First Proper CNC Router

You are always going to have this problem even with larger bolts unless the holes are reamed and a very close fit to the bolts. ie Sholder bolts. It will be to a lesser degree because you'll have more torque with larger bolts but still it could move. Epoxy will help but only upto a point, it certainly won't hurt until you come to take it apart again or decide to weld it up, then it will be a bitch to get off.!!

Don't you know anyone with a welder.? it will take 20Mins max to weld those few pieces together and it will be so much stronger. Forever.!!

Unfortunately not, atleast not near me. Going to test the epoxy method on some scrap before trying on the frame.

On a separate note, my ballscrew arive from china today. How would you prepare the screws before assembly? Is it worth pulling them apart, cleaning, and re greasing?

Turns out there was a mig welder sitting no less than 5m away from my machine in my neighbours shed!
Just waiting on a new mask and gloves before I can start welding.

Whilst I wait, im thinking about my limt/home switch setup. I currently have 3 NPN proximity sensors.
For the X and Y I will use 1 sensor mounted on the moving parts as both the limit and home switch.

For Z do i need both limit and home?

Also thinking about cable chain sizes. Will the 37x18mm stuff be big enough?

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For Z do i need both limit and home?

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Generally you don't use a bottom limit switch but you can use soft limits. on all axis.

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Originally Posted by Clive S

Generally you don't use a bottom limit switch but you can use soft limits. on all axis.

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I've gone with common sensors for limits and homing plus soft limits. Sooooo easy in LinuxCNC. I have a low limit switch on my Z axis, but that's because on my design there's a crash risk with the gantry ends if it gets too low. There is a soft limit as well so it's really belt and braces.

In practice you should never need limit switches to prevent a crash as long as you have the soft limits set correctly and always home the machine before you do anything else after switching it on.

BUT. There may be a risk if you have a pendant for manual control of the machine which does not operate through the controlling software and therefore moves the machine without the software knowing. I think this is possible with some of the cheap Chinese break-out boards and is a train-wreck waiting to happen for the blissfully ignorant.

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Originally Posted by JAZZCNC

Use the one that allows the shortest belt arrangement. They will all work equally well as each other but shorter belts are easier to find and implement.

This is my preferred setup.

Attachment 27732

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Dean what size is that profile that allows for easy mounting the 16xx ball screw?

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Originally Posted by Boyan Silyavski

Dean what size is that profile that allows for easy mounting the 16xx ball screw?

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This one.

https://www.motedis.co.uk/shop/Slot-...:99999415.html

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After welding the frame, i did a quick check to see how straight and planer the two Y axis tubes are using a small surface plate with a DTI on a long arm. The surface plate was placed on a piece of plywood with three jack screws used to level the plate to three reference points on the tubes at the front left, rear left, and rear right.

Both tubes are now convex, and not planer. Measurements are below. Max deviation is 3mm!
I cant tell you how much is from the welding, and much was there before, but given that both are now convex my bet is its dominated by the welding.
Attachment 28210

My original plan was to use shims under rails to bring them into alignment, but given the level of error I'm having second thoughts about that.
Is my only option epoxy?

I'm not sure I'd trust your method of measuring as it won't be very accurate, just the length of the arm its self will deflect a fair bit. Unless you have a flat reference surface to measure from then you'll never truly know for sure how far your measurements are off.

To me you have 2 choices, Fit the rails as it is and see how it cuts and then shim out any issues. Or just bite the bullet and go with epoxy.

What size machine and what's the main usage.?