I have watched lots of tramming videos on YouTube and here. Why not just use a bit and get the top of the waste board measurements in Z for all of the nine rapid areas, use the highest in Z as your starting Z depth and run a surfacing job until you cut on all nine areas? Wouldn’t that make your waste board perpendicular to your spindle and not have to take the time to fool around with a dial indicator and a piece of glass?
That will ensure that the MDF filler strips have been brought down to a level as defined by the movement of the tool.
That works for some folks, and many of our customers leave it at that.
A three-step process where one:
- trams the MDF so as to get a level surface
- uses a sheet of plate glass or other similarly flat/consistent thickness material and adjusts the spindle so as to ensure that it is level and plumb (assuming the balance of the machine structure is suitably level/parallel/at right angles/plumb)
- the MDF is leveled again
will result in a flatter surface w/o ridges and will ensure that cutting is oriented with machine motion
To add to Will’s answer;
Not quite.
There’s two sets of alignment going on here.
-
The ‘gross’ alignment where we get the spoilboard level with the plane the Z axis travels in, defined by the X and Y axes of the machine. The above will, as you say, achieve this.
-
The ‘fine’ alignment where we get the spindle and therefore the tool to be ‘vertical’ against that plane of Z carriage movement (normal to the plane) so that it goes up and down only not a bit of left / right or front / back. The major visible outcome of this is that the cutting edges at the bottom of the bit are ‘flat’ (coplanar) with this ‘gross’ spoilboard plane. If the cutter and spoilboard planes are not aligned you will get ridges, tramlines, lots of names for them but basically, the cutter will be a little high or low compared to the adjacent pass and your surface will look more like a plowed field than a plate of glass (with a sub-mm plow of course)
HTH
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LiamN,
I’ve taken measurements of my MDF boards that came with my 5 Pro in machine readings. The difference between my high and low is 0.037". Is this excessive and I have other issues or is this in the realm of normal and I should proceed in surfacing based on the numbers I have?
It depends how accurate you want to be. .037 is in my ballpark for wood. .002 is what I strive for when I am doing plastic or aluminium.
Of course we all want perfect. Getting close eliminates hand work we will have to do because of variance.
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Hey,
Sorry, was travelling for work, just seen this.
I’d agree with Zman, 1mm seems like a lot, especially if it’s spindle tram.
Did you already surface the spoilboard? Is this the pass to pass step left behind after a surfacing run? How large was the surfacing cutter?
LiamN, I was just getting ready to surface today, and was surprised at how much the readings had changed since Wednesday. 0.360", and it’s not uniform. I’m inside a two car garage in Northwestern SC. And the difference between the high and low of just the closest 6 rapid movement spots to the front is 0.052". It hasn’t started raining yet today, so it may change more as the day goes on. If this is normal, I’d have to surface my CNC the first thing before using it! What can I do?
I am not far from you, I’m just outside Savannah. I my garage is air conditioned because I hate sweating in my work. I could see the MDF having some swelling but wouldn’t think it would vary that much.
I have seen some people talk about making the spoilboard out of HDPE to prevent that but it sounds expensive to me. I have just done some work with PVC though and am thinking it would make a good alternative. I think a 7.25” x .75” x 8’ board at Lowe’s is $45. I can’t remember the width of the strips off hand so not sure if you could get 2 out of that. They also carry 9.25” wide boards. Something to consider if the humidity issues really warrant it. But MDF is a lot cheaper to replace.
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PVC can work well:
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I remember reading that post earlier this year while looking at cutting my MDF strips. I have to admit that I didn’t really follow your scenario though. So here we are several years later, how did the plan work out? Did you end up replacing with just 1/4” layers? Did I understand that correctly?
Still using them.
I did add 1/4" MDF fillers underneath to lift them up which worked well and let me get more usage out of strips before replacing them.
How did the 45 degree cut pan out. Was it worth the effort?
Ah, so you added 1/4” MDF under the PVC. Makes sense given the PVC cost. When time to surface again and replace the PVC you can just set the MDF aside till needed. Or keep it there I guess and just start with a taller surface?
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The 45 degree cut seems a nice trade-off in terms of simplicity and hardware reduction — just should have realized earlier that I could just use a 90 degree V to re-cut to shorten them when raising them up.
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But wouldn’t the MDF still swell and shrink with the humidity and throw the PVC off as well?
Yes, except my machines are in a finished basement which has air intakes for my heat pump and outputs as well.
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