We bought a used Sheffield D28 that has a Tesastar-M probe head. We mostly use star probes, so dont really need a rotating head. And I've heard that this model head can be a problem... thinking of switching to a PH6 or at least getting a used one to have as a backup if the Tesastar conks out. But I dont know whats involved in swapping out different probe heads... Any info about this would be appreciated.
First, contact your local Hexagon Service Department for a quotation.
There will be lots of wiring harness differences, this is not a plug-n-play operation.
It would be a permanent change.
Next, the Tesastar-M heads are almost always killed by having long extension bars between the wrist and probe, the weight hurts them over time.
Being a used machine (D28 predates Tesa, so the wrist is probably a recent addition!), you don't know how much the previous owner abused the wrist.
The good news is that when they begin to go bad they advertise it with long hesitations trying to lock in place and a loud click or pop when they finally make it.
So fire it up and run it through a bunch of angle changes, watch and listen.
Finally, wrists are amazing problem solvers. You can measure things with a wrist machine that you could never hope to get with a star cluster.
I'm working on a job this week where I have an L-star stylus flipped upwards at A90 so the stylus points up in the air, sneaking under a part to pick up the hidden datums with no drama at all.
Thanks Josh, that helps clear up some basic concepts for me.
This used machine (made in 2009) doesn't look like it was used very much. It might not have been used after the 1st year since the original calibration tag was never updated. But it did sit in a dirty sheet metal shop environment for years. It has the Sheffield RCU, thus the Sheffield MP. We wanted another discovery because the D8 and a Discovery II D28 we've had for so long have been such great machines - no hardware problems at least... Anyway, it was purchased with the Tesastar per the copy of the original PO the seller provided.
Bad News is: It does make a bad clunking sound as it seats itself at A0B0.
I do like some things about rotating heads. Especially for slight angles for shank clearance as you mention. We have a PH10 on our D8, but we use multiple part fixtures with smallish parts and often have to measure right alongside the fixture where a bulky rotating head would not be able to fit. So parts can run on any cmm, we go to some pains to avoid using a rotated tip - I even had a special 45° star adapter made by Renishaw some years ago.
A_Shomshor I have such a probe and i calibrate it on the +Y , -X and -Y spheres. The wrist angle is A90B-whatever-i-need and the stylus is pointing at +Z. Never had a problem calibrating it.
Update: the doubts about the reliability of the TesaStar-m are being proven this morning. It wont seat reliably. I had to power cycle the control box several times before it stopped all the blinking and gave me green lights. Then one rotation later its back to blinking everything again! Once again it needed multiple power cycles to get green lights. cant use it! I guess i will have to replace it after all.
Sounds like it was abused.
I talked to our Service Manager, replacing it with a Renishaw wrist is a complex undertaking. Your call...
Just curious as to how you are calibrating that L-probe with it pointing at Z+? Where is the shank of the sphere?
You have to create a new tool definition: a version of your qual sphere with a horizontal vector, then mount the sphere horizontally to match. Then locate it with your master probe by saying "Yes Moved DCC hit", then calibrate the up-facing tip angle of the L-star by saying "No not moved."
two questions - can you define how long a long extension bar is, and does the line about long extension bars apply to the SM-80?
200mm bars kill wrists of all brands, over time.
Some wrists last longer than others. Tesa models usually don't fare well for longevity under load.
UKCMM thanks for the info! Is resetting the parameters a stand alone thing that's done on the tesastar-e control box? That is, it doesn't need pcdmis installed hopefully? At this point with this used cmm we have only installed MeasureMax. We'll be doing something about the pcdmis license a year or so from now.
Josh Carpenter Josh, whats involved in 'resetting the parameters' of a tesastar-m (as
UKCMM mentioned0? Is it something that's done on the -e control box or on the head itself? any help would be appreciated.
Josh Carpenter Maybe my question, "whats involved in 'resetting the parameters' of a tesastar-m" was considered unfair by you since it might be construed that I might be able to fix it myself and thereby not hire Hexagon to fix it? Unless its very simple I wouldn't have the time to try and fix it myself anyway... Just would like to know the rough idea of if its a big job or not.
Anyone else able to enlighten me a little?
