Whether to Paint Cabinets Before or After Assembly

A shop that mass-produces cabinetry looks for a way to speed up its finishing operation. December 23, 2014

We are a small factory of 150 people building mid/high end residential cabinets. Our construction is plywood carcass, solid wood face frames with inset doors. Our main bottle neck is in our paint department. Our cabinets are spray painted with a latex paint, no stains or lacquers used. The final coat is a hand painted brush finish. Our customer wants that “hand made/brushed” look. We do not use any particle board or MDF. All doors are inset with traditional butt hinges, no euro hinges. All cabinets are built in multiples of ten pieces. These cabinet are a mix between handmade and production cabinets. We are trying to decide what works best. I am hoping some of you may have some experience and knowledge in methods of painting.

We are looking at two options:

1. Purchasing a flatline semi-automatic painting system. All flat plywood panels and face frames to be pre-painted flat. After painting the plywood boxes are assembled and face frames attached. Doors will then be fitted to fit the openings and painted. Doors are then hung on the cabinet and the full cabinet is hand painted with a brush to give the “handmade” effect.

2. Our present method is to cut and assemble the plywood carcass, install the solid wood face frame and fit each inset door to the openings. Cabinets are then painted as an assemble carcass excluding doors. The doors are painted separate from the cabinet carcass. Doors are then re-hung and the full cabinet is then hand painted with a brush.

Our present method works but is a very time consuming job. We find sanding and painting assembled cabinets to have some challenges. When we think about sanding and painting flat panels and then assembling, it sounds like maybe it is a worthwhile idea. Has anyone here any experience with this that you can share? Before we invest money in a totally new system we want to make sure it is the right choice. Having no experience in flatline painting, this does look very interesting. But never using one before I do not fully understand the limitations or challenges we may face.

Forum Responses
(Finishing Forum)
From contributor K:
We use a Cefla flat line and it significantly increases production. I had a customer who wanted 30,000 square feet of paneling to have a "hand painted" look to it. The solution I came up with was attaching two wooden concrete brooms at the back end of the machine. This would brush threw the wet paint as the parts were conveyed passed it, giving the brushed look. The client was happy and I never had to pick up a paint brush.

From Contributor T:
What brand, type, sheen and etc. paint do you use?

From the original questioner
We are using a Valspar latex paint in an eggshell finish. Valspar have developed a paint formula for our production. We have one formula for the spraying of the cabinets and a second slightly adjusted formula for the handbrushed topcoat. We have another product line were we use a clear topcoat over a distressed finish.

From contributor M:
Most cabinet manufacturers do the finish first then put it together and most use CV. May I ask why latex? I would think that most production shop/factory would prefer using harder finish.

From the original questioner
We have a customer that is very particular to details. Many of the processes we do do not fall under the "normal" production ways. I would love to change to a CV finish but for several reasons we cannot do this. First reason is we must have a "hand painted" finish. Spraying a CV finish does not do this. Many of our cabinets have an oak top, no lacquer is ever used on our wood. We do a hand rubbed oil finish. We can argue about durability, ease of application, maintenance and etc. The bottom line is that our customer will not accept these finishes. We do as our customer wants - a hand rubbed/hand painted finish. This is why we spray first and hand painted the final coat. I do not believe this type of effect is possible with CV?

From contributor M:
Ok I understand. In your case I would do the spraying before assembly then do the hand finish after. It must be some nice work after it's all done. Is this customer the only one you have a contract with? Or do you have other work?

From contributor J:
The idea of a brush on the end of the flatline is great. I can see where you might have to hand brush after the line on say a frame and panel on the rails where you want the "brushed with the grain" look.

From contributor O:
If the brush strokes are in the primer then the casework could be sprayed with a final coat and still have the brush marks. The brush marks could be done in the primer with the flatline as suggested. I have done a brush glaze that way with a Makor molding sprayer. Maybe brush the solid wood with the grain before cutting and gluing up the face frames, assemble, touch up any places that need it and then spray a durable top coat?

From Contributor C:
The only possible issues we've run into pre-painting cab components are gluing and handling. If you don't rely on any glue joints (which could add masking time prior to the spray) and can easily assemble all units without needing to correct inadvertent scuffing, etc., I believe pre-spraying the flat stock will be a serious process improvement. Besides, machine sanding interiors can result in pad bouncing which could involve even more lost time to correct. At least that's been our experience in a small, custom appointments environment. I do like some of the innovations submitted here about duplicating the hand-worked appearance on a mass basis. It’s worth exploring.

