file Question Motor upgrade

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02 Jul 2019 11:14 #56995 by Theg
Replied by Theg on topic Motor upgrade
Hi All

Hope this is the correct thread, seems so. I have recently put the Y axis upagrade, which lets be honest should have come with the machine, however running some basic 1.6mm cuts at 22mm/sec with a 2mm end mill in Mdf yesterday saw the X stalling and snapping cutters..... The X axis is perfectly tuned as well as me adding the tightening lead screw nut to get rid of the mechanical backlash, which I still cannot understand is possible out of the box!

I spend hours looking at the specs of the old Y stepper and the current X stepper. They old Y has double the holding torque of the current X stepper and only draws 1.8A v 1.4A. The drivers on the Performance boards look to be all the same driving x2 2A steppers on the Y, I don't see why it cannot be reassigned with the old Y replacing the X stepper??

Anyone got thoughts on this?

Stepcraft V2/840 /w performance kit

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02 Jul 2019 23:02 #57004 by Theg
Replied by Theg on topic Motor upgrade
Right, so after much research and deliberation I decided this mod has to be done, without it, I cannot trust my machine. I checked the thermal temps of the Y v X drivers and the X was already lower after the motor swop, including the steppers. I tested the torque and what can I say, double! I decided some cooling should be in order anyway so designed the below which covers 80% top of board and c 20% below, all is running cool and super strong.

I can part with STL`s or completed parts for a small price


G

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19 Jul 2019 19:23 #57066 by Hurcokid
Replied by Hurcokid on topic Motor upgrade
"Hope this is the correct thread, seems so. I have recently put the Y axis upagrade, which lets be honest should have come with the machine, however running some basic 1.6mm cuts at 22mm/sec with a 2mm end mill in Mdf yesterday saw the X stalling and snapping cutters..... The X axis is perfectly tuned as well as me adding the tightening lead screw nut to get rid of the mechanical backlash, which I still cannot understand is possible out of the box!"
Hi Theg,
In my honest opinion based upon my cnc professional milling experience 22mm/sec(1320mm /min) is far too fast a feed rate speed for great results with your stepcraft machine.
I am used to working in mm/min,.
My sc 400 only moves at 1800 mm/min rapid, so I would not even think about going anywhere near that speed under load.
Max feed rate I have machined at is 800mm/min , 3mm hss slot drill, 1mm depth of cut, wood( fir tree , pine etc.)
I have had no problems to date with that feed rate.
If what you do with your stepcraft machine is for a hobby, then time is not money, its enjoyment.

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19 Jul 2019 20:22 #57068 by Theg
Replied by Theg on topic Motor upgrade
I don't disagree with you, coming from a multicam mt with a 9hp motor requires massive adjustment. That said the X axis stall on the 840 is simply unacceptable. My mod seems to be working well and have about 200hrs under the belt with that mod now which has seen 0 missed steps and with a tensioned lead screw nut you take away the backlash risk which exacerbates the need to compensate with a slower cut, software compensation is a non starter for me. that said, its the machine flex and profile that is the next happy medium to find. I have found the X-Axis rollers to be the biggest culprit here, the tension screws come loose and allow play which invariably causes bite enough to cause play in the machine, at that point its over :) most of this stems from trying to cut some wheel spacers I made for a friend, so may unnecessary variables with the machine, but mostly the X axis roller! the end results was hard fought, but tolerances we spot on

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07 Aug 2019 14:37 - 07 Aug 2019 14:37 #57163 by Doug
Replied by Doug on topic Motor upgrade
[quote="Hurcokid",
In my honest opinion based upon my cnc professional milling experience 22mm/sec(1320mm /min) is far too fast a feed rate speed for great results with your stepcraft machine.
I am used to working in mm/min,.
My sc 400 only moves at 1800 mm/min rapid, so I would not even think about going anywhere near that speed under load.[/quote]


I have a well tuned (but not perfectly tuned) Stepcraft 2/840 and have achieved a sustainable, reliable feed rate on XY axes of 2,500 mm/min for wood cutting at depths per pass up to 1.5 mm for several hours at a time. I believe that I could reliably run at 2,750 rpm when cutting wood. I have tried 3,000 mm/mm and my x axis will bind up.

I run considerably slower on rigid materials such as plastic, around 800-1200 mm/min.

Doug

Stepcraft 2/840, StoneyCNC industrial HF spindle, 4th axis, TurboCAD 2016 Professional 64 bit, MeshCAM, GWizard feeds & speeds calculator, UCCNC
Hobby use: guitar building (luthiery), www.facebook.com/DougShortGuitarBlog/
Last edit: 07 Aug 2019 14:37 by Doug.

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