MechMate CNC Router Forum

Go Back   MechMate CNC Router Forum > Personal Build Histories > MechMates already cutting
Register Options Profile Last 1 | 3 | 7 Days Search Today's Posts Mark Forums Read

Reply
 
Thread Tools
  #721  
Old Sat 09 March 2019, 18:17
racedirector
Just call me: Bruce #122
 
New South Wales
Australia
Wow its been a while since I updated things.

The Big Red beast is still going, been cutting a little here and there but nothing major.

My future plans call for stability and accuracy so I went ahead and started the twin 6mm mdf gantry revealing job and almost have it done. This last effort is to take 1.8mm out of one of the front wheels, just having a brain fade on which one

I have also ordered the Wixey WR525 digital measuring kit to get my distances spot on, hopefully that will arrive soon.

And the big one is I have just ordered a Centroid Acorn kit, a Mill Pro licence and one of their Wireless pendants, all a bit exy here in Aus ($AUD975.00) but I hope things will improve over using LinuxCNC/Pathpilot. Expensive mistake if it doesn't!

With Acorn I just have to figure out how to set the Axis "steps", Acorn does it differently than every other piece of software out there. The Rack & Pinion thing has me stumped at the moment, especially since I am using metric racks, metric pinion and pullies, Mod 1 to be exact. All part of the deep learning curve to come....

Cheers
Reply With Quote
  #722  
Old Mon 18 March 2019, 05:12
racedirector
Just call me: Bruce #122
 
New South Wales
Australia
Got a few goodies from Centroid, my wireless MPG, Acorn board, Power Supply and 8 relay board for the outputs. I am waiting on a new computer to run CNC12 but that should be with me tomorrow.
Attached Images
File Type: jpg goodies-small.jpg (81.8 KB, 144 views)
Reply With Quote
  #723  
Old Tue 16 April 2019, 05:49
racedirector
Just call me: Bruce #122
 
New South Wales
Australia
Slowly getting things happening with Centroid Acorn control. Heres a quick video air cutting a Mayan Calendar....

https://youtu.be/3DKkDJY7OFE

Getting there slowly
Reply With Quote
  #724  
Old Tue 16 April 2019, 06:35
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
Thanks for the details on the Acorn. Would love to see a picture of the cabinet.
Reply With Quote
  #725  
Old Tue 16 April 2019, 06:43
racedirector
Just call me: Bruce #122
 
New South Wales
Australia
I'll grab a shot once I am finished in there, still need to wire up the spindle/VFD under Acorn PWM control.

That video is an air cut of a 600mm Mayan calendar. I ran that under LinuxCNC using Tormach Pathpilot software and it took 2.5 hours. My aircut finished in 1:41, a full 50 minutes faster. That is with Smoothing on in CNC12. I will run another once the spindle is up and running for real and see if there is a difference in quality.

I have read multiple times that Acorn improves cut time, I wondered if it was true - it definitely is!

Cheers
Reply With Quote
  #726  
Old Sun 21 June 2020, 04:53
racedirector
Just call me: Bruce #122
 
New South Wales
Australia
Hi all

Been having issues lately with accuracy, The weird thing is the machine was told top cut 1090mm and it did it perfectly yet when it was told to cut 12.5mm, it cut 11.8 and then was told to cut 16mm andit cut 15.25.

I have 30 tooth pinions on a metric rack and do not get what is happening. Do I need smaller pinions? I want this machine to be as accurate as possible so am lost as to what is going on.....

Any suggestion or info would be appreciated.

Cheers
Reply With Quote
  #727  
Old Sun 21 June 2020, 05:29
Surfcnc
Just call me: Ross #74
 
Queensland
Australia
Accuracy Issues

Hi Bruce can't remember anything about our machine and too lazy to bone up on your build BUT

The machine has more torque (significantly more) at low feed speeds.
Torque is best described as falling off a cliff as the traverse speed increases.
Slow the machine right down and make your cuts again to ensure there are no missed steps.
Cut something soft like MDF to give it an easy job to do.
Or traverse the machine from point to point and check the distances x and y.

Next put the machine under load.
Fast traverse deep cuts to show up mechanical issues.

A mechanical problem probably pinions loose slipping under higher load is my best quess.
You should have two grub screws per pinion to ensure they are locked in properly.
If you have any belts and pulleys on reduction drives check they are also tight.

Cheers
Reply With Quote
  #728  
Old Sun 21 June 2020, 05:31
Surfcnc
Just call me: Ross #74
 
Queensland
Australia
Measure your cutters with a micrometer.
Reply With Quote
  #729  
Old Sun 21 June 2020, 06:32
racedirector
Just call me: Bruce #122
 
New South Wales
Australia
Hi Ross

Weird thing is I was cutting MDF and only cutting at 80ipm. I will check the pinions are tight and everything else in the drive line is OK. About to buy a Mitutoyo caliper so will measure the tool I was using too.