From the original questioner
Our cabinets are only brush stroked on the outside. All inner sides are spray painted. We have tried to brush before the final top coat but we have found that too much of the hand brush effect is lost. Our thinking here is we can flat line paint most flat pieces. Either tape or use wood spacers in the dadoes etc. before painting. Then the cabinets are glued and screwed together. Once this is done our final top coat of hand brushing should take care of normal damages from the assemble process. The steps we take to get the look we want is correct. What we are interested in determining is if flat line painting would really benefit us. To make this change we must totally reorganize our paint department and invest much money. Never having done this before we have no information on if the outcome would really be a benefit. Our gut feeling says yes but the change is major and difficult to turn back after it is completed. Here is a picture of one of our pieces. As for our customer, we build furniture only for our parent company.

Click here for higher quality, full size image

From contributor A:
I share the repulsion to the latex paint that many folks are sharing above (I've personally never seen a latex paint kitchen last more than a couple years, but I am not the final authority). I do respect your decision to stick to what your customers want. At the very least, you're not spraying a flammable paint, which has its advantages. So I won't say anything about changing products to improve your product quality despite the temptation (I'm a dyed-in-the-wool conversion varnish fan, although I do love Sherwin Williams "All Surface Enamel" oil based paint as well). Regarding your question on work flow, I would only do this with unassembled parts. I've done both, and still occasionally spray a whole cabinet, but I hate it as much as pulling my own teeth with pliers. You work in batches of ten, which is probably about a day's worth of work for a few people, right?

I would approach this like the following:

1. Ten cabinets worth of parts, unassembled.

2. Spray with a good sandable primer, similar to Sherwin-Williams Prep-rite or Kilz. Both are fairly thick and spray very nicely from an airless pressure pump.

3. Load the wet parts on racks designed to hold large items like face frames and large doors. Let them cure.

4. Cabinet interior parts would get their own rack. They would then be sanded and sprayed with the appropriate color, and left to dry. One primer and one topcoat should be more than sufficient for tops, bottoms, backs, and interior sides. I can't see brushing these to be an advantage. Steer your customers away from hand-painted interiors (I wouldn't even bring it up, just show them handpainted exteriors)

5. Exterior parts (finished exterior sides, doors, faceframes) would get a different rack, and possibly be sprayed first with color, and then cured, and then be rolled over to the section that hand-paints. If you tint your primer first to the right color, you can probably skip the middle spray coat of paint. In other words, tint the primer and be done in two coats. I've finished a lot of face-frame bookshelves in similar fashion as this, except they were done with a stain and a waterborn (Sher.Wms KemAqua).

From the original questioner
I never considered spraying the face frame as components. Our plan was to assemble the face frame and run thru the inline painter a whole piece. How do you deal with the joints? All of our joints are mortise and tenon. Do you mask these areas? This seems like a great deal of work. We are thinking about your suggestion. We do only hand brush the exterior of the completed cabinet. The interior surface is all spray painted. If we only had ten cabinets a day our problems would be much less. The number per day varies greatly because of the size of the many sizes of cabinets. We produce approximately 45 cubic meters a day presently. This quantity is rising continuously. Painting is our biggest bottleneck. We fight to keep up to the orders we have. If we did not have this bottleneck in the paint department our volume could increase.

From contributor O:
Why can't you use a floating tenon and mill after finish?

From contributor A:
I may have been vague. I wasn't suggesting that you spray the face frames as individual pieces. Assemble the face frames and sand them, and spray the whole face frame before you attach it to the cabinet. Obviously you will need to avoid using nails to stick it to the carcass. Regarding ten boxes a day, I thought that was what I read in your post about spraying, but I think I misunderstood you and I'm sure that you can increase that to any number you need with the appropriate amount of curing rack storage.

Another possibility: Consider purchasing pre-primed plywood for your cabinet interior parts. Thus, you'd only likely need one coat of color to be done with those. There's about half your time done right there on those parts. Even if you chose to paint the assembled carcass prior to attaching the face frame, you could sand the plywood first, assemble the carcass, and apply the paint. I still think it would be faster to cut the pre-primed plywood components, spray them flat, and assemble the carcass. Meanwhile you can have the face frames and doors primed, painted, and then brushed, ready to go. As soon as it's all cured, pocket screw or dowel/biscuit the face frames on.

