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4th Axis for Sieg KX1

Adventures with another axis!

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Ian Johnson 102/03/2019 19:23:30
141 forum posts
38 photos

As the description suggests I have recently bought a 4th Axis for my KX1 from Arc Euro, first impressions I am very impressed with the build quality and rigidity.

It is the 4 inch rotary with stepper (Arc's own fitment) which is just the right size for the KX1, plug and play and off we go with a little test program made with Vectric VCarve, using a piece of 20mm dia Acetal, I set about machining rotary text spelling 'ROTARY' and four slots. Using two tools, an engraver and 3mm end mill. Press start!

And soon stop! although the device was communicating with Mach3 there was no relation between the angles required for each letter or slot, they all merged into each other and overlapped, even though the Mach3 screen showed it machining okay. This was because the motor needed tuning, So by looking into the motor tuning menu I tweeked the 'steps per' and 'velocity' and some trial and error and maths I got the 'steps per' to the correct 400 (it was set at 2000), and the velocity to 2500, now everything machined as planned, although I will need to change the velocity so it matches the X axis feed rate.

Here's a couple of photos of my set up and first test piece. More to come as the adventure continues!



JasonB03/03/2019 07:26:04
16288 forum posts
1723 photos
1 articles

That looks good for a first go, I could have done with a 4th axis on for the helical cooling fins on teh Forest style engine I've recently.

Keep us posted of future work.

Ian Johnson 103/03/2019 12:34:56
141 forum posts
38 photos

Thanks Jason that was actually my fifth 'first go' laugh it was a lot of detective work to find out what the right settings were, there is not a lot of info out there, but I found a Youtube video with the maths to work out the ratio and steps. Now if I MDI for example G0A90 it will rotate 90 degrees exactly. Now I am busy racking my brains to find work for it to do! I was thinking of making a mini tomb stone fixture to fit on the back plate, but helical cooling fins sounds good though!


Andrew Johnston03/03/2019 18:39:45
4855 forum posts
544 photos

Looking good! thumbs up

I found that Mach3 simply ignored combined rotary and linear feedrates, which you need to machine a helix. I used ended up using G93, inverse time feedrate. Takes a bit of thinking about though! Here's what you can do with a helical toolpath:

final worms.jpg


Ian Johnson 103/03/2019 22:21:16
141 forum posts
38 photos

They look nice Andrew. A little bit too advanced for me just yet though! I am happy just to get some rotary engraving done for now.

Why does Mach3 ignore the combined rotary and linear feed rates? Is it an issue with your CAD/CAM? I am using Vectric VCarve which has the ability to do spiral fluting, I wonder if it would do helical gearing?


John Pace04/03/2019 09:28:38
156 forum posts
156 photos

A 4th axis is an essential accessory and opens up what is possible to do.The compressor wheel on the left is milled from 2014 t6 aluminium 68 mm in diameter ,the one on the right is a bought cast wheel 66 mm dia for a KJ 66 model gas turbine.

John68mm compressor wheel.jpg

Edited By John Pace on 04/03/2019 09:38:33

Andrew Johnston04/03/2019 09:35:34
4855 forum posts
544 photos
Posted by Ian Johnson 1 on 03/03/2019 22:21:16:

Why does Mach3 ignore the combined rotary and linear feed rates? Is it an issue with your CAD/CAM? I am using Vectric VCarve which has the ability to do spiral fluting, I wonder if it would do helical gearing?

Definitely a Mach3 issue. The G-code for the worm was hand written and the offsets needed to form the groove were determined from a large scale drawing on graph paper. So no CAD/CAM involved.

For any linear move in X, Y and Z the feedrate is in distance per unit time. For pure rotary movement the feedrate is degrees per unit time. But for combined linear and rotary motion the feedrate should be in distance per unit time. Of course it is complicated by the fact that over a given length the tool travels much further for a slow helix compared to a fast helix. Suffice it to say Mach3 simply can't cope with this; confirmed by Tormach when I contacted them. If there is interest the following link goes into the issues in much greater detail:


I don't know about VCarve, but I'd have no problem cutting a helical gear. The issue would be working out where I want the cutter to go. I'd write a subroutine for one space in incremental mode, and index the rotary table by one circular pitch for each call of the subroutine.


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