[Rodm1954]

Thanks Jack

Steve,
The 4th axis needs to be finished. I have to make a bed for it to be mounted on - not sure if I am going to utilize the T slot in the table or machine something else. It was an Ebay purchase originally for another project and I am very happy with the quality. It has a 100mm four jaw self centering chuck so good for square and round stock.
It connects to the driver through a microphone plug at the back of the machine. The addition of the rotary axis meant a longer Z axis travel so I had to change the design along the way and ended up with 130mm of Z axis travel. A bit to do there yet but I'm not in a hurry.

I call it the X axis and yes it has ballscrews both sides. This makes a machine rigid compared to a single screw down the center which can be prone to racking in heavy cuts. Both are attached to 387 oz/in steppers so together they have plenty of grunt to drive the gantry. I use pulleys and belts to connect the steppers as it negates mid band resonance that you get by direct coupling a motor to the ballscrew.

[Over Engineered]

Cool.

Yes, I'm still learning the lingo ...

Mounting the 4 axis onto the T slot table would give you the largest swing over depending on the mounts/brackets you use/make would it not?

Makes a lot of sense to run 2 steppers and 2 ballscrews to the X axis , do you also gear it down with different pulley sizes for more torque, eg 3:1, or is there no need for that and just use 1:1 and keep it simple?

1 last question... Do you use the fully supported linear rails from cncshop/cupcake or are they a different brand? I think I read you used different/better brand linear bearings previously so not sure on what rails you used. Eg is it better to keep the linear bearings and supported rails the same brand for tighter tolerances?

I'm in the middle of designing my first 1800 x 750 CNC (have to finish designing the gantry etc...) I'll get my own thread started when I've got something to show...

Thanks for the great ideas, info and your time!

Cheers

Steve

[Rodm1954]

Hi Steve,
Mounting the 4th axis on the T slot would provide the biggest swing. I haven't looked too seriously at that yet and will tackle it down the track.

On the X axis I used 20 tooth on the motor and 15 on the ballscrew. I knew I has going to have heaps of torque from the two motors so thought I would take advantage of an increase in speed in the ratios. As it turned out all axis have plenty of speed and I detuned them to 4m/min so that the machine operates within my reflexes. It also provides additional safeguard from loosing steps.

The linear rails I got from USA probably three of four years ago. The X axis runs on THK 20 and the Y axis is IKO 15 rails. They were priced well and a good opportunity at that time.
Cupcake sell Hiwin rails and trucks which are made in Taiwan and should be OK too. On another Forum somebody from Aus recently posted this link for a cheaper supplier. I can't vouch for them so make up you own mind and watch freight costs.
genuine HIWIN Linear Motion Rail HGR20 L2000mm with 2pcs HGH20CA Narrow linear carriages-in Linear Bearings from Industry & Business on Aliexpress.com

Good luck with your build.