I would do this confidently with conversion varnish (we do it quite frequently even though face frames aren't our main staple, we still do them frequently enough to speak with experience). I do not know if latex paint will withstand the last half of production without nicks, narks, and dings. You will know the answer to that more than I would.

A suggestion to greatly improve your finish durability is to look into Sherwin-Williams "Precatalyzed waterbased epoxy". I've painted several bathrooms with this product, and was rather shocked at how tough it is once cured. It stinks to high heaven, but that's nothing a good exhaust fan can't fix. It brushes quite nicely.

From the original questioner
Switching paint at this time is not something we can consider. We have spent the last year developing our present paint system. We have used it only one month. We have considered assembling the frames and then painting them. We can nail the frames after painting because we will give the cabinet an additional hand painted top coat. For the plywood carcass we are beginning to think that we should paint the full sheets of plywood sheets before cutting. We may have some surface damage from handling/assembly but maybe one light final spray coat may be easier than painting the a complete unpainted assembled cabinet.

From contributor A:
You'd have to ask yourself if you have a sufficient way of curing the large full sheets of plywood first. By the sound of things, you use a lot of plywood, and that would mean you need a lot of plywood curing space. Then you have to consider that you will inevitably be painting your drop unnecessarily. If the whole process saves you a lot of time, then it's worth it. My suspicion is that you will find (as we have) that painting the parts individually will save you much time, particularly if you buy pre-primed plywood. I personally can't imagine sanding the primer coat on a full sheet of plywood, day in-day-out unless I had a machine that did it for me.

From the original questioner
We do use a great deal of plywood. We have just recently set-up drying tunnels for our cabinets. We spray the assembled cabinets with the base coat. It then is goes through the first heat tunnel. As it comes out of the tunnel it is sanded. We then spray the first top coat. It goes into the second heat tunnel and then sanded. The assembled cabinet then gets fitted with drawers slides, doors, etc. and then the final hand brush coat is applied. What we are thinking now is to have the inline sprayer spray paint one side of the full sheet of plywood. It then goes through the heat tunnel. As it comes out the heat tunnel and is sanded and turned over the over side of the sheet is spray painted and sent through the heat tunnel. The sheet is sanded and turned over and the first top coat is applied and then second side is top coated. Painted sheets go to the CNC and are cut to size, dadoed and etc. Cabinets are assembled with painted face frames. Then one final hand painted coat is applied. This is the new process we are presently looking at.

From contributor M:
I think what you are thinking of doing is great. It sounds to me that you have the machines to keep production going. As long as those machines do not damage the finish you should be fine.

From contributor A:
I could see that working just fine. My own personal inclination is to ask if we'd gain anything by painting the whole sheets first rather than doing individual parts. If you have the means of spraying, sanding (if applicable), curing, and stacking them, then this may be a good option. I would think that one of the bigger hurdles you may encounter is what you do with them after you have them painted and heat-cured. I suspect that even heat-cured latex will tend to stick your sheets together if they are stacked for any amount of time. The pressure just from a couple sheets of plywood could put you at risk of the paint sticking together. So I'm assuming that perhaps you will have a method of stacking them that doesn't involve them touching each other (perhaps using some thin unpainted, reusable plywood/MDF dunnage strips in between)? You know your product far better than I do.

From the original questioner
The reason we are thinking of painting full sheets rather than cut plywood is because of all the dadoes etc. These all need to be masked off before painting. This seems to be a very time consuming job? If we paint full sheets we have nothing to protect from paint. We have set up a motorized conveyor system. Our thinking is the conveyor holds all the sheets. The conveyor will take the sheets out of the inline painter through the heat tunnel to sanding, back around to the inline sprayer, flip the sheet, paint the second side and then paint the first top coat and back around again. We paint enough sheets for our next day production. Full sheets are not stacked until the next morning when it is to go to the CNC. Our conveyor is actually our drying rack. I have not calculated yet how many sheets, how many feet of conveyor etc. we will need. We can always add more conveyor to hold more sheets.

From Contributor C:
Without examining your subassembly/assembly prints, I can't really assess all the possibilities, but what we have done on huge jobs that use common parts, is to rip the plywood to a common dimension (length or width) and then pre-spray all the smaller pieces which are also easier to rack. Then finish dimensioning the pieces after paint has cured. There is less handling and easier handling than 4x8’s. It really comes down to expeditious engineering. Even those dadoed or rabbeted surfaces could ideally be set into many pieces at once then separated into individual components after the spray operation (easier/faster to mask lots of pieces with a single strip of tape). I'm betting that there are several candidate component configurations that would qualify as a work saver. Others may not. So use discretion which ones you propose to automate. It's also possible that in parallel with your planned "painting bottle-neck cure" you may find a need to modify some of your joinery strategy to take full advantage of the peripheral cost saving area.

