Program Offsets changing by themselves

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mtrehy
Posts: 7
Joined: Wed 02 Feb , 2022 20:24 pm
Hardware/Software: Novamill, Microrouter & Novaturn

Program Offsets changing by themselves

Post by mtrehy » Sun 16 Oct , 2022 18:52 pm

HI,

Bit of an odd one and I can work around it.

I use this machine quite a lot and have made some fairly substantial items in the last few weeks.

Today I tried to machine a billet approx 100mm square. I had a 16mm carbide end mill that I wanted to try (normally use 6, 8's and 10's). This meant that I would be very close to the limits of Y travel. I ran the program and noticed that it took a bigger cut than I expected in the y direction so I stopped the machine and checked my Y offset and it was wrong by about 3 or 4 mm. So I reset the offset, double checked it by moving the tool over the datum and checking it was all reading 000 on the program offset display. All fine, ran it again and the same thing happened. Changed the tool to 10mm, regenerated my code, reset offsets and all is fine. Obviously the 10mm doesn't push the axis as far over for the first cut.

So it seems as if for some reason if I get too close to the Y axis limit something weird happens to the offsets. If It is completely out of limit I get the normal warning that I have exceeded limits. Has anyone else experienced this? When the Y axis gets close to the limits in the + direction it makes a pretty loud noise and hits the limit hard, when it gets close to the limit in the - direction it seems to slow down gently and quietly and hit the limit softly as I would expect.

It's a real shame that the Y axis is not 50mm more travel.

Also, I have seen 2 different numbers for Y travel, 150mm and 160mm. On my machine setup on VR milling mine is set to -150, can I change this to -160 and get an extra 10mm for free?

Cheers

Matt

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Re: Program Offsets changing by themselves

Post by TDIPower » Sun 16 Oct , 2022 22:20 pm

sounds to me like it might be binding on the travel and loosing steps. I'm not familiar with the VMC but on other machines there is no position feedback other than zero point switches, all it does is fires the steps to the motor and expects it to be moving. If it is binding on the travel it will skip a step or two and so on so when it thinks it has travelled say 50mm it has only travelled 45mm so when it returns to the limit switch it tries to move back 50mm so will slam into the end of travel and continue firing those 5mm of steps.
I've had this a lot on the microrouters and once on a novamill at work. In both cases a strip, clean and lube of the bedways, lead screw etc. sorted it all out.

Hope that helps
Pete

mtrehy
Posts: 7
Joined: Wed 02 Feb , 2022 20:24 pm
Hardware/Software: Novamill, Microrouter & Novaturn

Re: Program Offsets changing by themselves

Post by mtrehy » Mon 17 Oct , 2022 18:27 pm

Cheers Pete, took the bellows' off and have everything a good clean and lube and it's working great again.

https://youtu.be/WnGI_nFcwP0

https://youtu.be/Ej2WALRWjHw

https://youtu.be/WnGI_nFcwP0

TDIPower
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VR2 and VR5
Boxford VMC260
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Re: Program Offsets changing by themselves

Post by TDIPower » Tue 18 Oct , 2022 23:27 pm

Good stuff. Glad it was a simple thing

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