Shark HD4 extended isn't cutting square...

[JerkMcLaughlin]

Gotcha. I figured that was the best test because that’s the size dowels that I’ve seen people use for two-sided parts. I re-ran that same test(still with 1/4” holes) but turned my rpms all the way up while slowing the plunge speed down to 10ipm. Same results.
I guess in MY head it wouldn’t matter what size hole as long as each of them are the same. In theory they would all be inaccurate by the same amount yet still be perfectly square to each other.

Either way, I’m still stuck.

[Rando]

Gotcha. I figured that was the best test because that’s the size dowels that I’ve seen people use for two-sided parts. I re-ran that same test(still with 1/4” holes) but turned my rpms all the way up while slowing the plunge speed down to 10ipm. Same results.
I guess in MY head it wouldn’t matter what size hole as long as each of them are the same. In theory they would all be inaccurate by the same amount yet still be perfectly square to each other.

Well yeah, that would be the case, but only if that actually is the problem. That's what I'm kinda trying to say: the overall alignment of the system, being that much out, if it indeed is, HAS to be measurable in a simple way. Seriously. Jog to an end, all the way until it loses a step or two. Then let it relax, and see if one side really is not contacting that back wall at the same point. Measure it with calipers to 0.001" accuracy. If there's mismatch, that's where you'll see it. But other than the gantry being misaligned relative to the bed, that's all there is besides spindle deflection.

If what you want is greater accuracy, you have to use even-more accurate methods and tools.

Thom

[JerkMcLaughlin]

Thom,
I just checked the alignment of the bearing blocks to the back of the frame, it looks like that is indeed the problem. I can't get calipers in there to measure but there is around .1" gap on the left while the right is up against the back wall. That would explain it exactly. I just talked with tech support and they explained how to adjust it. I'll make the adjustment and run more tests.

I knew I wasn't crazy! haha

[JerkMcLaughlin]

Ok, I realigned the slide bearings to the back wall and now it's cutting nearly perfect.

Thanks so much for your help Thom!

[Rando]

Awesome! I knew it had to be there somewhere, if indeed it existed. Did they have you take off the bed to get to the center drive point? Or can it be adjusted just by loosening the ends, squaring it, then tightening?

Glad to hear you found it.

Thom

[Rando]

And for everyone reading this at home, this is a perfect example of the medical difference between a "sign" that a Doctor sees,
and a "symptom" that the patient reports.

So, in our case, the out-of-square cutting was a symptom: some bad outcome that is caused by something. The cutting isn't
the actual error, but the correctness of the cut is being ruined by the underlying error.

On the other hand, a SIGN, as recorded in your med records by the Doctor, is something that his trained eyes and hands are
able to detect, that exposes the underlying nature of the problem. Or, in our case, knowing that going to the end, and
seeing if the two sides are different, is a SIGN of what the problem is, leading to a possible cure.

When diagnosing a machine, a painful knee, or any system, it's important to try and tell whether what you're seeing
is a symptom of the problem, or is a sign leading you toward a solution. "Watch for signs" I suppose would be the wisdom .

See....learn something new everyday

Cheers!
Thom

[rungemach]

FWIW, I have never seen a shark that was perfectly square, and I have worked on several of different generations.

Do not assume that the front and back plates are parallel or square to anything. I have seen good discrepancies between the front to back plate distance on the right and left side. The front or rear plates may not really be square with the bearing rods that run front to back. From the top view you can get a trapezoid or parallelogram thing happening based on the squareness of the bottom plate. The "drive in the center" design is also prone to rocking out of square depending on where the cut is. The older the generation of shark, the worse the problem.

You need to square the gantry with the bearing rods. If adjusting the gantry by hitting the front or back plate still is off, you can put bolts as microadjusters in the front (or back) base plate. The bolts are positioned to touch the gantry bearing blocks. If you square the machine to the front (or back) plate and it not right, you then use a bolt as a microadjuster to make a new stop for the bearing to hit on the offending side.

The good news is that there is usually enough slop in the shark to allow it to be put square, and then tightened down.

[Dexter]

Thom,
I just checked the alignment of the bearing blocks to the back of the frame, it looks like that is indeed the problem. I can't get calipers in there to measure but there is around .1" gap on the left while the right is up against the back wall. That would explain it exactly. I just talked with tech support and they explained how to adjust it. I'll make the adjustment and run more tests.

I knew I wasn't crazy! haha

I'm having the same problem, but it's the weekend so I don't expect to hear back from Nextwave tech support until Monday. Would someone please be so kind as to post what tech support says is the proper method for adjusting X-Y alignment?

Thanks!

Dexter

[Dexter]

Jake, AKA JerkMcLaughlin, quickly responded to my request (thank you, Jake), and I thought I'd post the PM exchange here for anyone else who might encounter this problem:

Re: Shark HD4 extended isn't cutting square

Sent: Sat Nov 17, 2018 9:51 pm
by Dexter
Jake,
Thank you! That was a pretty quick response. No allen head bolts on mine; it has hex bolts with 13mm heads, 4 per side. I loosened all 8 of them, ran the Y up against 2 equal thickness shims at the travel limit, used a couple of clamps to hold the black cross plate ends up against the shims, and tightened the bolts. Before this procedure, X axis was out of square by 5/64" at 16" right from the front left corner. Now it's so close I can't detect any problem at all. Thanks again!

Dexter

Re: Shark HD4 extended isn't cutting square

Sent: Sat Nov 17, 2018 9:01 pm
by JerkMcLaughlin
Hi Dexter,
I just saw this. It’s been awhile now and I’m not near the machine so I’ll do the best I can from memory. It was a phone call, not an email unfortunately.
What I did was run the machine back in the y axis until it hit the end. Check both sides, if it’s out of square one gap will be larger than the other. Whichever end has the larger gap you loosen the 8 black Alan head screws that hold the slide block to the black cross plate and push it closer to the end until the gap matches the other side. Using two equal shims would work to get the gap perfect on both sides. It doesn’t matter what size the gap is, just matters that the gap is the same on both sides.
Give me a call if you need more help.
Jake
nnn-nnn-nnnn

Shark HD4 extended isn't cutting square

Sent: Sat Nov 17, 2018 1:26 pm
by Dexter
You posted to the subject "Shark HD4 extended isn't cutting square":

"I just checked the alignment of the bearing blocks to the back of the frame, it looks like that is indeed the problem. I can't get calipers in there to measure but there is around .1" gap on the left while the right is up against the back wall. That would explain it exactly. I just talked with tech support and they explained how to adjust it. I'll make the adjustment and run more tests."

I'm having the same problem and it sounds like that solved it for you. I've emailed tech support but I don't expect to hear back from them until after the weekend.

Do you have the adjustment instructions in written form that you could share with me?

Thanks!

Dexter