The Journey begins.. new to me.. my first CNC - Black Cat

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Originally Posted by Jonathan

Not bad, but I bet you can do better...

Use the indicator as you have set it up in the video. Move the gantry so that it is measuring over one of the 4 supports (bearings). Now take readings every 20mm (or whatever distance you can be bothered with) and record them in a spreadsheet. Plot the graph and you'll find there will be some small variations due to the aluminium not being flat and a linear error due to the bearings not being at the same height, which is the bit we're interested in. Suppose you get something like the blue line on this graph:

Attachment 7033
As you can see, if a straight line is plotted using the blue curve, it shows the average gradient of the bed. If this function is subtracted from the readings, you end up with the orange line which shows the 'flatness' of the bed with these reading if the perfect size spacer was added. So once you've got the readings, use your favourite spreadsheet program to find the linear regression line and equation, look at the gradient of this line - in this example it is -0.0015, so if the distance between the blocks is 300mm you would need to add a spacer which is 0.0015*300=0.45mm thick. You should then repeat this test measuring parallel to the other axis, then over the other two bearings and you should end up with it being extremely close. The advantage with this method over measuring directly above the bearings is it will account for local variations that could otherwise skew the readings.

Just watched the video again and it looks lie the bed is bowed, can you take the readings and post them here then we can work out if it's worth proceeding?

From the video it looks like you're close enough, but if it was my machine I'd try this to see how much closer I can get it.

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Thanks for the advice Jonathan but in all honesty I'm supprised I got so close and it was a pain in the arse to take everything apart, at some point I know I will want it perfect but for nowI want to move onto doing some actual CNC milling and as it mainly art type work 10th of a mill wont make stripping it again for a while worth it.. but like I said thanks for the advice :pride:

Basically for the vac clamp I used a 5mm nipple with a male pipe attachment.
From the vacuum chamber to a ball valve. and then up under the bed and into one of the clamp holes.
The ring is a seal off a cheap ASDA food saver box. I’ve poured some RTV silicone that was well past its sell by date and will cut that out for projects. I can do a very thin double ring (no rude remarks Mark !) :whistle:to hold my amplifier face plate so I can cut out the holes, that’s why the RTV is a lot thicker than the seal. Anyway he holds well and the vacuum seems to stay steady, all cost £7.50, and thanks to Brian at Tom Parkers in Preston for being so patient while I tried to explain my master plan and then finding the right parts ..lol

Inspired by Blackburn Marks thread

http://www.youtube.com/watch?v=ZfgXUkChWH4

Then I saw this at the end of the street, because I had my camera with me I filmed it :)

http://www.youtube.com/watch?v=XZdNI6F5ezQ

sweet !

i thought you where going to make your own seals with a bead of sealant. (would take a bit of doing)

so, are you saying you have basically buttered a flat plate with sealant and will cut custom seals from that ?

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Originally Posted by blackburn mark

sweet !

i thought you where going to make your own seals with a bead of sealant. (would take a bit of doing)

so, are you saying you have basically buttered a flat plate with sealant and will cut custom seals from that ?

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Sort of, I poured this RTV, but it’s so old its taking for ever to set lol then I’ll cut seals for the job I’m doing.. sorted ! Good thing is I can seal the other screw holes with screws so can cover most of the bed.

Did you like the fighter love um !!

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Did you like the fighter love um !!

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yea, i have a mate that works building the typhoon, saw one at salmbury years ago when they where still running it on tornado engines

some jammy 25 year old spotty kid tear arsing around the sky in a 90,000000 euro toy (bastard)

Could anyone hazard a guess of what the pulse rate for the CNC is , I know it’s a wild question but I don’t have a clue and I can’t find what I’m looking for on Google, because quite frankly I’ve no idea what I’m actually looking for :stupid:

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Originally Posted by Fivetide

Could anyone hazard a guess of what the pulse rate for the CNC is , I know it’s a wild question but I don’t have a clue and I can’t find what I’m looking for on Google, because quite frankly I’ve no idea what I’m actually looking for :stupid:

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Not quite sure what you mean by pulse rate, do you mean the maximum feedrate or the number of steps/mm for each axis, or something else? The latter is easy to work out if you know the pitch of the ballscrews, the drive ratio if there are any belts/pulleys involved and how many steps/rev the motors are set to.

Vacuum bed is looking promising...you could measure the force parallel to X/Y required to pull the material off the bed if you're keen.

Just tried the rubber replacement seals for jam pots and they vacuumn like a clamp, no movement at all works perfect, 3 sizes as well. they are slightly rough , this gives good grip.
Link ebay