a Steel Box Section Build with SBR20 & Ballscrews Plus a few questions

[pippin88]

You can also skin the frame with sheet material (rather than diagonal beams) for bracing

[JAZZCNC]

You can also skin the frame with sheet material (rather than diagonal beams) for bracing

Sheet material will do very little for it other than turn it into a Big Drum. It needs proper and substantial bracing to handle the forces a heavy gantry will put on it. If done properly it will also reduce resonance/vibrations.

[grain_r]

Thank you very much for the replies, I have been adding to the design of how I have made the frame, although I still have the horizontal cross members to put together.





Also wondering if anyone has used Fred from BST Automations own Linear rails ? or is Hiwin the way to go,

Thank you

[JAZZCNC]

Also wondering if anyone has used Fred from BST Automations own Linear rails ? or is Hiwin the way to go,

Yes, I use lots of them and they are good for the money, but they are not as good as Hi-win so don't expect Hi-win quality. That said they more than good enough for a serious Hobby level Router and if maintained properly will last for years and they are nearly half the price of Hi-wins so no one should expect them to match Hi-wins really.

If you're wanting the best Stiffness and working the machine hard in a production environment 10-12hrs per day 6 days a week then you should go with the Hi-wins.

Re the frames It's still a little weak on the bracing IMO, because the sides are so tall the short end diagonals don't extend far enough across the beam, same down the sides, this will allow the cross beams to flex as the sides apply a bending motion to them. You would be better with another lower cross beam with diagonal braces between them.
My first machine was built similar to this design but with short sides and it flexed at this point, I later braced it up as mentioned above and it was much stiffer.

If you don't need to pass material thru the machine I would also fit triangle plates to the ends to brace the sides. Those tall sides with spindly tubes are a massive weak link in this design, why such tall sides with such a short Z-axis.?

[grain_r]

Hey dean great thank you very much for the information on the Rails I have been looking and will be most likely going for those OEM rails, It will be purely a home Cnc just for hobby work so sounds good enough for me.

I will add some more bracing to the design higher up too.

The original plan was to make foam moulds for fibreglass parts for a car I was building so I could then keep layering up the foam and moving the shelf down to create the arches and other large parts, But that has changed now :(maybe one day) but its going to have a movable shelf for sheet woodwork so once the shelf is in that should also add to the strength too.

I originally left the ends open for end-grain cutting but I will add the end bracing too and I can always take them off when I'm doing normal sheet work.

thank you

[grain_r]

I have been Emailing Fred to get a quote for the rails

I have my 1605 ball Screws from my original design and order but I see everyone seems to use the 1610 ball screws on a 1:1 pulley instead of the 2:1 Ratio but would it be okay to use the existing 1605's or is it worth buying the 1610's from Fred whilst I'm getting the rest shipped over.

I wasn't sure if I make any gains of Torque and speed this way?

I also have a pricing of the 2.2 Spindle and VFD I thought again just one shipping might be good but I haven't really heard of anyone having the spindle from Fred. I know the old adage of the finish the other things before they are needed but I am buying some of this to use in my business and trying to save a little from my Tax bill

any help would be most appreciated.

Thank you

Rob

[JAZZCNC]

If you are ordering anyway then I would get 1610's if it's being used mostly as a wood router because you'll want the extra speed they offer. Don't worry about torque because if you use correct size steppers with a decent amount of volts you'll have more than enough torque. If your just cutting aluminium with it then 1605 will be fine with a 1:1 ratio as you won't cut much above 3mtr/min and you'll get around 5-6mtr/min rapid speeds which is more than enough for smaller machines.

Fred's spindles are fine, I have fit dozens and not had any troubles yet, they are pretty much all the same and in general, I have fit 100's over the years, and less than 6 have gone faulty on me.

[grain_r]

If you are ordering anyway then I would get 1610's if it's being used mostly as a wood router because you'll want the extra speed they offer. Don't worry about torque because if you use correct size steppers with a decent amount of volts you'll have more than enough torque. If your just cutting aluminum with it then 1605 will be fine with a 1:1 ratio as you won't cut much above 3mtr/min and you'll get around 5-6mtr/min rapid speeds which is more than enough for smaller machines.

Fred's spindles are fine, I have fit dozens and not had any troubles yet, they are pretty much all the same and in general, I have fit 100's over the years, and less than 6 have gone faulty on me.

Hey Jazz Thank you very much for that, Righty Oh I will add them to the order it won't be a bad thing because the originals I have don't have much room for a pulley. I'm sure they will get used for something else one day.

I will add the spindle too and then just hope that the customs people don't think it looks interesting enough to open :)

I'm still undecided to go with the oem or Hiwin Rails the difference is $325 dollars and because I want to do it right I'm leaning to the Hiwin.

Thanks

Rob

[JAZZCNC]

I will add the spindle too and then just hope that the customs people don't think it looks interesting enough to open :)

They won't probably open it but that doesn't mean anything really, they will always charge you VAT and duty based on the invoice amount.

I'm still undecided to go with the oem or Hiwin Rails the difference is $325 dollars and because I want to do it right I'm leaning to the Hiwin.

Well in that case then I'd go with Hi-wins.

[Clive S]

I have don't have much room for a pulley.

Fred will machine what ever length you want for the pulley, tell him what length you want the F length to be.

That is where the pully fits.if you make it too long you can always cut it off.25-30mm is fine