!