I would do a feasibility study before sinking any dollars into any process revision. Test simulating a small sample to the proposed change the best you can with your current equipment. Sure, you will tie up a few employees for a few days recording the process durations, but it only requires a stop watch and a calculator. Exactly how long is the minimum cure time between those latex coats? I noticed you mentioned a heat line within the thread and wondered if the pieces were ready to handle/repaint immediately after they left the curing process.

From contributor A:
Ok, I see the kink in what I was suggesting. The paint would seal up the dados/rabbets in places that would need a good clean glue joint, I assume. I know that conversion varnish doesn't fill in a dado enough to make the back too tight of a fit, but we don't use the dado for a glue joint, so it's no big deal. I'm not sure about latex, it could be a lot worse. Have you also considered just using a prefinished (clear maple/birch) plywood for your interior cabinet parts? Yes, they are quite a bit more expensive than unpainted ply, but the drastically reduced labor is worth it. I've built a lot of face-frame cabinets with prefinished maple interiors. The shop I did this at was a bit archaic, they insisted that I tape/cardboard everything off. In your case, you have the FF's painted beforehand, and can touch them up afterward. I am still personally sold on the notion that either pre-primed or pre-finished plywood interiors will do very, very much to reducing your finish booth bottleneck. The pre-primed stuff cuts your finishing to a single coat, and the prefinished clear birch/maple cuts the whole spray booth out for everything except open cabinets or glass-door cabinets.

From the original questioner
We think paint cut components will be a huge job and will require many drying racks. Painting with CV is not really an option that we can choose. Also purchasing prefinished maple board is not an option. All our surfaces are painted with solid colors. Before I did not realize exactly how many full size sheets we cut in one day, 200 sheets! This is the main reason we are looking at painting full sheets. To handle all the full size painted sheets we are looking at standing the sheets upright during the drying time.

The basic process will be:

1. First side is base coated with inline sprayer.

2. Immediately goes into the dry tunnel and exits on the conveyor.

3. Within five minutes of exiting the tunnel it can be handled.

4. The sheets are then stood upright on specially made racks and left to dry.

5. The sheets are then painted on the second side with base coat.

6. Through heat tunnel, placed in stand up racks.

7. After four hours of dry time between coats the sheets are then run through the sander and then directly into the inline painter.

8. The complete process is repeated for the top coat on other side.

9. Sheets are left to dry overnight in stand up racks. Next day they are placed on carts and brought to the CNC for cutting

The only handling we have to do is load the conveyor and offload after painting. The racks will be along the wall following the conveyor so sheets will not be transported between coats, handling should be minimal. We are hoping that any surface damage is minimal from assembly and that our final hand painted top coat will cover most surface damage. This is the process that we are seriously considering at this point of time.

From Contributor S:
You say you have problems painting pre-assembled cabinets. What are the problems? I don’t get it. Double coat the first coat of primer on the inside and the same on the face frame. Run through the tunnel, sand and top coat. A double topcoat on inside should be smooth as glass. How can this not be done efficiently and with superior results especially with a crew of people? One guy with a sander, one guy with a 3M purple sanding block and one with a caulk gun should be able to rip these out fast. Then maybe your hand painters should brush faster. A three man team should be able to prep for top coat perfectly in five-ten minutes. Caulking will be bottleneck. Maybe add another person there. You be able to do 30-40 a day. I would think you need more hand painters.

From Contributor C:
I am assuming the Original Poster and his team are looking at the typical drying tunnels used for flat pieces. There are several configurations available but generally the feed clear space is no more than four-eight inches from the conveyor belt. Any drying utility able to accept full cabinets would be more of an oven, apparatus that you would commonly find in the automotive industry. Space is a major consideration in any event. Not only for the dryer itself but to rack the assembled cabinets between coats. He could clarify better the dryer models he has been considering. I am guessing he is balancing available floor space in the overall feasibility assessment.

From Contributor S:
It seems like way too much handling to me. Think about it. There is no way to handle all of these sheets in finishing, drying and cutting faster than cutting raw, assemble then paint. What kind of acreage do you think 200 4x8’s take? Maybe just more bodies are needed in paint. This is the problem most of the time.