Cheers
Bruce
Reply With Quote
  #730  
Old Sun 21 June 2020, 07:04
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
The first thing I notice is that you're saying you were off by 0mm, then 0.7mm, then 0.75mm. The 0mm occurred on a very large cut (1090mm), and it isn't clear to me that you would be able to accurately notice a 0.7mm error on that. So I'm going to assume you have a fairly consistent 0.7mm error, probably in one axis.

Since it doesn't vary with distance, presumably all your ratio calculations are correct.

Does it occur only on one axis? Is the error just along the X or Y direction, but not the other?

Have you tried climb vs conventional milling to see if it changes the outcome?

I'll make a wild leap here based on a bunch of assumptions: You have a little bit of slop in the Y axis, moving the car across the gantry. Either that Y gear isn't tight to the pinion, or there's a little wiggle in the spider when extended to cutting depth ( remove bit, extend, push with hand ), or the tool mounting was imperfect.
Reply With Quote
  #731  
Old Sun 21 June 2020, 07:24
racedirector
Just call me: Bruce #122
 
New South Wales
Australia
HI Brad

I had just recalculated the steps so they are correct. The 1090mm was in the Y direction as were all the rest. Thats what I find weird, why it cuts larger distances correctly yet it doesn't cut smaller distances. I run a 2.2Kw spindle with ER20 collets, so that rules out the tool mounting, I always make sure the collets are done up tight. All these cuts were completed with a CMT downcut 0.25" bit.

I use Fusion 360 to supply my gcode and always select conventional milling versus climb.

I will check slop in the Y and the Z in the morning, the machine hasn't been used for over 10months while I waited for my garage to be built. It could be from not being used that it is punishing me for not using it

Cheers
Reply With Quote
  #732  
Old Sun 21 June 2020, 07:42
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
Sure, take away all the easy answers, Bruce.

So, I'd definitely try climb milling a test piece. If it's still under, we're looking for axis slop somewhere or tool size. If it's now oversize, then you've got tool deflection potential.

You might also consider trying a roughing pass 1-2 mm out, and then a finishing pass to see if the accuracy improves.

No other differences in cutting ( slot vs edging, etc ) on your large vs small cut?
Reply With Quote
  #733  
Old Sun 21 June 2020, 08:00
racedirector
Just call me: Bruce #122
 
New South Wales
Australia
I will try all that and report the results

The 1090mm was the overall width of the part, the 12 & 16mm were pockets. To add to the strangeness it cut the length perfectly also at 2200mm

Cheers
Reply With Quote
  #734  
Old Sun 21 June 2020, 08:44
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
Pockets, you say? And you were moving in the direction that tends to deflect the bit into the material, and not away from the material?

Since I'm going out on limbs this morning (here), I'm now hot on the bit deflection theory. Reverse direction in your pockets and/or cut it with two passes ( can be the same location for a climbing bit ), and I'm guessing it just works.
Reply With Quote
  #735  
Old Sun 21 June 2020, 19:44
racedirector
Just call me: Bruce #122
 
New South Wales
Australia
Well, well.... found 1 X-axis motor with both a loose pinion and loose drive pullies. I am going to check all motors etc and try things again.
Reply With Quote
  #736  
Old Mon 22 June 2020, 00:38
racedirector
Just call me: Bruce #122
 
New South Wales
Australia
Close but not yet exact......

Recut the pockets with climb cutting at 80ipm 16000 rpm. Designed as 16.5 wide and 12.3 wide at 6mm deep. Came out at 16.15 and 12.1 at 6.4 deep. Will recalulate the steps involved along with accurate measuring with my Wixey system and restest after that.
Reply With Quote
Reply

Register Options Profile Last 1 | 3 | 7 Days Search Today's Posts Mark Forums Read

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Ordering Parts - Sydney Australia Bazza Construction started, but not cutting yet 43 Thu 13 August 2015 19:20
Belt Drives, Control Systems & Machining islaww The Market Place 2 Fri 18 July 2014 11:25
12/14 free machining mild steel Quadro Cutting various materials - bit selection, feeds, speeds 8 Tue 02 October 2012 21:31
New Sydney Mech Mate, 3700x2100 G30ff0 Introduce yourself and start planning 8 Fri 08 October 2010 07:33
Machining of the rails jeff Archives 23 Wed 20 June 2007 07:43


All times are GMT -6. The time now is 09:24.


Powered by vBulletin® Version 3.8.3
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.